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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 V1.76.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" title="JEMALLOC"><a name="id286949159"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>jemalloc &#8212; general purpose memory allocation functions</p></div><div class="refsect1" title="LIBRARY"><a name="library"></a><h2>LIBRARY</h2><p>This manual describes jemalloc 3.2.0-0-g87499f6748ebe4817571e817e9f680ccb5bf54a9.  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" title="SYNOPSIS"><h2>SYNOPSIS</h2><div class="funcsynopsis"><pre class="funcsynopsisinfo">#include &lt;<code class="filename">stdlib.h</code>&gt;
    3. 

  3. #include &lt;<code class="filename">jemalloc/jemalloc.h</code>&gt;</pre><div class="refsect2" title="Standard API"><a name="id286901505"></a><h3>Standard API</h3><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><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" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><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" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><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" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><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" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><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" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><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" title="Non-standard API"><a name="id286900549"></a><h3>Non-standard API</h3><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><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" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">malloc_stats_print</b>(</code></td><td>void <var class="pdparam">(*write_cb)</var>
    4. 

  4.             <code>(</code>void *, const char *<code>)</code>
    5. 

  5.           , </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" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><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" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><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" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><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" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><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 class="refsect2" title="Experimental API"><a name="id286900756"></a><h3>Experimental API</h3><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">allocm</b>(</code></td><td>void **<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">rsize</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" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">rallocm</b>(</code></td><td>void **<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">rsize</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" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">sallocm</b>(</code></td><td>const void *<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">rsize</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" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">dallocm</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" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">nallocm</b>(</code></td><td>size_t *<var class="pdparam">rsize</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></div></div></div><div class="refsect1" title="DESCRIPTION"><a name="description"></a><h2>DESCRIPTION</h2><div class="refsect2" title="Standard API"><a name="id286949297"></a><h3>Standard API</h3><p>The <code class="function">malloc</code>(<em class="parameter"><code></code></em>) function allocates
    6. 

  6.       <em class="parameter"><code>size</code></em> bytes of uninitialized memory.  The allocated
    7. 

  7.       space is suitably aligned (after possible pointer coercion) for storage
    8. 

  8.       of any type of object.</p><p>The <code class="function">calloc</code>(<em class="parameter"><code></code></em>) function allocates
    9. 

  9.       space for <em class="parameter"><code>number</code></em> objects, each
    10. 

  10.       <em class="parameter"><code>size</code></em> bytes in length.  The result is identical to
    11. 

  11.       calling <code class="function">malloc</code>(<em class="parameter"><code></code></em>) with an argument of
    12. 

  12.       <em class="parameter"><code>number</code></em> * <em class="parameter"><code>size</code></em>, with the
    13. 

  13.       exception that the allocated memory is explicitly initialized to zero
    14. 

  14.       bytes.</p><p>The <code class="function">posix_memalign</code>(<em class="parameter"><code></code></em>) function
    15. 

  15.       allocates <em class="parameter"><code>size</code></em> bytes of memory such that the
    16. 

  16.       allocation's base address is an even multiple of
    17. 

  17.       <em class="parameter"><code>alignment</code></em>, and returns the allocation in the value
    18. 

  18.       pointed to by <em class="parameter"><code>ptr</code></em>.  The requested
    19. 

  19.       <em class="parameter"><code>alignment</code></em> must be a power of 2 at least as large
    20. 

  20.       as <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
    21. 

  21.       allocates <em class="parameter"><code>size</code></em> bytes of memory such that the
    22. 

  22.       allocation's base address is an even multiple of
    23. 

  23.       <em class="parameter"><code>alignment</code></em>.  The requested
    24. 

  24.       <em class="parameter"><code>alignment</code></em> must be a power of 2.  Behavior is
    25. 

  25.       undefined if <em class="parameter"><code>size</code></em> is not an integral multiple of
    26. 

  26.       <em class="parameter"><code>alignment</code></em>.</p><p>The <code class="function">realloc</code>(<em class="parameter"><code></code></em>) function changes the
    27. 

  27.       size of the previously allocated memory referenced by
    28. 

  28.       <em class="parameter"><code>ptr</code></em> to <em class="parameter"><code>size</code></em> bytes.  The
    29. 

  29.       contents of the memory are unchanged up to the lesser of the new and old
    30. 

  30.       sizes.  If the new size is larger, the contents of the newly allocated
    31. 

  31.       portion of the memory are undefined.  Upon success, the memory referenced
    32. 

  32.       by <em class="parameter"><code>ptr</code></em> is freed and a pointer to the newly
    33. 

  33.       allocated memory is returned.  Note that
    34. 

  34.       <code class="function">realloc</code>(<em class="parameter"><code></code></em>) may move the memory allocation,
    35. 

  35.       resulting in a different return value than <em class="parameter"><code>ptr</code></em>.
    36. 

  36.       If <em class="parameter"><code>ptr</code></em> is <code class="constant">NULL</code>, the
    37. 

  37.       <code class="function">realloc</code>(<em class="parameter"><code></code></em>) function behaves identically to
    38. 

  38.       <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
    39. 

  39.       allocated memory referenced by <em class="parameter"><code>ptr</code></em> to be made
    40. 

  40.       available for future allocations.  If <em class="parameter"><code>ptr</code></em> is
    41. 

  41.       <code class="constant">NULL</code>, no action occurs.</p></div><div class="refsect2" title="Non-standard API"><a name="id286949561"></a><h3>Non-standard API</h3><p>The <code class="function">malloc_usable_size</code>(<em class="parameter"><code></code></em>) function
    42. 

  42.       returns the usable size of the allocation pointed to by
    43. 

  43.       <em class="parameter"><code>ptr</code></em>.  The return value may be larger than the size
    44. 

  44.       that was requested during allocation.  The
    45. 

  45.       <code class="function">malloc_usable_size</code>(<em class="parameter"><code></code></em>) function is not a
    46. 

  46.       mechanism for in-place <code class="function">realloc</code>(<em class="parameter"><code></code></em>); rather
    47. 

  47.       it is provided solely as a tool for introspection purposes.  Any
    48. 

  48.       discrepancy between the requested allocation size and the size reported
    49. 

  49.       by <code class="function">malloc_usable_size</code>(<em class="parameter"><code></code></em>) should not be
    50. 

  50.       depended on, since such behavior is entirely implementation-dependent.
    51. 

  51.       </p><p>The <code class="function">malloc_stats_print</code>(<em class="parameter"><code></code></em>) function
    52. 

  52.       writes human-readable summary statistics via the
    53. 

  53.       <em class="parameter"><code>write_cb</code></em> callback function pointer and
    54. 

  54.       <em class="parameter"><code>cbopaque</code></em> data passed to
    55. 

  55.       <em class="parameter"><code>write_cb</code></em>, or
    56. 

  56.       <code class="function">malloc_message</code>(<em class="parameter"><code></code></em>) if
    57. 

  57.       <em class="parameter"><code>write_cb</code></em> is <code class="constant">NULL</code>.  This
    58. 

  58.       function can be called repeatedly.  General information that never
    59. 

  59.       changes during execution can be omitted by specifying "g" as a character
    60. 

  60.       within the <em class="parameter"><code>opts</code></em> string.  Note that
    61. 

  61.       <code class="function">malloc_message</code>(<em class="parameter"><code></code></em>) uses the
    62. 

  62.       <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) functions internally, so
    63. 

  63.       inconsistent statistics can be reported if multiple threads use these
    64. 

  64.       functions simultaneously.  If <code class="option">--enable-stats</code> is
    65. 

  65.       specified during configuration, &#8220;m&#8221; and &#8220;a&#8221; can
    66. 

  66.       be specified to omit merged arena and per arena statistics, respectively;
    67. 

  67.       &#8220;b&#8221; and &#8220;l&#8221; can be specified to omit per size
    68. 

  68.       class statistics for bins and large objects, respectively.  Unrecognized
    69. 

  69.       characters are silently ignored.  Note that thread caching may prevent
    70. 

  70.       some statistics from being completely up to date, since extra locking
    71. 

  71.       would be required to merge counters that track thread cache operations.
    72. 

  72.       </p><p>The <code class="function">mallctl</code>(<em class="parameter"><code></code></em>) function provides a
    73. 

  73.       general interface for introspecting the memory allocator, as well as
    74. 

  74.       setting modifiable parameters and triggering actions.  The
    75. 

  75.       period-separated <em class="parameter"><code>name</code></em> argument specifies a
    76. 

  76.       location in a tree-structured namespace; see the <a class="xref" href="#mallctl_namespace" title="MALLCTL NAMESPACE">MALLCTL NAMESPACE</a> section for
    77. 

  77.       documentation on the tree contents.  To read a value, pass a pointer via
    78. 

  78.       <em class="parameter"><code>oldp</code></em> to adequate space to contain the value, and a
    79. 

  79.       pointer to its length via <em class="parameter"><code>oldlenp</code></em>; otherwise pass
    80. 

  80.       <code class="constant">NULL</code> and <code class="constant">NULL</code>.  Similarly, to
    81. 

  81.       write a value, pass a pointer to the value via
    82. 

  82.       <em class="parameter"><code>newp</code></em>, and its length via
    83. 

  83.       <em class="parameter"><code>newlen</code></em>; otherwise pass <code class="constant">NULL</code>
    84. 

  84.       and <code class="constant">0</code>.</p><p>The <code class="function">mallctlnametomib</code>(<em class="parameter"><code></code></em>) function
    85. 

  85.       provides a way to avoid repeated name lookups for applications that
    86. 

  86.       repeatedly query the same portion of the namespace, by translating a name
    87. 

  87.       to a &#8220;Management Information Base&#8221; (MIB) that can be passed
    88. 

  88.       repeatedly to <code class="function">mallctlbymib</code>(<em class="parameter"><code></code></em>).  Upon
    89. 

  89.       successful return from <code class="function">mallctlnametomib</code>(<em class="parameter"><code></code></em>),
    90. 

  90.       <em class="parameter"><code>mibp</code></em> contains an array of
    91. 

  91.       <em class="parameter"><code>*miblenp</code></em> integers, where
    92. 

  92.       <em class="parameter"><code>*miblenp</code></em> is the lesser of the number of components
    93. 

  93.       in <em class="parameter"><code>name</code></em> and the input value of
    94. 

  94.       <em class="parameter"><code>*miblenp</code></em>.  Thus it is possible to pass a
    95. 

  95.       <em class="parameter"><code>*miblenp</code></em> that is smaller than the number of
    96. 

  96.       period-separated name components, which results in a partial MIB that can
    97. 

  97.       be used as the basis for constructing a complete MIB.  For name
    98. 

  98.       components that are integers (e.g. the 2 in
    99. 

  99.       <a class="link" href="#arenas.bin.i.size">
    100. 

  100.     "<code class="mallctl">arenas.bin.2.size</code>"
    101. 

  101.   </a>),
    102. 

  102.       the corresponding MIB component will always be that integer.  Therefore,
    103. 

  103.       it is legitimate to construct code like the following: </p><pre class="programlisting">
    104. 

  104. unsigned nbins, i;
    105. 

  105. 

  106. int mib[4];
    107. 

  107. size_t len, miblen;
    108. 

  108. 

  109. len = sizeof(nbins);
    110. 

  110. mallctl("arenas.nbins", &amp;nbins, &amp;len, NULL, 0);
    111. 

  111. 

  112. miblen = 4;
    113. 

  113. mallnametomib("arenas.bin.0.size", mib, &amp;miblen);
    114. 

  114. for (i = 0; i &lt; nbins; i++) {
    115. 

  115. 	size_t bin_size;
    116. 

  116. 

  117. 	mib[2] = i;
    118. 

  118. 	len = sizeof(bin_size);
    119. 

  119. 	mallctlbymib(mib, miblen, &amp;bin_size, &amp;len, NULL, 0);
    120. 

  120. 	/* Do something with bin_size... */
    121. 

  121. }</pre></div><div class="refsect2" title="Experimental API"><a name="id286949870"></a><h3>Experimental API</h3><p>The experimental API is subject to change or removal without regard
    122. 

  122.       for backward compatibility.  If <code class="option">--disable-experimental</code>
    123. 

  123.       is specified during configuration, the experimental API is
    124. 

  124.       omitted.</p><p>The <code class="function">allocm</code>(<em class="parameter"><code></code></em>),
    125. 

  125.       <code class="function">rallocm</code>(<em class="parameter"><code></code></em>),
    126. 

  126.       <code class="function">sallocm</code>(<em class="parameter"><code></code></em>),
    127. 

  127.       <code class="function">dallocm</code>(<em class="parameter"><code></code></em>), and
    128. 

  128.       <code class="function">nallocm</code>(<em class="parameter"><code></code></em>) functions all have a
    129. 

  129.       <em class="parameter"><code>flags</code></em> argument that can be used to specify
    130. 

  130.       options.  The functions only check the options that are contextually
    131. 

  131.       relevant.  Use bitwise or (<code class="code">|</code>) operations to
    132. 

  132.       specify one or more of the following:
    133. 

  133.         </p><div class="variablelist"><dl><dt><span class="term"><code class="constant">ALLOCM_LG_ALIGN(<em class="parameter"><code>la</code></em>)
    134. 

  134.             </code></span></dt><dd><p>Align the memory allocation to start at an address
    135. 

