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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 V1.75.2"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" title="JEMALLOC"><a name="id2783946"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>jemalloc — general purpose memory allocation functions</p></div><div class="refsect1" title="LIBRARY"><a name="library"></a><h2>LIBRARY</h2><p>This manual describes jemalloc 2.2.1-0-g5ef7abf6d846720fb3fb8c737861c99b5ad1d862. 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" title="SYNOPSIS"><h2>SYNOPSIS</h2><div class="funcsynopsis"><pre class="funcsynopsisinfo">#include <<code class="filename">stdlib.h</code>>
+#include <<code class="filename">jemalloc/jemalloc.h</code>></pre><div class="refsect2" title="Standard API"><a name="id2830421"></a><h3>Standard API</h3><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void *<b class="fsfunc">malloc</b>(</code></td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void *<b class="fsfunc">calloc</b>(</code></td><td>size_t <var class="pdparam">number</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">posix_memalign</b>(</code></td><td>void **<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">alignment</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void *<b class="fsfunc">realloc</b>(</code></td><td>void *<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">free</b>(</code></td><td>void *<var class="pdparam">ptr</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="refsect2" title="Non-standard API"><a name="id2837717"></a><h3>Non-standard API</h3><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">size_t <b class="fsfunc">malloc_usable_size</b>(</code></td><td>const void *<var class="pdparam">ptr</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">malloc_stats_print</b>(</code></td><td>void <var class="pdparam">(*write_cb)</var>
+ <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" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">mallctl</b>(</code></td><td>const char *<var class="pdparam">name</var>, </td></tr><tr><td> </td><td>void *<var class="pdparam">oldp</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">oldlenp</var>, </td></tr><tr><td> </td><td>void *<var class="pdparam">newp</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">newlen</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">mallctlnametomib</b>(</code></td><td>const char *<var class="pdparam">name</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">mibp</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">miblenp</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">mallctlbymib</b>(</code></td><td>const size_t *<var class="pdparam">mib</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">miblen</var>, </td></tr><tr><td> </td><td>void *<var class="pdparam">oldp</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">oldlenp</var>, </td></tr><tr><td> </td><td>void *<var class="pdparam">newp</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">newlen</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">(*malloc_message)</b>(</code></td><td>void *<var class="pdparam">cbopaque</var>, </td></tr><tr><td> </td><td>const char *<var class="pdparam">s</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><p><span class="type">const char *</span><code class="varname">malloc_conf</code>;</p></div><div class="refsect2" title="Experimental API"><a name="id2830042"></a><h3>Experimental API</h3><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">allocm</b>(</code></td><td>void **<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">rsize</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">rallocm</b>(</code></td><td>void **<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">rsize</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">extra</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">sallocm</b>(</code></td><td>const void *<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">rsize</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">dallocm</b>(</code></td><td>void *<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div></div><div class="refsect1" title="DESCRIPTION"><a name="description"></a><h2>DESCRIPTION</h2><div class="refsect2" title="Standard API"><a name="id2840968"></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 an even 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">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" title="Non-standard API"><a name="id2827225"></a><h3>Non-standard API</h3><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><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” and “l” can be specified to omit per size
+ class statistics for bins and large 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">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;
+
+int mib[4];
+size_t len, miblen;
+
+len = sizeof(nbins);
+mallctl("arenas.nbins", &nbins, &len, NULL, 0);
+
+miblen = 4;
+mallnametomib("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></div><div class="refsect2" title="Experimental API"><a name="id2807945"></a><h3>Experimental API</h3><p>The experimental API is subject to change or removal without regard
