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
  1. <html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>JEMALLOC</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry"><a name="idp45223136"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>jemalloc &#8212; general purpose memory allocation functions</p></div><div class="refsect1"><a name="library"></a><h2>LIBRARY</h2><p>This manual describes jemalloc 4.0.3-0-ge9192eacf8935e29fc62fddc2701f7942b1cc02c.  More information
    2. 

  2.     can be found at the <a class="ulink" href="http://www.canonware.com/jemalloc/" target="_top">jemalloc website</a>.</p></div><div class="refsynopsisdiv"><h2>SYNOPSIS</h2><div class="funcsynopsis"><pre class="funcsynopsisinfo">#include &lt;<code class="filename">jemalloc/jemalloc.h</code>&gt;</pre><div class="refsect2"><a name="idp44244480"></a><h3>Standard API</h3><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void *<b class="fsfunc">malloc</b>(</code></td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void *<b class="fsfunc">calloc</b>(</code></td><td>size_t <var class="pdparam">number</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">posix_memalign</b>(</code></td><td>void **<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">alignment</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void *<b class="fsfunc">aligned_alloc</b>(</code></td><td>size_t <var class="pdparam">alignment</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void *<b class="fsfunc">realloc</b>(</code></td><td>void *<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <b class="fsfunc">free</b>(</code></td><td>void *<var class="pdparam">ptr</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="refsect2"><a name="idp46062768"></a><h3>Non-standard API</h3><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void *<b class="fsfunc">mallocx</b>(</code></td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void *<b class="fsfunc">rallocx</b>(</code></td><td>void *<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">size_t <b class="fsfunc">xallocx</b>(</code></td><td>void *<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">extra</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">size_t <b class="fsfunc">sallocx</b>(</code></td><td>void *<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <b class="fsfunc">dallocx</b>(</code></td><td>void *<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <b class="fsfunc">sdallocx</b>(</code></td><td>void *<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">size_t <b class="fsfunc">nallocx</b>(</code></td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">mallctl</b>(</code></td><td>const char *<var class="pdparam">name</var>, </td></tr><tr><td> </td><td>void *<var class="pdparam">oldp</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">oldlenp</var>, </td></tr><tr><td> </td><td>void *<var class="pdparam">newp</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">newlen</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">mallctlnametomib</b>(</code></td><td>const char *<var class="pdparam">name</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">mibp</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">miblenp</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">mallctlbymib</b>(</code></td><td>const size_t *<var class="pdparam">mib</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">miblen</var>, </td></tr><tr><td> </td><td>void *<var class="pdparam">oldp</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">oldlenp</var>, </td></tr><tr><td> </td><td>void *<var class="pdparam">newp</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">newlen</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <b class="fsfunc">malloc_stats_print</b>(</code></td><td>void <var class="pdparam">(*write_cb)</var>
    3. 

  3.             <code>(</code>void *, const char *<code>)</code>
    4. 

  4.           , </td></tr><tr><td> </td><td>void *<var class="pdparam">cbopaque</var>, </td></tr><tr><td> </td><td>const char *<var class="pdparam">opts</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">size_t <b class="fsfunc">malloc_usable_size</b>(</code></td><td>const void *<var class="pdparam">ptr</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <b class="fsfunc">(*malloc_message)</b>(</code></td><td>void *<var class="pdparam">cbopaque</var>, </td></tr><tr><td> </td><td>const char *<var class="pdparam">s</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><p><span class="type">const char *</span><code class="varname">malloc_conf</code>;</p></div></div></div><div class="refsect1"><a name="description"></a><h2>DESCRIPTION</h2><div class="refsect2"><a name="idp46115952"></a><h3>Standard API</h3><p>The <code class="function">malloc</code>(<em class="parameter"><code></code></em>) function allocates
    5. 

  5.       <em class="parameter"><code>size</code></em> bytes of uninitialized memory.  The allocated
    6. 

  6.       space is suitably aligned (after possible pointer coercion) for storage
    7. 

  7.       of any type of object.</p><p>The <code class="function">calloc</code>(<em class="parameter"><code></code></em>) function allocates
    8. 

  8.       space for <em class="parameter"><code>number</code></em> objects, each
    9. 

  9.       <em class="parameter"><code>size</code></em> bytes in length.  The result is identical to
    10. 

  10.       calling <code class="function">malloc</code>(<em class="parameter"><code></code></em>) with an argument of
    11. 

  11.       <em class="parameter"><code>number</code></em> * <em class="parameter"><code>size</code></em>, with the
    12. 

  12.       exception that the allocated memory is explicitly initialized to zero
    13. 

  13.       bytes.</p><p>The <code class="function">posix_memalign</code>(<em class="parameter"><code></code></em>) function
    14. 

  14.       allocates <em class="parameter"><code>size</code></em> bytes of memory such that the
    15. 

  15.       allocation's base address is a multiple of
    16. 

  16.       <em class="parameter"><code>alignment</code></em>, and returns the allocation in the value
    17. 

  17.       pointed to by <em class="parameter"><code>ptr</code></em>.  The requested
    18. 

  18.       <em class="parameter"><code>alignment</code></em> must be a power of 2 at least as large as
    19. 

  19.       <code class="code">sizeof(<span class="type">void *</span>)</code>.</p><p>The <code class="function">aligned_alloc</code>(<em class="parameter"><code></code></em>) function
    20. 

  20.       allocates <em class="parameter"><code>size</code></em> bytes of memory such that the
    21. 

  21.       allocation's base address is a multiple of
    22. 

  22.       <em class="parameter"><code>alignment</code></em>.  The requested
    23. 

  23.       <em class="parameter"><code>alignment</code></em> must be a power of 2.  Behavior is
    24. 

  24.       undefined if <em class="parameter"><code>size</code></em> is not an integral multiple of
    25. 

  25.       <em class="parameter"><code>alignment</code></em>.</p><p>The <code class="function">realloc</code>(<em class="parameter"><code></code></em>) function changes the
    26. 

  26.       size of the previously allocated memory referenced by
    27. 

  27.       <em class="parameter"><code>ptr</code></em> to <em class="parameter"><code>size</code></em> bytes.  The
    28. 

  28.       contents of the memory are unchanged up to the lesser of the new and old
    29. 

  29.       sizes.  If the new size is larger, the contents of the newly allocated
    30. 

  30.       portion of the memory are undefined.  Upon success, the memory referenced
    31. 

  31.       by <em class="parameter"><code>ptr</code></em> is freed and a pointer to the newly
    32. 

  32.       allocated memory is returned.  Note that
    33. 

  33.       <code class="function">realloc</code>(<em class="parameter"><code></code></em>) may move the memory allocation,
    34. 

  34.       resulting in a different return value than <em class="parameter"><code>ptr</code></em>.
    35. 

  35.       If <em class="parameter"><code>ptr</code></em> is <code class="constant">NULL</code>, the
    36. 

  36.       <code class="function">realloc</code>(<em class="parameter"><code></code></em>) function behaves identically to
    37. 

  37.       <code class="function">malloc</code>(<em class="parameter"><code></code></em>) for the specified size.</p><p>The <code class="function">free</code>(<em class="parameter"><code></code></em>) function causes the
    38. 

  38.       allocated memory referenced by <em class="parameter"><code>ptr</code></em> to be made
    39. 

  39.       available for future allocations.  If <em class="parameter"><code>ptr</code></em> is
    40. 

  40.       <code class="constant">NULL</code>, no action occurs.</p></div><div class="refsect2"><a name="idp46144704"></a><h3>Non-standard API</h3><p>The <code class="function">mallocx</code>(<em class="parameter"><code></code></em>),
    41. 

  41.       <code class="function">rallocx</code>(<em class="parameter"><code></code></em>),
    42. 

  42.       <code class="function">xallocx</code>(<em class="parameter"><code></code></em>),
    43. 

  43.       <code class="function">sallocx</code>(<em class="parameter"><code></code></em>),
    44. 

  44.       <code class="function">dallocx</code>(<em class="parameter"><code></code></em>),
    45. 

  45.       <code class="function">sdallocx</code>(<em class="parameter"><code></code></em>), and
    46. 

  46.       <code class="function">nallocx</code>(<em class="parameter"><code></code></em>) functions all have a
    47. 

  47.       <em class="parameter"><code>flags</code></em> argument that can be used to specify
    48. 

  48.       options.  The functions only check the options that are contextually
    49. 

  49.       relevant.  Use bitwise or (<code class="code">|</code>) operations to
    50. 

  50.       specify one or more of the following:
    51. 

  51.         </p><div class="variablelist"><dl class="variablelist"><dt><a name="MALLOCX_LG_ALIGN"></a><span class="term"><code class="constant">MALLOCX_LG_ALIGN(<em class="parameter"><code>la</code></em>)
    52. 

  52.             </code></span></dt><dd><p>Align the memory allocation to start at an address
    53. 

  53.             that is a multiple of <code class="code">(1 &lt;&lt;
    54. 

  54.             <em class="parameter"><code>la</code></em>)</code>.  This macro does not validate
    55. 

  55.             that <em class="parameter"><code>la</code></em> is within the valid
    56. 

  56.             range.</p></dd><dt><a name="MALLOCX_ALIGN"></a><span class="term"><code class="constant">MALLOCX_ALIGN(<em class="parameter"><code>a</code></em>)
    57. 

  57.             </code></span></dt><dd><p>Align the memory allocation to start at an address
    58. 

  58.             that is a multiple of <em class="parameter"><code>a</code></em>, where
    59. 

  59.             <em class="parameter"><code>a</code></em> is a power of two.  This macro does not
    60. 

  60.             validate that <em class="parameter"><code>a</code></em> is a power of 2.
    61. 

  61.             </p></dd><dt><a name="MALLOCX_ZERO"></a><span class="term"><code class="constant">MALLOCX_ZERO</code></span></dt><dd><p>Initialize newly allocated memory to contain zero
    62. 

  62.             bytes.  In the growing reallocation case, the real size prior to
    63. 

  63.             reallocation defines the boundary between untouched bytes and those
    64. 

  64.             that are initialized to contain zero bytes.  If this macro is
    65. 

  65.             absent, newly allocated memory is uninitialized.</p></dd><dt><a name="MALLOCX_TCACHE"></a><span class="term"><code class="constant">MALLOCX_TCACHE(<em class="parameter"><code>tc</code></em>)
    66. 

  66.             </code></span></dt><dd><p>Use the thread-specific cache (tcache) specified by
    67. 

  67.             the identifier <em class="parameter"><code>tc</code></em>, which must have been
    68. 

  68.             acquired via the <a class="link" href="#tcache.create">
    69. 

  69.     "<code class="mallctl">tcache.create</code>"
    70. 

  70.   </a>
    71. 

  71.             mallctl.  This macro does not validate that
    72. 

  72.             <em class="parameter"><code>tc</code></em> specifies a valid
    73. 

  73.             identifier.</p></dd><dt><a name="MALLOC_TCACHE_NONE"></a><span class="term"><code class="constant">MALLOCX_TCACHE_NONE</code></span></dt><dd><p>Do not use a thread-specific cache (tcache).  Unless
    74. 

  74.             <code class="constant">MALLOCX_TCACHE(<em class="parameter"><code>tc</code></em>)</code> or
    75. 

  75.             <code class="constant">MALLOCX_TCACHE_NONE</code> is specified, an
    76. 

  76.             automatically managed tcache will be used under many circumstances.
    77. 

  77.             This macro cannot be used in the same <em class="parameter"><code>flags</code></em>
    78. 

  78.             argument as
    79. 

  79.             <code class="constant">MALLOCX_TCACHE(<em class="parameter"><code>tc</code></em>)</code>.</p></dd><dt><a name="MALLOCX_ARENA"></a><span class="term"><code class="constant">MALLOCX_ARENA(<em class="parameter"><code>a</code></em>)
    80. 

  80.             </code></span></dt><dd><p>Use the arena specified by the index
    81. 

  81.             <em class="parameter"><code>a</code></em>.  This macro has no effect for regions that
    82. 

  82.             were allocated via an arena other than the one specified.  This
    83. 

  83.             macro does not validate that <em class="parameter"><code>a</code></em> specifies an
    84. 

  84.             arena index in the valid range.</p></dd></dl></div><p>
    85. 

  85.       </p><p>The <code class="function">mallocx</code>(<em class="parameter"><code></code></em>) function allocates at
    86. 

  86.       least <em class="parameter"><code>size</code></em> bytes of memory, and returns a pointer
    87. 

  87.       to the base address of the allocation.  Behavior is undefined if
    88. 

  88.       <em class="parameter"><code>size</code></em> is <code class="constant">0</code>, or if request size
    89. 

  89.       overflows due to size class and/or alignment constraints.</p><p>The <code class="function">rallocx</code>(<em class="parameter"><code></code></em>) function resizes the
    90. 

  90.       allocation at <em class="parameter"><code>ptr</code></em> to be at least
    91. 

  91.       <em class="parameter"><code>size</code></em> bytes, and returns a pointer to the base
    92. 

  92.       address of the resulting allocation, which may or may not have moved from
    93. 

  93.       its original location.  Behavior is undefined if
    94. 

  94.       <em class="parameter"><code>size</code></em> is <code class="constant">0</code>, or if request size
    95. 

  95.       overflows due to size class and/or alignment constraints.</p><p>The <code class="function">xallocx</code>(<em class="parameter"><code></code></em>) function resizes the
    96. 

  96.       allocation at <em class="parameter"><code>ptr</code></em> in place to be at least
    97. 

  97.       <em class="parameter"><code>size</code></em> bytes, and returns the real size of the
    98. 

  98.       allocation.  If <em class="parameter"><code>extra</code></em> is non-zero, an attempt is
    99. 

  99.       made to resize the allocation to be at least <code class="code">(<em class="parameter"><code>size</code></em> +
    100. 

  100.       <em class="parameter"><code>extra</code></em>)</code> bytes, though inability to allocate
    101. 

  101.       the extra byte(s) will not by itself result in failure to resize.
    102. 

  102.       Behavior is undefined if <em class="parameter"><code>size</code></em> is
    103. 

  103.       <code class="constant">0</code>, or if <code class="code">(<em class="parameter"><code>size</code></em> + <em class="parameter"><code>extra</code></em>
    104. 

  104.       &gt; <code class="constant">SIZE_T_MAX</code>)</code>.</p><p>The <code class="function">sallocx</code>(<em class="parameter"><code></code></em>) function returns the
    105. 

  105.       real size of the allocation at <em class="parameter"><code>ptr</code></em>.</p><p>The <code class="function">dallocx</code>(<em class="parameter"><code></code></em>) function causes the
    106. 

  106.       memory referenced by <em class="parameter"><code>ptr</code></em> to be made available for
    107. 

  107.       future allocations.</p><p>The <code class="function">sdallocx</code>(<em class="parameter"><code></code></em>) function is an
    108. 

  108.       extension of <code class="function">dallocx</code>(<em class="parameter"><code></code></em>) with a
    109. 

  109.       <em class="parameter"><code>size</code></em> parameter to allow the caller to pass in the
    110. 

  110.       allocation size as an optimization.  The minimum valid input size is the
    111. 

  111.       original requested size of the allocation, and the maximum valid input
    112. 

  112.       size is the corresponding value returned by
    113. 

  113.       <code class="function">nallocx</code>(<em class="parameter"><code></code></em>) or
    114. 

  114.       <code class="function">sallocx</code>(<em class="parameter"><code></code></em>).</p><p>The <code class="function">nallocx</code>(<em class="parameter"><code></code></em>) function allocates no
    115. 

  115.       memory, but it performs the same size computation as the
    116. 

  116.       <code class="function">mallocx</code>(<em class="parameter"><code></code></em>) function, and returns the real
    117. 

  117.       size of the allocation that would result from the equivalent
    118. 

  118.       <code class="function">mallocx</code>(<em class="parameter"><code></code></em>) function call.  Behavior is
    119. 

  119.       undefined if <em class="parameter"><code>size</code></em> is <code class="constant">0</code>, or if
    120. 

  120.       request size overflows due to size class and/or alignment
    121. 

  121.       constraints.</p><p>The <code class="function">mallctl</code>(<em class="parameter"><code></code></em>) function provides a
    122. 

  122.       general interface for introspecting the memory allocator, as well as
    123. 

  123.       setting modifiable parameters and triggering actions.  The
    124. 

  124.       period-separated <em class="parameter"><code>name</code></em> argument specifies a
    125. 

  125.       location in a tree-structured namespace; see the <a class="xref" href="#mallctl_namespace" title="MALLCTL NAMESPACE">MALLCTL NAMESPACE</a> section for
    126. 

  126.       documentation on the tree contents.  To read a value, pass a pointer via
    127. 

  127.       <em class="parameter"><code>oldp</code></em> to adequate space to contain the value, and a
    128. 

  128.       pointer to its length via <em class="parameter"><code>oldlenp</code></em>; otherwise pass
    129. 

  129.       <code class="constant">NULL</code> and <code class="constant">NULL</code>.  Similarly, to
    130. 

  130.       write a value, pass a pointer to the value via
    131. 

  131.       <em class="parameter"><code>newp</code></em>, and its length via
    132. 

  132.       <em class="parameter"><code>newlen</code></em>; otherwise pass <code class="constant">NULL</code>
    133. 

  133.       and <code class="constant">0</code>.</p><p>The <code class="function">mallctlnametomib</code>(<em class="parameter"><code></code></em>) function
    134. 

  134.       provides a way to avoid repeated name lookups for applications that
    135. 

  135.       repeatedly query the same portion of the namespace, by translating a name
    136. 

  136.       to a &#8220;Management Information Base&#8221; (MIB) that can be passed
    137. 

  137.       repeatedly to <code class="function">mallctlbymib</code>(<em class="parameter"><code></code></em>).  Upon
    138. 

  138.       successful return from <code class="function">mallctlnametomib</code>(<em class="parameter"><code></code></em>),
    139. 

  139.       <em class="parameter"><code>mibp</code></em> contains an array of
    140. 

  140.       <em class="parameter"><code>*miblenp</code></em> integers, where
    141. 

  141.       <em class="parameter"><code>*miblenp</code></em> is the lesser of the number of components
    142. 

  142.       in <em class="parameter"><code>name</code></em> and the input value of
    143. 

  143.       <em class="parameter"><code>*miblenp</code></em>.  Thus it is possible to pass a
    144. 

  144.       <em class="parameter"><code>*miblenp</code></em> that is smaller than the number of
    145. 

  145.       period-separated name components, which results in a partial MIB that can
    146. 

  146.       be used as the basis for constructing a complete MIB.  For name
    147. 

  147.       components that are integers (e.g. the 2 in
    148. 

  148.       <a class="link" href="#arenas.bin.i.size">
    149. 

  149.     "<code class="mallctl">arenas.bin.2.size</code>"
    150. 

  150.   </a>),
    151. 

  151.       the corresponding MIB component will always be that integer.  Therefore,
    152. 

  152.       it is legitimate to construct code like the following: </p><pre class="programlisting">
    153. 