  135.             that is a multiple of <code class="code">(1 &lt;&lt;
    136. 

  136.             <em class="parameter"><code>la</code></em>)</code>.  This macro does not validate
    137. 

  137.             that <em class="parameter"><code>la</code></em> is within the valid
    138. 

  138.             range.</p></dd><dt><span class="term"><code class="constant">ALLOCM_ALIGN(<em class="parameter"><code>a</code></em>)
    139. 

  139.             </code></span></dt><dd><p>Align the memory allocation to start at an address
    140. 

  140.             that is a multiple of <em class="parameter"><code>a</code></em>, where
    141. 

  141.             <em class="parameter"><code>a</code></em> is a power of two.  This macro does not
    142. 

  142.             validate that <em class="parameter"><code>a</code></em> is a power of 2.
    143. 

  143.             </p></dd><dt><span class="term"><code class="constant">ALLOCM_ZERO</code></span></dt><dd><p>Initialize newly allocated memory to contain zero
    144. 

  144.             bytes.  In the growing reallocation case, the real size prior to
    145. 

  145.             reallocation defines the boundary between untouched bytes and those
    146. 

  146.             that are initialized to contain zero bytes.  If this option is
    147. 

  147.             absent, newly allocated memory is uninitialized.</p></dd><dt><span class="term"><code class="constant">ALLOCM_NO_MOVE</code></span></dt><dd><p>For reallocation, fail rather than moving the
    148. 

  148.             object.  This constraint can apply to both growth and
    149. 

  149.             shrinkage.</p></dd><dt><span class="term"><code class="constant">ALLOCM_ARENA(<em class="parameter"><code>a</code></em>)
    150. 

  150.             </code></span></dt><dd><p>Use the arena specified by the index
    151. 

  151.             <em class="parameter"><code>a</code></em>.  This macro does not validate that
    152. 

  152.             <em class="parameter"><code>a</code></em> specifies an arena in the valid
    153. 

  153.             range.</p></dd></dl></div><p>
    154. 

  154.       </p><p>The <code class="function">allocm</code>(<em class="parameter"><code></code></em>) function allocates at
    155. 

  155.       least <em class="parameter"><code>size</code></em> bytes of memory, sets
    156. 

  156.       <em class="parameter"><code>*ptr</code></em> to the base address of the allocation, and
    157. 

  157.       sets <em class="parameter"><code>*rsize</code></em> to the real size of the allocation if
    158. 

  158.       <em class="parameter"><code>rsize</code></em> is not <code class="constant">NULL</code>.  Behavior
    159. 

  159.       is undefined if <em class="parameter"><code>size</code></em> is
    160. 

  160.       <code class="constant">0</code>.</p><p>The <code class="function">rallocm</code>(<em class="parameter"><code></code></em>) function resizes the
    161. 

  161.       allocation at <em class="parameter"><code>*ptr</code></em> to be at least
    162. 

  162.       <em class="parameter"><code>size</code></em> bytes, sets <em class="parameter"><code>*ptr</code></em> to
    163. 

  163.       the base address of the allocation if it moved, and sets
    164. 

  164.       <em class="parameter"><code>*rsize</code></em> to the real size of the allocation if
    165. 

  165.       <em class="parameter"><code>rsize</code></em> is not <code class="constant">NULL</code>.  If
    166. 

  166.       <em class="parameter"><code>extra</code></em> is non-zero, an attempt is made to resize
    167. 

  167.       the allocation to be at least <code class="code"><em class="parameter"><code>size</code></em> +
    168. 

  168.       <em class="parameter"><code>extra</code></em>)</code> bytes, though inability to allocate
    169. 

  169.       the extra byte(s) will not by itself result in failure.  Behavior is
    170. 

  170.       undefined if <em class="parameter"><code>size</code></em> is <code class="constant">0</code>, or if
    171. 

  171.       <code class="code">(<em class="parameter"><code>size</code></em> +
    172. 

  172.       <em class="parameter"><code>extra</code></em> &gt;
    173. 

  173.       <code class="constant">SIZE_T_MAX</code>)</code>.</p><p>The <code class="function">sallocm</code>(<em class="parameter"><code></code></em>) function sets
    174. 

  174.       <em class="parameter"><code>*rsize</code></em> to the real size of the allocation.</p><p>The <code class="function">dallocm</code>(<em class="parameter"><code></code></em>) function causes the
    175. 

  175.       memory referenced by <em class="parameter"><code>ptr</code></em> to be made available for
    176. 

  176.       future allocations.</p><p>The <code class="function">nallocm</code>(<em class="parameter"><code></code></em>) function allocates no
    177. 

  177.       memory, but it performs the same size computation as the
    178. 

  178.       <code class="function">allocm</code>(<em class="parameter"><code></code></em>) function, and if
    179. 

  179.       <em class="parameter"><code>rsize</code></em> is not <code class="constant">NULL</code> it sets
    180. 

  180.       <em class="parameter"><code>*rsize</code></em> to the real size of the allocation that
    181. 

  181.       would result from the equivalent <code class="function">allocm</code>(<em class="parameter"><code></code></em>)
    182. 

  182.       function call.  Behavior is undefined if
    183. 

  183.       <em class="parameter"><code>size</code></em> is <code class="constant">0</code>.</p></div></div><div class="refsect1" title="TUNING"><a name="tuning"></a><h2>TUNING</h2><p>Once, when the first call is made to one of the memory allocation
    184. 

  184.     routines, the allocator initializes its internals based in part on various
    185. 

  185.     options that can be specified at compile- or run-time.</p><p>The string pointed to by the global variable
    186. 

  186.     <code class="varname">malloc_conf</code>, the &#8220;name&#8221; of the file
    187. 

  187.     referenced by the symbolic link named <code class="filename">/etc/malloc.conf</code>, and the value of the
    188. 

  188.     environment variable <code class="envar">MALLOC_CONF</code>, will be interpreted, in
    189. 

  189.     that order, from left to right as options.</p><p>An options string is a comma-separated list of option:value pairs.
    190. 

  190.     There is one key corresponding to each <a class="link" href="#opt.abort">
    191. 

  191.     "<code class="mallctl">opt.*</code>"
    192. 

  192.   </a> mallctl (see the <a class="xref" href="#mallctl_namespace" title="MALLCTL NAMESPACE">MALLCTL NAMESPACE</a> section for options
    193. 

  193.     documentation).  For example, <code class="literal">abort:true,narenas:1</code> sets
    194. 

  194.     the <a class="link" href="#opt.abort">
    195. 

  195.     "<code class="mallctl">opt.abort</code>"
    196. 

  196.   </a> and <a class="link" href="#opt.narenas">
    197. 

  197.     "<code class="mallctl">opt.narenas</code>"
    198. 

  198.   </a> options.  Some
    199. 

  199.     options have boolean values (true/false), others have integer values (base
    200. 

  200.     8, 10, or 16, depending on prefix), and yet others have raw string
    201. 

  201.     values.</p></div><div class="refsect1" title="IMPLEMENTATION NOTES"><a name="implementation_notes"></a><h2>IMPLEMENTATION NOTES</h2><p>Traditionally, allocators have used
    202. 

  202.     <span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span> to obtain memory, which is
    203. 

  203.     suboptimal for several reasons, including race conditions, increased
    204. 

  204.     fragmentation, and artificial limitations on maximum usable memory.  If
    205. 

  205.     <code class="option">--enable-dss</code> is specified during configuration, this
    206. 

  206.     allocator uses both <span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span> and
    207. 

  207.     <span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span>, in that order of preference;
    208. 

  208.     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
    209. 

  209.     contention for threaded programs on multi-processor systems.  This works
    210. 

  210.     well with regard to threading scalability, but incurs some costs.  There is
    211. 

  211.     a small fixed per-arena overhead, and additionally, arenas manage memory
    212. 

  212.     completely independently of each other, which means a small fixed increase
    213. 

  213.     in overall memory fragmentation.  These overheads are not generally an
    214. 

  214.     issue, given the number of arenas normally used.  Note that using
    215. 

  215.     substantially more arenas than the default is not likely to improve
    216. 

  216.     performance, mainly due to reduced cache performance.  However, it may make
    217. 

  217.     sense to reduce the number of arenas if an application does not make much
    218. 

  218.     use of the allocation functions.</p><p>In addition to multiple arenas, unless
    219. 

  219.     <code class="option">--disable-tcache</code> is specified during configuration, this
    220. 

  220.     allocator supports thread-specific caching for small and large objects, in
    221. 

  221.     order to make it possible to completely avoid synchronization for most
    222. 

  222.     allocation requests.  Such caching allows very fast allocation in the
    223. 

  223.     common case, but it increases memory usage and fragmentation, since a
    224. 

  224.     bounded number of objects can remain allocated in each thread cache.</p><p>Memory is conceptually broken into equal-sized chunks, where the
    225. 

  225.     chunk size is a power of two that is greater than the page size.  Chunks
    226. 

  226.     are always aligned to multiples of the chunk size.  This alignment makes it
    227. 

  227.     possible to find metadata for user objects very quickly.</p><p>User objects are broken into three categories according to size:
    228. 

  228.     small, large, and huge.  Small objects are smaller than one page.  Large
    229. 

  229.     objects are smaller than the chunk size.  Huge objects are a multiple of
    230. 

  230.     the chunk size.  Small and large objects are managed by arenas; huge
    231. 

  231.     objects are managed separately in a single data structure that is shared by
    232. 

  232.     all threads.  Huge objects are used by applications infrequently enough
    233. 

  233.     that this single data structure is not a scalability issue.</p><p>Each chunk that is managed by an arena tracks its contents as runs of
    234. 

  234.     contiguous pages (unused, backing a set of small objects, or backing one
    235. 

  235.     large object).  The combination of chunk alignment and chunk page maps
    236. 

  236.     makes it possible to determine all metadata regarding small and large
    237. 

  237.     allocations in constant time.</p><p>Small objects are managed in groups by page runs.  Each run maintains
    238. 

  238.     a frontier and free list to track which regions are in use.  Allocation
    239. 

  239.     requests that are no more than half the quantum (8 or 16, depending on
    240. 

  240.     architecture) are rounded up to the nearest power of two that is at least
    241. 

  241.     <code class="code">sizeof(<span class="type">double</span>)</code>.  All other small
    242. 

  242.     object size classes are multiples of the quantum, spaced such that internal
    243. 

  243.     fragmentation is limited to approximately 25% for all but the smallest size
    244. 

  244.     classes.  Allocation requests that are larger than the maximum small size
    245. 

  245.     class, but small enough to fit in an arena-managed chunk (see the <a class="link" href="#opt.lg_chunk">
    246. 

  246.     "<code class="mallctl">opt.lg_chunk</code>"
    247. 

  247.   </a> option), are
    248. 

  248.     rounded up to the nearest run size.  Allocation requests that are too large
    249. 

  249.     to fit in an arena-managed chunk are rounded up to the nearest multiple of
    250. 

  250.     the chunk size.</p><p>Allocations are packed tightly together, which can be an issue for
    251. 

  251.     multi-threaded applications.  If you need to assure that allocations do not
    252. 

  252.     suffer from cacheline sharing, round your allocation requests up to the
    253. 

  253.     nearest multiple of the cacheline size, or specify cacheline alignment when
    254. 

  254.     allocating.</p><p>Assuming 4 MiB chunks, 4 KiB pages, and a 16-byte quantum on a 64-bit
    255. 

  255.     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="7" 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, ..., 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]</td></tr><tr><td align="left">Large</td><td align="right">4 KiB</td><td align="left">[4 KiB, 8 KiB, 12 KiB, ..., 4072 KiB]</td></tr><tr><td align="left">Huge</td><td align="right">4 MiB</td><td align="left">[4 MiB, 8 MiB, 12 MiB, ...]</td></tr></tbody></table></div></div><br class="table-break"></div><div class="refsect1" title="MALLCTL NAMESPACE"><a name="mallctl_namespace"></a><h2>MALLCTL NAMESPACE</h2><p>The following names are defined in the namespace accessible via the
    256. 

  256.     <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) functions.  Value types are
    257. 

  257.     specified in parentheses, their readable/writable statuses are encoded as
    258. 

  258.     <code class="literal">rw</code>, <code class="literal">r-</code>, <code class="literal">-w</code>, or
    259. 

  259.     <code class="literal">--</code>, and required build configuration flags follow, if
    260. 

  260.     any.  A name element encoded as <code class="literal">&lt;i&gt;</code> or
    261. 

  261.     <code class="literal">&lt;j&gt;</code> indicates an integer component, where the
    262. 

  262.     integer varies from 0 to some upper value that must be determined via
    263. 

  263.     introspection.  In the case of 
    264. 

  264.     "<code class="mallctl">stats.arenas.&lt;i&gt;.*</code>"
    265. 

  265.   ,
    266. 

  266.     <code class="literal">&lt;i&gt;</code> equal to <a class="link" href="#arenas.narenas">
    267. 

  267.     "<code class="mallctl">arenas.narenas</code>"
    268. 

  268.   </a> can be
    269. 

  269.     used to access the summation of statistics from all arenas.  Take special
    270. 

  270.     note of the <a class="link" href="#epoch">
    271. 

  271.     "<code class="mallctl">epoch</code>"
    272. 