+ for backward compatibility.</p><p>The <code class="function">allocm</code>(<em class="parameter"><code></code></em>),
+ <code class="function">rallocm</code>(<em class="parameter"><code></code></em>),
+ <code class="function">sallocm</code>(<em class="parameter"><code></code></em>), and
+ <code class="function">dallocm</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><dt><span class="term"><code class="constant">ALLOCM_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><span class="term"><code class="constant">ALLOCM_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><span class="term"><code class="constant">ALLOCM_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 option is
+ absent, newly allocated memory is uninitialized.</p></dd><dt><span class="term"><code class="constant">ALLOCM_NO_MOVE</code></span></dt><dd><p>For reallocation, fail rather than moving the
+ object. This constraint can apply to both growth and
+ shrinkage.</p></dd></dl></div><p>
+ </p><p>The <code class="function">allocm</code>(<em class="parameter"><code></code></em>) function allocates at
+ least <em class="parameter"><code>size</code></em> bytes of memory, sets
+ <em class="parameter"><code>*ptr</code></em> to the base address of the allocation, and
+ sets <em class="parameter"><code>*rsize</code></em> to the real size of the allocation if
+ <em class="parameter"><code>rsize</code></em> is not <code class="constant">NULL</code>.</p><p>The <code class="function">rallocm</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, sets <em class="parameter"><code>*ptr</code></em> to
+ the base address of the allocation if it moved, and sets
+ <em class="parameter"><code>*rsize</code></em> to the real size of the allocation if
+ <em class="parameter"><code>rsize</code></em> is not <code class="constant">NULL</code>. 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. Behavior is
+ undefined 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">sallocm</code>(<em class="parameter"><code></code></em>) function sets
+ <em class="parameter"><code>*rsize</code></em> to the real size of the allocation.</p><p>The <code class="function">dallocm</code>(<em class="parameter"><code></code></em>) function causes the
+ memory referenced by <em class="parameter"><code>ptr</code></em> to be made available for
+ future allocations.</p></div></div><div class="refsect1" title="TUNING"><a name="tuning"></a><h2>TUNING</h2><p>Once, when the first call is made to one of the memory allocation
+ 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.</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" title="IMPLEMENTATION NOTES"><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
+ <code class="option">--enable-dss</code> is specified during configuration, this
+ allocator uses both <span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span> and
+ <span class="citerefentry"><span class="refentrytitle">mmap</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 objects are smaller than one page. Large
+ objects are smaller than the chunk size. Huge objects are a multiple of
+ the chunk size. Small and large objects are managed by arenas; huge
+ objects are managed separately in a single data structure that is shared by
+ all threads. Huge objects are 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 frontier and free list to track which regions are in use. Unless
+ <code class="option">--disable-tiny</code> is specified during configuration,
+ 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">void *</span>)</code>.
+ Allocation requests that are more than half the quantum, but no more than
+ the minimum cacheline-multiple size class (see the <a class="link" href="#opt.lg_qspace_max">
+ "<code class="mallctl">opt.lg_qspace_max</code>"
+ </a>
+ option) are rounded up to the nearest multiple of the quantum. Allocation
+ requests that are more than the minimum cacheline-multiple size class, but
+ no more than the minimum subpage-multiple size class (see the <a class="link" href="#opt.lg_cspace_max">
+ "<code class="mallctl">opt.lg_cspace_max</code>"
+ </a>
+ option) are rounded up to the nearest multiple of the cacheline size (64).
+ Allocation requests that are more than the minimum subpage-multiple size
+ class, but no more than the maximum subpage-multiple size class are rounded
+ up to the nearest multiple of the subpage size (256). Allocation requests
+ that are more than the maximum subpage-multiple size class, but small
+ enough to fit in an arena-managed chunk (see the <a class="link" href="#opt.lg_chunk">
+ "<code class="mallctl">opt.lg_chunk</code>"
+ </a> option), are
+ rounded up to the nearest run size. Allocation requests that are too large
+ to fit in an arena-managed chunk are rounded up to the nearest multiple of
