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- <html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>JEMALLOC</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry"><a name="idp45223136"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>jemalloc — general purpose memory allocation functions</p></div><div class="refsect1"><a name="library"></a><h2>LIBRARY</h2><p>This manual describes jemalloc 4.0.3-0-ge9192eacf8935e29fc62fddc2701f7942b1cc02c. More information
- can be found at the <a class="ulink" href="http://www.canonware.com/jemalloc/" target="_top">jemalloc website</a>.</p></div><div class="refsynopsisdiv"><h2>SYNOPSIS</h2><div class="funcsynopsis"><pre class="funcsynopsisinfo">#include <<code class="filename">jemalloc/jemalloc.h</code>></pre><div class="refsect2"><a name="idp44244480"></a><h3>Standard API</h3><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void *<b class="fsfunc">malloc</b>(</code></td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void *<b class="fsfunc">calloc</b>(</code></td><td>size_t <var class="pdparam">number</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">posix_memalign</b>(</code></td><td>void **<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">alignment</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void *<b class="fsfunc">aligned_alloc</b>(</code></td><td>size_t <var class="pdparam">alignment</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void *<b class="fsfunc">realloc</b>(</code></td><td>void *<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <b class="fsfunc">free</b>(</code></td><td>void *<var class="pdparam">ptr</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="refsect2"><a name="idp46062768"></a><h3>Non-standard API</h3><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void *<b class="fsfunc">mallocx</b>(</code></td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void *<b class="fsfunc">rallocx</b>(</code></td><td>void *<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">size_t <b class="fsfunc">xallocx</b>(</code></td><td>void *<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">extra</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">size_t <b class="fsfunc">sallocx</b>(</code></td><td>void *<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <b class="fsfunc">dallocx</b>(</code></td><td>void *<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <b class="fsfunc">sdallocx</b>(</code></td><td>void *<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">size_t <b class="fsfunc">nallocx</b>(</code></td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">mallctl</b>(</code></td><td>const char *<var class="pdparam">name</var>, </td></tr><tr><td> </td><td>void *<var class="pdparam">oldp</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">oldlenp</var>, </td></tr><tr><td> </td><td>void *<var class="pdparam">newp</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">newlen</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">mallctlnametomib</b>(</code></td><td>const char *<var class="pdparam">name</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">mibp</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">miblenp</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">mallctlbymib</b>(</code></td><td>const size_t *<var class="pdparam">mib</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">miblen</var>, </td></tr><tr><td> </td><td>void *<var class="pdparam">oldp</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">oldlenp</var>, </td></tr><tr><td> </td><td>void *<var class="pdparam">newp</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">newlen</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <b class="fsfunc">malloc_stats_print</b>(</code></td><td>void <var class="pdparam">(*write_cb)</var>
- <code>(</code>void *, const char *<code>)</code>
- , </td></tr><tr><td> </td><td>void *<var class="pdparam">cbopaque</var>, </td></tr><tr><td> </td><td>const char *<var class="pdparam">opts</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">size_t <b class="fsfunc">malloc_usable_size</b>(</code></td><td>const void *<var class="pdparam">ptr</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <b class="fsfunc">(*malloc_message)</b>(</code></td><td>void *<var class="pdparam">cbopaque</var>, </td></tr><tr><td> </td><td>const char *<var class="pdparam">s</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><p><span class="type">const char *</span><code class="varname">malloc_conf</code>;</p></div></div></div><div class="refsect1"><a name="description"></a><h2>DESCRIPTION</h2><div class="refsect2"><a name="idp46115952"></a><h3>Standard API</h3><p>The <code class="function">malloc</code>(<em class="parameter"><code></code></em>) function allocates
- <em class="parameter"><code>size</code></em> bytes of uninitialized memory. The allocated
- space is suitably aligned (after possible pointer coercion) for storage
- of any type of object.</p><p>The <code class="function">calloc</code>(<em class="parameter"><code></code></em>) function allocates
- space for <em class="parameter"><code>number</code></em> objects, each
- <em class="parameter"><code>size</code></em> bytes in length. The result is identical to
- calling <code class="function">malloc</code>(<em class="parameter"><code></code></em>) with an argument of
- <em class="parameter"><code>number</code></em> * <em class="parameter"><code>size</code></em>, with the
- exception that the allocated memory is explicitly initialized to zero
- bytes.</p><p>The <code class="function">posix_memalign</code>(<em class="parameter"><code></code></em>) function
- allocates <em class="parameter"><code>size</code></em> bytes of memory such that the
- allocation's base address is a multiple of
- <em class="parameter"><code>alignment</code></em>, and returns the allocation in the value
- pointed to by <em class="parameter"><code>ptr</code></em>. The requested
- <em class="parameter"><code>alignment</code></em> must be a power of 2 at least as large 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
- allocates <em class="parameter"><code>size</code></em> bytes of memory such that the
- allocation's base address is a multiple of
- <em class="parameter"><code>alignment</code></em>. The requested
- <em class="parameter"><code>alignment</code></em> must be a power of 2. Behavior is
- undefined if <em class="parameter"><code>size</code></em> is not an integral multiple of
- <em class="parameter"><code>alignment</code></em>.</p><p>The <code class="function">realloc</code>(<em class="parameter"><code></code></em>) function changes the
- size of the previously allocated memory referenced by
- <em class="parameter"><code>ptr</code></em> to <em class="parameter"><code>size</code></em> bytes. The
- contents of the memory are unchanged up to the lesser of the new and old
- sizes. If the new size is larger, the contents of the newly allocated
- portion of the memory are undefined. Upon success, the memory referenced
- by <em class="parameter"><code>ptr</code></em> is freed and a pointer to the newly
- allocated memory is returned. Note that
- <code class="function">realloc</code>(<em class="parameter"><code></code></em>) may move the memory allocation,
- resulting in a different return value than <em class="parameter"><code>ptr</code></em>.
- If <em class="parameter"><code>ptr</code></em> is <code class="constant">NULL</code>, the
- <code class="function">realloc</code>(<em class="parameter"><code></code></em>) function behaves identically to
- <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
- allocated memory referenced by <em class="parameter"><code>ptr</code></em> to be made
- available for future allocations. If <em class="parameter"><code>ptr</code></em> is
- <code class="constant">NULL</code>, no action occurs.</p></div><div class="refsect2"><a name="idp46144704"></a><h3>Non-standard API</h3><p>The <code class="function">mallocx</code>(<em class="parameter"><code></code></em>),
- <code class="function">rallocx</code>(<em class="parameter"><code></code></em>),
- <code class="function">xallocx</code>(<em class="parameter"><code></code></em>),
- <code class="function">sallocx</code>(<em class="parameter"><code></code></em>),
- <code class="function">dallocx</code>(<em class="parameter"><code></code></em>),
- <code class="function">sdallocx</code>(<em class="parameter"><code></code></em>), and
- <code class="function">nallocx</code>(<em class="parameter"><code></code></em>) functions all have a
- <em class="parameter"><code>flags</code></em> argument that can be used to specify
- options. The functions only check the options that are contextually
- relevant. Use bitwise or (<code class="code">|</code>) operations to
- specify one or more of the following:
- </p><div class="variablelist"><dl class="variablelist"><dt><a name="MALLOCX_LG_ALIGN"></a><span class="term"><code class="constant">MALLOCX_LG_ALIGN(<em class="parameter"><code>la</code></em>)
- </code></span></dt><dd><p>Align the memory allocation to start at an address
- that is a multiple of <code class="code">(1 <<
- <em class="parameter"><code>la</code></em>)</code>. This macro does not validate
- that <em class="parameter"><code>la</code></em> is within the valid
- range.</p></dd><dt><a name="MALLOCX_ALIGN"></a><span class="term"><code class="constant">MALLOCX_ALIGN(<em class="parameter"><code>a</code></em>)
- </code></span></dt><dd><p>Align the memory allocation to start at an address
- that is a multiple of <em class="parameter"><code>a</code></em>, where
- <em class="parameter"><code>a</code></em> is a power of two. This macro does not
- validate that <em class="parameter"><code>a</code></em> is a power of 2.
- </p></dd><dt><a name="MALLOCX_ZERO"></a><span class="term"><code class="constant">MALLOCX_ZERO</code></span></dt><dd><p>Initialize newly allocated memory to contain zero
- bytes. In the growing reallocation case, the real size prior to
- reallocation defines the boundary between untouched bytes and those
- that are initialized to contain zero bytes. If this macro is
- absent, newly allocated memory is uninitialized.</p></dd><dt><a name="MALLOCX_TCACHE"></a><span class="term"><code class="constant">MALLOCX_TCACHE(<em class="parameter"><code>tc</code></em>)
- </code></span></dt><dd><p>Use the thread-specific cache (tcache) specified by
- the identifier <em class="parameter"><code>tc</code></em>, which must have been
- acquired via the <a class="link" href="#tcache.create">
- "<code class="mallctl">tcache.create</code>"
- </a>
- mallctl. This macro does not validate that
- <em class="parameter"><code>tc</code></em> specifies a valid
- identifier.</p></dd><dt><a name="MALLOC_TCACHE_NONE"></a><span class="term"><code class="constant">MALLOCX_TCACHE_NONE</code></span></dt><dd><p>Do not use a thread-specific cache (tcache). Unless
- <code class="constant">MALLOCX_TCACHE(<em class="parameter"><code>tc</code></em>)</code> or
- <code class="constant">MALLOCX_TCACHE_NONE</code> is specified, an
- automatically managed tcache will be used under many circumstances.
- This macro cannot be used in the same <em class="parameter"><code>flags</code></em>
- argument as
- <code class="constant">MALLOCX_TCACHE(<em class="parameter"><code>tc</code></em>)</code>.</p></dd><dt><a name="MALLOCX_ARENA"></a><span class="term"><code class="constant">MALLOCX_ARENA(<em class="parameter"><code>a</code></em>)
- </code></span></dt><dd><p>Use the arena specified by the index
- <em class="parameter"><code>a</code></em>. This macro has no effect for regions that
- were allocated via an arena other than the one specified. This
- macro does not validate that <em class="parameter"><code>a</code></em> specifies an
- arena index in the valid range.</p></dd></dl></div><p>
- </p><p>The <code class="function">mallocx</code>(<em class="parameter"><code></code></em>) function allocates at
- least <em class="parameter"><code>size</code></em> bytes of memory, and returns a pointer
- to the base address of the allocation. Behavior is undefined if
- <em class="parameter"><code>size</code></em> is <code class="constant">0</code>, or if request size
- overflows due to size class and/or alignment constraints.</p><p>The <code class="function">rallocx</code>(<em class="parameter"><code></code></em>) function resizes the
- allocation at <em class="parameter"><code>ptr</code></em> to be at least
- <em class="parameter"><code>size</code></em> bytes, and returns a pointer to the base
- address of the resulting allocation, which may or may not have moved from
- its original location. Behavior is undefined if
- <em class="parameter"><code>size</code></em> is <code class="constant">0</code>, or if request size
- overflows due to size class and/or alignment constraints.</p><p>The <code class="function">xallocx</code>(<em class="parameter"><code></code></em>) function resizes the
- allocation at <em class="parameter"><code>ptr</code></em> in place to be at least
- <em class="parameter"><code>size</code></em> bytes, and returns the real size of the
- allocation. If <em class="parameter"><code>extra</code></em> is non-zero, an attempt is
- made to resize the allocation to be at least <code class="code">(<em class="parameter"><code>size</code></em> +
- <em class="parameter"><code>extra</code></em>)</code> bytes, though inability to allocate
- the extra byte(s) will not by itself result in failure to resize.