  272.   </a> mallctl,
    273. 

  273.     which controls refreshing of cached dynamic statistics.</p><div class="variablelist"><dl><dt><span class="term">
    274. 

  274.           
    275. 

  275.     "<code class="mallctl">version</code>"
    276. 

  276.   
    277. 

  277.           (<span class="type">const char *</span>)
    278. 

  278.           <code class="literal">r-</code>
    279. 

  279.         </span></dt><dd><p>Return the jemalloc version string.</p></dd><dt><a name="epoch"></a><span class="term">
    280. 

  280.           
    281. 

  281.     "<code class="mallctl">epoch</code>"
    282. 

  282.   
    283. 

  283.           (<span class="type">uint64_t</span>)
    284. 

  284.           <code class="literal">rw</code>
    285. 

  285.         </span></dt><dd><p>If a value is passed in, refresh the data from which
    286. 

  286.         the <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) functions report values,
    287. 

  287.         and increment the epoch.  Return the current epoch.  This is useful for
    288. 

  288.         detecting whether another thread caused a refresh.</p></dd><dt><span class="term">
    289. 

  289.           
    290. 

  290.     "<code class="mallctl">config.debug</code>"
    291. 

  291.   
    292. 

  292.           (<span class="type">bool</span>)
    293. 

  293.           <code class="literal">r-</code>
    294. 

  294.         </span></dt><dd><p><code class="option">--enable-debug</code> was specified during
    295. 

  295.         build configuration.</p></dd><dt><span class="term">
    296. 

  296.           
    297. 

  297.     "<code class="mallctl">config.dss</code>"
    298. 

  298.   
    299. 

  299.           (<span class="type">bool</span>)
    300. 

  300.           <code class="literal">r-</code>
    301. 

  301.         </span></dt><dd><p><code class="option">--enable-dss</code> was specified during
    302. 

  302.         build configuration.</p></dd><dt><span class="term">
    303. 

  303.           
    304. 

  304.     "<code class="mallctl">config.fill</code>"
    305. 

  305.   
    306. 

  306.           (<span class="type">bool</span>)
    307. 

  307.           <code class="literal">r-</code>
    308. 

  308.         </span></dt><dd><p><code class="option">--enable-fill</code> was specified during
    309. 

  309.         build configuration.</p></dd><dt><span class="term">
    310. 

  310.           
    311. 

  311.     "<code class="mallctl">config.lazy_lock</code>"
    312. 

  312.   
    313. 

  313.           (<span class="type">bool</span>)
    314. 

  314.           <code class="literal">r-</code>
    315. 

  315.         </span></dt><dd><p><code class="option">--enable-lazy-lock</code> was specified
    316. 

  316.         during build configuration.</p></dd><dt><span class="term">
    317. 

  317.           
    318. 

  318.     "<code class="mallctl">config.mremap</code>"
    319. 

  319.   
    320. 

  320.           (<span class="type">bool</span>)
    321. 

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

  322.         </span></dt><dd><p><code class="option">--enable-mremap</code> was specified during
    323. 

  323.         build configuration.</p></dd><dt><span class="term">
    324. 

  324.           
    325. 

  325.     "<code class="mallctl">config.munmap</code>"
    326. 

  326.   
    327. 

  327.           (<span class="type">bool</span>)
    328. 

  328.           <code class="literal">r-</code>
    329. 

  329.         </span></dt><dd><p><code class="option">--enable-munmap</code> was specified during
    330. 

  330.         build configuration.</p></dd><dt><span class="term">
    331. 

  331.           
    332. 

  332.     "<code class="mallctl">config.prof</code>"
    333. 

  333.   
    334. 

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

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

  336.         </span></dt><dd><p><code class="option">--enable-prof</code> was specified during
    337. 

  337.         build configuration.</p></dd><dt><span class="term">
    338. 

  338.           
    339. 

  339.     "<code class="mallctl">config.prof_libgcc</code>"
    340. 

  340.   
    341. 

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

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

  343.         </span></dt><dd><p><code class="option">--disable-prof-libgcc</code> was not
    344. 

  344.         specified during build configuration.</p></dd><dt><span class="term">
    345. 

  345.           
    346. 

  346.     "<code class="mallctl">config.prof_libunwind</code>"
    347. 

  347.   
    348. 

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

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

  350.         </span></dt><dd><p><code class="option">--enable-prof-libunwind</code> was specified
    351. 

  351.         during build configuration.</p></dd><dt><span class="term">
    352. 

  352.           
    353. 

  353.     "<code class="mallctl">config.stats</code>"
    354. 

  354.   
    355. 

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

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

  357.         </span></dt><dd><p><code class="option">--enable-stats</code> was specified during
    358. 

  358.         build configuration.</p></dd><dt><span class="term">
    359. 

  359.           
    360. 

  360.     "<code class="mallctl">config.tcache</code>"
    361. 

  361.   
    362. 

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

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

  364.         </span></dt><dd><p><code class="option">--disable-tcache</code> was not specified
    365. 

  365.         during build configuration.</p></dd><dt><span class="term">
    366. 

  366.           
    367. 

  367.     "<code class="mallctl">config.tls</code>"
    368. 

  368.   
    369. 

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

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

  371.         </span></dt><dd><p><code class="option">--disable-tls</code> was not specified during
    372. 

  372.         build configuration.</p></dd><dt><span class="term">
    373. 

  373.           
    374. 

  374.     "<code class="mallctl">config.utrace</code>"
    375. 

  375.   
    376. 

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

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

  378.         </span></dt><dd><p><code class="option">--enable-utrace</code> was specified during
    379. 

  379.         build configuration.</p></dd><dt><span class="term">
    380. 

  380.           
    381. 

  381.     "<code class="mallctl">config.valgrind</code>"
    382. 

  382.   
    383. 

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

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

  385.         </span></dt><dd><p><code class="option">--enable-valgrind</code> was specified during
    386. 

  386.         build configuration.</p></dd><dt><span class="term">
    387. 

  387.           
    388. 

  388.     "<code class="mallctl">config.xmalloc</code>"
    389. 

  389.   
    390. 

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

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

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

  393.         build configuration.</p></dd><dt><a name="opt.abort"></a><span class="term">
    394. 

  394.           
    395. 

  395.     "<code class="mallctl">opt.abort</code>"
    396. 

  396.   
    397. 

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

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

  399.         </span></dt><dd><p>Abort-on-warning enabled/disabled.  If true, most
    400. 

  400.         warnings are fatal.  The process will call
    401. 

  401.         <span class="citerefentry"><span class="refentrytitle">abort</span>(3)</span> in these cases.  This option is
    402. 

  402.         disabled by default unless <code class="option">--enable-debug</code> is
    403. 

  403.         specified during configuration, in which case it is enabled by default.
    404. 

  404.         </p></dd><dt><a name="opt.lg_chunk"></a><span class="term">
    405. 

  405.           
    406. 

  406.     "<code class="mallctl">opt.lg_chunk</code>"
    407. 

  407.   
    408. 

  408.           (<span class="type">size_t</span>)
    409. 

  409.           <code class="literal">r-</code>
    410. 

  410.         </span></dt><dd><p>Virtual memory chunk size (log base 2).  The default
    411. 

  411.         chunk size is 4 MiB (2^22).</p></dd><dt><a name="opt.dss"></a><span class="term">
    412. 

  412.           
    413. 

  413.     "<code class="mallctl">opt.dss</code>"
    414. 

  414.   
    415. 

  415.           (<span class="type">const char *</span>)
    416. 

  416.           <code class="literal">r-</code>
    417. 

  417.         </span></dt><dd><p>dss (<span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span>) allocation precedence as
    418. 

  418.         related to <span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span> allocation.  The following
    419. 

  419.         settings are supported: &#8220;disabled&#8221;, &#8220;primary&#8221;,
    420. 

  420.         and &#8220;secondary&#8221; (default).</p></dd><dt><a name="opt.narenas"></a><span class="term">
    421. 

  421.           
    422. 

  422.     "<code class="mallctl">opt.narenas</code>"
    423. 

  423.   
    424. 

  424.           (<span class="type">size_t</span>)
    425. 

  425.           <code class="literal">r-</code>
    426. 

  426.         </span></dt><dd><p>Maximum number of arenas to use for automatic
    427. 

  427.         multiplexing of threads and arenas.  The default is four times the
    428. 

  428.         number of CPUs, or one if there is a single CPU.</p></dd><dt><a name="opt.lg_dirty_mult"></a><span class="term">
    429. 

  429.           
    430. 

  430.     "<code class="mallctl">opt.lg_dirty_mult</code>"
    431. 

  431.   
    432. 

  432.           (<span class="type">ssize_t</span>)
    433. 

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

  434.         </span></dt><dd><p>Per-arena minimum ratio (log base 2) of active to dirty
    435. 

  435.         pages.  Some dirty unused pages may be allowed to accumulate, within
    436. 

  436.         the limit set by the ratio (or one chunk worth of dirty pages,
    437. 

  437.         whichever is greater), before informing the kernel about some of those
    438. 

  438.         pages via <span class="citerefentry"><span class="refentrytitle">madvise</span>(2)</span> or a similar system call.  This
    439. 

  439.         provides the kernel with sufficient information to recycle dirty pages
    440. 

  440.         if physical memory becomes scarce and the pages remain unused.  The
    441. 

  441.         default minimum ratio is 8:1 (2^3:1); an option value of -1 will
    442. 

  442.         disable dirty page purging.</p></dd><dt><a name="opt.stats_print"></a><span class="term">
    443. 

  443.           
    444. 

  444.     "<code class="mallctl">opt.stats_print</code>"
    445. 

  445.   
    446. 

  446.           (<span class="type">bool</span>)
    447. 

  447.           <code class="literal">r-</code>
    448. 

  448.         </span></dt><dd><p>Enable/disable statistics printing at exit.  If
    449. 

  449.         enabled, the <code class="function">malloc_stats_print</code>(<em class="parameter"><code></code></em>)
    450. 

  450.         function is called at program exit via an
    451. 

  451.         <span class="citerefentry"><span class="refentrytitle">atexit</span>(3)</span> function.  If
    452. 

  452.         <code class="option">--enable-stats</code> is specified during configuration, this
    453. 

  453.         has the potential to cause deadlock for a multi-threaded process that
    454. 

  454.         exits while one or more threads are executing in the memory allocation
    455. 

  455.         functions.  Therefore, this option should only be used with care; it is
    456. 

  456.         primarily intended as a performance tuning aid during application
    457. 

  457.         development.  This option is disabled by default.</p></dd><dt><a name="opt.junk"></a><span class="term">
    458. 

  458.           
    459. 

  459.     "<code class="mallctl">opt.junk</code>"
    460. 

  460.   
    461. 

  461.           (<span class="type">bool</span>)
    462. 

  462.           <code class="literal">r-</code>
    463. 

  463.           [<code class="option">--enable-fill</code>]
    464. 

  464.         </span></dt><dd><p>Junk filling enabled/disabled.  If enabled, each byte
    465. 

  465.         of uninitialized allocated memory will be initialized to
    466. 

  466.         <code class="literal">0xa5</code>.  All deallocated memory will be initialized to
    467. 

  467.         <code class="literal">0x5a</code>.  This is intended for debugging and will
    468. 

  468.         impact performance negatively.  This option is disabled by default
    469. 

  469.         unless <code class="option">--enable-debug</code> is specified during
    470. 

  470.         configuration, in which case it is enabled by default unless running
    471. 

  471.         inside <a class="ulink" href="http://valgrind.org/" target="_top">Valgrind</a>.</p></dd><dt><a name="opt.quarantine"></a><span class="term">
    472. 

  472.           
    473. 

  473.     "<code class="mallctl">opt.quarantine</code>"
    474. 

  474.   
    475. 

  475.           (<span class="type">size_t</span>)
    476. 

  476.           <code class="literal">r-</code>
    477. 

  477.           [<code class="option">--enable-fill</code>]
    478. 

  478.         </span></dt><dd><p>Per thread quarantine size in bytes.  If non-zero, each
    479. 

  479.         thread maintains a FIFO object quarantine that stores up to the
    480. 

  480.         specified number of bytes of memory.  The quarantined memory is not
    481. 

  481.         freed until it is released from quarantine, though it is immediately
    482. 

  482.         junk-filled if the <a class="link" href="#opt.junk">
    483. 

  483.     "<code class="mallctl">opt.junk</code>"
    484. 

  484.   </a> option is
    485. 

  485.         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
    486. 

  486.         to access quarantined objects.  This is intended for debugging and will
    487. 

  487.         impact performance negatively.  The default quarantine size is 0 unless
    488. 

  488.         running inside Valgrind, in which case the default is 16
    489. 

  489.         MiB.</p></dd><dt><a name="opt.redzone"></a><span class="term">
    490. 

  490.           
    491. 

  491.     "<code class="mallctl">opt.redzone</code>"
    492. 

  492.   
    493. 

  493.           (<span class="type">bool</span>)
    494. 

  494.           <code class="literal">r-</code>
    495. 

  495.           [<code class="option">--enable-fill</code>]
    496. 

  496.         </span></dt><dd><p>Redzones enabled/disabled.  If enabled, small
    497. 

  497.         allocations have redzones before and after them.  Furthermore, if the
    498. 

