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authorMatt A. Tobin <mattatobin@localhost.localdomain>2018-02-02 04:16:08 -0500
committerMatt A. Tobin <mattatobin@localhost.localdomain>2018-02-02 04:16:08 -0500
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+<?xml version='1.0' encoding='UTF-8'?>
+<?xml-stylesheet type="text/xsl"
+ href="http://docbook.sourceforge.net/release/xsl/current/manpages/docbook.xsl"?>
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
+ "http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd" [
+]>
+
+<refentry>
+ <refentryinfo>
+ <title>User Manual</title>
+ <productname>jemalloc</productname>
+ <releaseinfo role="version">@jemalloc_version@</releaseinfo>
+ <authorgroup>
+ <author>
+ <firstname>Jason</firstname>
+ <surname>Evans</surname>
+ <personblurb>Author</personblurb>
+ </author>
+ </authorgroup>
+ </refentryinfo>
+ <refmeta>
+ <refentrytitle>JEMALLOC</refentrytitle>
+ <manvolnum>3</manvolnum>
+ </refmeta>
+ <refnamediv>
+ <refdescriptor>jemalloc</refdescriptor>
+ <refname>jemalloc</refname>
+ <!-- Each refname causes a man page file to be created. Only if this were
+ the system malloc(3) implementation would these files be appropriate.
+ <refname>malloc</refname>
+ <refname>calloc</refname>
+ <refname>posix_memalign</refname>
+ <refname>aligned_alloc</refname>
+ <refname>realloc</refname>
+ <refname>free</refname>
+ <refname>mallocx</refname>
+ <refname>rallocx</refname>
+ <refname>xallocx</refname>
+ <refname>sallocx</refname>
+ <refname>dallocx</refname>
+ <refname>sdallocx</refname>
+ <refname>nallocx</refname>
+ <refname>mallctl</refname>
+ <refname>mallctlnametomib</refname>
+ <refname>mallctlbymib</refname>
+ <refname>malloc_stats_print</refname>
+ <refname>malloc_usable_size</refname>
+ -->
+ <refpurpose>general purpose memory allocation functions</refpurpose>
+ </refnamediv>
+ <refsect1 id="library">
+ <title>LIBRARY</title>
+ <para>This manual describes jemalloc @jemalloc_version@. More information
+ can be found at the <ulink
+ url="http://jemalloc.net/">jemalloc website</ulink>.</para>
+ </refsect1>
+ <refsynopsisdiv>
+ <title>SYNOPSIS</title>
+ <funcsynopsis>
+ <funcsynopsisinfo>#include &lt;<filename class="headerfile">jemalloc/jemalloc.h</filename>&gt;</funcsynopsisinfo>
+ <refsect2>
+ <title>Standard API</title>
+ <funcprototype>
+ <funcdef>void *<function>malloc</function></funcdef>
+ <paramdef>size_t <parameter>size</parameter></paramdef>
+ </funcprototype>
+ <funcprototype>
+ <funcdef>void *<function>calloc</function></funcdef>
+ <paramdef>size_t <parameter>number</parameter></paramdef>
+ <paramdef>size_t <parameter>size</parameter></paramdef>
+ </funcprototype>
+ <funcprototype>
+ <funcdef>int <function>posix_memalign</function></funcdef>
+ <paramdef>void **<parameter>ptr</parameter></paramdef>
+ <paramdef>size_t <parameter>alignment</parameter></paramdef>
+ <paramdef>size_t <parameter>size</parameter></paramdef>
+ </funcprototype>
+ <funcprototype>
+ <funcdef>void *<function>aligned_alloc</function></funcdef>
+ <paramdef>size_t <parameter>alignment</parameter></paramdef>
+ <paramdef>size_t <parameter>size</parameter></paramdef>
+ </funcprototype>
+ <funcprototype>
+ <funcdef>void *<function>realloc</function></funcdef>
+ <paramdef>void *<parameter>ptr</parameter></paramdef>
+ <paramdef>size_t <parameter>size</parameter></paramdef>
+ </funcprototype>
+ <funcprototype>
+ <funcdef>void <function>free</function></funcdef>
+ <paramdef>void *<parameter>ptr</parameter></paramdef>
+ </funcprototype>
+ </refsect2>
+ <refsect2>
+ <title>Non-standard API</title>
+ <funcprototype>
+ <funcdef>void *<function>mallocx</function></funcdef>
+ <paramdef>size_t <parameter>size</parameter></paramdef>
+ <paramdef>int <parameter>flags</parameter></paramdef>
+ </funcprototype>
+ <funcprototype>
+ <funcdef>void *<function>rallocx</function></funcdef>
+ <paramdef>void *<parameter>ptr</parameter></paramdef>
+ <paramdef>size_t <parameter>size</parameter></paramdef>
+ <paramdef>int <parameter>flags</parameter></paramdef>
+ </funcprototype>
+ <funcprototype>
+ <funcdef>size_t <function>xallocx</function></funcdef>
+ <paramdef>void *<parameter>ptr</parameter></paramdef>
+ <paramdef>size_t <parameter>size</parameter></paramdef>
+ <paramdef>size_t <parameter>extra</parameter></paramdef>
+ <paramdef>int <parameter>flags</parameter></paramdef>
+ </funcprototype>
+ <funcprototype>
+ <funcdef>size_t <function>sallocx</function></funcdef>
+ <paramdef>void *<parameter>ptr</parameter></paramdef>
+ <paramdef>int <parameter>flags</parameter></paramdef>
+ </funcprototype>
+ <funcprototype>
+ <funcdef>void <function>dallocx</function></funcdef>