- Behavior is undefined if <em class="parameter"><code>size</code></em> is
- <code class="constant">0</code>, or if <code class="code">(<em class="parameter"><code>size</code></em> + <em class="parameter"><code>extra</code></em>
- > <code class="constant">SIZE_T_MAX</code>)</code>.</p><p>The <code class="function">sallocx</code>(<em class="parameter"><code></code></em>) function returns the
- real size of the allocation at <em class="parameter"><code>ptr</code></em>.</p><p>The <code class="function">dallocx</code>(<em class="parameter"><code></code></em>) function causes the
- memory referenced by <em class="parameter"><code>ptr</code></em> to be made available for
- future allocations.</p><p>The <code class="function">sdallocx</code>(<em class="parameter"><code></code></em>) function is an
- extension of <code class="function">dallocx</code>(<em class="parameter"><code></code></em>) with a
- <em class="parameter"><code>size</code></em> parameter to allow the caller to pass in the
- allocation size as an optimization. The minimum valid input size is the
- original requested size of the allocation, and the maximum valid input
- size is the corresponding value returned by
- <code class="function">nallocx</code>(<em class="parameter"><code></code></em>) or
- <code class="function">sallocx</code>(<em class="parameter"><code></code></em>).</p><p>The <code class="function">nallocx</code>(<em class="parameter"><code></code></em>) function allocates no
- memory, but it performs the same size computation as the
- <code class="function">mallocx</code>(<em class="parameter"><code></code></em>) function, and returns the real
- size of the allocation that would result from the equivalent
- <code class="function">mallocx</code>(<em class="parameter"><code></code></em>) function call. Behavior is
- undefined if <em class="parameter"><code>size</code></em> is <code class="constant">0</code>, or if
- request size overflows due to size class and/or alignment
- constraints.</p><p>The <code class="function">mallctl</code>(<em class="parameter"><code></code></em>) function provides a
- general interface for introspecting the memory allocator, as well as
- setting modifiable parameters and triggering actions. The
- period-separated <em class="parameter"><code>name</code></em> argument specifies a
- location in a tree-structured namespace; see the <a class="xref" href="#mallctl_namespace" title="MALLCTL NAMESPACE">MALLCTL NAMESPACE</a> section for
- documentation on the tree contents. To read a value, pass a pointer via
- <em class="parameter"><code>oldp</code></em> to adequate space to contain the value, and a
- pointer to its length via <em class="parameter"><code>oldlenp</code></em>; otherwise pass
- <code class="constant">NULL</code> and <code class="constant">NULL</code>. Similarly, to
- write a value, pass a pointer to the value via
- <em class="parameter"><code>newp</code></em>, and its length via
- <em class="parameter"><code>newlen</code></em>; otherwise pass <code class="constant">NULL</code>
- and <code class="constant">0</code>.</p><p>The <code class="function">mallctlnametomib</code>(<em class="parameter"><code></code></em>) function
- provides a way to avoid repeated name lookups for applications that
- repeatedly query the same portion of the namespace, by translating a name
- to a “Management Information Base” (MIB) that can be passed
- repeatedly to <code class="function">mallctlbymib</code>(<em class="parameter"><code></code></em>). Upon
- successful return from <code class="function">mallctlnametomib</code>(<em class="parameter"><code></code></em>),
- <em class="parameter"><code>mibp</code></em> contains an array of
- <em class="parameter"><code>*miblenp</code></em> integers, where
- <em class="parameter"><code>*miblenp</code></em> is the lesser of the number of components
- in <em class="parameter"><code>name</code></em> and the input value of
- <em class="parameter"><code>*miblenp</code></em>. Thus it is possible to pass a
- <em class="parameter"><code>*miblenp</code></em> that is smaller than the number of
- period-separated name components, which results in a partial MIB that can
- be used as the basis for constructing a complete MIB. For name
- components that are integers (e.g. the 2 in
- <a class="link" href="#arenas.bin.i.size">
- "<code class="mallctl">arenas.bin.2.size</code>"
- </a>),
- the corresponding MIB component will always be that integer. Therefore,
- it is legitimate to construct code like the following: </p><pre class="programlisting">
- unsigned nbins, i;
- size_t mib[4];
- size_t len, miblen;
- len = sizeof(nbins);
- mallctl("arenas.nbins", &nbins, &len, NULL, 0);
- miblen = 4;
- mallctlnametomib("arenas.bin.0.size", mib, &miblen);
- for (i = 0; i < nbins; i++) {
- size_t bin_size;
- mib[2] = i;
- len = sizeof(bin_size);
- mallctlbymib(mib, miblen, &bin_size, &len, NULL, 0);
- /* Do something with bin_size... */
- }</pre><p>The <code class="function">malloc_stats_print</code>(<em class="parameter"><code></code></em>) function
- writes human-readable summary statistics via the
- <em class="parameter"><code>write_cb</code></em> callback function pointer and
- <em class="parameter"><code>cbopaque</code></em> data passed to
- <em class="parameter"><code>write_cb</code></em>, or
- <code class="function">malloc_message</code>(<em class="parameter"><code></code></em>) if
- <em class="parameter"><code>write_cb</code></em> is <code class="constant">NULL</code>. This
- function can be called repeatedly. General information that never
- changes during execution can be omitted by specifying "g" as a character
- within the <em class="parameter"><code>opts</code></em> string. Note that
- <code class="function">malloc_message</code>(<em class="parameter"><code></code></em>) uses the
- <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) functions internally, so
- inconsistent statistics can be reported if multiple threads use these
- functions simultaneously. If <code class="option">--enable-stats</code> is
- specified during configuration, “m” and “a” can
- be specified to omit merged arena and per arena statistics, respectively;
- “b”, “l”, and “h” can be specified to
- omit per size class statistics for bins, large objects, and huge objects,
- respectively. Unrecognized characters are silently ignored. Note that
- thread caching may prevent some statistics from being completely up to
- date, since extra locking would be required to merge counters that track
- thread cache operations.
- </p><p>The <code class="function">malloc_usable_size</code>(<em class="parameter"><code></code></em>) function
- returns the usable size of the allocation pointed to by
- <em class="parameter"><code>ptr</code></em>. The return value may be larger than the size
- that was requested during allocation. The
- <code class="function">malloc_usable_size</code>(<em class="parameter"><code></code></em>) function is not a
- mechanism for in-place <code class="function">realloc</code>(<em class="parameter"><code></code></em>); rather
- it is provided solely as a tool for introspection purposes. Any
- discrepancy between the requested allocation size and the size reported
- by <code class="function">malloc_usable_size</code>(<em class="parameter"><code></code></em>) should not be
- depended on, since such behavior is entirely implementation-dependent.
- </p></div></div><div class="refsect1"><a name="tuning"></a><h2>TUNING</h2><p>Once, when the first call is made to one of the memory allocation
- routines, the allocator initializes its internals based in part on various
- options that can be specified at compile- or run-time.</p><p>The string pointed to by the global variable
- <code class="varname">malloc_conf</code>, the “name” of the file
- referenced by the symbolic link named <code class="filename">/etc/malloc.conf</code>, and the value of the
- environment variable <code class="envar">MALLOC_CONF</code>, will be interpreted, in
- that order, from left to right as options. Note that
- <code class="varname">malloc_conf</code> may be read before
- <code class="function">main</code>(<em class="parameter"><code></code></em>) is entered, so the declaration of
- <code class="varname">malloc_conf</code> should specify an initializer that contains
- the final value to be read by jemalloc. <code class="varname">malloc_conf</code> is
- a compile-time setting, whereas <code class="filename">/etc/malloc.conf</code> and <code class="envar">MALLOC_CONF</code>
- can be safely set any time prior to program invocation.</p><p>An options string is a comma-separated list of option:value pairs.
- There is one key corresponding to each <a class="link" href="#opt.abort">
- "<code class="mallctl">opt.*</code>"
- </a> mallctl (see the <a class="xref" href="#mallctl_namespace" title="MALLCTL NAMESPACE">MALLCTL NAMESPACE</a> section for options
- documentation). For example, <code class="literal">abort:true,narenas:1</code> sets
- the <a class="link" href="#opt.abort">
- "<code class="mallctl">opt.abort</code>"
- </a> and <a class="link" href="#opt.narenas">
- "<code class="mallctl">opt.narenas</code>"
- </a> options. Some
- options have boolean values (true/false), others have integer values (base
- 8, 10, or 16, depending on prefix), and yet others have raw string
- values.</p></div><div class="refsect1"><a name="implementation_notes"></a><h2>IMPLEMENTATION NOTES</h2><p>Traditionally, allocators have used
- <span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span> to obtain memory, which is
- suboptimal for several reasons, including race conditions, increased
- fragmentation, and artificial limitations on maximum usable memory. If
- <span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span> is supported by the operating
- system, this allocator uses both
- <span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span> and
- <span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span>, in that order of preference;
- 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
- contention for threaded programs on multi-processor systems. This works
- well with regard to threading scalability, but incurs some costs. There is
- a small fixed per-arena overhead, and additionally, arenas manage memory
- completely independently of each other, which means a small fixed increase
- in overall memory fragmentation. These overheads are not generally an
- issue, given the number of arenas normally used. Note that using
- substantially more arenas than the default is not likely to improve
- performance, mainly due to reduced cache performance. However, it may make
- sense to reduce the number of arenas if an application does not make much
- use of the allocation functions.</p><p>In addition to multiple arenas, unless
- <code class="option">--disable-tcache</code> is specified during configuration, this
- allocator supports thread-specific caching for small and large objects, in
- order to make it possible to completely avoid synchronization for most
- allocation requests. Such caching allows very fast allocation in the
- common case, but it increases memory usage and fragmentation, since a
- bounded number of objects can remain allocated in each thread cache.</p><p>Memory is conceptually broken into equal-sized chunks, where the
- chunk size is a power of two that is greater than the page size. Chunks
- are always aligned to multiples of the chunk size. This alignment makes it
- possible to find metadata for user objects very quickly.</p><p>User objects are broken into three categories according to size:
- small, large, and huge. Small and large objects are managed entirely by
- arenas; huge objects are additionally aggregated in a single data structure
- that is shared by all threads. Huge objects are typically used by
- applications infrequently enough 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
- contiguous pages (unused, backing a set of small objects, or backing one
- large object). The combination of chunk alignment and chunk page maps
- makes it possible to determine all metadata regarding small and large
- allocations in constant time.</p><p>Small objects are managed in groups by page runs. Each run maintains
- a bitmap to track which regions are in use. Allocation requests that are no
- more than half the quantum (8 or 16, depending on architecture) are rounded
- up to the nearest power of two that is at least <code class="code">sizeof(<span class="type">double</span>)</code>. All other object size
- classes are multiples of the quantum, spaced such that there are four size
- classes for each doubling in size, which limits internal fragmentation to
- approximately 20% for all but the smallest size classes. Small size classes
- are smaller than four times the page size, large size classes are smaller
- than the chunk size (see the <a class="link" href="#opt.lg_chunk">
- "<code class="mallctl">opt.lg_chunk</code>"
- </a> option), and
- huge size classes extend from the chunk size up to one size class less than
- the full address space size.</p><p>Allocations are packed tightly together, which can be an issue for
- multi-threaded applications. If you need to assure that allocations do not
- suffer from cacheline sharing, round your allocation requests up to the
- nearest multiple of the cacheline size, or specify cacheline alignment when
- allocating.</p><p>The <code class="function">realloc</code>(<em class="parameter"><code></code></em>),
- <code class="function">rallocx</code>(<em class="parameter"><code></code></em>), and
- <code class="function">xallocx</code>(<em class="parameter"><code></code></em>) functions may resize allocations
- without moving them under limited circumstances. Unlike the
- <code class="function">*allocx</code>(<em class="parameter"><code></code></em>) API, the standard API does not
- officially round up the usable size of an allocation to the nearest size
- class, so technically it is necessary to call
- <code class="function">realloc</code>(<em class="parameter"><code></code></em>) to grow e.g. a 9-byte allocation to
- 16 bytes, or shrink a 16-byte allocation to 9 bytes. Growth and shrinkage
- trivially succeeds in place as long as the pre-size and post-size both round
- up to the same size class. No other API guarantees are made regarding
- in-place resizing, but the current implementation also tries to resize large
- and huge allocations in place, as long as the pre-size and post-size are
- both large or both huge. In such cases shrinkage always succeeds for large
- size classes, but for huge size classes the chunk allocator must support
- splitting (see <a class="link" href="#arena.i.chunk_hooks">
- "<code class="mallctl">arena.<i>.chunk_hooks</code>"
- </a>).