  153. unsigned nbins, i;
    154. 

  154. size_t mib[4];
    155. 

  155. size_t len, miblen;
    156. 

  156. 

  157. len = sizeof(nbins);
    158. 

  158. mallctl("arenas.nbins", &amp;nbins, &amp;len, NULL, 0);
    159. 

  159. 

  160. miblen = 4;
    161. 

  161. mallctlnametomib("arenas.bin.0.size", mib, &amp;miblen);
    162. 

  162. for (i = 0; i &lt; nbins; i++) {
    163. 

  163. 	size_t bin_size;
    164. 

  164. 

  165. 	mib[2] = i;
    166. 

  166. 	len = sizeof(bin_size);
    167. 

  167. 	mallctlbymib(mib, miblen, &amp;bin_size, &amp;len, NULL, 0);
    168. 

  168. 	/* Do something with bin_size... */
    169. 

  169. }</pre><p>The <code class="function">malloc_stats_print</code>(<em class="parameter"><code></code></em>) function
    170. 

  170.       writes human-readable summary statistics via the
    171. 

  171.       <em class="parameter"><code>write_cb</code></em> callback function pointer and
    172. 

  172.       <em class="parameter"><code>cbopaque</code></em> data passed to
    173. 

  173.       <em class="parameter"><code>write_cb</code></em>, or
    174. 

  174.       <code class="function">malloc_message</code>(<em class="parameter"><code></code></em>) if
    175. 

  175.       <em class="parameter"><code>write_cb</code></em> is <code class="constant">NULL</code>.  This
    176. 

  176.       function can be called repeatedly.  General information that never
    177. 

  177.       changes during execution can be omitted by specifying "g" as a character
    178. 

  178.       within the <em class="parameter"><code>opts</code></em> string.  Note that
    179. 

  179.       <code class="function">malloc_message</code>(<em class="parameter"><code></code></em>) uses the
    180. 

  180.       <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) functions internally, so
    181. 

  181.       inconsistent statistics can be reported if multiple threads use these
    182. 

  182.       functions simultaneously.  If <code class="option">--enable-stats</code> is
    183. 

  183.       specified during configuration, &#8220;m&#8221; and &#8220;a&#8221; can
    184. 

  184.       be specified to omit merged arena and per arena statistics, respectively;
    185. 

  185.       &#8220;b&#8221;, &#8220;l&#8221;, and &#8220;h&#8221; can be specified to
    186. 

  186.       omit per size class statistics for bins, large objects, and huge objects,
    187. 

  187.       respectively.  Unrecognized characters are silently ignored.  Note that
    188. 

  188.       thread caching may prevent some statistics from being completely up to
    189. 

  189.       date, since extra locking would be required to merge counters that track
    190. 

  190.       thread cache operations.
    191. 

  191.       </p><p>The <code class="function">malloc_usable_size</code>(<em class="parameter"><code></code></em>) function
    192. 

  192.       returns the usable size of the allocation pointed to by
    193. 

  193.       <em class="parameter"><code>ptr</code></em>.  The return value may be larger than the size
    194. 

  194.       that was requested during allocation.  The
    195. 

  195.       <code class="function">malloc_usable_size</code>(<em class="parameter"><code></code></em>) function is not a
    196. 

  196.       mechanism for in-place <code class="function">realloc</code>(<em class="parameter"><code></code></em>); rather
    197. 

  197.       it is provided solely as a tool for introspection purposes.  Any
    198. 

  198.       discrepancy between the requested allocation size and the size reported
    199. 

  199.       by <code class="function">malloc_usable_size</code>(<em class="parameter"><code></code></em>) should not be
    200. 

  200.       depended on, since such behavior is entirely implementation-dependent.
    201. 

  201.       </p></div></div><div class="refsect1"><a name="tuning"></a><h2>TUNING</h2><p>Once, when the first call is made to one of the memory allocation
    202. 

  202.     routines, the allocator initializes its internals based in part on various
    203. 

  203.     options that can be specified at compile- or run-time.</p><p>The string pointed to by the global variable
    204. 

  204.     <code class="varname">malloc_conf</code>, the &#8220;name&#8221; of the file
    205. 

  205.     referenced by the symbolic link named <code class="filename">/etc/malloc.conf</code>, and the value of the
    206. 

  206.     environment variable <code class="envar">MALLOC_CONF</code>, will be interpreted, in
    207. 

  207.     that order, from left to right as options.  Note that
    208. 

  208.     <code class="varname">malloc_conf</code> may be read before
    209. 

  209.     <code class="function">main</code>(<em class="parameter"><code></code></em>) is entered, so the declaration of
    210. 

  210.     <code class="varname">malloc_conf</code> should specify an initializer that contains
    211. 

  211.     the final value to be read by jemalloc.  <code class="varname">malloc_conf</code> is
    212. 

  212.     a compile-time setting, whereas <code class="filename">/etc/malloc.conf</code> and <code class="envar">MALLOC_CONF</code>
    213. 

  213.     can be safely set any time prior to program invocation.</p><p>An options string is a comma-separated list of option:value pairs.
    214. 

  214.     There is one key corresponding to each <a class="link" href="#opt.abort">
    215. 

  215.     "<code class="mallctl">opt.*</code>"
    216. 

  216.   </a> mallctl (see the <a class="xref" href="#mallctl_namespace" title="MALLCTL NAMESPACE">MALLCTL NAMESPACE</a> section for options
    217. 

  217.     documentation).  For example, <code class="literal">abort:true,narenas:1</code> sets
    218. 

  218.     the <a class="link" href="#opt.abort">
    219. 

  219.     "<code class="mallctl">opt.abort</code>"
    220. 

  220.   </a> and <a class="link" href="#opt.narenas">
    221. 

  221.     "<code class="mallctl">opt.narenas</code>"
    222. 

  222.   </a> options.  Some
    223. 

  223.     options have boolean values (true/false), others have integer values (base
    224. 

  224.     8, 10, or 16, depending on prefix), and yet others have raw string
    225. 

  225.     values.</p></div><div class="refsect1"><a name="implementation_notes"></a><h2>IMPLEMENTATION NOTES</h2><p>Traditionally, allocators have used
    226. 

  226.     <span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span> to obtain memory, which is
    227. 

  227.     suboptimal for several reasons, including race conditions, increased
    228. 

  228.     fragmentation, and artificial limitations on maximum usable memory.  If
    229. 

  229.     <span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span> is supported by the operating
    230. 

  230.     system, this allocator uses both
    231. 

  231.     <span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span> and
    232. 

  232.     <span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span>, in that order of preference;
    233. 

  233.     otherwise only <span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span> is used.</p><p>This allocator uses multiple arenas in order to reduce lock
    234. 

  234.     contention for threaded programs on multi-processor systems.  This works
    235. 

  235.     well with regard to threading scalability, but incurs some costs.  There is
    236. 

  236.     a small fixed per-arena overhead, and additionally, arenas manage memory
    237. 

  237.     completely independently of each other, which means a small fixed increase
    238. 

  238.     in overall memory fragmentation.  These overheads are not generally an
    239. 

  239.     issue, given the number of arenas normally used.  Note that using
    240. 

  240.     substantially more arenas than the default is not likely to improve
    241. 

  241.     performance, mainly due to reduced cache performance.  However, it may make
    242. 

  242.     sense to reduce the number of arenas if an application does not make much
    243. 

  243.     use of the allocation functions.</p><p>In addition to multiple arenas, unless
    244. 

  244.     <code class="option">--disable-tcache</code> is specified during configuration, this
    245. 

  245.     allocator supports thread-specific caching for small and large objects, in
    246. 

  246.     order to make it possible to completely avoid synchronization for most
    247. 

  247.     allocation requests.  Such caching allows very fast allocation in the
    248. 

  248.     common case, but it increases memory usage and fragmentation, since a
    249. 

  249.     bounded number of objects can remain allocated in each thread cache.</p><p>Memory is conceptually broken into equal-sized chunks, where the
    250. 

  250.     chunk size is a power of two that is greater than the page size.  Chunks
    251. 

  251.     are always aligned to multiples of the chunk size.  This alignment makes it
    252. 

  252.     possible to find metadata for user objects very quickly.</p><p>User objects are broken into three categories according to size:
    253. 

  253.     small, large, and huge.  Small and large objects are managed entirely by
    254. 

  254.     arenas; huge objects are additionally aggregated in a single data structure
    255. 

  255.     that is shared by all threads.  Huge objects are typically used by
    256. 

  256.     applications infrequently enough that this single data structure is not a
    257. 

  257.     scalability issue.</p><p>Each chunk that is managed by an arena tracks its contents as runs of
    258. 

  258.     contiguous pages (unused, backing a set of small objects, or backing one
    259. 

  259.     large object).  The combination of chunk alignment and chunk page maps
    260. 

  260.     makes it possible to determine all metadata regarding small and large
    261. 

  261.     allocations in constant time.</p><p>Small objects are managed in groups by page runs.  Each run maintains
    262. 

  262.     a bitmap to track which regions are in use.  Allocation requests that are no
    263. 

  263.     more than half the quantum (8 or 16, depending on architecture) are rounded
    264. 

  264.     up to the nearest power of two that is at least <code class="code">sizeof(<span class="type">double</span>)</code>.  All other object size
    265. 

  265.     classes are multiples of the quantum, spaced such that there are four size
    266. 

  266.     classes for each doubling in size, which limits internal fragmentation to
    267. 

  267.     approximately 20% for all but the smallest size classes.  Small size classes
    268. 

  268.     are smaller than four times the page size, large size classes are smaller
    269. 

  269.     than the chunk size (see the <a class="link" href="#opt.lg_chunk">
    270. 

  270.     "<code class="mallctl">opt.lg_chunk</code>"
    271. 

  271.   </a> option), and
    272. 

  272.     huge size classes extend from the chunk size up to one size class less than
    273. 

  273.     the full address space size.</p><p>Allocations are packed tightly together, which can be an issue for
    274. 

  274.     multi-threaded applications.  If you need to assure that allocations do not
    275. 

  275.     suffer from cacheline sharing, round your allocation requests up to the
    276. 

  276.     nearest multiple of the cacheline size, or specify cacheline alignment when
    277. 

  277.     allocating.</p><p>The <code class="function">realloc</code>(<em class="parameter"><code></code></em>),
    278. 

  278.     <code class="function">rallocx</code>(<em class="parameter"><code></code></em>), and
    279. 

  279.     <code class="function">xallocx</code>(<em class="parameter"><code></code></em>) functions may resize allocations
    280. 

  280.     without moving them under limited circumstances.  Unlike the
    281. 

  281.     <code class="function">*allocx</code>(<em class="parameter"><code></code></em>) API, the standard API does not
    282. 

  282.     officially round up the usable size of an allocation to the nearest size
    283. 

  283.     class, so technically it is necessary to call
    284. 

  284.     <code class="function">realloc</code>(<em class="parameter"><code></code></em>) to grow e.g. a 9-byte allocation to
    285. 

  285.     16 bytes, or shrink a 16-byte allocation to 9 bytes.  Growth and shrinkage
    286. 

  286.     trivially succeeds in place as long as the pre-size and post-size both round
    287. 

  287.     up to the same size class.  No other API guarantees are made regarding
    288. 

  288.     in-place resizing, but the current implementation also tries to resize large
    289. 

  289.     and huge allocations in place, as long as the pre-size and post-size are
    290. 

  290.     both large or both huge.  In such cases shrinkage always succeeds for large
    291. 

  291.     size classes, but for huge size classes the chunk allocator must support
    292. 

  292.     splitting (see <a class="link" href="#arena.i.chunk_hooks">
    293. 

  293.     "<code class="mallctl">arena.&lt;i&gt;.chunk_hooks</code>"
    294. 

  294.   </a>).
    295. 

  295.     Growth only succeeds if the trailing memory is currently available, and
    296. 

  296.     additionally for huge size classes the chunk allocator must support
    297. 

  297.     merging.</p><p>Assuming 2 MiB chunks, 4 KiB pages, and a 16-byte quantum on a
    298. 

  298.     64-bit system, the size classes in each category are as shown in <a class="xref" href="#size_classes" title="Table 1. Size classes">Table 1</a>.</p><div class="table"><a name="size_classes"></a><p class="title"><b>Table 1. Size classes</b></p><div class="table-contents"><table summary="Size classes" border="1"><colgroup><col align="left" class="c1"><col align="right" class="c2"><col align="left" class="c3"></colgroup><thead><tr><th align="left">Category</th><th align="right">Spacing</th><th align="left">Size</th></tr></thead><tbody><tr><td rowspan="9" align="left">Small</td><td align="right">lg</td><td align="left">[8]</td></tr><tr><td align="right">16</td><td align="left">[16, 32, 48, 64, 80, 96, 112, 128]</td></tr><tr><td align="right">32</td><td align="left">[160, 192, 224, 256]</td></tr><tr><td align="right">64</td><td align="left">[320, 384, 448, 512]</td></tr><tr><td align="right">128</td><td align="left">[640, 768, 896, 1024]</td></tr><tr><td align="right">256</td><td align="left">[1280, 1536, 1792, 2048]</td></tr><tr><td align="right">512</td><td align="left">[2560, 3072, 3584, 4096]</td></tr><tr><td align="right">1 KiB</td><td align="left">[5 KiB, 6 KiB, 7 KiB, 8 KiB]</td></tr><tr><td align="right">2 KiB</td><td align="left">[10 KiB, 12 KiB, 14 KiB]</td></tr><tr><td rowspan="8" align="left">Large</td><td align="right">2 KiB</td><td align="left">[16 KiB]</td></tr><tr><td align="right">4 KiB</td><td align="left">[20 KiB, 24 KiB, 28 KiB, 32 KiB]</td></tr><tr><td align="right">8 KiB</td><td align="left">[40 KiB, 48 KiB, 54 KiB, 64 KiB]</td></tr><tr><td align="right">16 KiB</td><td align="left">[80 KiB, 96 KiB, 112 KiB, 128 KiB]</td></tr><tr><td align="right">32 KiB</td><td align="left">[160 KiB, 192 KiB, 224 KiB, 256 KiB]</td></tr><tr><td align="right">64 KiB</td><td align="left">[320 KiB, 384 KiB, 448 KiB, 512 KiB]</td></tr><tr><td align="right">128 KiB</td><td align="left">[640 KiB, 768 KiB, 896 KiB, 1 MiB]</td></tr><tr><td align="right">256 KiB</td><td align="left">[1280 KiB, 1536 KiB, 1792 KiB]</td></tr><tr><td rowspan="7" align="left">Huge</td><td align="right">256 KiB</td><td align="left">[2 MiB]</td></tr><tr><td align="right">512 KiB</td><td align="left">[2560 KiB, 3 MiB, 3584 KiB, 4 MiB]</td></tr><tr><td align="right">1 MiB</td><td align="left">[5 MiB, 6 MiB, 7 MiB, 8 MiB]</td></tr><tr><td align="right">2 MiB</td><td align="left">[10 MiB, 12 MiB, 14 MiB, 16 MiB]</td></tr><tr><td align="right">4 MiB</td><td align="left">[20 MiB, 24 MiB, 28 MiB, 32 MiB]</td></tr><tr><td align="right">8 MiB</td><td align="left">[40 MiB, 48 MiB, 56 MiB, 64 MiB]</td></tr><tr><td align="right">...</td><td align="left">...</td></tr></tbody></table></div></div><br class="table-break"></div><div class="refsect1"><a name="mallctl_namespace"></a><h2>MALLCTL NAMESPACE</h2><p>The following names are defined in the namespace accessible via the
    299. 

  299.     <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) functions.  Value types are
    300. 

  300.     specified in parentheses, their readable/writable statuses are encoded as
    301. 

  301.     <code class="literal">rw</code>, <code class="literal">r-</code>, <code class="literal">-w</code>, or
    302. 

  302.     <code class="literal">--</code>, and required build configuration flags follow, if
    303. 

  303.     any.  A name element encoded as <code class="literal">&lt;i&gt;</code> or
    304. 

  304.     <code class="literal">&lt;j&gt;</code> indicates an integer component, where the
    305. 

  305.     integer varies from 0 to some upper value that must be determined via
    306. 

  306.     introspection.  In the case of 
    307. 

  307.     "<code class="mallctl">stats.arenas.&lt;i&gt;.*</code>"
    308. 

  308.   ,
    309. 

  309.     <code class="literal">&lt;i&gt;</code> equal to <a class="link" href="#arenas.narenas">
    310. 

  310.     "<code class="mallctl">arenas.narenas</code>"
    311. 

  311.   </a> can be
    312. 

  312.     used to access the summation of statistics from all arenas.  Take special
    313. 

  313.     note of the <a class="link" href="#epoch">
    314. 

  314.     "<code class="mallctl">epoch</code>"
    315. 

  315.   </a> mallctl,
    316. 

  316.     which controls refreshing of cached dynamic statistics.</p><div class="variablelist"><dl class="variablelist"><dt><a name="version"></a><span class="term">
    317. 

  317.           
    318. 

  318.     "<code class="mallctl">version</code>"
    319. 

  319.   
    320. 

  320.           (<span class="type">const char *</span>)
    321. 

  321.           <code class="literal">r-</code>
    322. 

  322.         </span></dt><dd><p>Return the jemalloc version string.</p></dd><dt><a name="epoch"></a><span class="term">
    323. 

  323.           
    324. 

  324.     "<code class="mallctl">epoch</code>"
    325. 

  325.   
    326. 

  326.           (<span class="type">uint64_t</span>)
    327. 

  327.           <code class="literal">rw</code>
    328. 

  328.         </span></dt><dd><p>If a value is passed in, refresh the data from which
    329. 

  329.         the <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) functions report values,
    330. 

  330.         and increment the epoch.  Return the current epoch.  This is useful for
    331. 

  331.         detecting whether another thread caused a refresh.</p></dd><dt><a name="config.cache_oblivious"></a><span class="term">
    332. 

  332.           
    333. 

  333.     "<code class="mallctl">config.cache_oblivious</code>"
    334. 

  334.   
    335. 

  335.           (<span class="type">bool</span>)
    336. 

  336.           <code class="literal">r-</code>
    337. 

  337.         </span></dt><dd><p><code class="option">--enable-cache-oblivious</code> was specified
    338. 

  338.         during build configuration.</p></dd><dt><a name="config.debug"></a><span class="term">
    339. 

  339.           
    340. 

  340.     "<code class="mallctl">config.debug</code>"
    341. 

  341.   
    342. 

  342.           (<span class="type">bool</span>)
    343. 

  343.           <code class="literal">r-</code>
    344. 

  344.         </span></dt><dd><p><code class="option">--enable-debug</code> was specified during
    345. 

  345.         build configuration.</p></dd><dt><a name="config.fill"></a><span class="term">
    346. 

  346.           
    347. 

  347.     "<code class="mallctl">config.fill</code>"
    348. 

  348.   
    349. 

  349.           (<span class="type">bool</span>)
    350. 