  498.         <a class="link" href="#opt.junk">
    499. 

  499.     "<code class="mallctl">opt.junk</code>"
    500. 

  500.   </a> option is
    501. 

  501.         enabled, the redzones are checked for corruption during deallocation.
    502. 

  502.         However, the primary intended purpose of this feature is to be used in
    503. 

  503.         combination with <a class="ulink" href="http://valgrind.org/" target="_top">Valgrind</a>,
    504. 

  504.         which needs redzones in order to do effective buffer overflow/underflow
    505. 

  505.         detection.  This option is intended for debugging and will impact
    506. 

  506.         performance negatively.  This option is disabled by
    507. 

  507.         default unless running inside Valgrind.</p></dd><dt><a name="opt.zero"></a><span class="term">
    508. 

  508.           
    509. 

  509.     "<code class="mallctl">opt.zero</code>"
    510. 

  510.   
    511. 

  511.           (<span class="type">bool</span>)
    512. 

  512.           <code class="literal">r-</code>
    513. 

  513.           [<code class="option">--enable-fill</code>]
    514. 

  514.         </span></dt><dd><p>Zero filling enabled/disabled.  If enabled, each byte
    515. 

  515.         of uninitialized allocated memory will be initialized to 0.  Note that
    516. 

  516.         this initialization only happens once for each byte, so
    517. 

  517.         <code class="function">realloc</code>(<em class="parameter"><code></code></em>) and
    518. 

  518.         <code class="function">rallocm</code>(<em class="parameter"><code></code></em>) calls do not zero memory that
    519. 

  519.         was previously allocated.  This is intended for debugging and will
    520. 

  520.         impact performance negatively.  This option is disabled by default.
    521. 

  521.         </p></dd><dt><a name="opt.utrace"></a><span class="term">
    522. 

  522.           
    523. 

  523.     "<code class="mallctl">opt.utrace</code>"
    524. 

  524.   
    525. 

  525.           (<span class="type">bool</span>)
    526. 

  526.           <code class="literal">r-</code>
    527. 

  527.           [<code class="option">--enable-utrace</code>]
    528. 

  528.         </span></dt><dd><p>Allocation tracing based on
    529. 

  529.         <span class="citerefentry"><span class="refentrytitle">utrace</span>(2)</span> enabled/disabled.  This option
    530. 

  530.         is disabled by default.</p></dd><dt><a name="opt.valgrind"></a><span class="term">
    531. 

  531.           
    532. 

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

  533.   
    534. 

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

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

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

  537.         </span></dt><dd><p><a class="ulink" href="http://valgrind.org/" target="_top">Valgrind</a>
    538. 

  538.         support enabled/disabled.  This option is vestigal because jemalloc
    539. 

  539.         auto-detects whether it is running inside Valgrind.  This option is
    540. 

  540.         disabled by default, unless running inside Valgrind.</p></dd><dt><a name="opt.xmalloc"></a><span class="term">
    541. 

  541.           
    542. 

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

  543.   
    544. 

  544.           (<span class="type">bool</span>)
    545. 

  545.           <code class="literal">r-</code>
    546. 

  546.           [<code class="option">--enable-xmalloc</code>]
    547. 

  547.         </span></dt><dd><p>Abort-on-out-of-memory enabled/disabled.  If enabled,
    548. 

  548.         rather than returning failure for any allocation function, display a
    549. 

  549.         diagnostic message on <code class="constant">STDERR_FILENO</code> and cause the
    550. 

  550.         program to drop core (using
    551. 

  551.         <span class="citerefentry"><span class="refentrytitle">abort</span>(3)</span>).  If an application is
    552. 

  552.         designed to depend on this behavior, set the option at compile time by
    553. 

  553.         including the following in the source code:
    554. 

  554.         </p><pre class="programlisting">
    555. 

  555. malloc_conf = "xmalloc:true";</pre><p>
    556. 

  556.         This option is disabled by default.</p></dd><dt><a name="opt.tcache"></a><span class="term">
    557. 

  557.           
    558. 

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

  559.   
    560. 

  560.           (<span class="type">bool</span>)
    561. 

  561.           <code class="literal">r-</code>
    562. 

  562.           [<code class="option">--enable-tcache</code>]
    563. 

  563.         </span></dt><dd><p>Thread-specific caching enabled/disabled.  When there
    564. 

  564.         are multiple threads, each thread uses a thread-specific cache for
    565. 

  565.         objects up to a certain size.  Thread-specific caching allows many
    566. 

  566.         allocations to be satisfied without performing any thread
    567. 

  567.         synchronization, at the cost of increased memory use.  See the
    568. 

  568.         <a class="link" href="#opt.lg_tcache_max">
    569. 

  569.     "<code class="mallctl">opt.lg_tcache_max</code>"
    570. 

  570.   </a>
    571. 

  571.         option for related tuning information.  This option is enabled by
    572. 

  572.         default unless running inside <a class="ulink" href="http://valgrind.org/" target="_top">Valgrind</a>.</p></dd><dt><a name="opt.lg_tcache_max"></a><span class="term">
    573. 

  573.           
    574. 

  574.     "<code class="mallctl">opt.lg_tcache_max</code>"
    575. 

  575.   
    576. 

  576.           (<span class="type">size_t</span>)
    577. 

  577.           <code class="literal">r-</code>
    578. 

  578.           [<code class="option">--enable-tcache</code>]
    579. 

  579.         </span></dt><dd><p>Maximum size class (log base 2) to cache in the
    580. 

  580.         thread-specific cache.  At a minimum, all small size classes are
    581. 

  581.         cached, and at a maximum all large size classes are cached.  The
    582. 

  582.         default maximum is 32 KiB (2^15).</p></dd><dt><a name="opt.prof"></a><span class="term">
    583. 

  583.           
    584. 

  584.     "<code class="mallctl">opt.prof</code>"
    585. 

  585.   
    586. 

  586.           (<span class="type">bool</span>)
    587. 

  587.           <code class="literal">r-</code>
    588. 

  588.           [<code class="option">--enable-prof</code>]
    589. 

  589.         </span></dt><dd><p>Memory profiling enabled/disabled.  If enabled, profile
    590. 

  590.         memory allocation activity.  See the <a class="link" href="#opt.prof_active">
    591. 

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

  592.   </a>
    593. 

  593.         option for on-the-fly activation/deactivation.  See the <a class="link" href="#opt.lg_prof_sample">
    594. 

  594.     "<code class="mallctl">opt.lg_prof_sample</code>"
    595. 

  595.   </a>
    596. 

  596.         option for probabilistic sampling control.  See the <a class="link" href="#opt.prof_accum">
    597. 

  597.     "<code class="mallctl">opt.prof_accum</code>"
    598. 

  598.   </a>
    599. 

  599.         option for control of cumulative sample reporting.  See the <a class="link" href="#opt.lg_prof_interval">
    600. 

  600.     "<code class="mallctl">opt.lg_prof_interval</code>"
    601. 

  601.   </a>
    602. 

  602.         option for information on interval-triggered profile dumping, the <a class="link" href="#opt.prof_gdump">
    603. 

  603.     "<code class="mallctl">opt.prof_gdump</code>"
    604. 

  604.   </a>
    605. 

  605.         option for information on high-water-triggered profile dumping, and the
    606. 

  606.         <a class="link" href="#opt.prof_final">
    607. 

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

  608.   </a>
    609. 

  609.         option for final profile dumping.  Profile output is compatible with
    610. 

  610.         the included <span class="command"><strong>pprof</strong></span> Perl script, which originates
    611. 

  611.         from the <a class="ulink" href="http://code.google.com/p/gperftools/" target="_top">gperftools
    612. 

  612.         package</a>.</p></dd><dt><a name="opt.prof_prefix"></a><span class="term">
    613. 

  613.           
    614. 

  614.     "<code class="mallctl">opt.prof_prefix</code>"
    615. 

  615.   
    616. 

  616.           (<span class="type">const char *</span>)
    617. 

  617.           <code class="literal">r-</code>
    618. 

  618.           [<code class="option">--enable-prof</code>]
    619. 

  619.         </span></dt><dd><p>Filename prefix for profile dumps.  If the prefix is
    620. 

  620.         set to the empty string, no automatic dumps will occur; this is
    621. 

  621.         primarily useful for disabling the automatic final heap dump (which
    622. 

  622.         also disables leak reporting, if enabled).  The default prefix is
    623. 

  623.         <code class="filename">jeprof</code>.</p></dd><dt><a name="opt.prof_active"></a><span class="term">
    624. 

  624.           
    625. 

  625.     "<code class="mallctl">opt.prof_active</code>"
    626. 

  626.   
    627. 

  627.           (<span class="type">bool</span>)
    628. 

  628.           <code class="literal">r-</code>
    629. 

  629.           [<code class="option">--enable-prof</code>]
    630. 

  630.         </span></dt><dd><p>Profiling activated/deactivated.  This is a secondary
    631. 

  631.         control mechanism that makes it possible to start the application with
    632. 

  632.         profiling enabled (see the <a class="link" href="#opt.prof">
    633. 

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

  634.   </a> option) but
    635. 

  635.         inactive, then toggle profiling at any time during program execution
    636. 

  636.         with the <a class="link" href="#prof.active">
    637. 

  637.     "<code class="mallctl">prof.active</code>"
    638. 

  638.   </a> mallctl.
    639. 

  639.         This option is enabled by default.</p></dd><dt><a name="opt.lg_prof_sample"></a><span class="term">
    640. 

  640.           
    641. 

  641.     "<code class="mallctl">opt.lg_prof_sample</code>"
    642. 

  642.   
    643. 

  643.           (<span class="type">ssize_t</span>)
    644. 

  644.           <code class="literal">r-</code>
    645. 

  645.           [<code class="option">--enable-prof</code>]
    646. 

  646.         </span></dt><dd><p>Average interval (log base 2) between allocation
    647. 

  647.         samples, as measured in bytes of allocation activity.  Increasing the
    648. 

  648.         sampling interval decreases profile fidelity, but also decreases the
    649. 

  649.         computational overhead.  The default sample interval is 512 KiB (2^19
    650. 

  650.         B).</p></dd><dt><a name="opt.prof_accum"></a><span class="term">
    651. 

  651.           
    652. 

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

  653.   
    654. 

  654.           (<span class="type">bool</span>)
    655. 

  655.           <code class="literal">r-</code>
    656. 

  656.           [<code class="option">--enable-prof</code>]
    657. 

  657.         </span></dt><dd><p>Reporting of cumulative object/byte counts in profile
    658. 

  658.         dumps enabled/disabled.  If this option is enabled, every unique
    659. 

  659.         backtrace must be stored for the duration of execution.  Depending on
    660. 

  660.         the application, this can impose a large memory overhead, and the
    661. 

  661.         cumulative counts are not always of interest.  This option is disabled
    662. 

  662.         by default.</p></dd><dt><a name="opt.lg_prof_interval"></a><span class="term">
    663. 

  663.           
    664. 

  664.     "<code class="mallctl">opt.lg_prof_interval</code>"
    665. 

  665.   
    666. 

  666.           (<span class="type">ssize_t</span>)
    667. 

  667.           <code class="literal">r-</code>
    668. 

  668.           [<code class="option">--enable-prof</code>]
    669. 

  669.         </span></dt><dd><p>Average interval (log base 2) between memory profile
    670. 

  670.         dumps, as measured in bytes of allocation activity.  The actual
    671. 

  671.         interval between dumps may be sporadic because decentralized allocation
    672. 

  672.         counters are used to avoid synchronization bottlenecks.  Profiles are
    673. 

  673.         dumped to files named according to the pattern
    674. 

  674.         <code class="filename">&lt;prefix&gt;.&lt;pid&gt;.&lt;seq&gt;.i&lt;iseq&gt;.heap</code>,
    675. 

  675.         where <code class="literal">&lt;prefix&gt;</code> is controlled by the
    676. 

  676.         <a class="link" href="#opt.prof_prefix">
    677. 

  677.     "<code class="mallctl">opt.prof_prefix</code>"
    678. 

  678.   </a>
    679. 

  679.         option.  By default, interval-triggered profile dumping is disabled
    680. 

  680.         (encoded as -1).
    681. 

  681.         </p></dd><dt><a name="opt.prof_gdump"></a><span class="term">
    682. 

  682.           
    683. 

  683.     "<code class="mallctl">opt.prof_gdump</code>"
    684. 

  684.   
    685. 

  685.           (<span class="type">bool</span>)
    686. 

  686.           <code class="literal">r-</code>
    687. 

  687.           [<code class="option">--enable-prof</code>]
    688. 

  688.         </span></dt><dd><p>Trigger a memory profile dump every time the total
    689. 

  689.         virtual memory exceeds the previous maximum.  Profiles are dumped to
    690. 

  690.         files named according to the pattern
    691. 

  691.         <code class="filename">&lt;prefix&gt;.&lt;pid&gt;.&lt;seq&gt;.u&lt;useq&gt;.heap</code>,
    692. 

  692.         where <code class="literal">&lt;prefix&gt;</code> is controlled by the <a class="link" href="#opt.prof_prefix">
    693. 

  693.     "<code class="mallctl">opt.prof_prefix</code>"
    694. 

  694.   </a>
    695. 