+ the chunk 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>Assuming 4 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"><col align="left"><col align="left"></colgroup><thead><tr><th align="left">Category</th><th align="left">Subcategory</th><th align="left">Size</th></tr></thead><tbody><tr><td rowspan="4" align="left">Small</td><td align="left">Tiny</td><td align="left">[8]</td></tr><tr><td align="left">Quantum-spaced</td><td align="left">[16, 32, 48, ..., 128]</td></tr><tr><td align="left">Cacheline-spaced</td><td align="left">[192, 256, 320, ..., 512]</td></tr><tr><td align="left">Subpage-spaced</td><td align="left">[768, 1024, 1280, ..., 3840]</td></tr><tr><td colspan="2" align="left">Large</td><td align="left">[4 KiB, 8 KiB, 12 KiB, ..., 4072 KiB]</td></tr><tr><td colspan="2" align="left">Huge</td><td align="left">[4 MiB, 8 MiB, 12 MiB, ...]</td></tr></tbody></table></div></div><br class="table-break"></div><div class="refsect1" title="MALLCTL NAMESPACE"><a name="mallctl_namespace"></a><h2>MALLCTL NAMESPACE</h2><p>The following names are defined in the namespace accessible via the
+ <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><dt><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><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><span class="term">
+
+ "<code class="mallctl">config.dss</code>"
+
+ (<span class="type">bool</span>)
+ <code class="literal">r-</code>
+ </span></dt><dd><p><code class="option">--enable-dss</code> was specified during
+ build configuration.</p></dd><dt><span class="term">
+
+ "<code class="mallctl">config.dynamic_page_shift</code>"
+
+ (<span class="type">bool</span>)
+ <code class="literal">r-</code>
+ </span></dt><dd><p><code class="option">--enable-dynamic-page-shift</code> was
+ specified during build configuration.</p></dd><dt><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><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><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><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><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><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><span class="term">
+
+ "<code class="mallctl">config.swap</code>"
+
+ (<span class="type">bool</span>)
+ <code class="literal">r-</code>
+ </span></dt><dd><p><code class="option">--enable-swap</code> was specified during
+ build configuration.</p></dd><dt><span class="term">
+
+ "<code class="mallctl">config.sysv</code>"
+
+ (<span class="type">bool</span>)
+ <code class="literal">r-</code>
+ </span></dt><dd><p><code class="option">--enable-sysv</code> was specified during
+ build configuration.</p></dd><dt><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><span class="term">
+
+ "<code class="mallctl">config.tiny</code>"
+
+ (<span class="type">bool</span>)
+ <code class="literal">r-</code>
+ </span></dt><dd><p><code class="option">--disable-tiny</code> was not specified
+ during build configuration.</p></dd><dt><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><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.lg_qspace_max"></a><span class="term">
+
+ "<code class="mallctl">opt.lg_qspace_max</code>"
+
+ (<span class="type">size_t</span>)
+ <code class="literal">r-</code>
+ </span></dt><dd><p>Size (log base 2) of the maximum size class that is a
+ multiple of the quantum (8 or 16 bytes, depending on architecture).
+ Above this size, cacheline spacing is used for size classes. The
+ default value is 128 bytes (2^7).</p></dd><dt><a name="opt.lg_cspace_max"></a><span class="term">
+
+ "<code class="mallctl">opt.lg_cspace_max</code>"
+
+ (<span class="type">size_t</span>)
+ <code class="literal">r-</code>
+ </span></dt><dd><p>Size (log base 2) of the maximum size class that is a
+ multiple of the cacheline size (64). Above this size, subpage spacing
+ (256 bytes) is used for size classes. The default value is 512 bytes
+ (2^9).</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). The default
+ chunk size is 4 MiB (2^22).</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. The default maximum
+ number of arenas 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 32:1 (2^5:1); an option value of -1 will
+ disable dirty page purging.</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. 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">bool</span>)
+ <code class="literal">r-</code>
+ [<code class="option">--enable-fill</code>]
+ </span></dt><dd><p>Junk filling enabled/disabled. If enabled, each byte
+ of uninitialized allocated memory will be initialized to
+ <code class="literal">0xa5</code>. All deallocated memory will be initialized to
+ <code class="literal">0x5a</code>. This is intended for debugging and will
+ impact performance negatively. 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.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">rallocm</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.sysv"></a><span class="term">
+
+ "<code class="mallctl">opt.sysv</code>"
+
+ (<span class="type">bool</span>)
+ <code class="literal">r-</code>
+ [<code class="option">--enable-sysv</code>]
+ </span></dt><dd><p>If enabled, attempting to allocate zero bytes will
+ return a <code class="constant">NULL</code> pointer instead of a valid pointer.
+ (The default behavior is to make a minimal allocation and return a
+ pointer to it.) This option is provided for System V compatibility.
+ This option is incompatible with the <a class="link" href="#opt.xmalloc">
+ "<code class="mallctl">opt.xmalloc</code>"
+ </a> option.