+ <paramdef>void *<parameter>ptr</parameter></paramdef>
+ <paramdef>int <parameter>flags</parameter></paramdef>
+ </funcprototype>
+ <funcprototype>
+ <funcdef>void <function>sdallocx</function></funcdef>
+ <paramdef>void *<parameter>ptr</parameter></paramdef>
+ <paramdef>size_t <parameter>size</parameter></paramdef>
+ <paramdef>int <parameter>flags</parameter></paramdef>
+ </funcprototype>
+ <funcprototype>
+ <funcdef>size_t <function>nallocx</function></funcdef>
+ <paramdef>size_t <parameter>size</parameter></paramdef>
+ <paramdef>int <parameter>flags</parameter></paramdef>
+ </funcprototype>
+ <funcprototype>
+ <funcdef>int <function>mallctl</function></funcdef>
+ <paramdef>const char *<parameter>name</parameter></paramdef>
+ <paramdef>void *<parameter>oldp</parameter></paramdef>
+ <paramdef>size_t *<parameter>oldlenp</parameter></paramdef>
+ <paramdef>void *<parameter>newp</parameter></paramdef>
+ <paramdef>size_t <parameter>newlen</parameter></paramdef>
+ </funcprototype>
+ <funcprototype>
+ <funcdef>int <function>mallctlnametomib</function></funcdef>
+ <paramdef>const char *<parameter>name</parameter></paramdef>
+ <paramdef>size_t *<parameter>mibp</parameter></paramdef>
+ <paramdef>size_t *<parameter>miblenp</parameter></paramdef>
+ </funcprototype>
+ <funcprototype>
+ <funcdef>int <function>mallctlbymib</function></funcdef>
+ <paramdef>const size_t *<parameter>mib</parameter></paramdef>
+ <paramdef>size_t <parameter>miblen</parameter></paramdef>
+ <paramdef>void *<parameter>oldp</parameter></paramdef>
+ <paramdef>size_t *<parameter>oldlenp</parameter></paramdef>
+ <paramdef>void *<parameter>newp</parameter></paramdef>
+ <paramdef>size_t <parameter>newlen</parameter></paramdef>
+ </funcprototype>
+ <funcprototype>
+ <funcdef>void <function>malloc_stats_print</function></funcdef>
+ <paramdef>void <parameter>(*write_cb)</parameter>
+ <funcparams>void *, const char *</funcparams>
+ </paramdef>
+ <paramdef>void *<parameter>cbopaque</parameter></paramdef>
+ <paramdef>const char *<parameter>opts</parameter></paramdef>
+ </funcprototype>
+ <funcprototype>
+ <funcdef>size_t <function>malloc_usable_size</function></funcdef>
+ <paramdef>const void *<parameter>ptr</parameter></paramdef>
+ </funcprototype>
+ <funcprototype>
+ <funcdef>void <function>(*malloc_message)</function></funcdef>
+ <paramdef>void *<parameter>cbopaque</parameter></paramdef>
+ <paramdef>const char *<parameter>s</parameter></paramdef>
+ </funcprototype>
+ <para><type>const char *</type><varname>malloc_conf</varname>;</para>
+ </refsect2>
+ </funcsynopsis>
+ </refsynopsisdiv>
+ <refsect1 id="description">
+ <title>DESCRIPTION</title>
+ <refsect2>
+ <title>Standard API</title>
+
+ <para>The <function>malloc()</function> function allocates
+ <parameter>size</parameter> bytes of uninitialized memory. The allocated
+ space is suitably aligned (after possible pointer coercion) for storage
+ of any type of object.</para>
+
+ <para>The <function>calloc()</function> function allocates
+ space for <parameter>number</parameter> objects, each
+ <parameter>size</parameter> bytes in length. The result is identical to
+ calling <function>malloc()</function> with an argument of
+ <parameter>number</parameter> * <parameter>size</parameter>, with the
+ exception that the allocated memory is explicitly initialized to zero
+ bytes.</para>
+
+ <para>The <function>posix_memalign()</function> function
+ allocates <parameter>size</parameter> bytes of memory such that the
+ allocation's base address is a multiple of
+ <parameter>alignment</parameter>, and returns the allocation in the value
+ pointed to by <parameter>ptr</parameter>. The requested
+ <parameter>alignment</parameter> must be a power of 2 at least as large as
+ <code language="C">sizeof(<type>void *</type>)</code>.</para>
+
+ <para>The <function>aligned_alloc()</function> function
+ allocates <parameter>size</parameter> bytes of memory such that the
+ allocation's base address is a multiple of
+ <parameter>alignment</parameter>. The requested
+ <parameter>alignment</parameter> must be a power of 2. Behavior is
+ undefined if <parameter>size</parameter> is not an integral multiple of
+ <parameter>alignment</parameter>.</para>
+
+ <para>The <function>realloc()</function> function changes the
+ size of the previously allocated memory referenced by
+ <parameter>ptr</parameter> to <parameter>size</parameter> 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 <parameter>ptr</parameter> is freed and a pointer to the newly
+ allocated memory is returned. Note that
+ <function>realloc()</function> may move the memory allocation,
+ resulting in a different return value than <parameter>ptr</parameter>.