- Growth only succeeds if the trailing memory is currently available, and
- additionally for huge size classes the chunk allocator must support
- merging.</p><p>Assuming 2 MiB chunks, 4 KiB pages, and a 16-byte quantum on a
- 64-bit system, the size classes in each category are as shown in <a class="xref" href="#size_classes" title="Table 1. Size classes">Table 1</a>.</p><div class="table"><a name="size_classes"></a><p class="title"><b>Table 1. Size classes</b></p><div class="table-contents"><table summary="Size classes" border="1"><colgroup><col align="left" class="c1"><col align="right" class="c2"><col align="left" class="c3"></colgroup><thead><tr><th align="left">Category</th><th align="right">Spacing</th><th align="left">Size</th></tr></thead><tbody><tr><td rowspan="9" align="left">Small</td><td align="right">lg</td><td align="left">[8]</td></tr><tr><td align="right">16</td><td align="left">[16, 32, 48, 64, 80, 96, 112, 128]</td></tr><tr><td align="right">32</td><td align="left">[160, 192, 224, 256]</td></tr><tr><td align="right">64</td><td align="left">[320, 384, 448, 512]</td></tr><tr><td align="right">128</td><td align="left">[640, 768, 896, 1024]</td></tr><tr><td align="right">256</td><td align="left">[1280, 1536, 1792, 2048]</td></tr><tr><td align="right">512</td><td align="left">[2560, 3072, 3584, 4096]</td></tr><tr><td align="right">1 KiB</td><td align="left">[5 KiB, 6 KiB, 7 KiB, 8 KiB]</td></tr><tr><td align="right">2 KiB</td><td align="left">[10 KiB, 12 KiB, 14 KiB]</td></tr><tr><td rowspan="8" align="left">Large</td><td align="right">2 KiB</td><td align="left">[16 KiB]</td></tr><tr><td align="right">4 KiB</td><td align="left">[20 KiB, 24 KiB, 28 KiB, 32 KiB]</td></tr><tr><td align="right">8 KiB</td><td align="left">[40 KiB, 48 KiB, 54 KiB, 64 KiB]</td></tr><tr><td align="right">16 KiB</td><td align="left">[80 KiB, 96 KiB, 112 KiB, 128 KiB]</td></tr><tr><td align="right">32 KiB</td><td align="left">[160 KiB, 192 KiB, 224 KiB, 256 KiB]</td></tr><tr><td align="right">64 KiB</td><td align="left">[320 KiB, 384 KiB, 448 KiB, 512 KiB]</td></tr><tr><td align="right">128 KiB</td><td align="left">[640 KiB, 768 KiB, 896 KiB, 1 MiB]</td></tr><tr><td align="right">256 KiB</td><td align="left">[1280 KiB, 1536 KiB, 1792 KiB]</td></tr><tr><td rowspan="7" align="left">Huge</td><td align="right">256 KiB</td><td align="left">[2 MiB]</td></tr><tr><td align="right">512 KiB</td><td align="left">[2560 KiB, 3 MiB, 3584 KiB, 4 MiB]</td></tr><tr><td align="right">1 MiB</td><td align="left">[5 MiB, 6 MiB, 7 MiB, 8 MiB]</td></tr><tr><td align="right">2 MiB</td><td align="left">[10 MiB, 12 MiB, 14 MiB, 16 MiB]</td></tr><tr><td align="right">4 MiB</td><td align="left">[20 MiB, 24 MiB, 28 MiB, 32 MiB]</td></tr><tr><td align="right">8 MiB</td><td align="left">[40 MiB, 48 MiB, 56 MiB, 64 MiB]</td></tr><tr><td align="right">...</td><td align="left">...</td></tr></tbody></table></div></div><br class="table-break"></div><div class="refsect1"><a name="mallctl_namespace"></a><h2>MALLCTL NAMESPACE</h2><p>The following names are defined in the namespace accessible via the
- <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) functions. Value types are
- specified in parentheses, their readable/writable statuses are encoded as
- <code class="literal">rw</code>, <code class="literal">r-</code>, <code class="literal">-w</code>, or
- <code class="literal">--</code>, and required build configuration flags follow, if
- any. A name element encoded as <code class="literal"><i></code> or
- <code class="literal"><j></code> indicates an integer component, where the
- integer varies from 0 to some upper value that must be determined via
- introspection. In the case of
- "<code class="mallctl">stats.arenas.<i>.*</code>"
- ,
- <code class="literal"><i></code> equal to <a class="link" href="#arenas.narenas">
- "<code class="mallctl">arenas.narenas</code>"
- </a> can be
- used to access the summation of statistics from all arenas. Take special
- note of the <a class="link" href="#epoch">
- "<code class="mallctl">epoch</code>"
- </a> mallctl,
- which controls refreshing of cached dynamic statistics.</p><div class="variablelist"><dl class="variablelist"><dt><a name="version"></a><span class="term">
-
- "<code class="mallctl">version</code>"
-
- (<span class="type">const char *</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p>Return the jemalloc version string.</p></dd><dt><a name="epoch"></a><span class="term">
-
- "<code class="mallctl">epoch</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">rw</code>
- </span></dt><dd><p>If a value is passed in, refresh the data from which
- the <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) functions report values,
- and increment the epoch. Return the current epoch. This is useful for
- detecting whether another thread caused a refresh.</p></dd><dt><a name="config.cache_oblivious"></a><span class="term">
-
- "<code class="mallctl">config.cache_oblivious</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p><code class="option">--enable-cache-oblivious</code> was specified
- during build configuration.</p></dd><dt><a name="config.debug"></a><span class="term">
-
- "<code class="mallctl">config.debug</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p><code class="option">--enable-debug</code> was specified during
- build configuration.</p></dd><dt><a name="config.fill"></a><span class="term">
-
- "<code class="mallctl">config.fill</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p><code class="option">--enable-fill</code> was specified during
- build configuration.</p></dd><dt><a name="config.lazy_lock"></a><span class="term">
-
- "<code class="mallctl">config.lazy_lock</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p><code class="option">--enable-lazy-lock</code> was specified
- during build configuration.</p></dd><dt><a name="config.munmap"></a><span class="term">
-
- "<code class="mallctl">config.munmap</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p><code class="option">--enable-munmap</code> was specified during
- build configuration.</p></dd><dt><a name="config.prof"></a><span class="term">
-
- "<code class="mallctl">config.prof</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p><code class="option">--enable-prof</code> was specified during
- build configuration.</p></dd><dt><a name="config.prof_libgcc"></a><span class="term">
-
- "<code class="mallctl">config.prof_libgcc</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p><code class="option">--disable-prof-libgcc</code> was not
- specified during build configuration.</p></dd><dt><a name="config.prof_libunwind"></a><span class="term">
-
- "<code class="mallctl">config.prof_libunwind</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p><code class="option">--enable-prof-libunwind</code> was specified
- during build configuration.</p></dd><dt><a name="config.stats"></a><span class="term">
-
- "<code class="mallctl">config.stats</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p><code class="option">--enable-stats</code> was specified during
- build configuration.</p></dd><dt><a name="config.tcache"></a><span class="term">
-
- "<code class="mallctl">config.tcache</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p><code class="option">--disable-tcache</code> was not specified
- during build configuration.</p></dd><dt><a name="config.tls"></a><span class="term">
-
- "<code class="mallctl">config.tls</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p><code class="option">--disable-tls</code> was not specified during
- build configuration.</p></dd><dt><a name="config.utrace"></a><span class="term">
-
- "<code class="mallctl">config.utrace</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p><code class="option">--enable-utrace</code> was specified during
- build configuration.</p></dd><dt><a name="config.valgrind"></a><span class="term">
-
- "<code class="mallctl">config.valgrind</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p><code class="option">--enable-valgrind</code> was specified during
- build configuration.</p></dd><dt><a name="config.xmalloc"></a><span class="term">
-
- "<code class="mallctl">config.xmalloc</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p><code class="option">--enable-xmalloc</code> was specified during
- build configuration.</p></dd><dt><a name="opt.abort"></a><span class="term">
-
- "<code class="mallctl">opt.abort</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p>Abort-on-warning enabled/disabled. If true, most
- warnings are fatal. The process will call
- <span class="citerefentry"><span class="refentrytitle">abort</span>(3)</span> in these cases. This option is
- disabled by default unless <code class="option">--enable-debug</code> is
- specified during configuration, in which case it is enabled by default.
- </p></dd><dt><a name="opt.dss"></a><span class="term">
-
- "<code class="mallctl">opt.dss</code>"
-
- (<span class="type">const char *</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p>dss (<span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span>) allocation precedence as
- related to <span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span> allocation. The following
- settings are supported if
- <span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span> is supported by the operating
- system: “disabled”, “primary”, and
- “secondary”; otherwise only “disabled” is
- supported. The default is “secondary” if
- <span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span> is supported by the operating
- system; “disabled” otherwise.
- </p></dd><dt><a name="opt.lg_chunk"></a><span class="term">
-
- "<code class="mallctl">opt.lg_chunk</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p>Virtual memory chunk size (log base 2). If a chunk
- size outside the supported size range is specified, the size is
- silently clipped to the minimum/maximum supported size. The default
- chunk size is 2 MiB (2^21).