+ 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 enabled/disabled. When there
+ are multiple threads, each thread uses a thread-specific cache 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_gc_sweep">
+ "<code class="mallctl">opt.lg_tcache_gc_sweep</code>"
+ </a>
+ and <a class="link" href="#opt.lg_tcache_max">
+ "<code class="mallctl">opt.lg_tcache_max</code>"
+ </a>
+ options for related tuning information. This option is enabled by
+ default.</p></dd><dt><a name="opt.lg_tcache_gc_sweep"></a><span class="term">
+
+ "<code class="mallctl">opt.lg_tcache_gc_sweep</code>"
+
+ (<span class="type">ssize_t</span>)
+ <code class="literal">r-</code>
+ [<code class="option">--enable-tcache</code>]
+ </span></dt><dd><p>Approximate interval (log base 2) between full
+ thread-specific cache garbage collection sweeps, counted in terms of
+ thread-specific cache allocation/deallocation events. Garbage
+ collection is actually performed incrementally, one size class at a
+ time, in order to avoid large collection pauses. The default sweep
+ interval is 8192 (2^13); setting this option to -1 will disable garbage
+ collection.</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. 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, and 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. See the <a class="link" href="#opt.lg_prof_bt_max">
+ "<code class="mallctl">opt.lg_prof_bt_max</code>"
+ </a>
+ option for backtrace depth control. 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_tcmax">
+ "<code class="mallctl">opt.lg_prof_tcmax</code>"
+ </a>
+ option for control of per thread backtrace caching. 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, and 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.
+ Profile output is compatible with the included <span class="command"><strong>pprof</strong></span>
+ Perl script, which originates from the <a class="ulink" href="http://code.google.com/p/google-perftools/" target="_top">google-perftools
+ 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.lg_prof_bt_max"></a><span class="term">
+
+ "<code class="mallctl">opt.lg_prof_bt_max</code>"
+
+ (<span class="type">size_t</span>)
+ <code class="literal">r-</code>
+ [<code class="option">--enable-prof</code>]
+ </span></dt><dd><p>Maximum backtrace depth (log base 2) when profiling
+ memory allocation activity. The default is 128 (2^7).</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.lg_prof_sample"></a><span class="term">
+
+ "<code class="mallctl">opt.lg_prof_sample</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 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 1 (2^0) (i.e.
+ all allocations are sampled).</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. See the
+ <a class="link" href="#opt.lg_prof_tcmax">
+ "<code class="mallctl">opt.lg_prof_tcmax</code>"
+ </a>
+ option for control of per thread backtrace caching, which has important
+ interactions. This option is enabled by default.</p></dd><dt><a name="opt.lg_prof_tcmax"></a><span class="term">
+
+ "<code class="mallctl">opt.lg_prof_tcmax</code>"
+
+ (<span class="type">ssize_t</span>)
+ <code class="literal">r-</code>
+ [<code class="option">--enable-prof</code>]
+ </span></dt><dd><p>Maximum per thread backtrace cache (log base 2) used
+ for heap profiling. A backtrace can only be discarded if the
+ <a class="link" href="#opt.prof_accum">
+ "<code class="mallctl">opt.prof_accum</code>"
+ </a>
+ option is disabled, and no thread caches currently refer to the
+ backtrace. Therefore, a backtrace cache limit should be imposed if the
+ intention is to limit how much memory is used by backtraces. By
+ default, no limit is imposed (encoded as -1).
+ </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>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. 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.lg_prof_bt_max">
+ "<code class="mallctl">opt.lg_prof_bt_max</code>"
+ </a>
+ option for backtrace depth control. 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="opt.overcommit"></a><span class="term">
+
+ "<code class="mallctl">opt.overcommit</code>"
+
+ (<span class="type">bool</span>)
+ <code class="literal">r-</code>
+ [<code class="option">--enable-swap</code>]
+ </span></dt><dd><p>Over-commit enabled/disabled. If enabled, over-commit
+ memory as a side effect of using anonymous
+ <span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span> or
+ <span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span> for virtual memory allocation.