  695.         option.  This option is disabled by default.</p></dd><dt><a name="opt.prof_final"></a><span class="term">
    696. 

  696.           
    697. 

  697.     "<code class="mallctl">opt.prof_final</code>"
    698. 

  698.   
    699. 

  699.           (<span class="type">bool</span>)
    700. 

  700.           <code class="literal">r-</code>
    701. 

  701.           [<code class="option">--enable-prof</code>]
    702. 

  702.         </span></dt><dd><p>Use an
    703. 

  703.         <span class="citerefentry"><span class="refentrytitle">atexit</span>(3)</span> function to dump final memory
    704. 

  704.         usage to a file named according to the pattern
    705. 

  705.         <code class="filename">&lt;prefix&gt;.&lt;pid&gt;.&lt;seq&gt;.f.heap</code>,
    706. 

  706.         where <code class="literal">&lt;prefix&gt;</code> is controlled by the <a class="link" href="#opt.prof_prefix">
    707. 

  707.     "<code class="mallctl">opt.prof_prefix</code>"
    708. 

  708.   </a>
    709. 

  709.         option.  This option is enabled by default.</p></dd><dt><a name="opt.prof_leak"></a><span class="term">
    710. 

  710.           
    711. 

  711.     "<code class="mallctl">opt.prof_leak</code>"
    712. 

  712.   
    713. 

  713.           (<span class="type">bool</span>)
    714. 

  714.           <code class="literal">r-</code>
    715. 

  715.           [<code class="option">--enable-prof</code>]
    716. 

  716.         </span></dt><dd><p>Leak reporting enabled/disabled.  If enabled, use an
    717. 

  717.         <span class="citerefentry"><span class="refentrytitle">atexit</span>(3)</span> function to report memory leaks
    718. 

  718.         detected by allocation sampling.  See the
    719. 

  719.         <a class="link" href="#opt.prof">
    720. 

  720.     "<code class="mallctl">opt.prof</code>"
    721. 

  721.   </a> option for
    722. 

  722.         information on analyzing heap profile output.  This option is disabled
    723. 

  723.         by default.</p></dd><dt><span class="term">
    724. 

  724.           
    725. 

  725.     "<code class="mallctl">thread.arena</code>"
    726. 

  726.   
    727. 

  727.           (<span class="type">unsigned</span>)
    728. 

  728.           <code class="literal">rw</code>
    729. 

  729.         </span></dt><dd><p>Get or set the arena associated with the calling
    730. 

  730.         thread.  If the specified arena was not initialized beforehand (see the
    731. 

  731.         <a class="link" href="#arenas.initialized">
    732. 

  732.     "<code class="mallctl">arenas.initialized</code>"
    733. 

  733.   </a>
    734. 

  734.         mallctl), it will be automatically initialized as a side effect of
    735. 

  735.         calling this interface.</p></dd><dt><a name="thread.allocated"></a><span class="term">
    736. 

  736.           
    737. 

  737.     "<code class="mallctl">thread.allocated</code>"
    738. 

  738.   
    739. 

  739.           (<span class="type">uint64_t</span>)
    740. 

  740.           <code class="literal">r-</code>
    741. 

  741.           [<code class="option">--enable-stats</code>]
    742. 

  742.         </span></dt><dd><p>Get the total number of bytes ever allocated by the
    743. 

  743.         calling thread.  This counter has the potential to wrap around; it is
    744. 

  744.         up to the application to appropriately interpret the counter in such
    745. 

  745.         cases.</p></dd><dt><span class="term">
    746. 

  746.           
    747. 

  747.     "<code class="mallctl">thread.allocatedp</code>"
    748. 

  748.   
    749. 

  749.           (<span class="type">uint64_t *</span>)
    750. 

  750.           <code class="literal">r-</code>
    751. 

  751.           [<code class="option">--enable-stats</code>]
    752. 

  752.         </span></dt><dd><p>Get a pointer to the the value that is returned by the
    753. 

  753.         <a class="link" href="#thread.allocated">
    754. 

  754.     "<code class="mallctl">thread.allocated</code>"
    755. 

  755.   </a>
    756. 

  756.         mallctl.  This is useful for avoiding the overhead of repeated
    757. 

  757.         <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) calls.</p></dd><dt><a name="thread.deallocated"></a><span class="term">
    758. 

  758.           
    759. 

  759.     "<code class="mallctl">thread.deallocated</code>"
    760. 

  760.   
    761. 

  761.           (<span class="type">uint64_t</span>)
    762. 

  762.           <code class="literal">r-</code>
    763. 

  763.           [<code class="option">--enable-stats</code>]
    764. 

  764.         </span></dt><dd><p>Get the total number of bytes ever deallocated by the
    765. 

  765.         calling thread.  This counter has the potential to wrap around; it is
    766. 

  766.         up to the application to appropriately interpret the counter in such
    767. 

  767.         cases.</p></dd><dt><span class="term">
    768. 

  768.           
    769. 

  769.     "<code class="mallctl">thread.deallocatedp</code>"
    770. 

  770.   
    771. 

  771.           (<span class="type">uint64_t *</span>)
    772. 

  772.           <code class="literal">r-</code>
    773. 

  773.           [<code class="option">--enable-stats</code>]
    774. 

  774.         </span></dt><dd><p>Get a pointer to the the value that is returned by the
    775. 

  775.         <a class="link" href="#thread.deallocated">
    776. 

  776.     "<code class="mallctl">thread.deallocated</code>"
    777. 

  777.   </a>
    778. 

  778.         mallctl.  This is useful for avoiding the overhead of repeated
    779. 

  779.         <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) calls.</p></dd><dt><span class="term">
    780. 

  780.           
    781. 

  781.     "<code class="mallctl">thread.tcache.enabled</code>"
    782. 

  782.   
    783. 

  783.           (<span class="type">bool</span>)
    784. 

  784.           <code class="literal">rw</code>
    785. 

  785.           [<code class="option">--enable-tcache</code>]
    786. 

  786.         </span></dt><dd><p>Enable/disable calling thread's tcache.  The tcache is
    787. 

  787.         implicitly flushed as a side effect of becoming
    788. 

  788.         disabled (see 
    789. 

  789.     "<code class="mallctl">thread.tcache.flush</code>"
    790. 

  790.   ).
    791. 

  791.         </p></dd><dt><span class="term">
    792. 

  792.           
    793. 

  793.     "<code class="mallctl">thread.tcache.flush</code>"
    794. 

  794.   
    795. 

  795.           (<span class="type">void</span>)
    796. 

  796.           <code class="literal">--</code>
    797. 

  797.           [<code class="option">--enable-tcache</code>]
    798. 

  798.         </span></dt><dd><p>Flush calling thread's tcache.  This interface releases
    799. 

  799.         all cached objects and internal data structures associated with the
    800. 

  800.         calling thread's thread-specific cache.  Ordinarily, this interface
    801. 

  801.         need not be called, since automatic periodic incremental garbage
    802. 

  802.         collection occurs, and the thread cache is automatically discarded when
    803. 

  803.         a thread exits.  However, garbage collection is triggered by allocation
    804. 

  804.         activity, so it is possible for a thread that stops
    805. 

  805.         allocating/deallocating to retain its cache indefinitely, in which case
    806. 

  806.         the developer may find manual flushing useful.</p></dd><dt><a name="arena.i.purge"></a><span class="term">
    807. 

  807.           
    808. 

  808.     "<code class="mallctl">arena.&lt;i&gt;.purge</code>"
    809. 

  809.   
    810. 

  810.           (<span class="type">unsigned</span>)
    811. 

  811.           <code class="literal">--</code>
    812. 

  812.         </span></dt><dd><p>Purge unused dirty pages for arena &lt;i&gt;, or for
    813. 

  813.         all arenas if &lt;i&gt; equals <a class="link" href="#arenas.narenas">
    814. 

  814.     "<code class="mallctl">arenas.narenas</code>"
    815. 

  815.   </a>.
    816. 

  816.         </p></dd><dt><a name="arena.i.dss"></a><span class="term">
    817. 

  817.           
    818. 

  818.     "<code class="mallctl">arena.&lt;i&gt;.dss</code>"
    819. 

  819.   
    820. 

  820.           (<span class="type">const char *</span>)
    821. 

  821.           <code class="literal">rw</code>
    822. 

  822.         </span></dt><dd><p>Set the precedence of dss allocation as related to mmap
    823. 

  823.         allocation for arena &lt;i&gt;, or for all arenas if &lt;i&gt; equals
    824. 

  824.         <a class="link" href="#arenas.narenas">
    825. 

  825.     "<code class="mallctl">arenas.narenas</code>"
    826. 

  826.   </a>.  See
    827. 

  827.         <a class="link" href="#opt.dss">
    828. 

  828.     "<code class="mallctl">opt.dss</code>"
    829. 

  829.   </a> for supported
    830. 

  830.         settings.
    831. 

  831.         </p></dd><dt><a name="arenas.narenas"></a><span class="term">
    832. 

  832.           
    833. 

  833.     "<code class="mallctl">arenas.narenas</code>"
    834. 

  834.   
    835. 

  835.           (<span class="type">unsigned</span>)
    836. 

  836.           <code class="literal">r-</code>
    837. 

  837.         </span></dt><dd><p>Current limit on number of arenas.</p></dd><dt><a name="arenas.initialized"></a><span class="term">
    838. 

  838.           
    839. 

  839.     "<code class="mallctl">arenas.initialized</code>"
    840. 

  840.   
    841. 

  841.           (<span class="type">bool *</span>)
    842. 

  842.           <code class="literal">r-</code>
    843. 

  843.         </span></dt><dd><p>An array of <a class="link" href="#arenas.narenas">
    844. 

  844.     "<code class="mallctl">arenas.narenas</code>"
    845. 

  845.   </a>
    846. 

  846.         booleans.  Each boolean indicates whether the corresponding arena is
    847. 

  847.         initialized.</p></dd><dt><span class="term">
    848. 

  848.           
    849. 

  849.     "<code class="mallctl">arenas.quantum</code>"
    850. 

  850.   
    851. 

  851.           (<span class="type">size_t</span>)
    852. 

  852.           <code class="literal">r-</code>
    853. 

  853.         </span></dt><dd><p>Quantum size.</p></dd><dt><span class="term">
    854. 

  854.           
    855. 

  855.     "<code class="mallctl">arenas.page</code>"
    856. 

  856.   
    857. 

  857.           (<span class="type">size_t</span>)
    858. 

  858.           <code class="literal">r-</code>
    859. 

  859.         </span></dt><dd><p>Page size.</p></dd><dt><span class="term">
    860. 

  860.           
    861. 

  861.     "<code class="mallctl">arenas.tcache_max</code>"
    862. 

  862.   
    863. 

  863.           (<span class="type">size_t</span>)
    864. 

  864.           <code class="literal">r-</code>
    865. 

  865.           [<code class="option">--enable-tcache</code>]
    866. 

  866.         </span></dt><dd><p>Maximum thread-cached size class.</p></dd><dt><span class="term">
    867. 

  867.           
    868. 

  868.     "<code class="mallctl">arenas.nbins</code>"
    869. 

  869.   
    870. 

  870.           (<span class="type">unsigned</span>)
    871. 

  871.           <code class="literal">r-</code>
    872. 

  872.         </span></dt><dd><p>Number of bin size classes.</p></dd><dt><span class="term">
    873. 

  873.           
    874. 

  874.     "<code class="mallctl">arenas.nhbins</code>"
    875. 

  875.   
    876. 

  876.           (<span class="type">unsigned</span>)
    877. 

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

  878.           [<code class="option">--enable-tcache</code>]
    879. 

  879.         </span></dt><dd><p>Total number of thread cache bin size
    880. 

  880.         classes.</p></dd><dt><a name="arenas.bin.i.size"></a><span class="term">
    881. 

  881.           
    882. 

  882.     "<code class="mallctl">arenas.bin.&lt;i&gt;.size</code>"
    883. 

  883.   
    884. 

  884.           (<span class="type">size_t</span>)
    885. 

  885.           <code class="literal">r-</code>
    886. 

  886.         </span></dt><dd><p>Maximum size supported by size class.</p></dd><dt><span class="term">
    887. 

  887.           
    888. 

  888.     "<code class="mallctl">arenas.bin.&lt;i&gt;.nregs</code>"
    889. 

  889.   
    890. 

  890.           (<span class="type">uint32_t</span>)
    891. 

  891.           <code class="literal">r-</code>
    892. 

  892.         </span></dt><dd><p>Number of regions per page run.</p></dd><dt><span class="term">
    893. 

  893.           
    894. 

  894.     "<code class="mallctl">arenas.bin.&lt;i&gt;.run_size</code>"
    895. 

  895.   
    896. 

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

  897.           <code class="literal">r-</code>
    898. 

  898.         </span></dt><dd><p>Number of bytes per page run.</p></dd><dt><span class="term">
    899. 

  899.           
    900. 

  900.     "<code class="mallctl">arenas.nlruns</code>"
    901. 

  901.   
    902. 

  902.           (<span class="type">size_t</span>)
    903. 

  903.           <code class="literal">r-</code>
    904. 

  904.         </span></dt><dd><p>Total number of large size classes.</p></dd><dt><span class="term">
    905. 

  905.           
    906. 