  350.           <code class="literal">r-</code>
    351. 

  351.         </span></dt><dd><p><code class="option">--enable-fill</code> was specified during
    352. 

  352.         build configuration.</p></dd><dt><a name="config.lazy_lock"></a><span class="term">
    353. 

  353.           
    354. 

  354.     "<code class="mallctl">config.lazy_lock</code>"
    355. 

  355.   
    356. 

  356.           (<span class="type">bool</span>)
    357. 

  357.           <code class="literal">r-</code>
    358. 

  358.         </span></dt><dd><p><code class="option">--enable-lazy-lock</code> was specified
    359. 

  359.         during build configuration.</p></dd><dt><a name="config.munmap"></a><span class="term">
    360. 

  360.           
    361. 

  361.     "<code class="mallctl">config.munmap</code>"
    362. 

  362.   
    363. 

  363.           (<span class="type">bool</span>)
    364. 

  364.           <code class="literal">r-</code>
    365. 

  365.         </span></dt><dd><p><code class="option">--enable-munmap</code> was specified during
    366. 

  366.         build configuration.</p></dd><dt><a name="config.prof"></a><span class="term">
    367. 

  367.           
    368. 

  368.     "<code class="mallctl">config.prof</code>"
    369. 

  369.   
    370. 

  370.           (<span class="type">bool</span>)
    371. 

  371.           <code class="literal">r-</code>
    372. 

  372.         </span></dt><dd><p><code class="option">--enable-prof</code> was specified during
    373. 

  373.         build configuration.</p></dd><dt><a name="config.prof_libgcc"></a><span class="term">
    374. 

  374.           
    375. 

  375.     "<code class="mallctl">config.prof_libgcc</code>"
    376. 

  376.   
    377. 

  377.           (<span class="type">bool</span>)
    378. 

  378.           <code class="literal">r-</code>
    379. 

  379.         </span></dt><dd><p><code class="option">--disable-prof-libgcc</code> was not
    380. 

  380.         specified during build configuration.</p></dd><dt><a name="config.prof_libunwind"></a><span class="term">
    381. 

  381.           
    382. 

  382.     "<code class="mallctl">config.prof_libunwind</code>"
    383. 

  383.   
    384. 

  384.           (<span class="type">bool</span>)
    385. 

  385.           <code class="literal">r-</code>
    386. 

  386.         </span></dt><dd><p><code class="option">--enable-prof-libunwind</code> was specified
    387. 

  387.         during build configuration.</p></dd><dt><a name="config.stats"></a><span class="term">
    388. 

  388.           
    389. 

  389.     "<code class="mallctl">config.stats</code>"
    390. 

  390.   
    391. 

  391.           (<span class="type">bool</span>)
    392. 

  392.           <code class="literal">r-</code>
    393. 

  393.         </span></dt><dd><p><code class="option">--enable-stats</code> was specified during
    394. 

  394.         build configuration.</p></dd><dt><a name="config.tcache"></a><span class="term">
    395. 

  395.           
    396. 

  396.     "<code class="mallctl">config.tcache</code>"
    397. 

  397.   
    398. 

  398.           (<span class="type">bool</span>)
    399. 

  399.           <code class="literal">r-</code>
    400. 

  400.         </span></dt><dd><p><code class="option">--disable-tcache</code> was not specified
    401. 

  401.         during build configuration.</p></dd><dt><a name="config.tls"></a><span class="term">
    402. 

  402.           
    403. 

  403.     "<code class="mallctl">config.tls</code>"
    404. 

  404.   
    405. 

  405.           (<span class="type">bool</span>)
    406. 

  406.           <code class="literal">r-</code>
    407. 

  407.         </span></dt><dd><p><code class="option">--disable-tls</code> was not specified during
    408. 

  408.         build configuration.</p></dd><dt><a name="config.utrace"></a><span class="term">
    409. 

  409.           
    410. 

  410.     "<code class="mallctl">config.utrace</code>"
    411. 

  411.   
    412. 

  412.           (<span class="type">bool</span>)
    413. 

  413.           <code class="literal">r-</code>
    414. 

  414.         </span></dt><dd><p><code class="option">--enable-utrace</code> was specified during
    415. 

  415.         build configuration.</p></dd><dt><a name="config.valgrind"></a><span class="term">
    416. 

  416.           
    417. 

  417.     "<code class="mallctl">config.valgrind</code>"
    418. 

  418.   
    419. 

  419.           (<span class="type">bool</span>)
    420. 

  420.           <code class="literal">r-</code>
    421. 

  421.         </span></dt><dd><p><code class="option">--enable-valgrind</code> was specified during
    422. 

  422.         build configuration.</p></dd><dt><a name="config.xmalloc"></a><span class="term">
    423. 

  423.           
    424. 

  424.     "<code class="mallctl">config.xmalloc</code>"
    425. 

  425.   
    426. 

  426.           (<span class="type">bool</span>)
    427. 

  427.           <code class="literal">r-</code>
    428. 

  428.         </span></dt><dd><p><code class="option">--enable-xmalloc</code> was specified during
    429. 

  429.         build configuration.</p></dd><dt><a name="opt.abort"></a><span class="term">
    430. 

  430.           
    431. 

  431.     "<code class="mallctl">opt.abort</code>"
    432. 

  432.   
    433. 

  433.           (<span class="type">bool</span>)
    434. 

  434.           <code class="literal">r-</code>
    435. 

  435.         </span></dt><dd><p>Abort-on-warning enabled/disabled.  If true, most
    436. 

  436.         warnings are fatal.  The process will call
    437. 

  437.         <span class="citerefentry"><span class="refentrytitle">abort</span>(3)</span> in these cases.  This option is
    438. 

  438.         disabled by default unless <code class="option">--enable-debug</code> is
    439. 

  439.         specified during configuration, in which case it is enabled by default.
    440. 

  440.         </p></dd><dt><a name="opt.dss"></a><span class="term">
    441. 

  441.           
    442. 

  442.     "<code class="mallctl">opt.dss</code>"
    443. 

  443.   
    444. 

  444.           (<span class="type">const char *</span>)
    445. 

  445.           <code class="literal">r-</code>
    446. 

  446.         </span></dt><dd><p>dss (<span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span>) allocation precedence as
    447. 

  447.         related to <span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span> allocation.  The following
    448. 

  448.         settings are supported if
    449. 

  449.         <span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span> is supported by the operating
    450. 

  450.         system: &#8220;disabled&#8221;, &#8220;primary&#8221;, and
    451. 

  451.         &#8220;secondary&#8221;; otherwise only &#8220;disabled&#8221; is
    452. 

  452.         supported.  The default is &#8220;secondary&#8221; if
    453. 

  453.         <span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span> is supported by the operating
    454. 

  454.         system; &#8220;disabled&#8221; otherwise.
    455. 

  455.         </p></dd><dt><a name="opt.lg_chunk"></a><span class="term">
    456. 

  456.           
    457. 

  457.     "<code class="mallctl">opt.lg_chunk</code>"
    458. 

  458.   
    459. 

  459.           (<span class="type">size_t</span>)
    460. 

  460.           <code class="literal">r-</code>
    461. 

  461.         </span></dt><dd><p>Virtual memory chunk size (log base 2).  If a chunk
    462. 

  462.         size outside the supported size range is specified, the size is
    463. 

  463.         silently clipped to the minimum/maximum supported size.  The default
    464. 

  464.         chunk size is 2 MiB (2^21).
    465. 

  465.         </p></dd><dt><a name="opt.narenas"></a><span class="term">
    466. 

  466.           
    467. 

  467.     "<code class="mallctl">opt.narenas</code>"
    468. 

  468.   
    469. 

  469.           (<span class="type">size_t</span>)
    470. 

  470.           <code class="literal">r-</code>
    471. 

  471.         </span></dt><dd><p>Maximum number of arenas to use for automatic
    472. 

  472.         multiplexing of threads and arenas.  The default is four times the
    473. 

  473.         number of CPUs, or one if there is a single CPU.</p></dd><dt><a name="opt.lg_dirty_mult"></a><span class="term">
    474. 

  474.           
    475. 

  475.     "<code class="mallctl">opt.lg_dirty_mult</code>"
    476. 

  476.   
    477. 

  477.           (<span class="type">ssize_t</span>)
    478. 

  478.           <code class="literal">r-</code>
    479. 

  479.         </span></dt><dd><p>Per-arena minimum ratio (log base 2) of active to dirty
    480. 

  480.         pages.  Some dirty unused pages may be allowed to accumulate, within
    481. 

  481.         the limit set by the ratio (or one chunk worth of dirty pages,
    482. 

  482.         whichever is greater), before informing the kernel about some of those
    483. 

  483.         pages via <span class="citerefentry"><span class="refentrytitle">madvise</span>(2)</span> or a similar system call.  This
    484. 

  484.         provides the kernel with sufficient information to recycle dirty pages
    485. 

  485.         if physical memory becomes scarce and the pages remain unused.  The
    486. 

  486.         default minimum ratio is 8:1 (2^3:1); an option value of -1 will
    487. 

  487.         disable dirty page purging.  See <a class="link" href="#arenas.lg_dirty_mult">
    488. 

  488.     "<code class="mallctl">arenas.lg_dirty_mult</code>"
    489. 

  489.   </a>
    490. 

  490.         and <a class="link" href="#arena.i.lg_dirty_mult">
    491. 

  491.     "<code class="mallctl">arena.&lt;i&gt;.lg_dirty_mult</code>"
    492. 

  492.   </a>
    493. 

  493.         for related dynamic control options.</p></dd><dt><a name="opt.stats_print"></a><span class="term">
    494. 

  494.           
    495. 

  495.     "<code class="mallctl">opt.stats_print</code>"
    496. 

  496.   
    497. 

  497.           (<span class="type">bool</span>)
    498. 

  498.           <code class="literal">r-</code>
    499. 

  499.         </span></dt><dd><p>Enable/disable statistics printing at exit.  If
    500. 

  500.         enabled, the <code class="function">malloc_stats_print</code>(<em class="parameter"><code></code></em>)
    501. 

  501.         function is called at program exit via an
    502. 

  502.         <span class="citerefentry"><span class="refentrytitle">atexit</span>(3)</span> function.  If
    503. 

  503.         <code class="option">--enable-stats</code> is specified during configuration, this
    504. 

  504.         has the potential to cause deadlock for a multi-threaded process that
    505. 

  505.         exits while one or more threads are executing in the memory allocation
    506. 

  506.         functions.  Furthermore, <code class="function">atexit</code>(<em class="parameter"><code></code></em>) may
    507. 

  507.         allocate memory during application initialization and then deadlock
    508. 

  508.         internally when jemalloc in turn calls
    509. 

  509.         <code class="function">atexit</code>(<em class="parameter"><code></code></em>), so this option is not
    510. 

  510.         univerally usable (though the application can register its own
    511. 

  511.         <code class="function">atexit</code>(<em class="parameter"><code></code></em>) function with equivalent
    512. 

  512.         functionality).  Therefore, this option should only be used with care;
    513. 

  513.         it is primarily intended as a performance tuning aid during application
    514. 

  514.         development.  This option is disabled by default.</p></dd><dt><a name="opt.junk"></a><span class="term">
    515. 

  515.           
    516. 

  516.     "<code class="mallctl">opt.junk</code>"
    517. 

  517.   
    518. 

  518.           (<span class="type">const char *</span>)
    519. 

  519.           <code class="literal">r-</code>
    520. 

  520.           [<code class="option">--enable-fill</code>]
    521. 

  521.         </span></dt><dd><p>Junk filling.  If set to "alloc", each byte of
    522. 

  522.         uninitialized allocated memory will be initialized to
    523. 

  523.         <code class="literal">0xa5</code>.  If set to "free", all deallocated memory will
    524. 

  524.         be initialized to <code class="literal">0x5a</code>.  If set to "true", both
    525. 

  525.         allocated and deallocated memory will be initialized, and if set to
    526. 

  526.         "false", junk filling be disabled entirely.  This is intended for
    527. 

  527.         debugging and will impact performance negatively.  This option is
    528. 

  528.         "false" by default unless <code class="option">--enable-debug</code> is specified
    529. 

  529.         during configuration, in which case it is "true" by default unless
    530. 

  530.         running inside <a class="ulink" href="http://valgrind.org/" target="_top">Valgrind</a>.</p></dd><dt><a name="opt.quarantine"></a><span class="term">
    531. 

  531.           
    532. 

  532.     "<code class="mallctl">opt.quarantine</code>"
    533. 

  533.   
    534. 

  534.           (<span class="type">size_t</span>)
    535. 

  535.           <code class="literal">r-</code>
    536. 

  536.           [<code class="option">--enable-fill</code>]
    537. 

  537.         </span></dt><dd><p>Per thread quarantine size in bytes.  If non-zero, each
    538. 

  538.         thread maintains a FIFO object quarantine that stores up to the
    539. 

  539.         specified number of bytes of memory.  The quarantined memory is not
    540. 

  540.         freed until it is released from quarantine, though it is immediately
    541. 

  541.         junk-filled if the <a class="link" href="#opt.junk">
    542. 

  542.     "<code class="mallctl">opt.junk</code>"
    543. 

  543.   </a> option is
    544. 

  544.         enabled.  This feature is of particular use in combination with <a class="ulink" href="http://valgrind.org/" target="_top">Valgrind</a>, which can detect attempts
    545. 

  545.         to access quarantined objects.  This is intended for debugging and will
    546. 

  546.         impact performance negatively.  The default quarantine size is 0 unless
    547. 

  547.         running inside Valgrind, in which case the default is 16
    548. 

  548.         MiB.</p></dd><dt><a name="opt.redzone"></a><span class="term">
    549. 

  549.           
    550. 

  550.     "<code class="mallctl">opt.redzone</code>"
    551. 

  551.   
    552. 

  552.           (<span class="type">bool</span>)
    553. 

  553.           <code class="literal">r-</code>
    554. 

  554.           [<code class="option">--enable-fill</code>]
    555. 

  555.         </span></dt><dd><p>Redzones enabled/disabled.  If enabled, small
    556. 

  556.         allocations have redzones before and after them.  Furthermore, if the
    557. 

  557.         <a class="link" href="#opt.junk">
    558. 

  558.     "<code class="mallctl">opt.junk</code>"
    559. 

  559.   </a> option is
    560. 

  560.         enabled, the redzones are checked for corruption during deallocation.
    561. 

  561.         However, the primary intended purpose of this feature is to be used in
    562. 

  562.         combination with <a class="ulink" href="http://valgrind.org/" target="_top">Valgrind</a>,
    563. 

  563.         which needs redzones in order to do effective buffer overflow/underflow
    564. 

  564.         detection.  This option is intended for debugging and will impact
    565. 

  565.         performance negatively.  This option is disabled by
    566. 

  566.         default unless running inside Valgrind.</p></dd><dt><a name="opt.zero"></a><span class="term">
    567. 

  567.           
    568. 

  568.     "<code class="mallctl">opt.zero</code>"
    569. 

  569.   
    570. 

  570.           (<span class="type">bool</span>)
    571. 

  571.           <code class="literal">r-</code>
    572. 

  572.           [<code class="option">--enable-fill</code>]
    573. 

  573.         </span></dt><dd><p>Zero filling enabled/disabled.  If enabled, each byte
    574. 

  574.         of uninitialized allocated memory will be initialized to 0.  Note that
    575. 

  575.         this initialization only happens once for each byte, so
    576. 

  576.         <code class="function">realloc</code>(<em class="parameter"><code></code></em>) and
    577. 

  577.         <code class="function">rallocx</code>(<em class="parameter"><code></code></em>) calls do not zero memory that
    578. 

  578.         was previously allocated.  This is intended for debugging and will
    579. 

  579.         impact performance negatively.  This option is disabled by default.
    580. 

  580.         </p></dd><dt><a name="opt.utrace"></a><span class="term">
    581. 

  581.           
    582. 

  582.     "<code class="mallctl">opt.utrace</code>"
    583. 

  583.   
    584. 

  584.           (<span class="type">bool</span>)
    585. 

  585.           <code class="literal">r-</code>
    586. 

  586.           [<code class="option">--enable-utrace</code>]
    587. 

  587.         </span></dt><dd><p>Allocation tracing based on
    588. 

  588.         <span class="citerefentry"><span class="refentrytitle">utrace</span>(2)</span> enabled/disabled.  This option
    589. 

  589.         is disabled by default.</p></dd><dt><a name="opt.xmalloc"></a><span class="term">
    590. 

  590.           
    591. 

  591.     "<code class="mallctl">opt.xmalloc</code>"
    592. 

  592.   
    593. 

  593.           (<span class="type">bool</span>)
    594. 

  594.           <code class="literal">r-</code>
    595. 

  595.           [<code class="option">--enable-xmalloc</code>]
    596. 

  596.         </span></dt><dd><p>Abort-on-out-of-memory enabled/disabled.  If enabled,
    597. 

  597.         rather than returning failure for any allocation function, display a
    598. 

  598.         diagnostic message on <code class="constant">STDERR_FILENO</code> and cause the
    599. 

  599.         program to drop core (using
    600. 

  600.         <span class="citerefentry"><span class="refentrytitle">abort</span>(3)</span>).  If an application is
    601. 

  601.         designed to depend on this behavior, set the option at compile time by
    602. 

  602.         including the following in the source code:
    603. 

  603.         </p><pre class="programlisting">
    604. 

  604. malloc_conf = "xmalloc:true";</pre><p>
    605. 

  605.         This option is disabled by default.</p></dd><dt><a name="opt.tcache"></a><span class="term">
    606. 

  606.           
    607. 

  607.     "<code class="mallctl">opt.tcache</code>"
    608. 

  608.   
    609. 

  609.           (<span class="type">bool</span>)
    610. 

  610.           <code class="literal">r-</code>
    611. 

  611.           [<code class="option">--enable-tcache</code>]
    612. 

  612.         </span></dt><dd><p>Thread-specific caching (tcache) enabled/disabled.  When
    613. 

  613.         there are multiple threads, each thread uses a tcache for objects up to
    614. 

  614.         a certain size.  Thread-specific caching allows many allocations to be
    615. 

  615.         satisfied without performing any thread synchronization, at the cost of
    616. 

  616.         increased memory use.  See the <a class="link" href="#opt.lg_tcache_max">
    617. 

  617.     "<code class="mallctl">opt.lg_tcache_max</code>"
    618. 

  618.   </a>
    619. 

  619.         option for related tuning information.  This option is enabled by
    620. 

  620.         default unless running inside <a class="ulink" href="http://valgrind.org/" target="_top">Valgrind</a>, in which case it is
    621. 

  621.         forcefully disabled.</p></dd><dt><a name="opt.lg_tcache_max"></a><span class="term">
    622. 

  622.           
    623. 

  623.     "<code class="mallctl">opt.lg_tcache_max</code>"
    624. 

  624.   
    625. 

  625.           (<span class="type">size_t</span>)
    626. 

  626.           <code class="literal">r-</code>
    627. 