+ In order for overcommit to be disabled, the <a class="link" href="#swap.fds">
+ "<code class="mallctl">swap.fds</code>"
+ </a> mallctl must have
+ been successfully written to. This option is enabled by
+ default.</p></dd><dt><span class="term">
+
+ "<code class="mallctl">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 tcache. This interface releases
+ all cached objects and internal data structures associated with the
+ calling thread's thread-specific cache. 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><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. The arena index must be less than the maximum number of arenas
+ (see the <a class="link" href="#arenas.narenas">
+ "<code class="mallctl">arenas.narenas</code>"
+ </a>
+ mallctl). 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><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><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="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>Maximum 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><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><span class="term">
+
+ "<code class="mallctl">arenas.cacheline</code>"
+
+ (<span class="type">size_t</span>)
+ <code class="literal">r-</code>
+ </span></dt><dd><p>Assumed cacheline size.</p></dd><dt><span class="term">
+
+ "<code class="mallctl">arenas.subpage</code>"
+
+ (<span class="type">size_t</span>)
+ <code class="literal">r-</code>
+ </span></dt><dd><p>Subpage size class interval.</p></dd><dt><span class="term">
+
+ "<code class="mallctl">arenas.pagesize</code>"
+
+ (<span class="type">size_t</span>)
+ <code class="literal">r-</code>
+ </span></dt><dd><p>Page size.</p></dd><dt><span class="term">
+
+ "<code class="mallctl">arenas.chunksize</code>"
+
+ (<span class="type">size_t</span>)
+ <code class="literal">r-</code>
+ </span></dt><dd><p>Chunk size.</p></dd><dt><span class="term">
+
+ "<code class="mallctl">arenas.tspace_min</code>"
+
+ (<span class="type">size_t</span>)
+ <code class="literal">r-</code>
+ </span></dt><dd><p>Minimum tiny size class. Tiny size classes are powers
+ of two.</p></dd><dt><span class="term">
+
+ "<code class="mallctl">arenas.tspace_max</code>"
+
+ (<span class="type">size_t</span>)
+ <code class="literal">r-</code>
+ </span></dt><dd><p>Maximum tiny size class. Tiny size classes are powers
+ of two.</p></dd><dt><span class="term">
+
+ "<code class="mallctl">arenas.qspace_min</code>"
+
+ (<span class="type">size_t</span>)
+ <code class="literal">r-</code>
+ </span></dt><dd><p>Minimum quantum-spaced size class.</p></dd><dt><span class="term">
+
+ "<code class="mallctl">arenas.qspace_max</code>"
+
+ (<span class="type">size_t</span>)
+ <code class="literal">r-</code>
+ </span></dt><dd><p>Maximum quantum-spaced size class.</p></dd><dt><span class="term">
+
+ "<code class="mallctl">arenas.cspace_min</code>"
+
+ (<span class="type">size_t</span>)
+ <code class="literal">r-</code>
+ </span></dt><dd><p>Minimum cacheline-spaced size class.</p></dd><dt><span class="term">
+
+ "<code class="mallctl">arenas.cspace_max</code>"
+
+ (<span class="type">size_t</span>)
+ <code class="literal">r-</code>
+ </span></dt><dd><p>Maximum cacheline-spaced size class.</p></dd><dt><span class="term">
+
+ "<code class="mallctl">arenas.sspace_min</code>"
+
+ (<span class="type">size_t</span>)
+ <code class="literal">r-</code>
+ </span></dt><dd><p>Minimum subpage-spaced size class.</p></dd><dt><span class="term">
+
+ "<code class="mallctl">arenas.sspace_max</code>"
+
+ (<span class="type">size_t</span>)
+ <code class="literal">r-</code>
+ </span></dt><dd><p>Maximum subpage-spaced size class.</p></dd><dt><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><span class="term">
+
+ "<code class="mallctl">arenas.ntbins</code>"
+
+ (<span class="type">unsigned</span>)
+ <code class="literal">r-</code>
+ </span></dt><dd><p>Number of tiny bin size classes.</p></dd><dt><span class="term">
+
+ "<code class="mallctl">arenas.nqbins</code>"
+
+ (<span class="type">unsigned</span>)
+ <code class="literal">r-</code>
+ </span></dt><dd><p>Number of quantum-spaced bin size
+ classes.</p></dd><dt><span class="term">
+
+ "<code class="mallctl">arenas.ncbins</code>"
+
+ (<span class="type">unsigned</span>)
+ <code class="literal">r-</code>
+ </span></dt><dd><p>Number of cacheline-spaced bin size
+ classes.</p></dd><dt><span class="term">
+
+ "<code class="mallctl">arenas.nsbins</code>"
+
+ (<span class="type">unsigned</span>)
+ <code class="literal">r-</code>
+ </span></dt><dd><p>Number of subpage-spaced bin size
+ classes.</p></dd><dt><span class="term">
+
+ "<code class="mallctl">arenas.nbins</code>"
+
+ (<span class="type">unsigned</span>)
+ <code class="literal">r-</code>
+ </span></dt><dd><p>Total number of bin size classes.</p></dd><dt><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><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><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><span class="term">
+
+ "<code class="mallctl">arenas.nlruns</code>"
+
+ (<span class="type">size_t</span>)
+ <code class="literal">r-</code>
+ </span></dt><dd><p>Total number of large size classes.</p></dd><dt><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><span class="term">
+
+ "<code class="mallctl">arenas.purge</code>"
+
+ (<span class="type">unsigned</span>)
+ <code class="literal">-w</code>
+ </span></dt><dd><p>Purge unused dirty pages for the specified arena, or
+ for all arenas if none is specified.</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.