- </p></dd><dt><a name="opt.narenas"></a><span class="term">
-
- "<code class="mallctl">opt.narenas</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p>Maximum number of arenas to use for automatic
- multiplexing of threads and arenas. The default is four times the
- number of CPUs, or one if there is a single CPU.</p></dd><dt><a name="opt.lg_dirty_mult"></a><span class="term">
-
- "<code class="mallctl">opt.lg_dirty_mult</code>"
-
- (<span class="type">ssize_t</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p>Per-arena minimum ratio (log base 2) of active to dirty
- pages. Some dirty unused pages may be allowed to accumulate, within
- the limit set by the ratio (or one chunk worth of dirty pages,
- whichever is greater), before informing the kernel about some of those
- pages via <span class="citerefentry"><span class="refentrytitle">madvise</span>(2)</span> or a similar system call. This
- provides the kernel with sufficient information to recycle dirty pages
- if physical memory becomes scarce and the pages remain unused. The
- default minimum ratio is 8:1 (2^3:1); an option value of -1 will
- disable dirty page purging. See <a class="link" href="#arenas.lg_dirty_mult">
- "<code class="mallctl">arenas.lg_dirty_mult</code>"
- </a>
- and <a class="link" href="#arena.i.lg_dirty_mult">
- "<code class="mallctl">arena.<i>.lg_dirty_mult</code>"
- </a>
- for related dynamic control options.</p></dd><dt><a name="opt.stats_print"></a><span class="term">
-
- "<code class="mallctl">opt.stats_print</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p>Enable/disable statistics printing at exit. If
- enabled, the <code class="function">malloc_stats_print</code>(<em class="parameter"><code></code></em>)
- function is called at program exit via an
- <span class="citerefentry"><span class="refentrytitle">atexit</span>(3)</span> function. If
- <code class="option">--enable-stats</code> is specified during configuration, this
- has the potential to cause deadlock for a multi-threaded process that
- exits while one or more threads are executing in the memory allocation
- functions. Furthermore, <code class="function">atexit</code>(<em class="parameter"><code></code></em>) may
- allocate memory during application initialization and then deadlock
- internally when jemalloc in turn calls
- <code class="function">atexit</code>(<em class="parameter"><code></code></em>), so this option is not
- univerally usable (though the application can register its own
- <code class="function">atexit</code>(<em class="parameter"><code></code></em>) function with equivalent
- functionality). Therefore, this option should only be used with care;
- it is primarily intended as a performance tuning aid during application
- development. This option is disabled by default.</p></dd><dt><a name="opt.junk"></a><span class="term">
-
- "<code class="mallctl">opt.junk</code>"
-
- (<span class="type">const char *</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-fill</code>]
- </span></dt><dd><p>Junk filling. If set to "alloc", each byte of
- uninitialized allocated memory will be initialized to
- <code class="literal">0xa5</code>. If set to "free", all deallocated memory will
- be initialized to <code class="literal">0x5a</code>. If set to "true", both
- allocated and deallocated memory will be initialized, and if set to
- "false", junk filling be disabled entirely. This is intended for
- debugging and will impact performance negatively. This option is
- "false" by default unless <code class="option">--enable-debug</code> is specified
- during configuration, in which case it is "true" by default unless
- running inside <a class="ulink" href="http://valgrind.org/" target="_top">Valgrind</a>.</p></dd><dt><a name="opt.quarantine"></a><span class="term">
-
- "<code class="mallctl">opt.quarantine</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-fill</code>]
- </span></dt><dd><p>Per thread quarantine size in bytes. If non-zero, each
- thread maintains a FIFO object quarantine that stores up to the
- specified number of bytes of memory. The quarantined memory is not
- freed until it is released from quarantine, though it is immediately
- junk-filled if the <a class="link" href="#opt.junk">
- "<code class="mallctl">opt.junk</code>"
- </a> option is
- 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
- to access quarantined objects. This is intended for debugging and will
- impact performance negatively. The default quarantine size is 0 unless
- running inside Valgrind, in which case the default is 16
- MiB.</p></dd><dt><a name="opt.redzone"></a><span class="term">
-
- "<code class="mallctl">opt.redzone</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-fill</code>]
- </span></dt><dd><p>Redzones enabled/disabled. If enabled, small
- allocations have redzones before and after them. Furthermore, if the
- <a class="link" href="#opt.junk">
- "<code class="mallctl">opt.junk</code>"
- </a> option is
- enabled, the redzones are checked for corruption during deallocation.
- However, the primary intended purpose of this feature is to be used in
- combination with <a class="ulink" href="http://valgrind.org/" target="_top">Valgrind</a>,
- which needs redzones in order to do effective buffer overflow/underflow
- detection. This option is intended for debugging and will impact
- performance negatively. This option is disabled by
- default unless running inside Valgrind.</p></dd><dt><a name="opt.zero"></a><span class="term">
-
- "<code class="mallctl">opt.zero</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-fill</code>]
- </span></dt><dd><p>Zero filling enabled/disabled. If enabled, each byte
- of uninitialized allocated memory will be initialized to 0. Note that
- this initialization only happens once for each byte, so
- <code class="function">realloc</code>(<em class="parameter"><code></code></em>) and
- <code class="function">rallocx</code>(<em class="parameter"><code></code></em>) calls do not zero memory that
- was previously allocated. This is intended for debugging and will
- impact performance negatively. This option is disabled by default.
- </p></dd><dt><a name="opt.utrace"></a><span class="term">
-
- "<code class="mallctl">opt.utrace</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-utrace</code>]
- </span></dt><dd><p>Allocation tracing based on
- <span class="citerefentry"><span class="refentrytitle">utrace</span>(2)</span> enabled/disabled. This option
- is disabled by default.</p></dd><dt><a name="opt.xmalloc"></a><span class="term">
-
- "<code class="mallctl">opt.xmalloc</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-xmalloc</code>]
- </span></dt><dd><p>Abort-on-out-of-memory enabled/disabled. If enabled,
- rather than returning failure for any allocation function, display a
- diagnostic message on <code class="constant">STDERR_FILENO</code> and cause the
- program to drop core (using
- <span class="citerefentry"><span class="refentrytitle">abort</span>(3)</span>). If an application is
- designed to depend on this behavior, set the option at compile time by
- including the following in the source code:
- </p><pre class="programlisting">
- malloc_conf = "xmalloc:true";</pre><p>
- This option is disabled by default.</p></dd><dt><a name="opt.tcache"></a><span class="term">
-
- "<code class="mallctl">opt.tcache</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-tcache</code>]
- </span></dt><dd><p>Thread-specific caching (tcache) enabled/disabled. When
- there are multiple threads, each thread uses a tcache for objects up to
- a certain size. Thread-specific caching allows many allocations to be
- satisfied without performing any thread synchronization, at the cost of
- increased memory use. See the <a class="link" href="#opt.lg_tcache_max">
- "<code class="mallctl">opt.lg_tcache_max</code>"
- </a>
- option for related tuning information. This option is enabled by
- default unless running inside <a class="ulink" href="http://valgrind.org/" target="_top">Valgrind</a>, in which case it is
- forcefully disabled.</p></dd><dt><a name="opt.lg_tcache_max"></a><span class="term">
-
- "<code class="mallctl">opt.lg_tcache_max</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-tcache</code>]
- </span></dt><dd><p>Maximum size class (log base 2) to cache in the
- thread-specific cache (tcache). At a minimum, all small size classes
- are cached, and at a maximum all large size classes are cached. The
- default maximum is 32 KiB (2^15).</p></dd><dt><a name="opt.prof"></a><span class="term">
-
- "<code class="mallctl">opt.prof</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-prof</code>]
- </span></dt><dd><p>Memory profiling enabled/disabled. If enabled, profile
- memory allocation activity. See the <a class="link" href="#opt.prof_active">
- "<code class="mallctl">opt.prof_active</code>"
- </a>
- option for on-the-fly activation/deactivation. See the <a class="link" href="#opt.lg_prof_sample">
- "<code class="mallctl">opt.lg_prof_sample</code>"
- </a>
- option for probabilistic sampling control. See the <a class="link" href="#opt.prof_accum">
- "<code class="mallctl">opt.prof_accum</code>"
- </a>
- option for control of cumulative sample reporting. See the <a class="link" href="#opt.lg_prof_interval">
- "<code class="mallctl">opt.lg_prof_interval</code>"
- </a>
- option for information on interval-triggered profile dumping, the <a class="link" href="#opt.prof_gdump">
- "<code class="mallctl">opt.prof_gdump</code>"
- </a>
- option for information on high-water-triggered profile dumping, and the
- <a class="link" href="#opt.prof_final">
- "<code class="mallctl">opt.prof_final</code>"
- </a>
- option for final profile dumping. Profile output is compatible with
- the <span class="command"><strong>jeprof</strong></span> command, which is based on the
- <span class="command"><strong>pprof</strong></span> that is developed as part of the <a class="ulink" href="http://code.google.com/p/gperftools/" target="_top">gperftools
- package</a>.</p></dd><dt><a name="opt.prof_prefix"></a><span class="term">
-
- "<code class="mallctl">opt.prof_prefix</code>"
-
- (<span class="type">const char *</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-prof</code>]
- </span></dt><dd><p>Filename prefix for profile dumps. If the prefix is
- set to the empty string, no automatic dumps will occur; this is
- primarily useful for disabling the automatic final heap dump (which
- also disables leak reporting, if enabled). The default prefix is
- <code class="filename">jeprof</code>.</p></dd><dt><a name="opt.prof_active"></a><span class="term">
-
- "<code class="mallctl">opt.prof_active</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-prof</code>]
- </span></dt><dd><p>Profiling activated/deactivated. This is a secondary
- control mechanism that makes it possible to start the application with
- profiling enabled (see the <a class="link" href="#opt.prof">
- "<code class="mallctl">opt.prof</code>"
- </a> option) but
- inactive, then toggle profiling at any time during program execution
- with the <a class="link" href="#prof.active">
- "<code class="mallctl">prof.active</code>"
- </a> mallctl.
- This option is enabled by default.</p></dd><dt><a name="opt.prof_thread_active_init"></a><span class="term">
-
- "<code class="mallctl">opt.prof_thread_active_init</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-prof</code>]
- </span></dt><dd><p>Initial setting for <a class="link" href="#thread.prof.active">
- "<code class="mallctl">thread.prof.active</code>"
- </a>
- in newly created threads. The initial setting for newly created threads
- can also be changed during execution via the <a class="link" href="#prof.thread_active_init">
- "<code class="mallctl">prof.thread_active_init</code>"
- </a>
- mallctl. This option is enabled by default.</p></dd><dt><a name="opt.lg_prof_sample"></a><span class="term">
-
- "<code class="mallctl">opt.lg_prof_sample</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-prof</code>]
- </span></dt><dd><p>Average interval (log base 2) between allocation
- samples, as measured in bytes of allocation activity. Increasing the
- sampling interval decreases profile fidelity, but also decreases the
- computational overhead. The default sample interval is 512 KiB (2^19
- B).</p></dd><dt><a name="opt.prof_accum"></a><span class="term">
-
- "<code class="mallctl">opt.prof_accum</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-prof</code>]
- </span></dt><dd><p>Reporting of cumulative object/byte counts in profile
- dumps enabled/disabled. If this option is enabled, every unique
- backtrace must be stored for the duration of execution. Depending on
- the application, this can impose a large memory overhead, and the
- cumulative counts are not always of interest. This option is disabled
- by default.</p></dd><dt><a name="opt.lg_prof_interval"></a><span class="term">
-
- "<code class="mallctl">opt.lg_prof_interval</code>"
-
- (<span class="type">ssize_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-prof</code>]
- </span></dt><dd><p>Average interval (log base 2) between memory profile
- dumps, as measured in bytes of allocation activity. The actual
- interval between dumps may be sporadic because decentralized allocation
- counters are used to avoid synchronization bottlenecks. Profiles are
- dumped to files named according to the pattern
- <code class="filename"><prefix>.<pid>.<seq>.i<iseq>.heap</code>,
- where <code class="literal"><prefix></code> is controlled by the
- <a class="link" href="#opt.prof_prefix">
- "<code class="mallctl">opt.prof_prefix</code>"
- </a>
- option. By default, interval-triggered profile dumping is disabled
- (encoded as -1).