  627.           [<code class="option">--enable-tcache</code>]
    628. 

  628.         </span></dt><dd><p>Maximum size class (log base 2) to cache in the
    629. 

  629.         thread-specific cache (tcache).  At a minimum, all small size classes
    630. 

  630.         are cached, and at a maximum all large size classes are cached.  The
    631. 

  631.         default maximum is 32 KiB (2^15).</p></dd><dt><a name="opt.prof"></a><span class="term">
    632. 

  632.           
    633. 

  633.     "<code class="mallctl">opt.prof</code>"
    634. 

  634.   
    635. 

  635.           (<span class="type">bool</span>)
    636. 

  636.           <code class="literal">r-</code>
    637. 

  637.           [<code class="option">--enable-prof</code>]
    638. 

  638.         </span></dt><dd><p>Memory profiling enabled/disabled.  If enabled, profile
    639. 

  639.         memory allocation activity.  See the <a class="link" href="#opt.prof_active">
    640. 

  640.     "<code class="mallctl">opt.prof_active</code>"
    641. 

  641.   </a>
    642. 

  642.         option for on-the-fly activation/deactivation.  See the <a class="link" href="#opt.lg_prof_sample">
    643. 

  643.     "<code class="mallctl">opt.lg_prof_sample</code>"
    644. 

  644.   </a>
    645. 

  645.         option for probabilistic sampling control.  See the <a class="link" href="#opt.prof_accum">
    646. 

  646.     "<code class="mallctl">opt.prof_accum</code>"
    647. 

  647.   </a>
    648. 

  648.         option for control of cumulative sample reporting.  See the <a class="link" href="#opt.lg_prof_interval">
    649. 

  649.     "<code class="mallctl">opt.lg_prof_interval</code>"
    650. 

  650.   </a>
    651. 

  651.         option for information on interval-triggered profile dumping, the <a class="link" href="#opt.prof_gdump">
    652. 

  652.     "<code class="mallctl">opt.prof_gdump</code>"
    653. 

  653.   </a>
    654. 

  654.         option for information on high-water-triggered profile dumping, and the
    655. 

  655.         <a class="link" href="#opt.prof_final">
    656. 

  656.     "<code class="mallctl">opt.prof_final</code>"
    657. 

  657.   </a>
    658. 

  658.         option for final profile dumping.  Profile output is compatible with
    659. 

  659.         the <span class="command"><strong>jeprof</strong></span> command, which is based on the
    660. 

  660.         <span class="command"><strong>pprof</strong></span> that is developed as part of the <a class="ulink" href="http://code.google.com/p/gperftools/" target="_top">gperftools
    661. 

  661.         package</a>.</p></dd><dt><a name="opt.prof_prefix"></a><span class="term">
    662. 

  662.           
    663. 

  663.     "<code class="mallctl">opt.prof_prefix</code>"
    664. 

  664.   
    665. 

  665.           (<span class="type">const char *</span>)
    666. 

  666.           <code class="literal">r-</code>
    667. 

  667.           [<code class="option">--enable-prof</code>]
    668. 

  668.         </span></dt><dd><p>Filename prefix for profile dumps.  If the prefix is
    669. 

  669.         set to the empty string, no automatic dumps will occur; this is
    670. 

  670.         primarily useful for disabling the automatic final heap dump (which
    671. 

  671.         also disables leak reporting, if enabled).  The default prefix is
    672. 

  672.         <code class="filename">jeprof</code>.</p></dd><dt><a name="opt.prof_active"></a><span class="term">
    673. 

  673.           
    674. 

  674.     "<code class="mallctl">opt.prof_active</code>"
    675. 

  675.   
    676. 

  676.           (<span class="type">bool</span>)
    677. 

  677.           <code class="literal">r-</code>
    678. 

  678.           [<code class="option">--enable-prof</code>]
    679. 

  679.         </span></dt><dd><p>Profiling activated/deactivated.  This is a secondary
    680. 

  680.         control mechanism that makes it possible to start the application with
    681. 

  681.         profiling enabled (see the <a class="link" href="#opt.prof">
    682. 

  682.     "<code class="mallctl">opt.prof</code>"
    683. 

  683.   </a> option) but
    684. 

  684.         inactive, then toggle profiling at any time during program execution
    685. 

  685.         with the <a class="link" href="#prof.active">
    686. 

  686.     "<code class="mallctl">prof.active</code>"
    687. 

  687.   </a> mallctl.
    688. 

  688.         This option is enabled by default.</p></dd><dt><a name="opt.prof_thread_active_init"></a><span class="term">
    689. 

  689.           
    690. 

  690.     "<code class="mallctl">opt.prof_thread_active_init</code>"
    691. 

  691.   
    692. 

  692.           (<span class="type">bool</span>)
    693. 

  693.           <code class="literal">r-</code>
    694. 

  694.           [<code class="option">--enable-prof</code>]
    695. 

  695.         </span></dt><dd><p>Initial setting for <a class="link" href="#thread.prof.active">
    696. 

  696.     "<code class="mallctl">thread.prof.active</code>"
    697. 

  697.   </a>
    698. 

  698.         in newly created threads.  The initial setting for newly created threads
    699. 

  699.         can also be changed during execution via the <a class="link" href="#prof.thread_active_init">
    700. 

  700.     "<code class="mallctl">prof.thread_active_init</code>"
    701. 

  701.   </a>
    702. 

  702.         mallctl.  This option is enabled by default.</p></dd><dt><a name="opt.lg_prof_sample"></a><span class="term">
    703. 

  703.           
    704. 

  704.     "<code class="mallctl">opt.lg_prof_sample</code>"
    705. 

  705.   
    706. 

  706.           (<span class="type">size_t</span>)
    707. 

  707.           <code class="literal">r-</code>
    708. 

  708.           [<code class="option">--enable-prof</code>]
    709. 

  709.         </span></dt><dd><p>Average interval (log base 2) between allocation
    710. 

  710.         samples, as measured in bytes of allocation activity.  Increasing the
    711. 

  711.         sampling interval decreases profile fidelity, but also decreases the
    712. 

  712.         computational overhead.  The default sample interval is 512 KiB (2^19
    713. 

  713.         B).</p></dd><dt><a name="opt.prof_accum"></a><span class="term">
    714. 

  714.           
    715. 

  715.     "<code class="mallctl">opt.prof_accum</code>"
    716. 

  716.   
    717. 

  717.           (<span class="type">bool</span>)
    718. 

  718.           <code class="literal">r-</code>
    719. 

  719.           [<code class="option">--enable-prof</code>]
    720. 

  720.         </span></dt><dd><p>Reporting of cumulative object/byte counts in profile
    721. 

  721.         dumps enabled/disabled.  If this option is enabled, every unique
    722. 

  722.         backtrace must be stored for the duration of execution.  Depending on
    723. 

  723.         the application, this can impose a large memory overhead, and the
    724. 

  724.         cumulative counts are not always of interest.  This option is disabled
    725. 

  725.         by default.</p></dd><dt><a name="opt.lg_prof_interval"></a><span class="term">
    726. 

  726.           
    727. 

  727.     "<code class="mallctl">opt.lg_prof_interval</code>"
    728. 

  728.   
    729. 

  729.           (<span class="type">ssize_t</span>)
    730. 

  730.           <code class="literal">r-</code>
    731. 

  731.           [<code class="option">--enable-prof</code>]
    732. 

  732.         </span></dt><dd><p>Average interval (log base 2) between memory profile
    733. 

  733.         dumps, as measured in bytes of allocation activity.  The actual
    734. 

  734.         interval between dumps may be sporadic because decentralized allocation
    735. 

  735.         counters are used to avoid synchronization bottlenecks.  Profiles are
    736. 

  736.         dumped to files named according to the pattern
    737. 

  737.         <code class="filename">&lt;prefix&gt;.&lt;pid&gt;.&lt;seq&gt;.i&lt;iseq&gt;.heap</code>,
    738. 

  738.         where <code class="literal">&lt;prefix&gt;</code> is controlled by the
    739. 

  739.         <a class="link" href="#opt.prof_prefix">
    740. 

  740.     "<code class="mallctl">opt.prof_prefix</code>"
    741. 

  741.   </a>
    742. 

  742.         option.  By default, interval-triggered profile dumping is disabled
    743. 

  743.         (encoded as -1).
    744. 

  744.         </p></dd><dt><a name="opt.prof_gdump"></a><span class="term">
    745. 

  745.           
    746. 

  746.     "<code class="mallctl">opt.prof_gdump</code>"
    747. 

  747.   
    748. 

  748.           (<span class="type">bool</span>)
    749. 

  749.           <code class="literal">r-</code>
    750. 

  750.           [<code class="option">--enable-prof</code>]
    751. 

  751.         </span></dt><dd><p>Set the initial state of <a class="link" href="#prof.gdump">
    752. 

  752.     "<code class="mallctl">prof.gdump</code>"
    753. 

  753.   </a>, which when
    754. 

  754.         enabled triggers a memory profile dump every time the total virtual
    755. 

  755.         memory exceeds the previous maximum.  This option is disabled by
    756. 

  756.         default.</p></dd><dt><a name="opt.prof_final"></a><span class="term">
    757. 

  757.           
    758. 

  758.     "<code class="mallctl">opt.prof_final</code>"
    759. 

  759.   
    760. 

  760.           (<span class="type">bool</span>)
    761. 

  761.           <code class="literal">r-</code>
    762. 

  762.           [<code class="option">--enable-prof</code>]
    763. 

  763.         </span></dt><dd><p>Use an
    764. 

  764.         <span class="citerefentry"><span class="refentrytitle">atexit</span>(3)</span> function to dump final memory
    765. 

  765.         usage to a file named according to the pattern
    766. 

  766.         <code class="filename">&lt;prefix&gt;.&lt;pid&gt;.&lt;seq&gt;.f.heap</code>,
    767. 

  767.         where <code class="literal">&lt;prefix&gt;</code> is controlled by the <a class="link" href="#opt.prof_prefix">
    768. 

  768.     "<code class="mallctl">opt.prof_prefix</code>"
    769. 

  769.   </a>
    770. 

  770.         option.  Note that <code class="function">atexit</code>(<em class="parameter"><code></code></em>) may allocate
    771. 

  771.         memory during application initialization and then deadlock internally
    772. 

  772.         when jemalloc in turn calls <code class="function">atexit</code>(<em class="parameter"><code></code></em>), so
    773. 

  773.         this option is not univerally usable (though the application can
    774. 

  774.         register its own <code class="function">atexit</code>(<em class="parameter"><code></code></em>) function with
    775. 

  775.         equivalent functionality).  This option is disabled by
    776. 

  776.         default.</p></dd><dt><a name="opt.prof_leak"></a><span class="term">
    777. 

  777.           
    778. 

  778.     "<code class="mallctl">opt.prof_leak</code>"
    779. 

  779.   
    780. 

  780.           (<span class="type">bool</span>)
    781. 

  781.           <code class="literal">r-</code>
    782. 

  782.           [<code class="option">--enable-prof</code>]
    783. 

  783.         </span></dt><dd><p>Leak reporting enabled/disabled.  If enabled, use an
    784. 

  784.         <span class="citerefentry"><span class="refentrytitle">atexit</span>(3)</span> function to report memory leaks
    785. 

  785.         detected by allocation sampling.  See the
    786. 

  786.         <a class="link" href="#opt.prof">
    787. 

  787.     "<code class="mallctl">opt.prof</code>"
    788. 

  788.   </a> option for
    789. 

  789.         information on analyzing heap profile output.  This option is disabled
    790. 

  790.         by default.</p></dd><dt><a name="thread.arena"></a><span class="term">
    791. 

  791.           
    792. 

  792.     "<code class="mallctl">thread.arena</code>"
    793. 

  793.   
    794. 

  794.           (<span class="type">unsigned</span>)
    795. 

  795.           <code class="literal">rw</code>
    796. 

  796.         </span></dt><dd><p>Get or set the arena associated with the calling
    797. 

  797.         thread.  If the specified arena was not initialized beforehand (see the
    798. 

  798.         <a class="link" href="#arenas.initialized">
    799. 

  799.     "<code class="mallctl">arenas.initialized</code>"
    800. 

  800.   </a>
    801. 

  801.         mallctl), it will be automatically initialized as a side effect of
    802. 

  802.         calling this interface.</p></dd><dt><a name="thread.allocated"></a><span class="term">
    803. 

  803.           
    804. 

  804.     "<code class="mallctl">thread.allocated</code>"
    805. 

  805.   
    806. 

  806.           (<span class="type">uint64_t</span>)
    807. 

  807.           <code class="literal">r-</code>
    808. 

  808.           [<code class="option">--enable-stats</code>]
    809. 

  809.         </span></dt><dd><p>Get the total number of bytes ever allocated by the
    810. 

  810.         calling thread.  This counter has the potential to wrap around; it is
    811. 

  811.         up to the application to appropriately interpret the counter in such
    812. 

  812.         cases.</p></dd><dt><a name="thread.allocatedp"></a><span class="term">
    813. 

  813.           
    814. 

  814.     "<code class="mallctl">thread.allocatedp</code>"
    815. 

  815.   
    816. 

  816.           (<span class="type">uint64_t *</span>)
    817. 

  817.           <code class="literal">r-</code>
    818. 

  818.           [<code class="option">--enable-stats</code>]
    819. 

  819.         </span></dt><dd><p>Get a pointer to the the value that is returned by the
    820. 

  820.         <a class="link" href="#thread.allocated">
    821. 

  821.     "<code class="mallctl">thread.allocated</code>"
    822. 

  822.   </a>
    823. 

  823.         mallctl.  This is useful for avoiding the overhead of repeated
    824. 

  824.         <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) calls.</p></dd><dt><a name="thread.deallocated"></a><span class="term">
    825. 

  825.           
    826. 

  826.     "<code class="mallctl">thread.deallocated</code>"
    827. 

  827.   
    828. 

  828.           (<span class="type">uint64_t</span>)
    829. 

  829.           <code class="literal">r-</code>
    830. 

  830.           [<code class="option">--enable-stats</code>]
    831. 

  831.         </span></dt><dd><p>Get the total number of bytes ever deallocated by the
    832. 

  832.         calling thread.  This counter has the potential to wrap around; it is
    833. 

  833.         up to the application to appropriately interpret the counter in such
    834. 

  834.         cases.</p></dd><dt><a name="thread.deallocatedp"></a><span class="term">
    835. 

  835.           
    836. 

  836.     "<code class="mallctl">thread.deallocatedp</code>"
    837. 

  837.   
    838. 

  838.           (<span class="type">uint64_t *</span>)
    839. 

  839.           <code class="literal">r-</code>
    840. 

  840.           [<code class="option">--enable-stats</code>]
    841. 

  841.         </span></dt><dd><p>Get a pointer to the the value that is returned by the
    842. 

  842.         <a class="link" href="#thread.deallocated">
    843. 

  843.     "<code class="mallctl">thread.deallocated</code>"
    844. 

  844.   </a>
    845. 

  845.         mallctl.  This is useful for avoiding the overhead of repeated
    846. 

  846.         <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) calls.</p></dd><dt><a name="thread.tcache.enabled"></a><span class="term">
    847. 

  847.           
    848. 

  848.     "<code class="mallctl">thread.tcache.enabled</code>"
    849. 

  849.   
    850. 

  850.           (<span class="type">bool</span>)
    851. 

  851.           <code class="literal">rw</code>
    852. 

  852.           [<code class="option">--enable-tcache</code>]
    853. 

  853.         </span></dt><dd><p>Enable/disable calling thread's tcache.  The tcache is
    854. 

  854.         implicitly flushed as a side effect of becoming
    855. 

  855.         disabled (see <a class="link" href="#thread.tcache.flush">
    856. 

  856.     "<code class="mallctl">thread.tcache.flush</code>"
    857. 

  857.   </a>).
    858. 

  858.         </p></dd><dt><a name="thread.tcache.flush"></a><span class="term">
    859. 

  859.           
    860. 

  860.     "<code class="mallctl">thread.tcache.flush</code>"
    861. 

  861.   
    862. 

  862.           (<span class="type">void</span>)
    863. 

  863.           <code class="literal">--</code>
    864. 

  864.           [<code class="option">--enable-tcache</code>]
    865. 

  865.         </span></dt><dd><p>Flush calling thread's thread-specific cache (tcache).
    866. 

  866.         This interface releases all cached objects and internal data structures
    867. 

  867.         associated with the calling thread's tcache.  Ordinarily, this interface
    868. 

  868.         need not be called, since automatic periodic incremental garbage
    869. 

  869.         collection occurs, and the thread cache is automatically discarded when
    870. 

  870.         a thread exits.  However, garbage collection is triggered by allocation
    871. 

  871.         activity, so it is possible for a thread that stops
    872. 

  872.         allocating/deallocating to retain its cache indefinitely, in which case
    873. 

  873.         the developer may find manual flushing useful.</p></dd><dt><a name="thread.prof.name"></a><span class="term">
    874. 

  874.           
    875. 

  875.     "<code class="mallctl">thread.prof.name</code>"
    876. 

  876.   
    877. 

  877.           (<span class="type">const char *</span>)
    878. 

  878.           <code class="literal">r-</code> or
    879. 

  879.           <code class="literal">-w</code>
    880. 

  880.           [<code class="option">--enable-prof</code>]
    881. 

  881.         </span></dt><dd><p>Get/set the descriptive name associated with the calling
    882. 

  882.         thread in memory profile dumps.  An internal copy of the name string is
    883. 

  883.         created, so the input string need not be maintained after this interface
    884. 

  884.         completes execution.  The output string of this interface should be
    885. 

  885.         copied for non-ephemeral uses, because multiple implementation details
    886. 

  886.         can cause asynchronous string deallocation.  Furthermore, each
    887. 

  887.         invocation of this interface can only read or write; simultaneous
    888. 

  888.         read/write is not supported due to string lifetime limitations.  The
    889. 

  889.         name string must nil-terminated and comprised only of characters in the
    890. 

  890.         sets recognized
    891. 

  891.         by <span class="citerefentry"><span class="refentrytitle">isgraph</span>(3)</span> and
    892. 

  892.         <span class="citerefentry"><span class="refentrytitle">isblank</span>(3)</span>.</p></dd><dt><a name="thread.prof.active"></a><span class="term">
    893. 

  893.           
    894. 

  894.     "<code class="mallctl">thread.prof.active</code>"
    895. 

  895.   
    896. 

  896.           (<span class="type">bool</span>)
    897. 

  897.           <code class="literal">rw</code>
    898. 

  898.           [<code class="option">--enable-prof</code>]
    899. 

  899.         </span></dt><dd><p>Control whether sampling is currently active for the
    900. 

  900.         calling thread.  This is an activation mechanism in addition to <a class="link" href="#prof.active">
    901. 

  901.     "<code class="mallctl">prof.active</code>"
    902. 

  902.   </a>; both must
    903. 

  903.         be active for the calling thread to sample.  This flag is enabled by
    904. 