+ </p></dd><dt><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><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 to the nearest
+ multiple of the chunk size 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>.
+ </p></dd><dt><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 chunks mapped on behalf of the
+ application. This is a multiple of the chunk size, and is at least as
+ large as <a class="link" href="#stats.active">
+ "<code class="mallctl">stats.active</code>"
+ </a>. This
+ does not include inactive chunks backed by swap files. his does not
+ include inactive chunks embedded in the DSS.</p></dd><dt><span class="term">
+
+ "<code class="mallctl">stats.chunks.current</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 chunks actively mapped on behalf of the
+ application. This does not include inactive chunks backed by swap
+ files. This does not include inactive chunks embedded in the DSS.
+ </p></dd><dt><span class="term">
+
+ "<code class="mallctl">stats.chunks.total</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 chunks allocated.</p></dd><dt><span class="term">
+
+ "<code class="mallctl">stats.chunks.high</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 active chunks at any time thus far.
+ </p></dd><dt><span class="term">
+
+ "<code class="mallctl">stats.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><span class="term">
+
+ "<code class="mallctl">stats.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.
+ </p></dd><dt><span class="term">
+
+ "<code class="mallctl">stats.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.
+ </p></dd><dt><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><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><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><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><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><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><span class="term">
+
+ "<code class="mallctl">stats.arenas.<i>.npurged</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><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><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><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><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><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><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><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><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><span class="term">
+
+ "<code class="mallctl">stats.arenas.<i>.bins.<j>.allocated</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 bytes allocated by
+ bin.</p></dd><dt><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><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><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><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><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><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><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><span class="term">
+
+ "<code class="mallctl">stats.arenas.<i>.bins.<j>.highruns</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 runs at any time thus far.
+ </p></dd><dt><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><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><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><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><span class="term">
+
+ "<code class="mallctl">stats.arenas.<i>.lruns.<j>.highruns</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 runs at any time thus far for this
+ size class.</p></dd><dt><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><span class="term">
+
+ "<code class="mallctl">swap.avail</code>"
+
+ (<span class="type">size_t</span>)
+ <code class="literal">r-</code>
+ [<code class="option">--enable-stats --enable-swap</code>]
+ </span></dt><dd><p>Number of swap file bytes that are currently not
+ associated with any chunk (i.e. mapped, but otherwise completely
+ unmanaged).</p></dd><dt><a name="swap.prezeroed"></a><span class="term">
+
+ "<code class="mallctl">swap.prezeroed</code>"
+
+ (<span class="type">bool</span>)
+ <code class="literal">rw</code>
+ [<code class="option">--enable-swap</code>]
+ </span></dt><dd><p>If true, the allocator assumes that the swap file(s)
+ contain nothing but nil bytes. If this assumption is violated,
+ allocator behavior is undefined. This value becomes read-only after
+ <a class="link" href="#swap.fds">
+ "<code class="mallctl">swap.fds</code>"
+ </a> is
+ successfully written to.</p></dd><dt><span class="term">
+
+ "<code class="mallctl">swap.nfds</code>"
+
+ (<span class="type">size_t</span>)
+ <code class="literal">r-</code>
+ [<code class="option">--enable-swap</code>]
+ </span></dt><dd><p>Number of file descriptors in use for swap.