  906.     "<code class="mallctl">arenas.lrun.&lt;i&gt;.size</code>"
    907. 

  907.   
    908. 

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

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

  910.         </span></dt><dd><p>Maximum size supported by this large size
    911. 

  911.         class.</p></dd><dt><span class="term">
    912. 

  912.           
    913. 

  913.     "<code class="mallctl">arenas.purge</code>"
    914. 

  914.   
    915. 

  915.           (<span class="type">unsigned</span>)
    916. 

  916.           <code class="literal">-w</code>
    917. 

  917.         </span></dt><dd><p>Purge unused dirty pages for the specified arena, or
    918. 

  918.         for all arenas if none is specified.</p></dd><dt><span class="term">
    919. 

  919.           
    920. 

  920.     "<code class="mallctl">arenas.extend</code>"
    921. 

  921.   
    922. 

  922.           (<span class="type">unsigned</span>)
    923. 

  923.           <code class="literal">r-</code>
    924. 

  924.         </span></dt><dd><p>Extend the array of arenas by appending a new arena,
    925. 

  925.         and returning the new arena index.</p></dd><dt><a name="prof.active"></a><span class="term">
    926. 

  926.           
    927. 

  927.     "<code class="mallctl">prof.active</code>"
    928. 

  928.   
    929. 

  929.           (<span class="type">bool</span>)
    930. 

  930.           <code class="literal">rw</code>
    931. 

  931.           [<code class="option">--enable-prof</code>]
    932. 

  932.         </span></dt><dd><p>Control whether sampling is currently active.  See the
    933. 

  933.         <a class="link" href="#opt.prof_active">
    934. 

  934.     "<code class="mallctl">opt.prof_active</code>"
    935. 

  935.   </a>
    936. 

  936.         option for additional information.
    937. 

  937.         </p></dd><dt><span class="term">
    938. 

  938.           
    939. 

  939.     "<code class="mallctl">prof.dump</code>"
    940. 

  940.   
    941. 

  941.           (<span class="type">const char *</span>)
    942. 

  942.           <code class="literal">-w</code>
    943. 

  943.           [<code class="option">--enable-prof</code>]
    944. 

  944.         </span></dt><dd><p>Dump a memory profile to the specified file, or if NULL
    945. 

  945.         is specified, to a file according to the pattern
    946. 

  946.         <code class="filename">&lt;prefix&gt;.&lt;pid&gt;.&lt;seq&gt;.m&lt;mseq&gt;.heap</code>,
    947. 

  947.         where <code class="literal">&lt;prefix&gt;</code> is controlled by the
    948. 

  948.         <a class="link" href="#opt.prof_prefix">
    949. 

  949.     "<code class="mallctl">opt.prof_prefix</code>"
    950. 

  950.   </a>
    951. 

  951.         option.</p></dd><dt><span class="term">
    952. 

  952.           
    953. 

  953.     "<code class="mallctl">prof.interval</code>"
    954. 

  954.   
    955. 

  955.           (<span class="type">uint64_t</span>)
    956. 

  956.           <code class="literal">r-</code>
    957. 

  957.           [<code class="option">--enable-prof</code>]
    958. 

  958.         </span></dt><dd><p>Average number of bytes allocated between
    959. 

  959.         inverval-based profile dumps.  See the
    960. 

  960.         <a class="link" href="#opt.lg_prof_interval">
    961. 

  961.     "<code class="mallctl">opt.lg_prof_interval</code>"
    962. 

  962.   </a>
    963. 

  963.         option for additional information.</p></dd><dt><a name="stats.cactive"></a><span class="term">
    964. 

  964.           
    965. 

  965.     "<code class="mallctl">stats.cactive</code>"
    966. 

  966.   
    967. 

  967.           (<span class="type">size_t *</span>)
    968. 

  968.           <code class="literal">r-</code>
    969. 

  969.           [<code class="option">--enable-stats</code>]
    970. 

  970.         </span></dt><dd><p>Pointer to a counter that contains an approximate count
    971. 

  971.         of the current number of bytes in active pages.  The estimate may be
    972. 

  972.         high, but never low, because each arena rounds up to the nearest
    973. 

  973.         multiple of the chunk size when computing its contribution to the
    974. 

  974.         counter.  Note that the <a class="link" href="#epoch">
    975. 

  975.     "<code class="mallctl">epoch</code>"
    976. 

  976.   </a> mallctl has no bearing
    977. 

  977.         on this counter.  Furthermore, counter consistency is maintained via
    978. 

  978.         atomic operations, so it is necessary to use an atomic operation in
    979. 

  979.         order to guarantee a consistent read when dereferencing the pointer.
    980. 

  980.         </p></dd><dt><a name="stats.allocated"></a><span class="term">
    981. 

  981.           
    982. 

  982.     "<code class="mallctl">stats.allocated</code>"
    983. 

  983.   
    984. 

  984.           (<span class="type">size_t</span>)
    985. 

  985.           <code class="literal">r-</code>
    986. 

  986.           [<code class="option">--enable-stats</code>]
    987. 

  987.         </span></dt><dd><p>Total number of bytes allocated by the
    988. 

  988.         application.</p></dd><dt><a name="stats.active"></a><span class="term">
    989. 

  989.           
    990. 

  990.     "<code class="mallctl">stats.active</code>"
    991. 

  991.   
    992. 

  992.           (<span class="type">size_t</span>)
    993. 

  993.           <code class="literal">r-</code>
    994. 

  994.           [<code class="option">--enable-stats</code>]
    995. 

  995.         </span></dt><dd><p>Total number of bytes in active pages allocated by the
    996. 

  996.         application.  This is a multiple of the page size, and greater than or
    997. 

  997.         equal to <a class="link" href="#stats.allocated">
    998. 

  998.     "<code class="mallctl">stats.allocated</code>"
    999. 

  999.   </a>.
    1000. 

  1000.         This does not include <a class="link" href="#stats.arenas.i.pdirty">
    1001. 

  1001.         
    1002. 

  1002.     "<code class="mallctl">stats.arenas.&lt;i&gt;.pdirty</code>"
    1003. 

  1003.   </a> and pages
    1004. 

  1004.         entirely devoted to allocator metadata.</p></dd><dt><span class="term">
    1005. 

  1005.           
    1006. 

  1006.     "<code class="mallctl">stats.mapped</code>"
    1007. 

  1007.   
    1008. 

  1008.           (<span class="type">size_t</span>)
    1009. 

  1009.           <code class="literal">r-</code>
    1010. 

  1010.           [<code class="option">--enable-stats</code>]
    1011. 

  1011.         </span></dt><dd><p>Total number of bytes in chunks mapped on behalf of the
    1012. 

  1012.         application.  This is a multiple of the chunk size, and is at least as
    1013. 

  1013.         large as <a class="link" href="#stats.active">
    1014. 

  1014.     "<code class="mallctl">stats.active</code>"
    1015. 

  1015.   </a>.  This
    1016. 

  1016.         does not include inactive chunks.</p></dd><dt><span class="term">
    1017. 

  1017.           
    1018. 

  1018.     "<code class="mallctl">stats.chunks.current</code>"
    1019. 

  1019.   
    1020. 

  1020.           (<span class="type">size_t</span>)
    1021. 

  1021.           <code class="literal">r-</code>
    1022. 

  1022.           [<code class="option">--enable-stats</code>]
    1023. 

  1023.         </span></dt><dd><p>Total number of chunks actively mapped on behalf of the
    1024. 

  1024.         application.  This does not include inactive chunks.
    1025. 

  1025.         </p></dd><dt><span class="term">
    1026. 

  1026.           
    1027. 

  1027.     "<code class="mallctl">stats.chunks.total</code>"
    1028. 

  1028.   
    1029. 

  1029.           (<span class="type">uint64_t</span>)
    1030. 

  1030.           <code class="literal">r-</code>
    1031. 

  1031.           [<code class="option">--enable-stats</code>]
    1032. 

  1032.         </span></dt><dd><p>Cumulative number of chunks allocated.</p></dd><dt><span class="term">
    1033. 

  1033.           
    1034. 

  1034.     "<code class="mallctl">stats.chunks.high</code>"
    1035. 

  1035.   
    1036. 

  1036.           (<span class="type">size_t</span>)
    1037. 

  1037.           <code class="literal">r-</code>
    1038. 

  1038.           [<code class="option">--enable-stats</code>]
    1039. 

  1039.         </span></dt><dd><p>Maximum number of active chunks at any time thus far.
    1040. 

  1040.         </p></dd><dt><span class="term">
    1041. 

  1041.           
    1042. 

  1042.     "<code class="mallctl">stats.huge.allocated</code>"
    1043. 

  1043.   
    1044. 

  1044.           (<span class="type">size_t</span>)
    1045. 

  1045.           <code class="literal">r-</code>
    1046. 

  1046.           [<code class="option">--enable-stats</code>]
    1047. 

  1047.         </span></dt><dd><p>Number of bytes currently allocated by huge objects.
    1048. 

  1048.         </p></dd><dt><span class="term">
    1049. 

  1049.           
    1050. 

  1050.     "<code class="mallctl">stats.huge.nmalloc</code>"
    1051. 

  1051.   
    1052. 

  1052.           (<span class="type">uint64_t</span>)
    1053. 

  1053.           <code class="literal">r-</code>
    1054. 

  1054.           [<code class="option">--enable-stats</code>]
    1055. 

  1055.         </span></dt><dd><p>Cumulative number of huge allocation requests.
    1056. 

  1056.         </p></dd><dt><span class="term">
    1057. 

  1057.           
    1058. 

  1058.     "<code class="mallctl">stats.huge.ndalloc</code>"
    1059. 

  1059.   
    1060. 

  1060.           (<span class="type">uint64_t</span>)
    1061. 

  1061.           <code class="literal">r-</code>
    1062. 

  1062.           [<code class="option">--enable-stats</code>]
    1063. 

  1063.         </span></dt><dd><p>Cumulative number of huge deallocation requests.
    1064. 

  1064.         </p></dd><dt><span class="term">
    1065. 

  1065.           
    1066. 

  1066.     "<code class="mallctl">stats.arenas.&lt;i&gt;.dss</code>"
    1067. 

  1067.   
    1068. 

  1068.           (<span class="type">const char *</span>)
    1069. 

  1069.           <code class="literal">r-</code>
    1070. 

  1070.         </span></dt><dd><p>dss (<span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span>) allocation precedence as
    1071. 

  1071.         related to <span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span> allocation.  See <a class="link" href="#opt.dss">
    1072. 

  1072.     "<code class="mallctl">opt.dss</code>"
    1073. 

  1073.   </a> for details.
    1074. 

  1074.         </p></dd><dt><span class="term">
    1075. 

  1075.           
    1076. 

  1076.     "<code class="mallctl">stats.arenas.&lt;i&gt;.nthreads</code>"
    1077. 

  1077.   
    1078. 

  1078.           (<span class="type">unsigned</span>)
    1079. 

  1079.           <code class="literal">r-</code>
    1080. 

  1080.         </span></dt><dd><p>Number of threads currently assigned to
    1081. 

  1081.         arena.</p></dd><dt><span class="term">
    1082. 

  1082.           
    1083. 

  1083.     "<code class="mallctl">stats.arenas.&lt;i&gt;.pactive</code>"
    1084. 

  1084.   
    1085. 

  1085.           (<span class="type">size_t</span>)
    1086. 

  1086.           <code class="literal">r-</code>
    1087. 

  1087.         </span></dt><dd><p>Number of pages in active runs.</p></dd><dt><a name="stats.arenas.i.pdirty"></a><span class="term">
    1088. 

  1088.           
    1089. 

  1089.     "<code class="mallctl">stats.arenas.&lt;i&gt;.pdirty</code>"
    1090. 

  1090.   
    1091. 

  1091.           (<span class="type">size_t</span>)
    1092. 

  1092.           <code class="literal">r-</code>
    1093. 

  1093.         </span></dt><dd><p>Number of pages within unused runs that are potentially
    1094. 

  1094.         dirty, and for which <code class="function">madvise</code>(<em class="parameter"><code>...</code></em>, 
    1095. 

  1095.         <em class="parameter"><code><code class="constant">MADV_DONTNEED</code></code></em>) or
    1096. 

  1096.         similar has not been called.</p></dd><dt><span class="term">
    1097. 

  1097.           
    1098. 

  1098.     "<code class="mallctl">stats.arenas.&lt;i&gt;.mapped</code>"
    1099. 

  1099.   
    1100. 

  1100.           (<span class="type">size_t</span>)
    1101. 

  1101.           <code class="literal">r-</code>
    1102. 

  1102.           [<code class="option">--enable-stats</code>]
    1103. 

  1103.         </span></dt><dd><p>Number of mapped bytes.</p></dd><dt><span class="term">
    1104. 

  1104.           
    1105. 

  1105.     "<code class="mallctl">stats.arenas.&lt;i&gt;.npurge</code>"
    1106. 

  1106.   
    1107. 

  1107.           (<span class="type">uint64_t</span>)
    1108. 

  1108.           <code class="literal">r-</code>
    1109. 

  1109.           [<code class="option">--enable-stats</code>]
    1110. 

  1110.         </span></dt><dd><p>Number of dirty page purge sweeps performed.
    1111. 