  904.         default.</p></dd><dt><a name="tcache.create"></a><span class="term">
    905. 

  905.           
    906. 

  906.     "<code class="mallctl">tcache.create</code>"
    907. 

  907.   
    908. 

  908.           (<span class="type">unsigned</span>)
    909. 

  909.           <code class="literal">r-</code>
    910. 

  910.           [<code class="option">--enable-tcache</code>]
    911. 

  911.         </span></dt><dd><p>Create an explicit thread-specific cache (tcache) and
    912. 

  912.         return an identifier that can be passed to the <a class="link" href="#MALLOCX_TCACHE"><code class="constant">MALLOCX_TCACHE(<em class="parameter"><code>tc</code></em>)</code></a>
    913. 

  913.         macro to explicitly use the specified cache rather than the
    914. 

  914.         automatically managed one that is used by default.  Each explicit cache
    915. 

  915.         can be used by only one thread at a time; the application must assure
    916. 

  916.         that this constraint holds.
    917. 

  917.         </p></dd><dt><a name="tcache.flush"></a><span class="term">
    918. 

  918.           
    919. 

  919.     "<code class="mallctl">tcache.flush</code>"
    920. 

  920.   
    921. 

  921.           (<span class="type">unsigned</span>)
    922. 

  922.           <code class="literal">-w</code>
    923. 

  923.           [<code class="option">--enable-tcache</code>]
    924. 

  924.         </span></dt><dd><p>Flush the specified thread-specific cache (tcache).  The
    925. 

  925.         same considerations apply to this interface as to <a class="link" href="#thread.tcache.flush">
    926. 

  926.     "<code class="mallctl">thread.tcache.flush</code>"
    927. 

  927.   </a>,
    928. 

  928.         except that the tcache will never be automatically be discarded.
    929. 

  929.         </p></dd><dt><a name="tcache.destroy"></a><span class="term">
    930. 

  930.           
    931. 

  931.     "<code class="mallctl">tcache.destroy</code>"
    932. 

  932.   
    933. 

  933.           (<span class="type">unsigned</span>)
    934. 

  934.           <code class="literal">-w</code>
    935. 

  935.           [<code class="option">--enable-tcache</code>]
    936. 

  936.         </span></dt><dd><p>Flush the specified thread-specific cache (tcache) and
    937. 

  937.         make the identifier available for use during a future tcache creation.
    938. 

  938.         </p></dd><dt><a name="arena.i.purge"></a><span class="term">
    939. 

  939.           
    940. 

  940.     "<code class="mallctl">arena.&lt;i&gt;.purge</code>"
    941. 

  941.   
    942. 

  942.           (<span class="type">void</span>)
    943. 

  943.           <code class="literal">--</code>
    944. 

  944.         </span></dt><dd><p>Purge unused dirty pages for arena &lt;i&gt;, or for
    945. 

  945.         all arenas if &lt;i&gt; equals <a class="link" href="#arenas.narenas">
    946. 

  946.     "<code class="mallctl">arenas.narenas</code>"
    947. 

  947.   </a>.
    948. 

  948.         </p></dd><dt><a name="arena.i.dss"></a><span class="term">
    949. 

  949.           
    950. 

  950.     "<code class="mallctl">arena.&lt;i&gt;.dss</code>"
    951. 

  951.   
    952. 

  952.           (<span class="type">const char *</span>)
    953. 

  953.           <code class="literal">rw</code>
    954. 

  954.         </span></dt><dd><p>Set the precedence of dss allocation as related to mmap
    955. 

  955.         allocation for arena &lt;i&gt;, or for all arenas if &lt;i&gt; equals
    956. 

  956.         <a class="link" href="#arenas.narenas">
    957. 

  957.     "<code class="mallctl">arenas.narenas</code>"
    958. 

  958.   </a>.  See
    959. 

  959.         <a class="link" href="#opt.dss">
    960. 

  960.     "<code class="mallctl">opt.dss</code>"
    961. 

  961.   </a> for supported
    962. 

  962.         settings.</p></dd><dt><a name="arena.i.lg_dirty_mult"></a><span class="term">
    963. 

  963.           
    964. 

  964.     "<code class="mallctl">arena.&lt;i&gt;.lg_dirty_mult</code>"
    965. 

  965.   
    966. 

  966.           (<span class="type">ssize_t</span>)
    967. 

  967.           <code class="literal">rw</code>
    968. 

  968.         </span></dt><dd><p>Current per-arena minimum ratio (log base 2) of active
    969. 

  969.         to dirty pages for arena &lt;i&gt;.  Each time this interface is set and
    970. 

  970.         the ratio is increased, pages are synchronously purged as necessary to
    971. 

  971.         impose the new ratio.  See <a class="link" href="#opt.lg_dirty_mult">
    972. 

  972.     "<code class="mallctl">opt.lg_dirty_mult</code>"
    973. 

  973.   </a>
    974. 

  974.         for additional information.</p></dd><dt><a name="arena.i.chunk_hooks"></a><span class="term">
    975. 

  975.           
    976. 

  976.     "<code class="mallctl">arena.&lt;i&gt;.chunk_hooks</code>"
    977. 

  977.   
    978. 

  978.           (<span class="type">chunk_hooks_t</span>)
    979. 

  979.           <code class="literal">rw</code>
    980. 

  980.         </span></dt><dd><p>Get or set the chunk management hook functions for arena
    981. 

  981.         &lt;i&gt;.  The functions must be capable of operating on all extant
    982. 

  982.         chunks associated with arena &lt;i&gt;, usually by passing unknown
    983. 

  983.         chunks to the replaced functions.  In practice, it is feasible to
    984. 

  984.         control allocation for arenas created via <a class="link" href="#arenas.extend">
    985. 

  985.     "<code class="mallctl">arenas.extend</code>"
    986. 

  986.   </a> such
    987. 

  987.         that all chunks originate from an application-supplied chunk allocator
    988. 

  988.         (by setting custom chunk hook functions just after arena creation), but
    989. 

  989.         the automatically created arenas may have already created chunks prior
    990. 

  990.         to the application having an opportunity to take over chunk
    991. 

  991.         allocation.</p><pre class="programlisting">
    992. 

  992. typedef struct {
    993. 

  993. 	chunk_alloc_t		*alloc;
    994. 

  994. 	chunk_dalloc_t		*dalloc;
    995. 

  995. 	chunk_commit_t		*commit;
    996. 

  996. 	chunk_decommit_t	*decommit;
    997. 

  997. 	chunk_purge_t		*purge;
    998. 

  998. 	chunk_split_t		*split;
    999. 

  999. 	chunk_merge_t		*merge;
    1000. 

  1000. } chunk_hooks_t;</pre><p>The <span class="type">chunk_hooks_t</span> structure comprises function
    1001. 

  1001.         pointers which are described individually below.  jemalloc uses these
    1002. 

  1002.         functions to manage chunk lifetime, which starts off with allocation of
    1003. 

  1003.         mapped committed memory, in the simplest case followed by deallocation.
    1004. 

  1004.         However, there are performance and platform reasons to retain chunks for
    1005. 

  1005.         later reuse.  Cleanup attempts cascade from deallocation to decommit to
    1006. 

  1006.         purging, which gives the chunk management functions opportunities to
    1007. 

  1007.         reject the most permanent cleanup operations in favor of less permanent
    1008. 

  1008.         (and often less costly) operations.  The chunk splitting and merging
    1009. 

  1009.         operations can also be opted out of, but this is mainly intended to
    1010. 

  1010.         support platforms on which virtual memory mappings provided by the
    1011. 

  1011.         operating system kernel do not automatically coalesce and split, e.g.
    1012. 

  1012.         Windows.</p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">typedef void *<b class="fsfunc">(chunk_alloc_t)</b>(</code></td><td>void *<var class="pdparam">chunk</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">alignment</var>, </td></tr><tr><td> </td><td>bool *<var class="pdparam">zero</var>, </td></tr><tr><td> </td><td>bool *<var class="pdparam">commit</var>, </td></tr><tr><td> </td><td>unsigned <var class="pdparam">arena_ind</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="literallayout"><p></p></div><p>A chunk allocation function conforms to the
    1013. 

  1013.         <span class="type">chunk_alloc_t</span> type and upon success returns a pointer to
    1014. 

  1014.         <em class="parameter"><code>size</code></em> bytes of mapped memory on behalf of arena
    1015. 

  1015.         <em class="parameter"><code>arena_ind</code></em> such that the chunk's base address is a
    1016. 

  1016.         multiple of <em class="parameter"><code>alignment</code></em>, as well as setting
    1017. 

  1017.         <em class="parameter"><code>*zero</code></em> to indicate whether the chunk is zeroed and
    1018. 

  1018.         <em class="parameter"><code>*commit</code></em> to indicate whether the chunk is
    1019. 

  1019.         committed.  Upon error the function returns <code class="constant">NULL</code>
    1020. 

  1020.         and leaves <em class="parameter"><code>*zero</code></em> and
    1021. 

  1021.         <em class="parameter"><code>*commit</code></em> unmodified.  The
    1022. 

  1022.         <em class="parameter"><code>size</code></em> parameter is always a multiple of the chunk
    1023. 

  1023.         size.  The <em class="parameter"><code>alignment</code></em> parameter is always a power
    1024. 

  1024.         of two at least as large as the chunk size.  Zeroing is mandatory if
    1025. 

  1025.         <em class="parameter"><code>*zero</code></em> is true upon function entry.  Committing is
    1026. 

  1026.         mandatory if <em class="parameter"><code>*commit</code></em> is true upon function entry.
    1027. 

  1027.         If <em class="parameter"><code>chunk</code></em> is not <code class="constant">NULL</code>, the
    1028. 

  1028.         returned pointer must be <em class="parameter"><code>chunk</code></em> on success or
    1029. 

  1029.         <code class="constant">NULL</code> on error.  Committed memory may be committed
    1030. 

  1030.         in absolute terms as on a system that does not overcommit, or in
    1031. 

  1031.         implicit terms as on a system that overcommits and satisfies physical
    1032. 

  1032.         memory needs on demand via soft page faults.  Note that replacing the
    1033. 

  1033.         default chunk allocation function makes the arena's <a class="link" href="#arena.i.dss">
    1034. 

  1034.     "<code class="mallctl">arena.&lt;i&gt;.dss</code>"
    1035. 

  1035.   </a>
    1036. 

  1036.         setting irrelevant.</p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">typedef bool <b class="fsfunc">(chunk_dalloc_t)</b>(</code></td><td>void *<var class="pdparam">chunk</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>bool <var class="pdparam">committed</var>, </td></tr><tr><td> </td><td>unsigned <var class="pdparam">arena_ind</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="literallayout"><p></p></div><p>
    1037. 

  1037.         A chunk deallocation function conforms to the
    1038. 

  1038.         <span class="type">chunk_dalloc_t</span> type and deallocates a
    1039. 

  1039.         <em class="parameter"><code>chunk</code></em> of given <em class="parameter"><code>size</code></em> with
    1040. 

  1040.         <em class="parameter"><code>committed</code></em>/decommited memory as indicated, on
    1041. 

  1041.         behalf of arena <em class="parameter"><code>arena_ind</code></em>, returning false upon
    1042. 

  1042.         success.  If the function returns true, this indicates opt-out from
    1043. 

  1043.         deallocation; the virtual memory mapping associated with the chunk
    1044. 

  1044.         remains mapped, in the same commit state, and available for future use,
    1045. 

  1045.         in which case it will be automatically retained for later reuse.</p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">typedef bool <b class="fsfunc">(chunk_commit_t)</b>(</code></td><td>void *<var class="pdparam">chunk</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">offset</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">length</var>, </td></tr><tr><td> </td><td>unsigned <var class="pdparam">arena_ind</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="literallayout"><p></p></div><p>A chunk commit function conforms to the
    1046. 

  1046.         <span class="type">chunk_commit_t</span> type and commits zeroed physical memory to
    1047. 

  1047.         back pages within a <em class="parameter"><code>chunk</code></em> of given
    1048. 

  1048.         <em class="parameter"><code>size</code></em> at <em class="parameter"><code>offset</code></em> bytes,
    1049. 

  1049.         extending for <em class="parameter"><code>length</code></em> on behalf of arena
    1050. 

  1050.         <em class="parameter"><code>arena_ind</code></em>, returning false upon success.
    1051. 

  1051.         Committed memory may be committed in absolute terms as on a system that
    1052. 

  1052.         does not overcommit, or in implicit terms as on a system that
    1053. 

  1053.         overcommits and satisfies physical memory needs on demand via soft page
    1054. 

  1054.         faults. If the function returns true, this indicates insufficient
    1055. 

  1055.         physical memory to satisfy the request.</p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">typedef bool <b class="fsfunc">(chunk_decommit_t)</b>(</code></td><td>void *<var class="pdparam">chunk</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">offset</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">length</var>, </td></tr><tr><td> </td><td>unsigned <var class="pdparam">arena_ind</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="literallayout"><p></p></div><p>A chunk decommit function conforms to the
    1056. 

  1056.         <span class="type">chunk_decommit_t</span> type and decommits any physical memory
    1057. 

  1057.         that is backing pages within a <em class="parameter"><code>chunk</code></em> of given
    1058. 

  1058.         <em class="parameter"><code>size</code></em> at <em class="parameter"><code>offset</code></em> bytes,
    1059. 

  1059.         extending for <em class="parameter"><code>length</code></em> on behalf of arena
    1060. 

  1060.         <em class="parameter"><code>arena_ind</code></em>, returning false upon success, in which
    1061. 

  1061.         case the pages will be committed via the chunk commit function before
    1062. 

  1062.         being reused.  If the function returns true, this indicates opt-out from
    1063. 

  1063.         decommit; the memory remains committed and available for future use, in
    1064. 

  1064.         which case it will be automatically retained for later reuse.</p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">typedef bool <b class="fsfunc">(chunk_purge_t)</b>(</code></td><td>void *<var class="pdparam">chunk</var>, </td></tr><tr><td> </td><td>size_t<var class="pdparam">size</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">offset</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">length</var>, </td></tr><tr><td> </td><td>unsigned <var class="pdparam">arena_ind</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="literallayout"><p></p></div><p>A chunk purge function conforms to the <span class="type">chunk_purge_t</span>
    1065. 

  1065.         type and optionally discards physical pages within the virtual memory
    1066. 

  1066.         mapping associated with <em class="parameter"><code>chunk</code></em> of given
    1067. 

  1067.         <em class="parameter"><code>size</code></em> at <em class="parameter"><code>offset</code></em> bytes,
    1068. 

  1068.         extending for <em class="parameter"><code>length</code></em> on behalf of arena
    1069. 

  1069.         <em class="parameter"><code>arena_ind</code></em>, returning false if pages within the
    1070. 

  1070.         purged virtual memory range will be zero-filled the next time they are
    1071. 

  1071.         accessed.</p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">typedef bool <b class="fsfunc">(chunk_split_t)</b>(</code></td><td>void *<var class="pdparam">chunk</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size_a</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size_b</var>, </td></tr><tr><td> </td><td>bool <var class="pdparam">committed</var>, </td></tr><tr><td> </td><td>unsigned <var class="pdparam">arena_ind</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="literallayout"><p></p></div><p>A chunk split function conforms to the <span class="type">chunk_split_t</span>
    1072. 

  1072.         type and optionally splits <em class="parameter"><code>chunk</code></em> of given
    1073. 

  1073.         <em class="parameter"><code>size</code></em> into two adjacent chunks, the first of
    1074. 

  1074.         <em class="parameter"><code>size_a</code></em> bytes, and the second of
    1075. 

  1075.         <em class="parameter"><code>size_b</code></em> bytes, operating on
    1076. 

  1076.         <em class="parameter"><code>committed</code></em>/decommitted memory as indicated, on
    1077. 

  1077.         behalf of arena <em class="parameter"><code>arena_ind</code></em>, returning false upon
    1078. 

  1078.         success.  If the function returns true, this indicates that the chunk
    1079. 

  1079.         remains unsplit and therefore should continue to be operated on as a
    1080. 

  1080.         whole.</p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">typedef bool <b class="fsfunc">(chunk_merge_t)</b>(</code></td><td>void *<var class="pdparam">chunk_a</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size_a</var>, </td></tr><tr><td> </td><td>void *<var class="pdparam">chunk_b</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size_b</var>, </td></tr><tr><td> </td><td>bool <var class="pdparam">committed</var>, </td></tr><tr><td> </td><td>unsigned <var class="pdparam">arena_ind</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="literallayout"><p></p></div><p>A chunk merge function conforms to the <span class="type">chunk_merge_t</span>
    1081. 

  1081.         type and optionally merges adjacent chunks,
    1082. 

  1082.         <em class="parameter"><code>chunk_a</code></em> of given <em class="parameter"><code>size_a</code></em>
    1083. 

  1083.         and <em class="parameter"><code>chunk_b</code></em> of given
    1084. 

  1084.         <em class="parameter"><code>size_b</code></em> into one contiguous chunk, operating on
    1085. 

  1085.         <em class="parameter"><code>committed</code></em>/decommitted memory as indicated, on
    1086. 

  1086.         behalf of arena <em class="parameter"><code>arena_ind</code></em>, returning false upon
    1087. 

  1087.         success.  If the function returns true, this indicates that the chunks
    1088. 

  1088.         remain distinct mappings and therefore should continue to be operated on
    1089. 

  1089.         independently.</p></dd><dt><a name="arenas.narenas"></a><span class="term">
    1090. 

  1090.           
    1091. 

  1091.     "<code class="mallctl">arenas.narenas</code>"
    1092. 

  1092.   
    1093. 

  1093.           (<span class="type">unsigned</span>)
    1094. 

  1094.           <code class="literal">r-</code>
    1095. 

  1095.         </span></dt><dd><p>Current limit on number of arenas.</p></dd><dt><a name="arenas.initialized"></a><span class="term">
    1096. 

  1096.           
    1097. 

  1097.     "<code class="mallctl">arenas.initialized</code>"
    1098. 

  1098.   
    1099. 

  1099.           (<span class="type">bool *</span>)
    1100. 

  1100.           <code class="literal">r-</code>
    1101. 

  1101.         </span></dt><dd><p>An array of <a class="link" href="#arenas.narenas">
    1102. 

  1102.     "<code class="mallctl">arenas.narenas</code>"
    1103. 

  1103.   </a>
    1104. 

  1104.         booleans.  Each boolean indicates whether the corresponding arena is
    1105. 

  1105.         initialized.</p></dd><dt><a name="arenas.lg_dirty_mult"></a><span class="term">
    1106. 

  1106.           
    1107. 

  1107.     "<code class="mallctl">arenas.lg_dirty_mult</code>"
    1108. 

  1108.   
    1109. 

  1109.           (<span class="type">ssize_t</span>)
    1110. 

  1110.           <code class="literal">rw</code>
    1111. 

  1111.         </span></dt><dd><p>Current default per-arena minimum ratio (log base 2) of
    1112. 