+ </p></dd><dt><a name="swap.fds"></a><span class="term">
+
+ "<code class="mallctl">swap.fds</code>"
+
+ (<span class="type">int *</span>)
+ <code class="literal">r-</code>
+ [<code class="option">--enable-swap</code>]
+ </span></dt><dd><p>When written to, the files associated with the
+ specified file descriptors are contiguously mapped via
+ <span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span>. The resulting virtual memory
+ region is preferred over anonymous
+ <span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span> and
+ <span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span> memory. Note that if a file's
+ size is not a multiple of the page size, it is automatically truncated
+ to the nearest page size multiple. See the
+ <a class="link" href="#swap.prezeroed">
+ "<code class="mallctl">swap.prezeroed</code>"
+ </a>
+ mallctl for specifying that the files are pre-zeroed.</p></dd></dl></div></div><div class="refsect1" title="DEBUGGING MALLOC PROBLEMS"><a name="debugging_malloc_problems"></a><h2>DEBUGGING MALLOC PROBLEMS</h2><p>When debugging, it is a good idea to configure/build jemalloc with
+ 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. There are a number of allocator implementations
+ available on the Internet which focus on detecting and pinpointing problems
+ by trading performance for extra sanity checks and detailed
+ diagnostics.</p></div><div class="refsect1" title="DIAGNOSTIC MESSAGES"><a name="diagnostic_messages"></a><h2>DIAGNOSTIC MESSAGES</h2><p>If any of the memory allocation/deallocation functions detect an
+ 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" title="RETURN VALUES"><a name="return_values"></a><h2>RETURN VALUES</h2><div class="refsect2" title="Standard API"><a name="id2844722"></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><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">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" title="Non-standard API"><a name="id2844875"></a><h3>Non-standard API</h3><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><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><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">ENOMEM</span></span></dt><dd><p><em class="parameter"><code>*oldlenp</code></em> is too short to
+ hold the requested value.</p></dd><dt><span class="term"><span class="errorname">ENOENT</span></span></dt><dd><p><em class="parameter"><code>name</code></em> or
+ <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></div><div class="refsect2" title="Experimental API"><a name="id2845053"></a><h3>Experimental API</h3><p>The <code class="function">allocm</code>(<em class="parameter"><code></code></em>),
+ <code class="function">rallocm</code>(<em class="parameter"><code></code></em>),
+ <code class="function">sallocm</code>(<em class="parameter"><code></code></em>), and
+ <code class="function">dallocm</code>(<em class="parameter"><code></code></em>) functions return
+ <code class="constant">ALLOCM_SUCCESS</code> on success; otherwise they return an
+ error value. The <code class="function">allocm</code>(<em class="parameter"><code></code></em>) and
+ <code class="function">rallocm</code>(<em class="parameter"><code></code></em>) functions will fail if:
+ </p><div class="variablelist"><dl><dt><span class="term"><span class="errorname">ALLOCM_ERR_OOM</span></span></dt><dd><p>Out of memory. Insufficient contiguous memory was
+ available to service the allocation request. The
+ <code class="function">allocm</code>(<em class="parameter"><code></code></em>) function additionally sets
+ <em class="parameter"><code>*ptr</code></em> to <code class="constant">NULL</code>, whereas
+ the <code class="function">rallocm</code>(<em class="parameter"><code></code></em>) function leaves
+ <code class="constant">*ptr</code> unmodified.</p></dd></dl></div><p>
+ The <code class="function">rallocm</code>(<em class="parameter"><code></code></em>) function will also
+ fail if:
+ </p><div class="variablelist"><dl><dt><span class="term"><span class="errorname">ALLOCM_ERR_NOT_MOVED</span></span></dt><dd><p><code class="constant">ALLOCM_NO_MOVE</code> was specified,
+ but the reallocation request could not be serviced without moving
+ the object.</p></dd></dl></div><p>
+ </p></div></div><div class="refsect1" title="ENVIRONMENT"><a name="environment"></a><h2>ENVIRONMENT</h2><p>The following environment variable affects the execution of the
+ allocation functions:
+ </p><div class="variablelist"><dl><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" title="EXAMPLES"><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" title="SEE ALSO"><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">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" title="STANDARDS"><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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