  1111.         </p></dd><dt><span class="term">
    1112. 

  1112.           
    1113. 

  1113.     "<code class="mallctl">stats.arenas.&lt;i&gt;.nmadvise</code>"
    1114. 

  1114.   
    1115. 

  1115.           (<span class="type">uint64_t</span>)
    1116. 

  1116.           <code class="literal">r-</code>
    1117. 

  1117.           [<code class="option">--enable-stats</code>]
    1118. 

  1118.         </span></dt><dd><p>Number of <code class="function">madvise</code>(<em class="parameter"><code>...</code></em>, 
    1119. 

  1119.         <em class="parameter"><code><code class="constant">MADV_DONTNEED</code></code></em>) or
    1120. 

  1120.         similar calls made to purge dirty pages.</p></dd><dt><span class="term">
    1121. 

  1121.           
    1122. 

  1122.     "<code class="mallctl">stats.arenas.&lt;i&gt;.npurged</code>"
    1123. 

  1123.   
    1124. 

  1124.           (<span class="type">uint64_t</span>)
    1125. 

  1125.           <code class="literal">r-</code>
    1126. 

  1126.           [<code class="option">--enable-stats</code>]
    1127. 

  1127.         </span></dt><dd><p>Number of pages purged.</p></dd><dt><span class="term">
    1128. 

  1128.           
    1129. 

  1129.     "<code class="mallctl">stats.arenas.&lt;i&gt;.small.allocated</code>"
    1130. 

  1130.   
    1131. 

  1131.           (<span class="type">size_t</span>)
    1132. 

  1132.           <code class="literal">r-</code>
    1133. 

  1133.           [<code class="option">--enable-stats</code>]
    1134. 

  1134.         </span></dt><dd><p>Number of bytes currently allocated by small objects.
    1135. 

  1135.         </p></dd><dt><span class="term">
    1136. 

  1136.           
    1137. 

  1137.     "<code class="mallctl">stats.arenas.&lt;i&gt;.small.nmalloc</code>"
    1138. 

  1138.   
    1139. 

  1139.           (<span class="type">uint64_t</span>)
    1140. 

  1140.           <code class="literal">r-</code>
    1141. 

  1141.           [<code class="option">--enable-stats</code>]
    1142. 

  1142.         </span></dt><dd><p>Cumulative number of allocation requests served by
    1143. 

  1143.         small bins.</p></dd><dt><span class="term">
    1144. 

  1144.           
    1145. 

  1145.     "<code class="mallctl">stats.arenas.&lt;i&gt;.small.ndalloc</code>"
    1146. 

  1146.   
    1147. 

  1147.           (<span class="type">uint64_t</span>)
    1148. 

  1148.           <code class="literal">r-</code>
    1149. 

  1149.           [<code class="option">--enable-stats</code>]
    1150. 

  1150.         </span></dt><dd><p>Cumulative number of small objects returned to bins.
    1151. 

  1151.         </p></dd><dt><span class="term">
    1152. 

  1152.           
    1153. 

  1153.     "<code class="mallctl">stats.arenas.&lt;i&gt;.small.nrequests</code>"
    1154. 

  1154.   
    1155. 

  1155.           (<span class="type">uint64_t</span>)
    1156. 

  1156.           <code class="literal">r-</code>
    1157. 

  1157.           [<code class="option">--enable-stats</code>]
    1158. 

  1158.         </span></dt><dd><p>Cumulative number of small allocation requests.
    1159. 

  1159.         </p></dd><dt><span class="term">
    1160. 

  1160.           
    1161. 

  1161.     "<code class="mallctl">stats.arenas.&lt;i&gt;.large.allocated</code>"
    1162. 

  1162.   
    1163. 

  1163.           (<span class="type">size_t</span>)
    1164. 

  1164.           <code class="literal">r-</code>
    1165. 

  1165.           [<code class="option">--enable-stats</code>]
    1166. 

  1166.         </span></dt><dd><p>Number of bytes currently allocated by large objects.
    1167. 

  1167.         </p></dd><dt><span class="term">
    1168. 

  1168.           
    1169. 

  1169.     "<code class="mallctl">stats.arenas.&lt;i&gt;.large.nmalloc</code>"
    1170. 

  1170.   
    1171. 

  1171.           (<span class="type">uint64_t</span>)
    1172. 

  1172.           <code class="literal">r-</code>
    1173. 

  1173.           [<code class="option">--enable-stats</code>]
    1174. 

  1174.         </span></dt><dd><p>Cumulative number of large allocation requests served
    1175. 

  1175.         directly by the arena.</p></dd><dt><span class="term">
    1176. 

  1176.           
    1177. 

  1177.     "<code class="mallctl">stats.arenas.&lt;i&gt;.large.ndalloc</code>"
    1178. 

  1178.   
    1179. 

  1179.           (<span class="type">uint64_t</span>)
    1180. 

  1180.           <code class="literal">r-</code>
    1181. 

  1181.           [<code class="option">--enable-stats</code>]
    1182. 

  1182.         </span></dt><dd><p>Cumulative number of large deallocation requests served
    1183. 

  1183.         directly by the arena.</p></dd><dt><span class="term">
    1184. 

  1184.           
    1185. 

  1185.     "<code class="mallctl">stats.arenas.&lt;i&gt;.large.nrequests</code>"
    1186. 

  1186.   
    1187. 

  1187.           (<span class="type">uint64_t</span>)
    1188. 

  1188.           <code class="literal">r-</code>
    1189. 

  1189.           [<code class="option">--enable-stats</code>]
    1190. 

  1190.         </span></dt><dd><p>Cumulative number of large allocation requests.
    1191. 

  1191.         </p></dd><dt><span class="term">
    1192. 

  1192.           
    1193. 

  1193.     "<code class="mallctl">stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.allocated</code>"
    1194. 

  1194.   
    1195. 

  1195.           (<span class="type">size_t</span>)
    1196. 

  1196.           <code class="literal">r-</code>
    1197. 

  1197.           [<code class="option">--enable-stats</code>]
    1198. 

  1198.         </span></dt><dd><p>Current number of bytes allocated by
    1199. 

  1199.         bin.</p></dd><dt><span class="term">
    1200. 

  1200.           
    1201. 

  1201.     "<code class="mallctl">stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.nmalloc</code>"
    1202. 

  1202.   
    1203. 

  1203.           (<span class="type">uint64_t</span>)
    1204. 

  1204.           <code class="literal">r-</code>
    1205. 

  1205.           [<code class="option">--enable-stats</code>]
    1206. 

  1206.         </span></dt><dd><p>Cumulative number of allocations served by bin.
    1207. 

  1207.         </p></dd><dt><span class="term">
    1208. 

  1208.           
    1209. 

  1209.     "<code class="mallctl">stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.ndalloc</code>"
    1210. 

  1210.   
    1211. 

  1211.           (<span class="type">uint64_t</span>)
    1212. 

  1212.           <code class="literal">r-</code>
    1213. 

  1213.           [<code class="option">--enable-stats</code>]
    1214. 

  1214.         </span></dt><dd><p>Cumulative number of allocations returned to bin.
    1215. 

  1215.         </p></dd><dt><span class="term">
    1216. 

  1216.           
    1217. 

  1217.     "<code class="mallctl">stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.nrequests</code>"
    1218. 

  1218.   
    1219. 

  1219.           (<span class="type">uint64_t</span>)
    1220. 

  1220.           <code class="literal">r-</code>
    1221. 

  1221.           [<code class="option">--enable-stats</code>]
    1222. 

  1222.         </span></dt><dd><p>Cumulative number of allocation
    1223. 

  1223.         requests.</p></dd><dt><span class="term">
    1224. 

  1224.           
    1225. 

  1225.     "<code class="mallctl">stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.nfills</code>"
    1226. 

  1226.   
    1227. 

  1227.           (<span class="type">uint64_t</span>)
    1228. 

  1228.           <code class="literal">r-</code>
    1229. 

  1229.           [<code class="option">--enable-stats</code> <code class="option">--enable-tcache</code>]
    1230. 

  1230.         </span></dt><dd><p>Cumulative number of tcache fills.</p></dd><dt><span class="term">
    1231. 

  1231.           
    1232. 

  1232.     "<code class="mallctl">stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.nflushes</code>"
    1233. 

  1233.   
    1234. 

  1234.           (<span class="type">uint64_t</span>)
    1235. 

  1235.           <code class="literal">r-</code>
    1236. 

  1236.           [<code class="option">--enable-stats</code> <code class="option">--enable-tcache</code>]
    1237. 

  1237.         </span></dt><dd><p>Cumulative number of tcache flushes.</p></dd><dt><span class="term">
    1238. 

  1238.           
    1239. 

  1239.     "<code class="mallctl">stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.nruns</code>"
    1240. 

  1240.   
    1241. 

  1241.           (<span class="type">uint64_t</span>)
    1242. 

  1242.           <code class="literal">r-</code>
    1243. 

  1243.           [<code class="option">--enable-stats</code>]
    1244. 

  1244.         </span></dt><dd><p>Cumulative number of runs created.</p></dd><dt><span class="term">
    1245. 

  1245.           
    1246. 

  1246.     "<code class="mallctl">stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.nreruns</code>"
    1247. 

  1247.   
    1248. 

  1248.           (<span class="type">uint64_t</span>)
    1249. 

  1249.           <code class="literal">r-</code>
    1250. 

  1250.           [<code class="option">--enable-stats</code>]
    1251. 

  1251.         </span></dt><dd><p>Cumulative number of times the current run from which
    1252. 

  1252.         to allocate changed.</p></dd><dt><span class="term">
    1253. 

  1253.           
    1254. 

  1254.     "<code class="mallctl">stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.curruns</code>"
    1255. 

  1255.   
    1256. 

  1256.           (<span class="type">size_t</span>)
    1257. 

  1257.           <code class="literal">r-</code>
    1258. 

  1258.           [<code class="option">--enable-stats</code>]
    1259. 

  1259.         </span></dt><dd><p>Current number of runs.</p></dd><dt><span class="term">
    1260. 

  1260.           
    1261. 

  1261.     "<code class="mallctl">stats.arenas.&lt;i&gt;.lruns.&lt;j&gt;.nmalloc</code>"
    1262. 

  1262.   
    1263. 

  1263.           (<span class="type">uint64_t</span>)
    1264. 

  1264.           <code class="literal">r-</code>
    1265. 

  1265.           [<code class="option">--enable-stats</code>]
    1266. 

  1266.         </span></dt><dd><p>Cumulative number of allocation requests for this size
    1267. 

  1267.         class served directly by the arena.</p></dd><dt><span class="term">
    1268. 

  1268.           
    1269. 

  1269.     "<code class="mallctl">stats.arenas.&lt;i&gt;.lruns.&lt;j&gt;.ndalloc</code>"
    1270. 

  1270.   
    1271. 

  1271.           (<span class="type">uint64_t</span>)
    1272. 

  1272.           <code class="literal">r-</code>
    1273. 

  1273.           [<code class="option">--enable-stats</code>]
    1274. 

  1274.         </span></dt><dd><p>Cumulative number of deallocation requests for this
    1275. 

  1275.         size class served directly by the arena.</p></dd><dt><span class="term">
    1276. 

  1276.           
    1277. 

  1277.     "<code class="mallctl">stats.arenas.&lt;i&gt;.lruns.&lt;j&gt;.nrequests</code>"
    1278. 

  1278.   
    1279. 

  1279.           (<span class="type">uint64_t</span>)
    1280. 

  1280.           <code class="literal">r-</code>
    1281. 

  1281.           [<code class="option">--enable-stats</code>]
    1282. 

  1282.         </span></dt><dd><p>Cumulative number of allocation requests for this size
    1283. 

  1283.         class.</p></dd><dt><span class="term">
    1284. 

  1284.           
    1285. 

  1285.     "<code class="mallctl">stats.arenas.&lt;i&gt;.lruns.&lt;j&gt;.curruns</code>"
    1286. 

  1286.   
    1287. 

  1287.           (<span class="type">size_t</span>)
    1288. 

  1288.           <code class="literal">r-</code>
    1289. 

  1289.           [<code class="option">--enable-stats</code>]
    1290. 

  1290.         </span></dt><dd><p>Current number of runs for this size class.
    1291. 

  1291.         </p></dd></dl></div></div><div class="refsect1" title="DEBUGGING MALLOC PROBLEMS"><a name="debugging_malloc_problems"></a><h2>DEBUGGING MALLOC PROBLEMS</h2><p>When debugging, it is a good idea to configure/build jemalloc with
    1292. 

  1292.     the <code class="option">--enable-debug</code> and <code class="option">--enable-fill</code>
    1293. 

  1293.     options, and recompile the program with suitable options and symbols for
    1294. 

  1294.     debugger support.  When so configured, jemalloc incorporates a wide variety
    1295. 

  1295.     of run-time assertions that catch application errors such as double-free,
    1296. 

  1296.     write-after-free, etc.</p><p>Programs often accidentally depend on &#8220;uninitialized&#8221;
    1297. 

  1297.     memory actually being filled with zero bytes.  Junk filling
    1298. 

  1298.     (see the <a class="link" href="#opt.junk">
    1299. 

  1299.     "<code class="mallctl">opt.junk</code>"
    1300. 

  1300.   </a>
    1301. 