  1112.         active to dirty pages, used to initialize <a class="link" href="#arena.i.lg_dirty_mult">
    1113. 

  1113.     "<code class="mallctl">arena.&lt;i&gt;.lg_dirty_mult</code>"
    1114. 

  1114.   </a>
    1115. 

  1115.         during arena creation.  See <a class="link" href="#opt.lg_dirty_mult">
    1116. 

  1116.     "<code class="mallctl">opt.lg_dirty_mult</code>"
    1117. 

  1117.   </a>
    1118. 

  1118.         for additional information.</p></dd><dt><a name="arenas.quantum"></a><span class="term">
    1119. 

  1119.           
    1120. 

  1120.     "<code class="mallctl">arenas.quantum</code>"
    1121. 

  1121.   
    1122. 

  1122.           (<span class="type">size_t</span>)
    1123. 

  1123.           <code class="literal">r-</code>
    1124. 

  1124.         </span></dt><dd><p>Quantum size.</p></dd><dt><a name="arenas.page"></a><span class="term">
    1125. 

  1125.           
    1126. 

  1126.     "<code class="mallctl">arenas.page</code>"
    1127. 

  1127.   
    1128. 

  1128.           (<span class="type">size_t</span>)
    1129. 

  1129.           <code class="literal">r-</code>
    1130. 

  1130.         </span></dt><dd><p>Page size.</p></dd><dt><a name="arenas.tcache_max"></a><span class="term">
    1131. 

  1131.           
    1132. 

  1132.     "<code class="mallctl">arenas.tcache_max</code>"
    1133. 

  1133.   
    1134. 

  1134.           (<span class="type">size_t</span>)
    1135. 

  1135.           <code class="literal">r-</code>
    1136. 

  1136.           [<code class="option">--enable-tcache</code>]
    1137. 

  1137.         </span></dt><dd><p>Maximum thread-cached size class.</p></dd><dt><a name="arenas.nbins"></a><span class="term">
    1138. 

  1138.           
    1139. 

  1139.     "<code class="mallctl">arenas.nbins</code>"
    1140. 

  1140.   
    1141. 

  1141.           (<span class="type">unsigned</span>)
    1142. 

  1142.           <code class="literal">r-</code>
    1143. 

  1143.         </span></dt><dd><p>Number of bin size classes.</p></dd><dt><a name="arenas.nhbins"></a><span class="term">
    1144. 

  1144.           
    1145. 

  1145.     "<code class="mallctl">arenas.nhbins</code>"
    1146. 

  1146.   
    1147. 

  1147.           (<span class="type">unsigned</span>)
    1148. 

  1148.           <code class="literal">r-</code>
    1149. 

  1149.           [<code class="option">--enable-tcache</code>]
    1150. 

  1150.         </span></dt><dd><p>Total number of thread cache bin size
    1151. 

  1151.         classes.</p></dd><dt><a name="arenas.bin.i.size"></a><span class="term">
    1152. 

  1152.           
    1153. 

  1153.     "<code class="mallctl">arenas.bin.&lt;i&gt;.size</code>"
    1154. 

  1154.   
    1155. 

  1155.           (<span class="type">size_t</span>)
    1156. 

  1156.           <code class="literal">r-</code>
    1157. 

  1157.         </span></dt><dd><p>Maximum size supported by size class.</p></dd><dt><a name="arenas.bin.i.nregs"></a><span class="term">
    1158. 

  1158.           
    1159. 

  1159.     "<code class="mallctl">arenas.bin.&lt;i&gt;.nregs</code>"
    1160. 

  1160.   
    1161. 

  1161.           (<span class="type">uint32_t</span>)
    1162. 

  1162.           <code class="literal">r-</code>
    1163. 

  1163.         </span></dt><dd><p>Number of regions per page run.</p></dd><dt><a name="arenas.bin.i.run_size"></a><span class="term">
    1164. 

  1164.           
    1165. 

  1165.     "<code class="mallctl">arenas.bin.&lt;i&gt;.run_size</code>"
    1166. 

  1166.   
    1167. 

  1167.           (<span class="type">size_t</span>)
    1168. 

  1168.           <code class="literal">r-</code>
    1169. 

  1169.         </span></dt><dd><p>Number of bytes per page run.</p></dd><dt><a name="arenas.nlruns"></a><span class="term">
    1170. 

  1170.           
    1171. 

  1171.     "<code class="mallctl">arenas.nlruns</code>"
    1172. 

  1172.   
    1173. 

  1173.           (<span class="type">unsigned</span>)
    1174. 

  1174.           <code class="literal">r-</code>
    1175. 

  1175.         </span></dt><dd><p>Total number of large size classes.</p></dd><dt><a name="arenas.lrun.i.size"></a><span class="term">
    1176. 

  1176.           
    1177. 

  1177.     "<code class="mallctl">arenas.lrun.&lt;i&gt;.size</code>"
    1178. 

  1178.   
    1179. 

  1179.           (<span class="type">size_t</span>)
    1180. 

  1180.           <code class="literal">r-</code>
    1181. 

  1181.         </span></dt><dd><p>Maximum size supported by this large size
    1182. 

  1182.         class.</p></dd><dt><a name="arenas.nhchunks"></a><span class="term">
    1183. 

  1183.           
    1184. 

  1184.     "<code class="mallctl">arenas.nhchunks</code>"
    1185. 

  1185.   
    1186. 

  1186.           (<span class="type">unsigned</span>)
    1187. 

  1187.           <code class="literal">r-</code>
    1188. 

  1188.         </span></dt><dd><p>Total number of huge size classes.</p></dd><dt><a name="arenas.hchunk.i.size"></a><span class="term">
    1189. 

  1189.           
    1190. 

  1190.     "<code class="mallctl">arenas.hchunk.&lt;i&gt;.size</code>"
    1191. 

  1191.   
    1192. 

  1192.           (<span class="type">size_t</span>)
    1193. 

  1193.           <code class="literal">r-</code>
    1194. 

  1194.         </span></dt><dd><p>Maximum size supported by this huge size
    1195. 

  1195.         class.</p></dd><dt><a name="arenas.extend"></a><span class="term">
    1196. 

  1196.           
    1197. 

  1197.     "<code class="mallctl">arenas.extend</code>"
    1198. 

  1198.   
    1199. 

  1199.           (<span class="type">unsigned</span>)
    1200. 

  1200.           <code class="literal">r-</code>
    1201. 

  1201.         </span></dt><dd><p>Extend the array of arenas by appending a new arena,
    1202. 

  1202.         and returning the new arena index.</p></dd><dt><a name="prof.thread_active_init"></a><span class="term">
    1203. 

  1203.           
    1204. 

  1204.     "<code class="mallctl">prof.thread_active_init</code>"
    1205. 

  1205.   
    1206. 

  1206.           (<span class="type">bool</span>)
    1207. 

  1207.           <code class="literal">rw</code>
    1208. 

  1208.           [<code class="option">--enable-prof</code>]
    1209. 

  1209.         </span></dt><dd><p>Control the initial setting for <a class="link" href="#thread.prof.active">
    1210. 

  1210.     "<code class="mallctl">thread.prof.active</code>"
    1211. 

  1211.   </a>
    1212. 

  1212.         in newly created threads.  See the <a class="link" href="#opt.prof_thread_active_init">
    1213. 

  1213.     "<code class="mallctl">opt.prof_thread_active_init</code>"
    1214. 

  1214.   </a>
    1215. 

  1215.         option for additional information.</p></dd><dt><a name="prof.active"></a><span class="term">
    1216. 

  1216.           
    1217. 

  1217.     "<code class="mallctl">prof.active</code>"
    1218. 

  1218.   
    1219. 

  1219.           (<span class="type">bool</span>)
    1220. 

  1220.           <code class="literal">rw</code>
    1221. 

  1221.           [<code class="option">--enable-prof</code>]
    1222. 

  1222.         </span></dt><dd><p>Control whether sampling is currently active.  See the
    1223. 

  1223.         <a class="link" href="#opt.prof_active">
    1224. 

  1224.     "<code class="mallctl">opt.prof_active</code>"
    1225. 

  1225.   </a>
    1226. 

  1226.         option for additional information, as well as the interrelated <a class="link" href="#thread.prof.active">
    1227. 

  1227.     "<code class="mallctl">thread.prof.active</code>"
    1228. 

  1228.   </a>
    1229. 

  1229.         mallctl.</p></dd><dt><a name="prof.dump"></a><span class="term">
    1230. 

  1230.           
    1231. 

  1231.     "<code class="mallctl">prof.dump</code>"
    1232. 

  1232.   
    1233. 

  1233.           (<span class="type">const char *</span>)
    1234. 

  1234.           <code class="literal">-w</code>
    1235. 

  1235.           [<code class="option">--enable-prof</code>]
    1236. 

  1236.         </span></dt><dd><p>Dump a memory profile to the specified file, or if NULL
    1237. 

  1237.         is specified, to a file according to the pattern
    1238. 

  1238.         <code class="filename">&lt;prefix&gt;.&lt;pid&gt;.&lt;seq&gt;.m&lt;mseq&gt;.heap</code>,
    1239. 

  1239.         where <code class="literal">&lt;prefix&gt;</code> is controlled by the
    1240. 

  1240.         <a class="link" href="#opt.prof_prefix">
    1241. 

  1241.     "<code class="mallctl">opt.prof_prefix</code>"
    1242. 

  1242.   </a>
    1243. 

  1243.         option.</p></dd><dt><a name="prof.gdump"></a><span class="term">
    1244. 

  1244.           
    1245. 

  1245.     "<code class="mallctl">prof.gdump</code>"
    1246. 

  1246.   
    1247. 

  1247.           (<span class="type">bool</span>)
    1248. 

  1248.           <code class="literal">rw</code>
    1249. 

  1249.           [<code class="option">--enable-prof</code>]
    1250. 

  1250.         </span></dt><dd><p>When enabled, trigger a memory profile dump every time
    1251. 

  1251.         the total virtual memory exceeds the previous maximum.  Profiles are
    1252. 

  1252.         dumped to files named according to the pattern
    1253. 

  1253.         <code class="filename">&lt;prefix&gt;.&lt;pid&gt;.&lt;seq&gt;.u&lt;useq&gt;.heap</code>,
    1254. 

  1254.         where <code class="literal">&lt;prefix&gt;</code> is controlled by the <a class="link" href="#opt.prof_prefix">
    1255. 

  1255.     "<code class="mallctl">opt.prof_prefix</code>"
    1256. 

  1256.   </a>
    1257. 

  1257.         option.</p></dd><dt><a name="prof.reset"></a><span class="term">
    1258. 

  1258.           
    1259. 

  1259.     "<code class="mallctl">prof.reset</code>"
    1260. 

  1260.   
    1261. 

  1261.           (<span class="type">size_t</span>)
    1262. 

  1262.           <code class="literal">-w</code>
    1263. 

  1263.           [<code class="option">--enable-prof</code>]
    1264. 

  1264.         </span></dt><dd><p>Reset all memory profile statistics, and optionally
    1265. 

  1265.         update the sample rate (see <a class="link" href="#opt.lg_prof_sample">
    1266. 

  1266.     "<code class="mallctl">opt.lg_prof_sample</code>"
    1267. 

  1267.   </a>
    1268. 

  1268.         and <a class="link" href="#prof.lg_sample">
    1269. 

  1269.     "<code class="mallctl">prof.lg_sample</code>"
    1270. 

  1270.   </a>).
    1271. 

  1271.         </p></dd><dt><a name="prof.lg_sample"></a><span class="term">
    1272. 

  1272.           
    1273. 

  1273.     "<code class="mallctl">prof.lg_sample</code>"
    1274. 

  1274.   
    1275. 

  1275.           (<span class="type">size_t</span>)
    1276. 

  1276.           <code class="literal">r-</code>
    1277. 

  1277.           [<code class="option">--enable-prof</code>]
    1278. 

  1278.         </span></dt><dd><p>Get the current sample rate (see <a class="link" href="#opt.lg_prof_sample">
    1279. 

  1279.     "<code class="mallctl">opt.lg_prof_sample</code>"
    1280. 

  1280.   </a>).
    1281. 

  1281.         </p></dd><dt><a name="prof.interval"></a><span class="term">
    1282. 

  1282.           
    1283. 

  1283.     "<code class="mallctl">prof.interval</code>"
    1284. 

  1284.   
    1285. 

  1285.           (<span class="type">uint64_t</span>)
    1286. 

  1286.           <code class="literal">r-</code>
    1287. 

  1287.           [<code class="option">--enable-prof</code>]
    1288. 

  1288.         </span></dt><dd><p>Average number of bytes allocated between
    1289. 

  1289.         inverval-based profile dumps.  See the
    1290. 

  1290.         <a class="link" href="#opt.lg_prof_interval">
    1291. 

  1291.     "<code class="mallctl">opt.lg_prof_interval</code>"
    1292. 

  1292.   </a>
    1293. 

  1293.         option for additional information.</p></dd><dt><a name="stats.cactive"></a><span class="term">
    1294. 

  1294.           
    1295. 

  1295.     "<code class="mallctl">stats.cactive</code>"
    1296. 

  1296.   
    1297. 

  1297.           (<span class="type">size_t *</span>)
    1298. 

  1298.           <code class="literal">r-</code>
    1299. 

  1299.           [<code class="option">--enable-stats</code>]
    1300. 

  1300.         </span></dt><dd><p>Pointer to a counter that contains an approximate count
    1301. 

  1301.         of the current number of bytes in active pages.  The estimate may be
    1302. 

  1302.         high, but never low, because each arena rounds up when computing its
    1303. 

  1303.         contribution to the counter.  Note that the <a class="link" href="#epoch">
    1304. 

  1304.     "<code class="mallctl">epoch</code>"
    1305. 

  1305.   </a> mallctl has no bearing
    1306. 

  1306.         on this counter.  Furthermore, counter consistency is maintained via
    1307. 

  1307.         atomic operations, so it is necessary to use an atomic operation in
    1308. 

  1308.         order to guarantee a consistent read when dereferencing the pointer.
    1309. 

  1309.         </p></dd><dt><a name="stats.allocated"></a><span class="term">
    1310. 

  1310.           
    1311. 

  1311.     "<code class="mallctl">stats.allocated</code>"
    1312. 

  1312.   
    1313. 

  1313.           (<span class="type">size_t</span>)
    1314. 

  1314.           <code class="literal">r-</code>
    1315. 

  1315.           [<code class="option">--enable-stats</code>]
    1316. 

  1316.         </span></dt><dd><p>Total number of bytes allocated by the
    1317. 

  1317.         application.</p></dd><dt><a name="stats.active"></a><span class="term">
    1318. 

  1318.           
    1319. 

  1319.     "<code class="mallctl">stats.active</code>"
    1320. 

  1320.   
    1321. 

  1321.           (<span class="type">size_t</span>)
    1322. 

  1322.           <code class="literal">r-</code>
    1323. 

  1323.           [<code class="option">--enable-stats</code>]
    1324. 

  1324.         </span></dt><dd><p>Total number of bytes in active pages allocated by the
    1325. 

  1325.         application.  This is a multiple of the page size, and greater than or
    1326. 

  1326.         equal to <a class="link" href="#stats.allocated">
    1327. 

  1327.     "<code class="mallctl">stats.allocated</code>"
    1328. 

  1328.   </a>.
    1329. 

  1329.         This does not include <a class="link" href="#stats.arenas.i.pdirty">
    1330. 

  1330.         
    1331. 

  1331.     "<code class="mallctl">stats.arenas.&lt;i&gt;.pdirty</code>"
    1332. 

  1332.   </a>, nor pages
    1333. 

  1333.         entirely devoted to allocator metadata.</p></dd><dt><a name="stats.metadata"></a><span class="term">
    1334. 

  1334.           
    1335. 

  1335.     "<code class="mallctl">stats.metadata</code>"
    1336. 

  1336.   
    1337. 

  1337.           (<span class="type">size_t</span>)
    1338. 

  1338.           <code class="literal">r-</code>
    1339. 

  1339.           [<code class="option">--enable-stats</code>]
    1340. 

  1340.         </span></dt><dd><p>Total number of bytes dedicated to metadata, which
    1341. 

  1341.         comprise base allocations used for bootstrap-sensitive internal
    1342. 

  1342.         allocator data structures, arena chunk headers (see <a class="link" href="#stats.arenas.i.metadata.mapped">
    1343. 

  1343.     "<code class="mallctl">stats.arenas.&lt;i&gt;.metadata.mapped</code>"
    1344. 

  1344.   </a>),
    1345. 

  1345.         and internal allocations (see <a class="link" href="#stats.arenas.i.metadata.allocated">
    1346. 

  1346.     "<code class="mallctl">stats.arenas.&lt;i&gt;.metadata.allocated</code>"
    1347. 

  1347.   </a>).</p></dd><dt><a name="stats.resident"></a><span class="term">
    1348. 

  1348.           
    1349. 

  1349.     "<code class="mallctl">stats.resident</code>"
    1350. 

  1350.   
    1351. 

  1351.           (<span class="type">size_t</span>)
    1352. 

  1352.           <code class="literal">r-</code>
    1353. 

  1353.           [<code class="option">--enable-stats</code>]
    1354. 

  1354.         </span></dt><dd><p>Maximum number of bytes in physically resident data
    1355. 

  1355.         pages mapped by the allocator, comprising all pages dedicated to
    1356. 

  1356.         allocator metadata, pages backing active allocations, and unused dirty
    1357. 

  1357.         pages.  This is a maximum rather than precise because pages may not
    1358. 

  1358.         actually be physically resident if they correspond to demand-zeroed
    1359. 

  1359.         virtual memory that has not yet been touched.  This is a multiple of the
    1360. 

  1360.         page size, and is larger than <a class="link" href="#stats.active">
    1361. 

  1361.     "<code class="mallctl">stats.active</code>"
    1362. 

  1362.   </a>.</p></dd><dt><a name="stats.mapped"></a><span class="term">
    1363. 

  1363.           
    1364. 

  1364.     "<code class="mallctl">stats.mapped</code>"
    1365. 

  1365.   
    1366. 

  1366.           (<span class="type">size_t</span>)
    1367. 

  1367.           <code class="literal">r-</code>
    1368. 

  1368.           [<code class="option">--enable-stats</code>]
    1369. 

  1369.         </span></dt><dd><p>Total number of bytes in active chunks mapped by the
    1370. 

  1370.         allocator.  This is a multiple of the chunk size, and is larger than
    1371. 

  1371.         <a class="link" href="#stats.active">
    1372. 

  1372.     "<code class="mallctl">stats.active</code>"
    1373. 

  1373.   </a>.
    1374. 

  1374.         This does not include inactive chunks, even those that contain unused
    1375. 

  1375.         dirty pages, which means that there is no strict ordering between this
    1376. 

  1376.         and <a class="link" href="#stats.resident">
    1377. 

  1377.     "<code class="mallctl">stats.resident</code>"
    1378. 