- </p></dd><dt><a name="opt.prof_gdump"></a><span class="term">
-
- "<code class="mallctl">opt.prof_gdump</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-prof</code>]
- </span></dt><dd><p>Set the initial state of <a class="link" href="#prof.gdump">
- "<code class="mallctl">prof.gdump</code>"
- </a>, which when
- enabled triggers a memory profile dump every time the total virtual
- memory exceeds the previous maximum. This option is disabled by
- default.</p></dd><dt><a name="opt.prof_final"></a><span class="term">
-
- "<code class="mallctl">opt.prof_final</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-prof</code>]
- </span></dt><dd><p>Use an
- <span class="citerefentry"><span class="refentrytitle">atexit</span>(3)</span> function to dump final memory
- usage to a file named according to the pattern
- <code class="filename"><prefix>.<pid>.<seq>.f.heap</code>,
- where <code class="literal"><prefix></code> is controlled by the <a class="link" href="#opt.prof_prefix">
- "<code class="mallctl">opt.prof_prefix</code>"
- </a>
- option. Note that <code class="function">atexit</code>(<em class="parameter"><code></code></em>) may allocate
- memory during application initialization and then deadlock internally
- when jemalloc in turn calls <code class="function">atexit</code>(<em class="parameter"><code></code></em>), so
- this option is not univerally usable (though the application can
- register its own <code class="function">atexit</code>(<em class="parameter"><code></code></em>) function with
- equivalent functionality). This option is disabled by
- default.</p></dd><dt><a name="opt.prof_leak"></a><span class="term">
-
- "<code class="mallctl">opt.prof_leak</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-prof</code>]
- </span></dt><dd><p>Leak reporting enabled/disabled. If enabled, use an
- <span class="citerefentry"><span class="refentrytitle">atexit</span>(3)</span> function to report memory leaks
- detected by allocation sampling. See the
- <a class="link" href="#opt.prof">
- "<code class="mallctl">opt.prof</code>"
- </a> option for
- information on analyzing heap profile output. This option is disabled
- by default.</p></dd><dt><a name="thread.arena"></a><span class="term">
-
- "<code class="mallctl">thread.arena</code>"
-
- (<span class="type">unsigned</span>)
- <code class="literal">rw</code>
- </span></dt><dd><p>Get or set the arena associated with the calling
- thread. If the specified arena was not initialized beforehand (see the
- <a class="link" href="#arenas.initialized">
- "<code class="mallctl">arenas.initialized</code>"
- </a>
- mallctl), it will be automatically initialized as a side effect of
- calling this interface.</p></dd><dt><a name="thread.allocated"></a><span class="term">
-
- "<code class="mallctl">thread.allocated</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Get the total number of bytes ever allocated by the
- calling thread. This counter has the potential to wrap around; it is
- up to the application to appropriately interpret the counter in such
- cases.</p></dd><dt><a name="thread.allocatedp"></a><span class="term">
-
- "<code class="mallctl">thread.allocatedp</code>"
-
- (<span class="type">uint64_t *</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Get a pointer to the the value that is returned by the
- <a class="link" href="#thread.allocated">
- "<code class="mallctl">thread.allocated</code>"
- </a>
- mallctl. This is useful for avoiding the overhead of repeated
- <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) calls.</p></dd><dt><a name="thread.deallocated"></a><span class="term">
-
- "<code class="mallctl">thread.deallocated</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Get the total number of bytes ever deallocated by the
- calling thread. This counter has the potential to wrap around; it is
- up to the application to appropriately interpret the counter in such
- cases.</p></dd><dt><a name="thread.deallocatedp"></a><span class="term">
-
- "<code class="mallctl">thread.deallocatedp</code>"
-
- (<span class="type">uint64_t *</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Get a pointer to the the value that is returned by the
- <a class="link" href="#thread.deallocated">
- "<code class="mallctl">thread.deallocated</code>"
- </a>
- mallctl. This is useful for avoiding the overhead of repeated
- <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) calls.</p></dd><dt><a name="thread.tcache.enabled"></a><span class="term">
-
- "<code class="mallctl">thread.tcache.enabled</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">rw</code>
- [<code class="option">--enable-tcache</code>]
- </span></dt><dd><p>Enable/disable calling thread's tcache. The tcache is
- implicitly flushed as a side effect of becoming
- disabled (see <a class="link" href="#thread.tcache.flush">
- "<code class="mallctl">thread.tcache.flush</code>"
- </a>).
- </p></dd><dt><a name="thread.tcache.flush"></a><span class="term">
-
- "<code class="mallctl">thread.tcache.flush</code>"
-
- (<span class="type">void</span>)
- <code class="literal">--</code>
- [<code class="option">--enable-tcache</code>]
- </span></dt><dd><p>Flush calling thread's thread-specific cache (tcache).
- This interface releases all cached objects and internal data structures
- associated with the calling thread's tcache. Ordinarily, this interface
- need not be called, since automatic periodic incremental garbage
- collection occurs, and the thread cache is automatically discarded when
- a thread exits. However, garbage collection is triggered by allocation
- activity, so it is possible for a thread that stops
- allocating/deallocating to retain its cache indefinitely, in which case
- the developer may find manual flushing useful.</p></dd><dt><a name="thread.prof.name"></a><span class="term">
-
- "<code class="mallctl">thread.prof.name</code>"
-
- (<span class="type">const char *</span>)
- <code class="literal">r-</code> or
- <code class="literal">-w</code>
- [<code class="option">--enable-prof</code>]
- </span></dt><dd><p>Get/set the descriptive name associated with the calling
- thread in memory profile dumps. An internal copy of the name string is
- created, so the input string need not be maintained after this interface
- completes execution. The output string of this interface should be
- copied for non-ephemeral uses, because multiple implementation details
- can cause asynchronous string deallocation. Furthermore, each
- invocation of this interface can only read or write; simultaneous
- read/write is not supported due to string lifetime limitations. The
- name string must nil-terminated and comprised only of characters in the
- sets recognized
- by <span class="citerefentry"><span class="refentrytitle">isgraph</span>(3)</span> and
- <span class="citerefentry"><span class="refentrytitle">isblank</span>(3)</span>.</p></dd><dt><a name="thread.prof.active"></a><span class="term">
-
- "<code class="mallctl">thread.prof.active</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">rw</code>
- [<code class="option">--enable-prof</code>]
- </span></dt><dd><p>Control whether sampling is currently active for the
- calling thread. This is an activation mechanism in addition to <a class="link" href="#prof.active">
- "<code class="mallctl">prof.active</code>"
- </a>; both must
- be active for the calling thread to sample. This flag is enabled by
- default.</p></dd><dt><a name="tcache.create"></a><span class="term">
-
- "<code class="mallctl">tcache.create</code>"
-
- (<span class="type">unsigned</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-tcache</code>]
- </span></dt><dd><p>Create an explicit thread-specific cache (tcache) and
- return an identifier that can be passed to the <a class="link" href="#MALLOCX_TCACHE"><code class="constant">MALLOCX_TCACHE(<em class="parameter"><code>tc</code></em>)</code></a>
- macro to explicitly use the specified cache rather than the
- automatically managed one that is used by default. Each explicit cache
- can be used by only one thread at a time; the application must assure
- that this constraint holds.
- </p></dd><dt><a name="tcache.flush"></a><span class="term">
-
- "<code class="mallctl">tcache.flush</code>"
-
- (<span class="type">unsigned</span>)
- <code class="literal">-w</code>
- [<code class="option">--enable-tcache</code>]
- </span></dt><dd><p>Flush the specified thread-specific cache (tcache). The
- same considerations apply to this interface as to <a class="link" href="#thread.tcache.flush">
- "<code class="mallctl">thread.tcache.flush</code>"
- </a>,
- except that the tcache will never be automatically be discarded.
- </p></dd><dt><a name="tcache.destroy"></a><span class="term">
-
- "<code class="mallctl">tcache.destroy</code>"
-
- (<span class="type">unsigned</span>)
- <code class="literal">-w</code>
- [<code class="option">--enable-tcache</code>]
- </span></dt><dd><p>Flush the specified thread-specific cache (tcache) and
- make the identifier available for use during a future tcache creation.
- </p></dd><dt><a name="arena.i.purge"></a><span class="term">
-
- "<code class="mallctl">arena.<i>.purge</code>"
-
- (<span class="type">void</span>)
- <code class="literal">--</code>
- </span></dt><dd><p>Purge unused dirty pages for arena <i>, or for
- all arenas if <i> equals <a class="link" href="#arenas.narenas">
- "<code class="mallctl">arenas.narenas</code>"
- </a>.
- </p></dd><dt><a name="arena.i.dss"></a><span class="term">
-
- "<code class="mallctl">arena.<i>.dss</code>"
-
- (<span class="type">const char *</span>)
- <code class="literal">rw</code>
- </span></dt><dd><p>Set the precedence of dss allocation as related to mmap
- allocation for arena <i>, or for all arenas if <i> equals
- <a class="link" href="#arenas.narenas">
- "<code class="mallctl">arenas.narenas</code>"
- </a>. See
- <a class="link" href="#opt.dss">
- "<code class="mallctl">opt.dss</code>"
- </a> for supported
- settings.</p></dd><dt><a name="arena.i.lg_dirty_mult"></a><span class="term">
-
- "<code class="mallctl">arena.<i>.lg_dirty_mult</code>"
-
- (<span class="type">ssize_t</span>)
- <code class="literal">rw</code>
- </span></dt><dd><p>Current per-arena minimum ratio (log base 2) of active
- to dirty pages for arena <i>. Each time this interface is set and
- the ratio is increased, pages are synchronously purged as necessary to
- impose the new ratio. See <a class="link" href="#opt.lg_dirty_mult">
- "<code class="mallctl">opt.lg_dirty_mult</code>"
- </a>
- for additional information.</p></dd><dt><a name="arena.i.chunk_hooks"></a><span class="term">
-
- "<code class="mallctl">arena.<i>.chunk_hooks</code>"
-
- (<span class="type">chunk_hooks_t</span>)
- <code class="literal">rw</code>
- </span></dt><dd><p>Get or set the chunk management hook functions for arena
- <i>. The functions must be capable of operating on all extant
- chunks associated with arena <i>, usually by passing unknown
- chunks to the replaced functions. In practice, it is feasible to
- control allocation for arenas created via <a class="link" href="#arenas.extend">
- "<code class="mallctl">arenas.extend</code>"
- </a> such
- that all chunks originate from an application-supplied chunk allocator
- (by setting custom chunk hook functions just after arena creation), but
- the automatically created arenas may have already created chunks prior
- to the application having an opportunity to take over chunk
- allocation.</p><pre class="programlisting">
- typedef struct {
- chunk_alloc_t *alloc;
- chunk_dalloc_t *dalloc;
- chunk_commit_t *commit;
- chunk_decommit_t *decommit;
- chunk_purge_t *purge;
- chunk_split_t *split;
- chunk_merge_t *merge;
- } chunk_hooks_t;</pre><p>The <span class="type">chunk_hooks_t</span> structure comprises function
- pointers which are described individually below. jemalloc uses these
- functions to manage chunk lifetime, which starts off with allocation of
- mapped committed memory, in the simplest case followed by deallocation.
- However, there are performance and platform reasons to retain chunks for
- later reuse. Cleanup attempts cascade from deallocation to decommit to
- purging, which gives the chunk management functions opportunities to
- reject the most permanent cleanup operations in favor of less permanent
- (and often less costly) operations. The chunk splitting and merging
- operations can also be opted out of, but this is mainly intended to
- support platforms on which virtual memory mappings provided by the
- operating system kernel do not automatically coalesce and split, e.g.
- Windows.</p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">typedef void *<b class="fsfunc">(chunk_alloc_t)</b>(</code></td><td>void *<var class="pdparam">chunk</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">alignment</var>, </td></tr><tr><td> </td><td>bool *<var class="pdparam">zero</var>, </td></tr><tr><td> </td><td>bool *<var class="pdparam">commit</var>, </td></tr><tr><td> </td><td>unsigned <var class="pdparam">arena_ind</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="literallayout"><p></p></div><p>A chunk allocation function conforms to the
- <span class="type">chunk_alloc_t</span> type and upon success returns a pointer to
- <em class="parameter"><code>size</code></em> bytes of mapped memory on behalf of arena
- <em class="parameter"><code>arena_ind</code></em> such that the chunk's base address is a
- multiple of <em class="parameter"><code>alignment</code></em>, as well as setting
- <em class="parameter"><code>*zero</code></em> to indicate whether the chunk is zeroed and
- <em class="parameter"><code>*commit</code></em> to indicate whether the chunk is
- committed. Upon error the function returns <code class="constant">NULL</code>
- and leaves <em class="parameter"><code>*zero</code></em> and
- <em class="parameter"><code>*commit</code></em> unmodified. The
- <em class="parameter"><code>size</code></em> parameter is always a multiple of the chunk
- size. The <em class="parameter"><code>alignment</code></em> parameter is always a power
- of two at least as large as the chunk size. Zeroing is mandatory if
- <em class="parameter"><code>*zero</code></em> is true upon function entry. Committing is
- mandatory if <em class="parameter"><code>*commit</code></em> is true upon function entry.