  1301.     option) tends to expose such bugs in the form of obviously incorrect
    1302. 

  1302.     results and/or coredumps.  Conversely, zero
    1303. 

  1303.     filling (see the <a class="link" href="#opt.zero">
    1304. 

  1304.     "<code class="mallctl">opt.zero</code>"
    1305. 

  1305.   </a> option) eliminates
    1306. 

  1306.     the symptoms of such bugs.  Between these two options, it is usually
    1307. 

  1307.     possible to quickly detect, diagnose, and eliminate such bugs.</p><p>This implementation does not provide much detail about the problems
    1308. 

  1308.     it detects, because the performance impact for storing such information
    1309. 

  1309.     would be prohibitive.  However, jemalloc does integrate with the most
    1310. 

  1310.     excellent <a class="ulink" href="http://valgrind.org/" target="_top">Valgrind</a> tool if the
    1311. 

  1311.     <code class="option">--enable-valgrind</code> configuration option is enabled.</p></div><div class="refsect1" title="DIAGNOSTIC MESSAGES"><a name="diagnostic_messages"></a><h2>DIAGNOSTIC MESSAGES</h2><p>If any of the memory allocation/deallocation functions detect an
    1312. 

  1312.     error or warning condition, a message will be printed to file descriptor
    1313. 

  1313.     <code class="constant">STDERR_FILENO</code>.  Errors will result in the process
    1314. 

  1314.     dumping core.  If the <a class="link" href="#opt.abort">
    1315. 

  1315.     "<code class="mallctl">opt.abort</code>"
    1316. 

  1316.   </a> option is set, most
    1317. 

  1317.     warnings are treated as errors.</p><p>The <code class="varname">malloc_message</code> variable allows the programmer
    1318. 

  1318.     to override the function which emits the text strings forming the errors
    1319. 

  1319.     and warnings if for some reason the <code class="constant">STDERR_FILENO</code> file
    1320. 

  1320.     descriptor is not suitable for this.
    1321. 

  1321.     <code class="function">malloc_message</code>(<em class="parameter"><code></code></em>) takes the
    1322. 

  1322.     <em class="parameter"><code>cbopaque</code></em> pointer argument that is
    1323. 

  1323.     <code class="constant">NULL</code> unless overridden by the arguments in a call to
    1324. 

  1324.     <code class="function">malloc_stats_print</code>(<em class="parameter"><code></code></em>), followed by a string
    1325. 

  1325.     pointer.  Please note that doing anything which tries to allocate memory in
    1326. 

  1326.     this function is likely to result in a crash or deadlock.</p><p>All messages are prefixed by
    1327. 

  1327.     &#8220;<code class="computeroutput">&lt;jemalloc&gt;: </code>&#8221;.</p></div><div class="refsect1" title="RETURN VALUES"><a name="return_values"></a><h2>RETURN VALUES</h2><div class="refsect2" title="Standard API"><a name="id286954473"></a><h3>Standard API</h3><p>The <code class="function">malloc</code>(<em class="parameter"><code></code></em>) and
    1328. 

  1328.       <code class="function">calloc</code>(<em class="parameter"><code></code></em>) functions return a pointer to the
    1329. 

  1329.       allocated memory if successful; otherwise a <code class="constant">NULL</code>
    1330. 

  1330.       pointer is returned and <code class="varname">errno</code> is set to
    1331. 

  1331.       <span class="errorname">ENOMEM</span>.</p><p>The <code class="function">posix_memalign</code>(<em class="parameter"><code></code></em>) function
    1332. 

  1332.       returns the value 0 if successful; otherwise it returns an error value.
    1333. 

  1333.       The <code class="function">posix_memalign</code>(<em class="parameter"><code></code></em>) function will fail
    1334. 

  1334.       if:
    1335. 

  1335.         </p><div class="variablelist"><dl><dt><span class="term"><span class="errorname">EINVAL</span></span></dt><dd><p>The <em class="parameter"><code>alignment</code></em> parameter is
    1336. 

  1336.             not a power of 2 at least as large as
    1337. 

  1337.             <code class="code">sizeof(<span class="type">void *</span>)</code>.
    1338. 

  1338.             </p></dd><dt><span class="term"><span class="errorname">ENOMEM</span></span></dt><dd><p>Memory allocation error.</p></dd></dl></div><p>
    1339. 

  1339.       </p><p>The <code class="function">aligned_alloc</code>(<em class="parameter"><code></code></em>) function returns
    1340. 

  1340.       a pointer to the allocated memory if successful; otherwise a
    1341. 

  1341.       <code class="constant">NULL</code> pointer is returned and
    1342. 

  1342.       <code class="varname">errno</code> is set.  The
    1343. 

  1343.       <code class="function">aligned_alloc</code>(<em class="parameter"><code></code></em>) function will fail if:
    1344. 

  1344.         </p><div class="variablelist"><dl><dt><span class="term"><span class="errorname">EINVAL</span></span></dt><dd><p>The <em class="parameter"><code>alignment</code></em> parameter is
    1345. 

  1345.             not a power of 2.
    1346. 

  1346.             </p></dd><dt><span class="term"><span class="errorname">ENOMEM</span></span></dt><dd><p>Memory allocation error.</p></dd></dl></div><p>
    1347. 

  1347.       </p><p>The <code class="function">realloc</code>(<em class="parameter"><code></code></em>) function returns a
    1348. 

  1348.       pointer, possibly identical to <em class="parameter"><code>ptr</code></em>, to the
    1349. 

  1349.       allocated memory if successful; otherwise a <code class="constant">NULL</code>
    1350. 

  1350.       pointer is returned, and <code class="varname">errno</code> is set to
    1351. 

  1351.       <span class="errorname">ENOMEM</span> if the error was the result of an
    1352. 

  1352.       allocation failure.  The <code class="function">realloc</code>(<em class="parameter"><code></code></em>)
    1353. 

  1353.       function always leaves the original buffer intact when an error occurs.
    1354. 

  1354.       </p><p>The <code class="function">free</code>(<em class="parameter"><code></code></em>) function returns no
    1355. 

  1355.       value.</p></div><div class="refsect2" title="Non-standard API"><a name="id286954690"></a><h3>Non-standard API</h3><p>The <code class="function">malloc_usable_size</code>(<em class="parameter"><code></code></em>) function
    1356. 

  1356.       returns the usable size of the allocation pointed to by
    1357. 

  1357.       <em class="parameter"><code>ptr</code></em>.  </p><p>The <code class="function">mallctl</code>(<em class="parameter"><code></code></em>),
    1358. 

  1358.       <code class="function">mallctlnametomib</code>(<em class="parameter"><code></code></em>), and
    1359. 

  1359.       <code class="function">mallctlbymib</code>(<em class="parameter"><code></code></em>) functions return 0 on
    1360. 

  1360.       success; otherwise they return an error value.  The functions will fail
    1361. 

  1361.       if:
    1362. 

  1362.         </p><div class="variablelist"><dl><dt><span class="term"><span class="errorname">EINVAL</span></span></dt><dd><p><em class="parameter"><code>newp</code></em> is not
    1363. 

  1363.             <code class="constant">NULL</code>, and <em class="parameter"><code>newlen</code></em> is too
    1364. 

  1364.             large or too small.  Alternatively, <em class="parameter"><code>*oldlenp</code></em>
    1365. 

  1365.             is too large or too small; in this case as much data as possible
    1366. 

  1366.             are read despite the error.</p></dd><dt><span class="term"><span class="errorname">ENOMEM</span></span></dt><dd><p><em class="parameter"><code>*oldlenp</code></em> is too short to
    1367. 

  1367.             hold the requested value.</p></dd><dt><span class="term"><span class="errorname">ENOENT</span></span></dt><dd><p><em class="parameter"><code>name</code></em> or
    1368. 

  1368.             <em class="parameter"><code>mib</code></em> specifies an unknown/invalid
    1369. 

  1369.             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
    1370. 

  1370.             write read-only value.</p></dd><dt><span class="term"><span class="errorname">EAGAIN</span></span></dt><dd><p>A memory allocation failure
    1371. 

  1371.             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
    1372. 

  1372.             not directly related to <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>)
    1373. 

  1373.             read/write processing.</p></dd></dl></div><p>
    1374. 

  1374.       </p></div><div class="refsect2" title="Experimental API"><a name="id286954842"></a><h3>Experimental API</h3><p>The <code class="function">allocm</code>(<em class="parameter"><code></code></em>),
    1375. 

  1375.       <code class="function">rallocm</code>(<em class="parameter"><code></code></em>),
    1376. 

  1376.       <code class="function">sallocm</code>(<em class="parameter"><code></code></em>),
    1377. 

  1377.       <code class="function">dallocm</code>(<em class="parameter"><code></code></em>), and
    1378. 

  1378.       <code class="function">nallocm</code>(<em class="parameter"><code></code></em>) functions return
    1379. 

  1379.       <code class="constant">ALLOCM_SUCCESS</code> on success; otherwise they return an
    1380. 

  1380.       error value.  The <code class="function">allocm</code>(<em class="parameter"><code></code></em>),
    1381. 

  1381.       <code class="function">rallocm</code>(<em class="parameter"><code></code></em>), and
    1382. 

  1382.       <code class="function">nallocm</code>(<em class="parameter"><code></code></em>) functions will fail if:
    1383. 

  1383.         </p><div class="variablelist"><dl><dt><span class="term"><span class="errorname">ALLOCM_ERR_OOM</span></span></dt><dd><p>Out of memory.  Insufficient contiguous memory was
    1384. 

  1384.             available to service the allocation request.  The
    1385. 

  1385.             <code class="function">allocm</code>(<em class="parameter"><code></code></em>) function additionally sets
    1386. 

  1386.             <em class="parameter"><code>*ptr</code></em> to <code class="constant">NULL</code>, whereas
    1387. 

  1387.             the <code class="function">rallocm</code>(<em class="parameter"><code></code></em>) function leaves
    1388. 

  1388.             <code class="constant">*ptr</code> unmodified.</p></dd></dl></div><p>
    1389. 

  1389.       The <code class="function">rallocm</code>(<em class="parameter"><code></code></em>) function will also
    1390. 

  1390.       fail if:
    1391. 

  1391.         </p><div class="variablelist"><dl><dt><span class="term"><span class="errorname">ALLOCM_ERR_NOT_MOVED</span></span></dt><dd><p><code class="constant">ALLOCM_NO_MOVE</code> was specified,
    1392. 

  1392.             but the reallocation request could not be serviced without moving
    1393. 

  1393.             the object.</p></dd></dl></div><p>
    1394. 

  1394.       </p></div></div><div class="refsect1" title="ENVIRONMENT"><a name="environment"></a><h2>ENVIRONMENT</h2><p>The following environment variable affects the execution of the
    1395. 

  1395.     allocation functions:
    1396. 

  1396.       </p><div class="variablelist"><dl><dt><span class="term"><code class="envar">MALLOC_CONF</code></span></dt><dd><p>If the environment variable
    1397. 

  1397.           <code class="envar">MALLOC_CONF</code> is set, the characters it contains
    1398. 

  1398.           will be interpreted as options.</p></dd></dl></div><p>
    1399. 

  1399.     </p></div><div class="refsect1" title="EXAMPLES"><a name="examples"></a><h2>EXAMPLES</h2><p>To dump core whenever a problem occurs:
    1400. 

  1400.       </p><pre class="screen">ln -s 'abort:true' /etc/malloc.conf</pre><p>
    1401. 

  1401.     </p><p>To specify in the source a chunk size that is 16 MiB:
    1402. 

  1402.       </p><pre class="programlisting">
    1403. 

  1403. malloc_conf = "lg_chunk:24";</pre></div><div class="refsect1" title="SEE ALSO"><a name="see_also"></a><h2>SEE ALSO</h2><p><span class="citerefentry"><span class="refentrytitle">madvise</span>(2)</span>,
    1404. 

  1404.     <span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span>,
    1405. 

  1405.     <span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span>,
    1406. 

  1406.     <span class="citerefentry"><span class="refentrytitle">utrace</span>(2)</span>,
    1407. 

  1407.     <span class="citerefentry"><span class="refentrytitle">alloca</span>(3)</span>,
    1408. 

  1408.     <span class="citerefentry"><span class="refentrytitle">atexit</span>(3)</span>,
    1409. 

  1409.     <span class="citerefentry"><span class="refentrytitle">getpagesize</span>(3)</span></p></div><div class="refsect1" title="STANDARDS"><a name="standards"></a><h2>STANDARDS</h2><p>The <code class="function">malloc</code>(<em class="parameter"><code></code></em>),
    1410. 

  1410.     <code class="function">calloc</code>(<em class="parameter"><code></code></em>),
    1411. 

  1411.     <code class="function">realloc</code>(<em class="parameter"><code></code></em>), and
    1412. 

  1412.     <code class="function">free</code>(<em class="parameter"><code></code></em>) functions conform to ISO/IEC
    1413. 

  1413.     9899:1990 (&#8220;ISO C90&#8221;).</p><p>The <code class="function">posix_memalign</code>(<em class="parameter"><code></code></em>) function conforms
    1414. 

  1414.     to IEEE Std 1003.1-2001 (&#8220;POSIX.1&#8221;).</p></div></div></body></html>
    1415.