  1378.   </a>.</p></dd><dt><a name="stats.arenas.i.dss"></a><span class="term">
    1379. 

  1379.           
    1380. 

  1380.     "<code class="mallctl">stats.arenas.&lt;i&gt;.dss</code>"
    1381. 

  1381.   
    1382. 

  1382.           (<span class="type">const char *</span>)
    1383. 

  1383.           <code class="literal">r-</code>
    1384. 

  1384.         </span></dt><dd><p>dss (<span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span>) allocation precedence as
    1385. 

  1385.         related to <span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span> allocation.  See <a class="link" href="#opt.dss">
    1386. 

  1386.     "<code class="mallctl">opt.dss</code>"
    1387. 

  1387.   </a> for details.
    1388. 

  1388.         </p></dd><dt><a name="stats.arenas.i.lg_dirty_mult"></a><span class="term">
    1389. 

  1389.           
    1390. 

  1390.     "<code class="mallctl">stats.arenas.&lt;i&gt;.lg_dirty_mult</code>"
    1391. 

  1391.   
    1392. 

  1392.           (<span class="type">ssize_t</span>)
    1393. 

  1393.           <code class="literal">r-</code>
    1394. 

  1394.         </span></dt><dd><p>Minimum ratio (log base 2) of active to dirty pages.
    1395. 

  1395.         See <a class="link" href="#opt.lg_dirty_mult">
    1396. 

  1396.     "<code class="mallctl">opt.lg_dirty_mult</code>"
    1397. 

  1397.   </a>
    1398. 

  1398.         for details.</p></dd><dt><a name="stats.arenas.i.nthreads"></a><span class="term">
    1399. 

  1399.           
    1400. 

  1400.     "<code class="mallctl">stats.arenas.&lt;i&gt;.nthreads</code>"
    1401. 

  1401.   
    1402. 

  1402.           (<span class="type">unsigned</span>)
    1403. 

  1403.           <code class="literal">r-</code>
    1404. 

  1404.         </span></dt><dd><p>Number of threads currently assigned to
    1405. 

  1405.         arena.</p></dd><dt><a name="stats.arenas.i.pactive"></a><span class="term">
    1406. 

  1406.           
    1407. 

  1407.     "<code class="mallctl">stats.arenas.&lt;i&gt;.pactive</code>"
    1408. 

  1408.   
    1409. 

  1409.           (<span class="type">size_t</span>)
    1410. 

  1410.           <code class="literal">r-</code>
    1411. 

  1411.         </span></dt><dd><p>Number of pages in active runs.</p></dd><dt><a name="stats.arenas.i.pdirty"></a><span class="term">
    1412. 

  1412.           
    1413. 

  1413.     "<code class="mallctl">stats.arenas.&lt;i&gt;.pdirty</code>"
    1414. 

  1414.   
    1415. 

  1415.           (<span class="type">size_t</span>)
    1416. 

  1416.           <code class="literal">r-</code>
    1417. 

  1417.         </span></dt><dd><p>Number of pages within unused runs that are potentially
    1418. 

  1418.         dirty, and for which <code class="function">madvise</code>(<em class="parameter"><code>...</code></em>, 
    1419. 

  1419.         <em class="parameter"><code><code class="constant">MADV_DONTNEED</code></code></em>) or
    1420. 

  1420.         similar has not been called.</p></dd><dt><a name="stats.arenas.i.mapped"></a><span class="term">
    1421. 

  1421.           
    1422. 

  1422.     "<code class="mallctl">stats.arenas.&lt;i&gt;.mapped</code>"
    1423. 

  1423.   
    1424. 

  1424.           (<span class="type">size_t</span>)
    1425. 

  1425.           <code class="literal">r-</code>
    1426. 

  1426.           [<code class="option">--enable-stats</code>]
    1427. 

  1427.         </span></dt><dd><p>Number of mapped bytes.</p></dd><dt><a name="stats.arenas.i.metadata.mapped"></a><span class="term">
    1428. 

  1428.           
    1429. 

  1429.     "<code class="mallctl">stats.arenas.&lt;i&gt;.metadata.mapped</code>"
    1430. 

  1430.   
    1431. 

  1431.           (<span class="type">size_t</span>)
    1432. 

  1432.           <code class="literal">r-</code>
    1433. 

  1433.           [<code class="option">--enable-stats</code>]
    1434. 

  1434.         </span></dt><dd><p>Number of mapped bytes in arena chunk headers, which
    1435. 

  1435.         track the states of the non-metadata pages.</p></dd><dt><a name="stats.arenas.i.metadata.allocated"></a><span class="term">
    1436. 

  1436.           
    1437. 

  1437.     "<code class="mallctl">stats.arenas.&lt;i&gt;.metadata.allocated</code>"
    1438. 

  1438.   
    1439. 

  1439.           (<span class="type">size_t</span>)
    1440. 

  1440.           <code class="literal">r-</code>
    1441. 

  1441.           [<code class="option">--enable-stats</code>]
    1442. 

  1442.         </span></dt><dd><p>Number of bytes dedicated to internal allocations.
    1443. 

  1443.         Internal allocations differ from application-originated allocations in
    1444. 

  1444.         that they are for internal use, and that they are omitted from heap
    1445. 

  1445.         profiles.  This statistic is reported separately from <a class="link" href="#stats.metadata">
    1446. 

  1446.     "<code class="mallctl">stats.metadata</code>"
    1447. 

  1447.   </a> and
    1448. 

  1448.         <a class="link" href="#stats.arenas.i.metadata.mapped">
    1449. 

  1449.     "<code class="mallctl">stats.arenas.&lt;i&gt;.metadata.mapped</code>"
    1450. 

  1450.   </a>
    1451. 

  1451.         because it overlaps with e.g. the <a class="link" href="#stats.allocated">
    1452. 

  1452.     "<code class="mallctl">stats.allocated</code>"
    1453. 

  1453.   </a> and
    1454. 

  1454.         <a class="link" href="#stats.active">
    1455. 

  1455.     "<code class="mallctl">stats.active</code>"
    1456. 

  1456.   </a>
    1457. 

  1457.         statistics, whereas the other metadata statistics do
    1458. 

  1458.         not.</p></dd><dt><a name="stats.arenas.i.npurge"></a><span class="term">
    1459. 

  1459.           
    1460. 

  1460.     "<code class="mallctl">stats.arenas.&lt;i&gt;.npurge</code>"
    1461. 

  1461.   
    1462. 

  1462.           (<span class="type">uint64_t</span>)
    1463. 

  1463.           <code class="literal">r-</code>
    1464. 

  1464.           [<code class="option">--enable-stats</code>]
    1465. 

  1465.         </span></dt><dd><p>Number of dirty page purge sweeps performed.
    1466. 

  1466.         </p></dd><dt><a name="stats.arenas.i.nmadvise"></a><span class="term">
    1467. 

  1467.           
    1468. 

  1468.     "<code class="mallctl">stats.arenas.&lt;i&gt;.nmadvise</code>"
    1469. 

  1469.   
    1470. 

  1470.           (<span class="type">uint64_t</span>)
    1471. 

  1471.           <code class="literal">r-</code>
    1472. 

  1472.           [<code class="option">--enable-stats</code>]
    1473. 

  1473.         </span></dt><dd><p>Number of <code class="function">madvise</code>(<em class="parameter"><code>...</code></em>, 
    1474. 

  1474.         <em class="parameter"><code><code class="constant">MADV_DONTNEED</code></code></em>) or
    1475. 

  1475.         similar calls made to purge dirty pages.</p></dd><dt><a name="stats.arenas.i.purged"></a><span class="term">
    1476. 

  1476.           
    1477. 

  1477.     "<code class="mallctl">stats.arenas.&lt;i&gt;.purged</code>"
    1478. 

  1478.   
    1479. 

  1479.           (<span class="type">uint64_t</span>)
    1480. 

  1480.           <code class="literal">r-</code>
    1481. 

  1481.           [<code class="option">--enable-stats</code>]
    1482. 

  1482.         </span></dt><dd><p>Number of pages purged.</p></dd><dt><a name="stats.arenas.i.small.allocated"></a><span class="term">
    1483. 

  1483.           
    1484. 

  1484.     "<code class="mallctl">stats.arenas.&lt;i&gt;.small.allocated</code>"
    1485. 

  1485.   
    1486. 

  1486.           (<span class="type">size_t</span>)
    1487. 

  1487.           <code class="literal">r-</code>
    1488. 

  1488.           [<code class="option">--enable-stats</code>]
    1489. 

  1489.         </span></dt><dd><p>Number of bytes currently allocated by small objects.
    1490. 

  1490.         </p></dd><dt><a name="stats.arenas.i.small.nmalloc"></a><span class="term">
    1491. 

  1491.           
    1492. 

  1492.     "<code class="mallctl">stats.arenas.&lt;i&gt;.small.nmalloc</code>"
    1493. 

  1493.   
    1494. 

  1494.           (<span class="type">uint64_t</span>)
    1495. 

  1495.           <code class="literal">r-</code>
    1496. 

  1496.           [<code class="option">--enable-stats</code>]
    1497. 

  1497.         </span></dt><dd><p>Cumulative number of allocation requests served by
    1498. 

  1498.         small bins.</p></dd><dt><a name="stats.arenas.i.small.ndalloc"></a><span class="term">
    1499. 

  1499.           
    1500. 

  1500.     "<code class="mallctl">stats.arenas.&lt;i&gt;.small.ndalloc</code>"
    1501. 

  1501.   
    1502. 

  1502.           (<span class="type">uint64_t</span>)
    1503. 

  1503.           <code class="literal">r-</code>
    1504. 

  1504.           [<code class="option">--enable-stats</code>]
    1505. 

  1505.         </span></dt><dd><p>Cumulative number of small objects returned to bins.
    1506. 

  1506.         </p></dd><dt><a name="stats.arenas.i.small.nrequests"></a><span class="term">
    1507. 

  1507.           
    1508. 

  1508.     "<code class="mallctl">stats.arenas.&lt;i&gt;.small.nrequests</code>"
    1509. 

  1509.   
    1510. 

  1510.           (<span class="type">uint64_t</span>)
    1511. 

  1511.           <code class="literal">r-</code>
    1512. 

  1512.           [<code class="option">--enable-stats</code>]
    1513. 

  1513.         </span></dt><dd><p>Cumulative number of small allocation requests.
    1514. 

  1514.         </p></dd><dt><a name="stats.arenas.i.large.allocated"></a><span class="term">
    1515. 

  1515.           
    1516. 

  1516.     "<code class="mallctl">stats.arenas.&lt;i&gt;.large.allocated</code>"
    1517. 

  1517.   
    1518. 

  1518.           (<span class="type">size_t</span>)
    1519. 

  1519.           <code class="literal">r-</code>
    1520. 

  1520.           [<code class="option">--enable-stats</code>]
    1521. 

  1521.         </span></dt><dd><p>Number of bytes currently allocated by large objects.
    1522. 

  1522.         </p></dd><dt><a name="stats.arenas.i.large.nmalloc"></a><span class="term">
    1523. 

  1523.           
    1524. 

  1524.     "<code class="mallctl">stats.arenas.&lt;i&gt;.large.nmalloc</code>"
    1525. 

  1525.   
    1526. 

  1526.           (<span class="type">uint64_t</span>)
    1527. 

  1527.           <code class="literal">r-</code>
    1528. 

  1528.           [<code class="option">--enable-stats</code>]
    1529. 

  1529.         </span></dt><dd><p>Cumulative number of large allocation requests served
    1530. 

  1530.         directly by the arena.</p></dd><dt><a name="stats.arenas.i.large.ndalloc"></a><span class="term">
    1531. 

  1531.           
    1532. 

  1532.     "<code class="mallctl">stats.arenas.&lt;i&gt;.large.ndalloc</code>"
    1533. 

  1533.   
    1534. 

  1534.           (<span class="type">uint64_t</span>)
    1535. 

  1535.           <code class="literal">r-</code>
    1536. 

  1536.           [<code class="option">--enable-stats</code>]
    1537. 

  1537.         </span></dt><dd><p>Cumulative number of large deallocation requests served
    1538. 

  1538.         directly by the arena.</p></dd><dt><a name="stats.arenas.i.large.nrequests"></a><span class="term">
    1539. 

  1539.           
    1540. 

  1540.     "<code class="mallctl">stats.arenas.&lt;i&gt;.large.nrequests</code>"
    1541. 

  1541.   
    1542. 

  1542.           (<span class="type">uint64_t</span>)
    1543. 

  1543.           <code class="literal">r-</code>
    1544. 

  1544.           [<code class="option">--enable-stats</code>]
    1545. 

  1545.         </span></dt><dd><p>Cumulative number of large allocation requests.
    1546. 

  1546.         </p></dd><dt><a name="stats.arenas.i.huge.allocated"></a><span class="term">
    1547. 

  1547.           
    1548. 

  1548.     "<code class="mallctl">stats.arenas.&lt;i&gt;.huge.allocated</code>"
    1549. 

  1549.   
    1550. 

  1550.           (<span class="type">size_t</span>)
    1551. 

  1551.           <code class="literal">r-</code>
    1552. 

  1552.           [<code class="option">--enable-stats</code>]
    1553. 

  1553.         </span></dt><dd><p>Number of bytes currently allocated by huge objects.
    1554. 

  1554.         </p></dd><dt><a name="stats.arenas.i.huge.nmalloc"></a><span class="term">
    1555. 

  1555.           
    1556. 

  1556.     "<code class="mallctl">stats.arenas.&lt;i&gt;.huge.nmalloc</code>"
    1557. 

  1557.   
    1558. 

  1558.           (<span class="type">uint64_t</span>)
    1559. 

  1559.           <code class="literal">r-</code>
    1560. 

  1560.           [<code class="option">--enable-stats</code>]
    1561. 

  1561.         </span></dt><dd><p>Cumulative number of huge allocation requests served
    1562. 

  1562.         directly by the arena.</p></dd><dt><a name="stats.arenas.i.huge.ndalloc"></a><span class="term">
    1563. 

  1563.           
    1564. 

  1564.     "<code class="mallctl">stats.arenas.&lt;i&gt;.huge.ndalloc</code>"
    1565. 

  1565.   
    1566. 

  1566.           (<span class="type">uint64_t</span>)
    1567. 

  1567.           <code class="literal">r-</code>
    1568. 

  1568.           [<code class="option">--enable-stats</code>]
    1569. 

  1569.         </span></dt><dd><p>Cumulative number of huge deallocation requests served
    1570. 

  1570.         directly by the arena.</p></dd><dt><a name="stats.arenas.i.huge.nrequests"></a><span class="term">
    1571. 

  1571.           
    1572. 

  1572.     "<code class="mallctl">stats.arenas.&lt;i&gt;.huge.nrequests</code>"
    1573. 

  1573.   
    1574. 

  1574.           (<span class="type">uint64_t</span>)
    1575. 

  1575.           <code class="literal">r-</code>
    1576. 

  1576.           [<code class="option">--enable-stats</code>]
    1577. 

  1577.         </span></dt><dd><p>Cumulative number of huge allocation requests.
    1578. 

  1578.         </p></dd><dt><a name="stats.arenas.i.bins.j.nmalloc"></a><span class="term">
    1579. 

  1579.           
    1580. 

  1580.     "<code class="mallctl">stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.nmalloc</code>"
    1581. 

  1581.   
    1582. 

  1582.           (<span class="type">uint64_t</span>)
    1583. 

  1583.           <code class="literal">r-</code>
    1584. 

  1584.           [<code class="option">--enable-stats</code>]
    1585. 

  1585.         </span></dt><dd><p>Cumulative number of allocations served by bin.
    1586. 

  1586.         </p></dd><dt><a name="stats.arenas.i.bins.j.ndalloc"></a><span class="term">
    1587. 

  1587.           
    1588. 

  1588.     "<code class="mallctl">stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.ndalloc</code>"
    1589. 

  1589.   
    1590. 

  1590.           (<span class="type">uint64_t</span>)
    1591. 

  1591.           <code class="literal">r-</code>
    1592. 

  1592.           [<code class="option">--enable-stats</code>]
    1593. 

  1593.         </span></dt><dd><p>Cumulative number of allocations returned to bin.
    1594. 

  1594.         </p></dd><dt><a name="stats.arenas.i.bins.j.nrequests"></a><span class="term">
    1595. 

  1595.           
    1596. 

  1596.     "<code class="mallctl">stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.nrequests</code>"
    1597. 

  1597.   
    1598. 

  1598.           (<span class="type">uint64_t</span>)
    1599. 

  1599.           <code class="literal">r-</code>
    1600. 

  1600.           [<code class="option">--enable-stats</code>]
    1601. 

  1601.         </span></dt><dd><p>Cumulative number of allocation
    1602. 

  1602.         requests.</p></dd><dt><a name="stats.arenas.i.bins.j.curregs"></a><span class="term">
    1603. 

  1603.           
    1604. 

  1604.     "<code class="mallctl">stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.curregs</code>"
    1605. 

  1605.   
    1606. 

  1606.           (<span class="type">size_t</span>)
    1607. 

  1607.           <code class="literal">r-</code>
    1608. 

  1608.           [<code class="option">--enable-stats</code>]
    1609. 

  1609.         </span></dt><dd><p>Current number of regions for this size
    1610. 

  1610.         class.</p></dd><dt><a name="stats.arenas.i.bins.j.nfills"></a><span class="term">
    1611. 

  1611.           
    1612. 

  1612.     "<code class="mallctl">stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.nfills</code>"
    1613. 

  1613.   
    1614. 

  1614.           (<span class="type">uint64_t</span>)
    1615. 

  1615.           <code class="literal">r-</code>
    1616. 

  1616.           [<code class="option">--enable-stats</code> <code class="option">--enable-tcache</code>]
    1617. 

  1617.         </span></dt><dd><p>Cumulative number of tcache fills.</p></dd><dt><a name="stats.arenas.i.bins.j.nflushes"></a><span class="term">
    1618. 

  1618.           
    1619. 

  1619.     "<code class="mallctl">stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.nflushes</code>"
    1620. 

  1620.   
    1621. 

  1621.           (<span class="type">uint64_t</span>)
    1622. 

  1622.           <code class="literal">r-</code>
    1623. 

  1623.           [<code class="option">--enable-stats</code> <code class="option">--enable-tcache</code>]
    1624. 

  1624.         </span></dt><dd><p>Cumulative number of tcache flushes.</p></dd><dt><a name="stats.arenas.i.bins.j.nruns"></a><span class="term">
    1625. 

  1625.           
    1626. 

  1626.     "<code class="mallctl">stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.nruns</code>"
    1627. 

  1627.   
    1628. 

  1628.           (<span class="type">uint64_t</span>)
    1629. 

  1629.           <code class="literal">r-</code>
    1630. 

  1630.           [<code class="option">--enable-stats</code>]
    1631. 

  1631.         </span></dt><dd><p>Cumulative number of runs created.</p></dd><dt><a name="stats.arenas.i.bins.j.nreruns"></a><span class="term">
    1632. 