- If <em class="parameter"><code>chunk</code></em> is not <code class="constant">NULL</code>, the
- returned pointer must be <em class="parameter"><code>chunk</code></em> on success or
- <code class="constant">NULL</code> on error. Committed memory may be committed
- in absolute terms as on a system that does not overcommit, or in
- implicit terms as on a system that overcommits and satisfies physical
- memory needs on demand via soft page faults. Note that replacing the
- default chunk allocation function makes the arena's <a class="link" href="#arena.i.dss">
- "<code class="mallctl">arena.<i>.dss</code>"
- </a>
- setting irrelevant.</p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">typedef bool <b class="fsfunc">(chunk_dalloc_t)</b>(</code></td><td>void *<var class="pdparam">chunk</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>bool <var class="pdparam">committed</var>, </td></tr><tr><td> </td><td>unsigned <var class="pdparam">arena_ind</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="literallayout"><p></p></div><p>
- A chunk deallocation function conforms to the
- <span class="type">chunk_dalloc_t</span> type and deallocates a
- <em class="parameter"><code>chunk</code></em> of given <em class="parameter"><code>size</code></em> with
- <em class="parameter"><code>committed</code></em>/decommited memory as indicated, on
- behalf of arena <em class="parameter"><code>arena_ind</code></em>, returning false upon
- success. If the function returns true, this indicates opt-out from
- deallocation; the virtual memory mapping associated with the chunk
- remains mapped, in the same commit state, and available for future use,
- in which case it will be automatically retained for later reuse.</p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">typedef bool <b class="fsfunc">(chunk_commit_t)</b>(</code></td><td>void *<var class="pdparam">chunk</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">offset</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">length</var>, </td></tr><tr><td> </td><td>unsigned <var class="pdparam">arena_ind</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="literallayout"><p></p></div><p>A chunk commit function conforms to the
- <span class="type">chunk_commit_t</span> type and commits zeroed physical memory to
- back pages within a <em class="parameter"><code>chunk</code></em> of given
- <em class="parameter"><code>size</code></em> at <em class="parameter"><code>offset</code></em> bytes,
- extending for <em class="parameter"><code>length</code></em> on behalf of arena
- <em class="parameter"><code>arena_ind</code></em>, returning false upon success.
- Committed memory may be committed in absolute terms as on a system that
- does not overcommit, or in implicit terms as on a system that
- overcommits and satisfies physical memory needs on demand via soft page
- faults. If the function returns true, this indicates insufficient
- physical memory to satisfy the request.</p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">typedef bool <b class="fsfunc">(chunk_decommit_t)</b>(</code></td><td>void *<var class="pdparam">chunk</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">offset</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">length</var>, </td></tr><tr><td> </td><td>unsigned <var class="pdparam">arena_ind</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="literallayout"><p></p></div><p>A chunk decommit function conforms to the
- <span class="type">chunk_decommit_t</span> type and decommits any physical memory
- that is backing pages within a <em class="parameter"><code>chunk</code></em> of given
- <em class="parameter"><code>size</code></em> at <em class="parameter"><code>offset</code></em> bytes,
- extending for <em class="parameter"><code>length</code></em> on behalf of arena
- <em class="parameter"><code>arena_ind</code></em>, returning false upon success, in which
- case the pages will be committed via the chunk commit function before
- being reused. If the function returns true, this indicates opt-out from
- decommit; the memory remains committed and available for future use, in
- which case it will be automatically retained for later reuse.</p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">typedef bool <b class="fsfunc">(chunk_purge_t)</b>(</code></td><td>void *<var class="pdparam">chunk</var>, </td></tr><tr><td> </td><td>size_t<var class="pdparam">size</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">offset</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">length</var>, </td></tr><tr><td> </td><td>unsigned <var class="pdparam">arena_ind</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="literallayout"><p></p></div><p>A chunk purge function conforms to the <span class="type">chunk_purge_t</span>
- type and optionally discards physical pages within the virtual memory
- mapping associated with <em class="parameter"><code>chunk</code></em> of given
- <em class="parameter"><code>size</code></em> at <em class="parameter"><code>offset</code></em> bytes,
- extending for <em class="parameter"><code>length</code></em> on behalf of arena
- <em class="parameter"><code>arena_ind</code></em>, returning false if pages within the
- purged virtual memory range will be zero-filled the next time they are
- accessed.</p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">typedef bool <b class="fsfunc">(chunk_split_t)</b>(</code></td><td>void *<var class="pdparam">chunk</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size_a</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size_b</var>, </td></tr><tr><td> </td><td>bool <var class="pdparam">committed</var>, </td></tr><tr><td> </td><td>unsigned <var class="pdparam">arena_ind</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="literallayout"><p></p></div><p>A chunk split function conforms to the <span class="type">chunk_split_t</span>
- type and optionally splits <em class="parameter"><code>chunk</code></em> of given
- <em class="parameter"><code>size</code></em> into two adjacent chunks, the first of
- <em class="parameter"><code>size_a</code></em> bytes, and the second of
- <em class="parameter"><code>size_b</code></em> bytes, operating on
- <em class="parameter"><code>committed</code></em>/decommitted memory as indicated, on
- behalf of arena <em class="parameter"><code>arena_ind</code></em>, returning false upon
- success. If the function returns true, this indicates that the chunk
- remains unsplit and therefore should continue to be operated on as a
- whole.</p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">typedef bool <b class="fsfunc">(chunk_merge_t)</b>(</code></td><td>void *<var class="pdparam">chunk_a</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size_a</var>, </td></tr><tr><td> </td><td>void *<var class="pdparam">chunk_b</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size_b</var>, </td></tr><tr><td> </td><td>bool <var class="pdparam">committed</var>, </td></tr><tr><td> </td><td>unsigned <var class="pdparam">arena_ind</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="literallayout"><p></p></div><p>A chunk merge function conforms to the <span class="type">chunk_merge_t</span>
- type and optionally merges adjacent chunks,
- <em class="parameter"><code>chunk_a</code></em> of given <em class="parameter"><code>size_a</code></em>
- and <em class="parameter"><code>chunk_b</code></em> of given
- <em class="parameter"><code>size_b</code></em> into one contiguous chunk, operating on
- <em class="parameter"><code>committed</code></em>/decommitted memory as indicated, on
- behalf of arena <em class="parameter"><code>arena_ind</code></em>, returning false upon
- success. If the function returns true, this indicates that the chunks
- remain distinct mappings and therefore should continue to be operated on
- independently.</p></dd><dt><a name="arenas.narenas"></a><span class="term">
-
- "<code class="mallctl">arenas.narenas</code>"
-
- (<span class="type">unsigned</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p>Current limit on number of arenas.</p></dd><dt><a name="arenas.initialized"></a><span class="term">
-
- "<code class="mallctl">arenas.initialized</code>"
-
- (<span class="type">bool *</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p>An array of <a class="link" href="#arenas.narenas">
- "<code class="mallctl">arenas.narenas</code>"
- </a>
- booleans. Each boolean indicates whether the corresponding arena is
- initialized.</p></dd><dt><a name="arenas.lg_dirty_mult"></a><span class="term">
-
- "<code class="mallctl">arenas.lg_dirty_mult</code>"
-
- (<span class="type">ssize_t</span>)
- <code class="literal">rw</code>
- </span></dt><dd><p>Current default per-arena minimum ratio (log base 2) of
- active to dirty pages, used to initialize <a class="link" href="#arena.i.lg_dirty_mult">
- "<code class="mallctl">arena.<i>.lg_dirty_mult</code>"
- </a>
- during arena creation. See <a class="link" href="#opt.lg_dirty_mult">
- "<code class="mallctl">opt.lg_dirty_mult</code>"
- </a>
- for additional information.</p></dd><dt><a name="arenas.quantum"></a><span class="term">
-
- "<code class="mallctl">arenas.quantum</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p>Quantum size.</p></dd><dt><a name="arenas.page"></a><span class="term">
-
- "<code class="mallctl">arenas.page</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p>Page size.</p></dd><dt><a name="arenas.tcache_max"></a><span class="term">
-
- "<code class="mallctl">arenas.tcache_max</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-tcache</code>]
- </span></dt><dd><p>Maximum thread-cached size class.</p></dd><dt><a name="arenas.nbins"></a><span class="term">
-
- "<code class="mallctl">arenas.nbins</code>"
-
- (<span class="type">unsigned</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p>Number of bin size classes.</p></dd><dt><a name="arenas.nhbins"></a><span class="term">
-
- "<code class="mallctl">arenas.nhbins</code>"
-
- (<span class="type">unsigned</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-tcache</code>]
- </span></dt><dd><p>Total number of thread cache bin size
- classes.</p></dd><dt><a name="arenas.bin.i.size"></a><span class="term">
-
- "<code class="mallctl">arenas.bin.<i>.size</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p>Maximum size supported by size class.</p></dd><dt><a name="arenas.bin.i.nregs"></a><span class="term">
-
- "<code class="mallctl">arenas.bin.<i>.nregs</code>"
-
- (<span class="type">uint32_t</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p>Number of regions per page run.</p></dd><dt><a name="arenas.bin.i.run_size"></a><span class="term">
-
- "<code class="mallctl">arenas.bin.<i>.run_size</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p>Number of bytes per page run.</p></dd><dt><a name="arenas.nlruns"></a><span class="term">
-
- "<code class="mallctl">arenas.nlruns</code>"
-
- (<span class="type">unsigned</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p>Total number of large size classes.</p></dd><dt><a name="arenas.lrun.i.size"></a><span class="term">
-
- "<code class="mallctl">arenas.lrun.<i>.size</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p>Maximum size supported by this large size
- class.</p></dd><dt><a name="arenas.nhchunks"></a><span class="term">
-
- "<code class="mallctl">arenas.nhchunks</code>"
-
- (<span class="type">unsigned</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p>Total number of huge size classes.</p></dd><dt><a name="arenas.hchunk.i.size"></a><span class="term">
-
- "<code class="mallctl">arenas.hchunk.<i>.size</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p>Maximum size supported by this huge size
- class.</p></dd><dt><a name="arenas.extend"></a><span class="term">
-
- "<code class="mallctl">arenas.extend</code>"
-
- (<span class="type">unsigned</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p>Extend the array of arenas by appending a new arena,
- and returning the new arena index.</p></dd><dt><a name="prof.thread_active_init"></a><span class="term">
-
- "<code class="mallctl">prof.thread_active_init</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">rw</code>
- [<code class="option">--enable-prof</code>]
- </span></dt><dd><p>Control the initial setting for <a class="link" href="#thread.prof.active">
- "<code class="mallctl">thread.prof.active</code>"
- </a>
- in newly created threads. See the <a class="link" href="#opt.prof_thread_active_init">
- "<code class="mallctl">opt.prof_thread_active_init</code>"
- </a>
- option for additional information.</p></dd><dt><a name="prof.active"></a><span class="term">
-
- "<code class="mallctl">prof.active</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">rw</code>
- [<code class="option">--enable-prof</code>]
- </span></dt><dd><p>Control whether sampling is currently active. See the
- <a class="link" href="#opt.prof_active">
- "<code class="mallctl">opt.prof_active</code>"
- </a>
- option for additional information, as well as the interrelated <a class="link" href="#thread.prof.active">
- "<code class="mallctl">thread.prof.active</code>"
- </a>
- mallctl.</p></dd><dt><a name="prof.dump"></a><span class="term">
-
- "<code class="mallctl">prof.dump</code>"
-
- (<span class="type">const char *</span>)
- <code class="literal">-w</code>
- [<code class="option">--enable-prof</code>]
- </span></dt><dd><p>Dump a memory profile to the specified file, or if NULL
- is specified, to a file according to the pattern
- <code class="filename"><prefix>.<pid>.<seq>.m<mseq>.heap</code>,
- where <code class="literal"><prefix></code> is controlled by the
- <a class="link" href="#opt.prof_prefix">
- "<code class="mallctl">opt.prof_prefix</code>"
- </a>
- option.</p></dd><dt><a name="prof.gdump"></a><span class="term">
-
- "<code class="mallctl">prof.gdump</code>"
-
- (<span class="type">bool</span>)
- <code class="literal">rw</code>
- [<code class="option">--enable-prof</code>]
- </span></dt><dd><p>When enabled, trigger a memory profile dump every time
- the total virtual memory exceeds the previous maximum. Profiles are
- dumped to files named according to the pattern
- <code class="filename"><prefix>.<pid>.<seq>.u<useq>.heap</code>,
- where <code class="literal"><prefix></code> is controlled by the <a class="link" href="#opt.prof_prefix">
- "<code class="mallctl">opt.prof_prefix</code>"
- </a>
- option.</p></dd><dt><a name="prof.reset"></a><span class="term">
-
- "<code class="mallctl">prof.reset</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">-w</code>
- [<code class="option">--enable-prof</code>]
- </span></dt><dd><p>Reset all memory profile statistics, and optionally
- update the sample rate (see <a class="link" href="#opt.lg_prof_sample">
- "<code class="mallctl">opt.lg_prof_sample</code>"
- </a>
- and <a class="link" href="#prof.lg_sample">
- "<code class="mallctl">prof.lg_sample</code>"
- </a>).
- </p></dd><dt><a name="prof.lg_sample"></a><span class="term">
-
- "<code class="mallctl">prof.lg_sample</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-prof</code>]
- </span></dt><dd><p>Get the current sample rate (see <a class="link" href="#opt.lg_prof_sample">
- "<code class="mallctl">opt.lg_prof_sample</code>"
- </a>).
- </p></dd><dt><a name="prof.interval"></a><span class="term">
-
- "<code class="mallctl">prof.interval</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-prof</code>]
- </span></dt><dd><p>Average number of bytes allocated between
- inverval-based profile dumps. See the
- <a class="link" href="#opt.lg_prof_interval">
- "<code class="mallctl">opt.lg_prof_interval</code>"
- </a>
- option for additional information.</p></dd><dt><a name="stats.cactive"></a><span class="term">
-
- "<code class="mallctl">stats.cactive</code>"
-
- (<span class="type">size_t *</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Pointer to a counter that contains an approximate count
- of the current number of bytes in active pages. The estimate may be
- high, but never low, because each arena rounds up when computing its
- contribution to the counter. Note that the <a class="link" href="#epoch">
- "<code class="mallctl">epoch</code>"
- </a> mallctl has no bearing
- on this counter. Furthermore, counter consistency is maintained via
- atomic operations, so it is necessary to use an atomic operation in
- order to guarantee a consistent read when dereferencing the pointer.
- </p></dd><dt><a name="stats.allocated"></a><span class="term">
-
- "<code class="mallctl">stats.allocated</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Total number of bytes allocated by the
- application.</p></dd><dt><a name="stats.active"></a><span class="term">
-
- "<code class="mallctl">stats.active</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Total number of bytes in active pages allocated by the
- application. This is a multiple of the page size, and greater than or
- equal to <a class="link" href="#stats.allocated">
- "<code class="mallctl">stats.allocated</code>"
- </a>.
- This does not include <a class="link" href="#stats.arenas.i.pdirty">
-
- "<code class="mallctl">stats.arenas.<i>.pdirty</code>"
- </a>, nor pages
- entirely devoted to allocator metadata.</p></dd><dt><a name="stats.metadata"></a><span class="term">
-
- "<code class="mallctl">stats.metadata</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Total number of bytes dedicated to metadata, which
- comprise base allocations used for bootstrap-sensitive internal
- allocator data structures, arena chunk headers (see <a class="link" href="#stats.arenas.i.metadata.mapped">
- "<code class="mallctl">stats.arenas.<i>.metadata.mapped</code>"
- </a>),
- and internal allocations (see <a class="link" href="#stats.arenas.i.metadata.allocated">
- "<code class="mallctl">stats.arenas.<i>.metadata.allocated</code>"
- </a>).</p></dd><dt><a name="stats.resident"></a><span class="term">
-
- "<code class="mallctl">stats.resident</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Maximum number of bytes in physically resident data
- pages mapped by the allocator, comprising all pages dedicated to
- allocator metadata, pages backing active allocations, and unused dirty
- pages. This is a maximum rather than precise because pages may not
- actually be physically resident if they correspond to demand-zeroed
- virtual memory that has not yet been touched. This is a multiple of the
- page size, and is larger than <a class="link" href="#stats.active">
- "<code class="mallctl">stats.active</code>"
- </a>.</p></dd><dt><a name="stats.mapped"></a><span class="term">
-
- "<code class="mallctl">stats.mapped</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Total number of bytes in active chunks mapped by the
- allocator. This is a multiple of the chunk size, and is larger than
- <a class="link" href="#stats.active">
- "<code class="mallctl">stats.active</code>"
- </a>.
- This does not include inactive chunks, even those that contain unused
- dirty pages, which means that there is no strict ordering between this
- and <a class="link" href="#stats.resident">
- "<code class="mallctl">stats.resident</code>"
- </a>.</p></dd><dt><a name="stats.arenas.i.dss"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.dss</code>"
-
- (<span class="type">const char *</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p>dss (<span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span>) allocation precedence as
- related to <span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span> allocation. See <a class="link" href="#opt.dss">
- "<code class="mallctl">opt.dss</code>"
- </a> for details.
- </p></dd><dt><a name="stats.arenas.i.lg_dirty_mult"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.lg_dirty_mult</code>"
-
- (<span class="type">ssize_t</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p>Minimum ratio (log base 2) of active to dirty pages.
- See <a class="link" href="#opt.lg_dirty_mult">
- "<code class="mallctl">opt.lg_dirty_mult</code>"
- </a>
- for details.</p></dd><dt><a name="stats.arenas.i.nthreads"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.nthreads</code>"
-
- (<span class="type">unsigned</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p>Number of threads currently assigned to
- arena.</p></dd><dt><a name="stats.arenas.i.pactive"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.pactive</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p>Number of pages in active runs.</p></dd><dt><a name="stats.arenas.i.pdirty"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.pdirty</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- </span></dt><dd><p>Number of pages within unused runs that are potentially
- dirty, and for which <code class="function">madvise</code>(<em class="parameter"><code>...</code></em>,
- <em class="parameter"><code><code class="constant">MADV_DONTNEED</code></code></em>) or
- similar has not been called.</p></dd><dt><a name="stats.arenas.i.mapped"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.mapped</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Number of mapped bytes.</p></dd><dt><a name="stats.arenas.i.metadata.mapped"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.metadata.mapped</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Number of mapped bytes in arena chunk headers, which
- track the states of the non-metadata pages.</p></dd><dt><a name="stats.arenas.i.metadata.allocated"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.metadata.allocated</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Number of bytes dedicated to internal allocations.
- Internal allocations differ from application-originated allocations in
- that they are for internal use, and that they are omitted from heap
- profiles. This statistic is reported separately from <a class="link" href="#stats.metadata">
- "<code class="mallctl">stats.metadata</code>"
- </a> and
- <a class="link" href="#stats.arenas.i.metadata.mapped">
- "<code class="mallctl">stats.arenas.<i>.metadata.mapped</code>"
- </a>
- because it overlaps with e.g. the <a class="link" href="#stats.allocated">
- "<code class="mallctl">stats.allocated</code>"
- </a> and
- <a class="link" href="#stats.active">
- "<code class="mallctl">stats.active</code>"
- </a>
- statistics, whereas the other metadata statistics do
- not.</p></dd><dt><a name="stats.arenas.i.npurge"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.npurge</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Number of dirty page purge sweeps performed.
- </p></dd><dt><a name="stats.arenas.i.nmadvise"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.nmadvise</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Number of <code class="function">madvise</code>(<em class="parameter"><code>...</code></em>,
- <em class="parameter"><code><code class="constant">MADV_DONTNEED</code></code></em>) or
- similar calls made to purge dirty pages.</p></dd><dt><a name="stats.arenas.i.purged"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.purged</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Number of pages purged.</p></dd><dt><a name="stats.arenas.i.small.allocated"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.small.allocated</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Number of bytes currently allocated by small objects.
- </p></dd><dt><a name="stats.arenas.i.small.nmalloc"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.small.nmalloc</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Cumulative number of allocation requests served by
- small bins.</p></dd><dt><a name="stats.arenas.i.small.ndalloc"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.small.ndalloc</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Cumulative number of small objects returned to bins.
- </p></dd><dt><a name="stats.arenas.i.small.nrequests"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.small.nrequests</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Cumulative number of small allocation requests.
- </p></dd><dt><a name="stats.arenas.i.large.allocated"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.large.allocated</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Number of bytes currently allocated by large objects.
- </p></dd><dt><a name="stats.arenas.i.large.nmalloc"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.large.nmalloc</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Cumulative number of large allocation requests served
- directly by the arena.</p></dd><dt><a name="stats.arenas.i.large.ndalloc"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.large.ndalloc</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Cumulative number of large deallocation requests served
- directly by the arena.</p></dd><dt><a name="stats.arenas.i.large.nrequests"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.large.nrequests</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Cumulative number of large allocation requests.
- </p></dd><dt><a name="stats.arenas.i.huge.allocated"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.huge.allocated</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Number of bytes currently allocated by huge objects.
- </p></dd><dt><a name="stats.arenas.i.huge.nmalloc"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.huge.nmalloc</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Cumulative number of huge allocation requests served
- directly by the arena.</p></dd><dt><a name="stats.arenas.i.huge.ndalloc"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.huge.ndalloc</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Cumulative number of huge deallocation requests served
- directly by the arena.</p></dd><dt><a name="stats.arenas.i.huge.nrequests"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.huge.nrequests</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Cumulative number of huge allocation requests.
- </p></dd><dt><a name="stats.arenas.i.bins.j.nmalloc"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.bins.<j>.nmalloc</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Cumulative number of allocations served by bin.
- </p></dd><dt><a name="stats.arenas.i.bins.j.ndalloc"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.bins.<j>.ndalloc</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Cumulative number of allocations returned to bin.