  1632.           
    1633. 

  1633.     "<code class="mallctl">stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.nreruns</code>"
    1634. 

  1634.   
    1635. 

  1635.           (<span class="type">uint64_t</span>)
    1636. 

  1636.           <code class="literal">r-</code>
    1637. 

  1637.           [<code class="option">--enable-stats</code>]
    1638. 

  1638.         </span></dt><dd><p>Cumulative number of times the current run from which
    1639. 

  1639.         to allocate changed.</p></dd><dt><a name="stats.arenas.i.bins.j.curruns"></a><span class="term">
    1640. 

  1640.           
    1641. 

  1641.     "<code class="mallctl">stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.curruns</code>"
    1642. 

  1642.   
    1643. 

  1643.           (<span class="type">size_t</span>)
    1644. 

  1644.           <code class="literal">r-</code>
    1645. 

  1645.           [<code class="option">--enable-stats</code>]
    1646. 

  1646.         </span></dt><dd><p>Current number of runs.</p></dd><dt><a name="stats.arenas.i.lruns.j.nmalloc"></a><span class="term">
    1647. 

  1647.           
    1648. 

  1648.     "<code class="mallctl">stats.arenas.&lt;i&gt;.lruns.&lt;j&gt;.nmalloc</code>"
    1649. 

  1649.   
    1650. 

  1650.           (<span class="type">uint64_t</span>)
    1651. 

  1651.           <code class="literal">r-</code>
    1652. 

  1652.           [<code class="option">--enable-stats</code>]
    1653. 

  1653.         </span></dt><dd><p>Cumulative number of allocation requests for this size
    1654. 

  1654.         class served directly by the arena.</p></dd><dt><a name="stats.arenas.i.lruns.j.ndalloc"></a><span class="term">
    1655. 

  1655.           
    1656. 

  1656.     "<code class="mallctl">stats.arenas.&lt;i&gt;.lruns.&lt;j&gt;.ndalloc</code>"
    1657. 

  1657.   
    1658. 

  1658.           (<span class="type">uint64_t</span>)
    1659. 

  1659.           <code class="literal">r-</code>
    1660. 

  1660.           [<code class="option">--enable-stats</code>]
    1661. 

  1661.         </span></dt><dd><p>Cumulative number of deallocation requests for this
    1662. 

  1662.         size class served directly by the arena.</p></dd><dt><a name="stats.arenas.i.lruns.j.nrequests"></a><span class="term">
    1663. 

  1663.           
    1664. 

  1664.     "<code class="mallctl">stats.arenas.&lt;i&gt;.lruns.&lt;j&gt;.nrequests</code>"
    1665. 

  1665.   
    1666. 

  1666.           (<span class="type">uint64_t</span>)
    1667. 

  1667.           <code class="literal">r-</code>
    1668. 

  1668.           [<code class="option">--enable-stats</code>]
    1669. 

  1669.         </span></dt><dd><p>Cumulative number of allocation requests for this size
    1670. 

  1670.         class.</p></dd><dt><a name="stats.arenas.i.lruns.j.curruns"></a><span class="term">
    1671. 

  1671.           
    1672. 

  1672.     "<code class="mallctl">stats.arenas.&lt;i&gt;.lruns.&lt;j&gt;.curruns</code>"
    1673. 

  1673.   
    1674. 

  1674.           (<span class="type">size_t</span>)
    1675. 

  1675.           <code class="literal">r-</code>
    1676. 

  1676.           [<code class="option">--enable-stats</code>]
    1677. 

  1677.         </span></dt><dd><p>Current number of runs for this size class.
    1678. 

  1678.         </p></dd><dt><a name="stats.arenas.i.hchunks.j.nmalloc"></a><span class="term">
    1679. 

  1679.           
    1680. 

  1680.     "<code class="mallctl">stats.arenas.&lt;i&gt;.hchunks.&lt;j&gt;.nmalloc</code>"
    1681. 

  1681.   
    1682. 

  1682.           (<span class="type">uint64_t</span>)
    1683. 

  1683.           <code class="literal">r-</code>
    1684. 

  1684.           [<code class="option">--enable-stats</code>]
    1685. 

  1685.         </span></dt><dd><p>Cumulative number of allocation requests for this size
    1686. 

  1686.         class served directly by the arena.</p></dd><dt><a name="stats.arenas.i.hchunks.j.ndalloc"></a><span class="term">
    1687. 

  1687.           
    1688. 

  1688.     "<code class="mallctl">stats.arenas.&lt;i&gt;.hchunks.&lt;j&gt;.ndalloc</code>"
    1689. 

  1689.   
    1690. 

  1690.           (<span class="type">uint64_t</span>)
    1691. 

  1691.           <code class="literal">r-</code>
    1692. 

  1692.           [<code class="option">--enable-stats</code>]
    1693. 

  1693.         </span></dt><dd><p>Cumulative number of deallocation requests for this
    1694. 

  1694.         size class served directly by the arena.</p></dd><dt><a name="stats.arenas.i.hchunks.j.nrequests"></a><span class="term">
    1695. 

  1695.           
    1696. 

  1696.     "<code class="mallctl">stats.arenas.&lt;i&gt;.hchunks.&lt;j&gt;.nrequests</code>"
    1697. 

  1697.   
    1698. 

  1698.           (<span class="type">uint64_t</span>)
    1699. 

  1699.           <code class="literal">r-</code>
    1700. 

  1700.           [<code class="option">--enable-stats</code>]
    1701. 

  1701.         </span></dt><dd><p>Cumulative number of allocation requests for this size
    1702. 

  1702.         class.</p></dd><dt><a name="stats.arenas.i.hchunks.j.curhchunks"></a><span class="term">
    1703. 

  1703.           
    1704. 

  1704.     "<code class="mallctl">stats.arenas.&lt;i&gt;.hchunks.&lt;j&gt;.curhchunks</code>"
    1705. 

  1705.   
    1706. 

  1706.           (<span class="type">size_t</span>)
    1707. 

  1707.           <code class="literal">r-</code>
    1708. 

  1708.           [<code class="option">--enable-stats</code>]
    1709. 

  1709.         </span></dt><dd><p>Current number of huge allocations for this size class.
    1710. 

  1710.         </p></dd></dl></div></div><div class="refsect1"><a name="debugging_malloc_problems"></a><h2>DEBUGGING MALLOC PROBLEMS</h2><p>When debugging, it is a good idea to configure/build jemalloc with
    1711. 

  1711.     the <code class="option">--enable-debug</code> and <code class="option">--enable-fill</code>
    1712. 

  1712.     options, and recompile the program with suitable options and symbols for
    1713. 

  1713.     debugger support.  When so configured, jemalloc incorporates a wide variety
    1714. 

  1714.     of run-time assertions that catch application errors such as double-free,
    1715. 

  1715.     write-after-free, etc.</p><p>Programs often accidentally depend on &#8220;uninitialized&#8221;
    1716. 

  1716.     memory actually being filled with zero bytes.  Junk filling
    1717. 

  1717.     (see the <a class="link" href="#opt.junk">
    1718. 

  1718.     "<code class="mallctl">opt.junk</code>"
    1719. 

  1719.   </a>
    1720. 

  1720.     option) tends to expose such bugs in the form of obviously incorrect
    1721. 

  1721.     results and/or coredumps.  Conversely, zero
    1722. 

  1722.     filling (see the <a class="link" href="#opt.zero">
    1723. 

  1723.     "<code class="mallctl">opt.zero</code>"
    1724. 

  1724.   </a> option) eliminates
    1725. 

  1725.     the symptoms of such bugs.  Between these two options, it is usually
    1726. 

  1726.     possible to quickly detect, diagnose, and eliminate such bugs.</p><p>This implementation does not provide much detail about the problems
    1727. 

  1727.     it detects, because the performance impact for storing such information
    1728. 

  1728.     would be prohibitive.  However, jemalloc does integrate with the most
    1729. 

  1729.     excellent <a class="ulink" href="http://valgrind.org/" target="_top">Valgrind</a> tool if the
    1730. 

  1730.     <code class="option">--enable-valgrind</code> configuration option is enabled.</p></div><div class="refsect1"><a name="diagnostic_messages"></a><h2>DIAGNOSTIC MESSAGES</h2><p>If any of the memory allocation/deallocation functions detect an
    1731. 

  1731.     error or warning condition, a message will be printed to file descriptor
    1732. 

  1732.     <code class="constant">STDERR_FILENO</code>.  Errors will result in the process
    1733. 

  1733.     dumping core.  If the <a class="link" href="#opt.abort">
    1734. 

  1734.     "<code class="mallctl">opt.abort</code>"
    1735. 

  1735.   </a> option is set, most
    1736. 

  1736.     warnings are treated as errors.</p><p>The <code class="varname">malloc_message</code> variable allows the programmer
    1737. 

  1737.     to override the function which emits the text strings forming the errors
    1738. 

  1738.     and warnings if for some reason the <code class="constant">STDERR_FILENO</code> file
    1739. 

  1739.     descriptor is not suitable for this.
    1740. 

  1740.     <code class="function">malloc_message</code>(<em class="parameter"><code></code></em>) takes the
    1741. 

  1741.     <em class="parameter"><code>cbopaque</code></em> pointer argument that is
    1742. 

  1742.     <code class="constant">NULL</code> unless overridden by the arguments in a call to
    1743. 

  1743.     <code class="function">malloc_stats_print</code>(<em class="parameter"><code></code></em>), followed by a string
    1744. 

  1744.     pointer.  Please note that doing anything which tries to allocate memory in
    1745. 

  1745.     this function is likely to result in a crash or deadlock.</p><p>All messages are prefixed by
    1746. 

  1746.     &#8220;<code class="computeroutput">&lt;jemalloc&gt;: </code>&#8221;.</p></div><div class="refsect1"><a name="return_values"></a><h2>RETURN VALUES</h2><div class="refsect2"><a name="idp46949776"></a><h3>Standard API</h3><p>The <code class="function">malloc</code>(<em class="parameter"><code></code></em>) and
    1747. 

  1747.       <code class="function">calloc</code>(<em class="parameter"><code></code></em>) functions return a pointer to the
    1748. 

  1748.       allocated memory if successful; otherwise a <code class="constant">NULL</code>
    1749. 

  1749.       pointer is returned and <code class="varname">errno</code> is set to
    1750. 

  1750.       <span class="errorname">ENOMEM</span>.</p><p>The <code class="function">posix_memalign</code>(<em class="parameter"><code></code></em>) function
    1751. 

  1751.       returns the value 0 if successful; otherwise it returns an error value.
    1752. 

  1752.       The <code class="function">posix_memalign</code>(<em class="parameter"><code></code></em>) function will fail
    1753. 

  1753.       if:
    1754. 

  1754.         </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><span class="errorname">EINVAL</span></span></dt><dd><p>The <em class="parameter"><code>alignment</code></em> parameter is
    1755. 

  1755.             not a power of 2 at least as large as
    1756. 

  1756.             <code class="code">sizeof(<span class="type">void *</span>)</code>.
    1757. 

  1757.             </p></dd><dt><span class="term"><span class="errorname">ENOMEM</span></span></dt><dd><p>Memory allocation error.</p></dd></dl></div><p>
    1758. 

  1758.       </p><p>The <code class="function">aligned_alloc</code>(<em class="parameter"><code></code></em>) function returns
    1759. 

  1759.       a pointer to the allocated memory if successful; otherwise a
    1760. 

  1760.       <code class="constant">NULL</code> pointer is returned and
    1761. 

  1761.       <code class="varname">errno</code> is set.  The
    1762. 

  1762.       <code class="function">aligned_alloc</code>(<em class="parameter"><code></code></em>) function will fail if:
    1763. 

  1763.         </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><span class="errorname">EINVAL</span></span></dt><dd><p>The <em class="parameter"><code>alignment</code></em> parameter is
    1764. 

  1764.             not a power of 2.
    1765. 

  1765.             </p></dd><dt><span class="term"><span class="errorname">ENOMEM</span></span></dt><dd><p>Memory allocation error.</p></dd></dl></div><p>
    1766. 

  1766.       </p><p>The <code class="function">realloc</code>(<em class="parameter"><code></code></em>) function returns a
    1767. 

  1767.       pointer, possibly identical to <em class="parameter"><code>ptr</code></em>, to the
    1768. 

  1768.       allocated memory if successful; otherwise a <code class="constant">NULL</code>
    1769. 

  1769.       pointer is returned, and <code class="varname">errno</code> is set to
    1770. 

  1770.       <span class="errorname">ENOMEM</span> if the error was the result of an
    1771. 

  1771.       allocation failure.  The <code class="function">realloc</code>(<em class="parameter"><code></code></em>)
    1772. 

  1772.       function always leaves the original buffer intact when an error occurs.
    1773. 

  1773.       </p><p>The <code class="function">free</code>(<em class="parameter"><code></code></em>) function returns no
    1774. 

  1774.       value.</p></div><div class="refsect2"><a name="idp46974576"></a><h3>Non-standard API</h3><p>The <code class="function">mallocx</code>(<em class="parameter"><code></code></em>) and
    1775. 

  1775.       <code class="function">rallocx</code>(<em class="parameter"><code></code></em>) functions return a pointer to
    1776. 

  1776.       the allocated memory if successful; otherwise a <code class="constant">NULL</code>
    1777. 

  1777.       pointer is returned to indicate insufficient contiguous memory was
    1778. 

  1778.       available to service the allocation request.  </p><p>The <code class="function">xallocx</code>(<em class="parameter"><code></code></em>) function returns the
    1779. 

  1779.       real size of the resulting resized allocation pointed to by
    1780. 

  1780.       <em class="parameter"><code>ptr</code></em>, which is a value less than
    1781. 

  1781.       <em class="parameter"><code>size</code></em> if the allocation could not be adequately
    1782. 

  1782.       grown in place.  </p><p>The <code class="function">sallocx</code>(<em class="parameter"><code></code></em>) function returns the
    1783. 

  1783.       real size of the allocation pointed to by <em class="parameter"><code>ptr</code></em>.
    1784. 

  1784.       </p><p>The <code class="function">nallocx</code>(<em class="parameter"><code></code></em>) returns the real size
    1785. 

  1785.       that would result from a successful equivalent
    1786. 

  1786.       <code class="function">mallocx</code>(<em class="parameter"><code></code></em>) function call, or zero if
    1787. 

  1787.       insufficient memory is available to perform the size computation.  </p><p>The <code class="function">mallctl</code>(<em class="parameter"><code></code></em>),
    1788. 

  1788.       <code class="function">mallctlnametomib</code>(<em class="parameter"><code></code></em>), and
    1789. 

  1789.       <code class="function">mallctlbymib</code>(<em class="parameter"><code></code></em>) functions return 0 on
    1790. 

  1790.       success; otherwise they return an error value.  The functions will fail
    1791. 

  1791.       if:
    1792. 

  1792.         </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><span class="errorname">EINVAL</span></span></dt><dd><p><em class="parameter"><code>newp</code></em> is not
    1793. 

  1793.             <code class="constant">NULL</code>, and <em class="parameter"><code>newlen</code></em> is too
    1794. 

  1794.             large or too small.  Alternatively, <em class="parameter"><code>*oldlenp</code></em>
    1795. 

  1795.             is too large or too small; in this case as much data as possible
    1796. 

  1796.             are read despite the error.</p></dd><dt><span class="term"><span class="errorname">ENOENT</span></span></dt><dd><p><em class="parameter"><code>name</code></em> or
    1797. 

  1797.             <em class="parameter"><code>mib</code></em> specifies an unknown/invalid
    1798. 

  1798.             value.</p></dd><dt><span class="term"><span class="errorname">EPERM</span></span></dt><dd><p>Attempt to read or write void value, or attempt to
    1799. 

  1799.             write read-only value.</p></dd><dt><span class="term"><span class="errorname">EAGAIN</span></span></dt><dd><p>A memory allocation failure
    1800. 

  1800.             occurred.</p></dd><dt><span class="term"><span class="errorname">EFAULT</span></span></dt><dd><p>An interface with side effects failed in some way
    1801. 

  1801.             not directly related to <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>)
    1802. 

  1802.             read/write processing.</p></dd></dl></div><p>
    1803. 

  1803.       </p><p>The <code class="function">malloc_usable_size</code>(<em class="parameter"><code></code></em>) function
    1804. 

  1804.       returns the usable size of the allocation pointed to by
    1805. 

  1805.       <em class="parameter"><code>ptr</code></em>.  </p></div></div><div class="refsect1"><a name="environment"></a><h2>ENVIRONMENT</h2><p>The following environment variable affects the execution of the
    1806. 

  1806.     allocation functions:
    1807. 

  1807.       </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="envar">MALLOC_CONF</code></span></dt><dd><p>If the environment variable
    1808. 

  1808.           <code class="envar">MALLOC_CONF</code> is set, the characters it contains
    1809. 

  1809.           will be interpreted as options.</p></dd></dl></div><p>
    1810. 

  1810.     </p></div><div class="refsect1"><a name="examples"></a><h2>EXAMPLES</h2><p>To dump core whenever a problem occurs:
    1811. 

  1811.       </p><pre class="screen">ln -s 'abort:true' /etc/malloc.conf</pre><p>
    1812. 

  1812.     </p><p>To specify in the source a chunk size that is 16 MiB:
    1813. 

  1813.       </p><pre class="programlisting">
    1814. 

  1814. malloc_conf = "lg_chunk:24";</pre></div><div class="refsect1"><a name="see_also"></a><h2>SEE ALSO</h2><p><span class="citerefentry"><span class="refentrytitle">madvise</span>(2)</span>,
    1815. 

  1815.     <span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span>,
    1816. 

  1816.     <span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span>,
    1817. 

  1817.     <span class="citerefentry"><span class="refentrytitle">utrace</span>(2)</span>,
    1818. 

  1818.     <span class="citerefentry"><span class="refentrytitle">alloca</span>(3)</span>,
    1819. 

  1819.     <span class="citerefentry"><span class="refentrytitle">atexit</span>(3)</span>,
    1820. 

  1820.     <span class="citerefentry"><span class="refentrytitle">getpagesize</span>(3)</span></p></div><div class="refsect1"><a name="standards"></a><h2>STANDARDS</h2><p>The <code class="function">malloc</code>(<em class="parameter"><code></code></em>),
    1821. 

  1821.     <code class="function">calloc</code>(<em class="parameter"><code></code></em>),
    1822. 

  1822.     <code class="function">realloc</code>(<em class="parameter"><code></code></em>), and
    1823. 

  1823.     <code class="function">free</code>(<em class="parameter"><code></code></em>) functions conform to ISO/IEC
    1824. 

  1824.     9899:1990 (&#8220;ISO C90&#8221;).</p><p>The <code class="function">posix_memalign</code>(<em class="parameter"><code></code></em>) function conforms
    1825. 

  1825.     to IEEE Std 1003.1-2001 (&#8220;POSIX.1&#8221;).</p></div></div></body></html>
    1826.