- </p></dd><dt><a name="stats.arenas.i.bins.j.nrequests"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.bins.<j>.nrequests</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Cumulative number of allocation
- requests.</p></dd><dt><a name="stats.arenas.i.bins.j.curregs"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.bins.<j>.curregs</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Current number of regions for this size
- class.</p></dd><dt><a name="stats.arenas.i.bins.j.nfills"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.bins.<j>.nfills</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code> <code class="option">--enable-tcache</code>]
- </span></dt><dd><p>Cumulative number of tcache fills.</p></dd><dt><a name="stats.arenas.i.bins.j.nflushes"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.bins.<j>.nflushes</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code> <code class="option">--enable-tcache</code>]
- </span></dt><dd><p>Cumulative number of tcache flushes.</p></dd><dt><a name="stats.arenas.i.bins.j.nruns"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.bins.<j>.nruns</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Cumulative number of runs created.</p></dd><dt><a name="stats.arenas.i.bins.j.nreruns"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.bins.<j>.nreruns</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Cumulative number of times the current run from which
- to allocate changed.</p></dd><dt><a name="stats.arenas.i.bins.j.curruns"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.bins.<j>.curruns</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Current number of runs.</p></dd><dt><a name="stats.arenas.i.lruns.j.nmalloc"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.lruns.<j>.nmalloc</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Cumulative number of allocation requests for this size
- class served directly by the arena.</p></dd><dt><a name="stats.arenas.i.lruns.j.ndalloc"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.lruns.<j>.ndalloc</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Cumulative number of deallocation requests for this
- size class served directly by the arena.</p></dd><dt><a name="stats.arenas.i.lruns.j.nrequests"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.lruns.<j>.nrequests</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Cumulative number of allocation requests for this size
- class.</p></dd><dt><a name="stats.arenas.i.lruns.j.curruns"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.lruns.<j>.curruns</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Current number of runs for this size class.
- </p></dd><dt><a name="stats.arenas.i.hchunks.j.nmalloc"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.hchunks.<j>.nmalloc</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Cumulative number of allocation requests for this size
- class served directly by the arena.</p></dd><dt><a name="stats.arenas.i.hchunks.j.ndalloc"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.hchunks.<j>.ndalloc</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Cumulative number of deallocation requests for this
- size class served directly by the arena.</p></dd><dt><a name="stats.arenas.i.hchunks.j.nrequests"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.hchunks.<j>.nrequests</code>"
-
- (<span class="type">uint64_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Cumulative number of allocation requests for this size
- class.</p></dd><dt><a name="stats.arenas.i.hchunks.j.curhchunks"></a><span class="term">
-
- "<code class="mallctl">stats.arenas.<i>.hchunks.<j>.curhchunks</code>"
-
- (<span class="type">size_t</span>)
- <code class="literal">r-</code>
- [<code class="option">--enable-stats</code>]
- </span></dt><dd><p>Current number of huge allocations for this size class.
- </p></dd></dl></div></div><div class="refsect1"><a name="debugging_malloc_problems"></a><h2>DEBUGGING MALLOC PROBLEMS</h2><p>When debugging, it is a good idea to configure/build jemalloc with
- the <code class="option">--enable-debug</code> and <code class="option">--enable-fill</code>
- options, and recompile the program with suitable options and symbols for
- debugger support. When so configured, jemalloc incorporates a wide variety
- of run-time assertions that catch application errors such as double-free,
- write-after-free, etc.</p><p>Programs often accidentally depend on “uninitialized”
- memory actually being filled with zero bytes. Junk filling
- (see the <a class="link" href="#opt.junk">
- "<code class="mallctl">opt.junk</code>"
- </a>
- option) tends to expose such bugs in the form of obviously incorrect
- results and/or coredumps. Conversely, zero
- filling (see the <a class="link" href="#opt.zero">
- "<code class="mallctl">opt.zero</code>"
- </a> option) eliminates
- the symptoms of such bugs. Between these two options, it is usually
- possible to quickly detect, diagnose, and eliminate such bugs.</p><p>This implementation does not provide much detail about the problems
- it detects, because the performance impact for storing such information
- would be prohibitive. However, jemalloc does integrate with the most
- excellent <a class="ulink" href="http://valgrind.org/" target="_top">Valgrind</a> tool if the
- <code class="option">--enable-valgrind</code> configuration option is enabled.</p></div><div class="refsect1"><a name="diagnostic_messages"></a><h2>DIAGNOSTIC MESSAGES</h2><p>If any of the memory allocation/deallocation functions detect an
- error or warning condition, a message will be printed to file descriptor
- <code class="constant">STDERR_FILENO</code>. Errors will result in the process
- dumping core. If the <a class="link" href="#opt.abort">
- "<code class="mallctl">opt.abort</code>"
- </a> option is set, most
- warnings are treated as errors.</p><p>The <code class="varname">malloc_message</code> variable allows the programmer
- to override the function which emits the text strings forming the errors
- and warnings if for some reason the <code class="constant">STDERR_FILENO</code> file
- descriptor is not suitable for this.
- <code class="function">malloc_message</code>(<em class="parameter"><code></code></em>) takes the
- <em class="parameter"><code>cbopaque</code></em> pointer argument that is
- <code class="constant">NULL</code> unless overridden by the arguments in a call to
- <code class="function">malloc_stats_print</code>(<em class="parameter"><code></code></em>), followed by a string
- pointer. Please note that doing anything which tries to allocate memory in
- this function is likely to result in a crash or deadlock.</p><p>All messages are prefixed by
- “<code class="computeroutput"><jemalloc>: </code>”.</p></div><div class="refsect1"><a name="return_values"></a><h2>RETURN VALUES</h2><div class="refsect2"><a name="idp46949776"></a><h3>Standard API</h3><p>The <code class="function">malloc</code>(<em class="parameter"><code></code></em>) and
- <code class="function">calloc</code>(<em class="parameter"><code></code></em>) functions return a pointer to the
- allocated memory if successful; otherwise a <code class="constant">NULL</code>
- pointer is returned and <code class="varname">errno</code> is set to
- <span class="errorname">ENOMEM</span>.</p><p>The <code class="function">posix_memalign</code>(<em class="parameter"><code></code></em>) function
- returns the value 0 if successful; otherwise it returns an error value.
- The <code class="function">posix_memalign</code>(<em class="parameter"><code></code></em>) function will fail
- if:
- </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><span class="errorname">EINVAL</span></span></dt><dd><p>The <em class="parameter"><code>alignment</code></em> parameter is
- not a power of 2 at least as large as
- <code class="code">sizeof(<span class="type">void *</span>)</code>.
- </p></dd><dt><span class="term"><span class="errorname">ENOMEM</span></span></dt><dd><p>Memory allocation error.</p></dd></dl></div><p>
- </p><p>The <code class="function">aligned_alloc</code>(<em class="parameter"><code></code></em>) function returns
- a pointer to the allocated memory if successful; otherwise a
- <code class="constant">NULL</code> pointer is returned and
- <code class="varname">errno</code> is set. The
- <code class="function">aligned_alloc</code>(<em class="parameter"><code></code></em>) function will fail if:
- </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><span class="errorname">EINVAL</span></span></dt><dd><p>The <em class="parameter"><code>alignment</code></em> parameter is
- not a power of 2.
- </p></dd><dt><span class="term"><span class="errorname">ENOMEM</span></span></dt><dd><p>Memory allocation error.</p></dd></dl></div><p>
- </p><p>The <code class="function">realloc</code>(<em class="parameter"><code></code></em>) function returns a
- pointer, possibly identical to <em class="parameter"><code>ptr</code></em>, to the
- allocated memory if successful; otherwise a <code class="constant">NULL</code>
- pointer is returned, and <code class="varname">errno</code> is set to
- <span class="errorname">ENOMEM</span> if the error was the result of an
- allocation failure. The <code class="function">realloc</code>(<em class="parameter"><code></code></em>)
- function always leaves the original buffer intact when an error occurs.
- </p><p>The <code class="function">free</code>(<em class="parameter"><code></code></em>) function returns no
- value.</p></div><div class="refsect2"><a name="idp46974576"></a><h3>Non-standard API</h3><p>The <code class="function">mallocx</code>(<em class="parameter"><code></code></em>) and
- <code class="function">rallocx</code>(<em class="parameter"><code></code></em>) functions return a pointer to
- the allocated memory if successful; otherwise a <code class="constant">NULL</code>
- pointer is returned to indicate insufficient contiguous memory was
- available to service the allocation request. </p><p>The <code class="function">xallocx</code>(<em class="parameter"><code></code></em>) function returns the
- real size of the resulting resized allocation pointed to by
- <em class="parameter"><code>ptr</code></em>, which is a value less than
- <em class="parameter"><code>size</code></em> if the allocation could not be adequately
- grown in place. </p><p>The <code class="function">sallocx</code>(<em class="parameter"><code></code></em>) function returns the
- real size of the allocation pointed to by <em class="parameter"><code>ptr</code></em>.
- </p><p>The <code class="function">nallocx</code>(<em class="parameter"><code></code></em>) returns the real size
- that would result from a successful equivalent
- <code class="function">mallocx</code>(<em class="parameter"><code></code></em>) function call, or zero if
- insufficient memory is available to perform the size computation. </p><p>The <code class="function">mallctl</code>(<em class="parameter"><code></code></em>),
- <code class="function">mallctlnametomib</code>(<em class="parameter"><code></code></em>), and
- <code class="function">mallctlbymib</code>(<em class="parameter"><code></code></em>) functions return 0 on
- success; otherwise they return an error value. The functions will fail
- if:
- </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><span class="errorname">EINVAL</span></span></dt><dd><p><em class="parameter"><code>newp</code></em> is not
- <code class="constant">NULL</code>, and <em class="parameter"><code>newlen</code></em> is too
- large or too small. Alternatively, <em class="parameter"><code>*oldlenp</code></em>
- is too large or too small; in this case as much data as possible
- are read despite the error.</p></dd><dt><span class="term"><span class="errorname">ENOENT</span></span></dt><dd><p><em class="parameter"><code>name</code></em> or
- <em class="parameter"><code>mib</code></em> specifies an unknown/invalid
- 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
- write read-only value.</p></dd><dt><span class="term"><span class="errorname">EAGAIN</span></span></dt><dd><p>A memory allocation failure
- 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
- not directly related to <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>)
- read/write processing.</p></dd></dl></div><p>
- </p><p>The <code class="function">malloc_usable_size</code>(<em class="parameter"><code></code></em>) function
- returns the usable size of the allocation pointed to by
- <em class="parameter"><code>ptr</code></em>. </p></div></div><div class="refsect1"><a name="environment"></a><h2>ENVIRONMENT</h2><p>The following environment variable affects the execution of the
- allocation functions:
- </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="envar">MALLOC_CONF</code></span></dt><dd><p>If the environment variable
- <code class="envar">MALLOC_CONF</code> is set, the characters it contains
- will be interpreted as options.</p></dd></dl></div><p>
- </p></div><div class="refsect1"><a name="examples"></a><h2>EXAMPLES</h2><p>To dump core whenever a problem occurs:
- </p><pre class="screen">ln -s 'abort:true' /etc/malloc.conf</pre><p>
- </p><p>To specify in the source a chunk size that is 16 MiB:
- </p><pre class="programlisting">
- malloc_conf = "lg_chunk:24";</pre></div><div class="refsect1"><a name="see_also"></a><h2>SEE ALSO</h2><p><span class="citerefentry"><span class="refentrytitle">madvise</span>(2)</span>,
- <span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span>,
- <span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span>,
- <span class="citerefentry"><span class="refentrytitle">utrace</span>(2)</span>,
- <span class="citerefentry"><span class="refentrytitle">alloca</span>(3)</span>,
- <span class="citerefentry"><span class="refentrytitle">atexit</span>(3)</span>,
- <span class="citerefentry"><span class="refentrytitle">getpagesize</span>(3)</span></p></div><div class="refsect1"><a name="standards"></a><h2>STANDARDS</h2><p>The <code class="function">malloc</code>(<em class="parameter"><code></code></em>),
- <code class="function">calloc</code>(<em class="parameter"><code></code></em>),
- <code class="function">realloc</code>(<em class="parameter"><code></code></em>), and
- <code class="function">free</code>(<em class="parameter"><code></code></em>) functions conform to ISO/IEC
- 9899:1990 (“ISO C90”).</p><p>The <code class="function">posix_memalign</code>(<em class="parameter"><code></code></em>) function conforms
- to IEEE Std 1003.1-2001 (“POSIX.1”).</p></div></div></body></html>
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