+ If <parameter>ptr</parameter> is <constant>NULL</constant>, the
+ <function>realloc()</function> function behaves identically to
+ <function>malloc()</function> for the specified size.</para>
+
+ <para>The <function>free()</function> function causes the
+ allocated memory referenced by <parameter>ptr</parameter> to be made
+ available for future allocations. If <parameter>ptr</parameter> is
+ <constant>NULL</constant>, no action occurs.</para>
+ </refsect2>
+ <refsect2>
+ <title>Non-standard API</title>
+ <para>The <function>mallocx()</function>,
+ <function>rallocx()</function>,
+ <function>xallocx()</function>,
+ <function>sallocx()</function>,
+ <function>dallocx()</function>,
+ <function>sdallocx()</function>, and
+ <function>nallocx()</function> functions all have a
+ <parameter>flags</parameter> argument that can be used to specify
+ options. The functions only check the options that are contextually
+ relevant. Use bitwise or (<code language="C">|</code>) operations to
+ specify one or more of the following:
+ <variablelist>
+ <varlistentry id="MALLOCX_LG_ALIGN">
+ <term><constant>MALLOCX_LG_ALIGN(<parameter>la</parameter>)
+ </constant></term>
+
+ <listitem><para>Align the memory allocation to start at an address
+ that is a multiple of <code language="C">(1 &lt;&lt;
+ <parameter>la</parameter>)</code>. This macro does not validate
+ that <parameter>la</parameter> is within the valid
+ range.</para></listitem>
+ </varlistentry>
+ <varlistentry id="MALLOCX_ALIGN">
+ <term><constant>MALLOCX_ALIGN(<parameter>a</parameter>)
+ </constant></term>
+
+ <listitem><para>Align the memory allocation to start at an address
+ that is a multiple of <parameter>a</parameter>, where
+ <parameter>a</parameter> is a power of two. This macro does not
+ validate that <parameter>a</parameter> is a power of 2.
+ </para></listitem>
+ </varlistentry>
+ <varlistentry id="MALLOCX_ZERO">
+ <term><constant>MALLOCX_ZERO</constant></term>
+
+ <listitem><para>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.</para></listitem>
+ </varlistentry>
+ <varlistentry id="MALLOCX_TCACHE">
+ <term><constant>MALLOCX_TCACHE(<parameter>tc</parameter>)
+ </constant></term>
+
+ <listitem><para>Use the thread-specific cache (tcache) specified by
+ the identifier <parameter>tc</parameter>, which must have been
+ acquired via the <link
+ linkend="tcache.create"><mallctl>tcache.create</mallctl></link>
+ mallctl. This macro does not validate that
+ <parameter>tc</parameter> specifies a valid
+ identifier.</para></listitem>
+ </varlistentry>
+ <varlistentry id="MALLOC_TCACHE_NONE">
+ <term><constant>MALLOCX_TCACHE_NONE</constant></term>
+
+ <listitem><para>Do not use a thread-specific cache (tcache). Unless
+ <constant>MALLOCX_TCACHE(<parameter>tc</parameter>)</constant> or
+ <constant>MALLOCX_TCACHE_NONE</constant> is specified, an
+ automatically managed tcache will be used under many circumstances.
+ This macro cannot be used in the same <parameter>flags</parameter>
+ argument as
+ <constant>MALLOCX_TCACHE(<parameter>tc</parameter>)</constant>.</para></listitem>
+ </varlistentry>
+ <varlistentry id="MALLOCX_ARENA">
+ <term><constant>MALLOCX_ARENA(<parameter>a</parameter>)
+ </constant></term>
+
+ <listitem><para>Use the arena specified by the index
+ <parameter>a</parameter>. This macro has no effect for regions that
+ were allocated via an arena other than the one specified. This
+ macro does not validate that <parameter>a</parameter> specifies an
+ arena index in the valid range.</para></listitem>
+ </varlistentry>
+ </variablelist>
+ </para>
+
+ <para>The <function>mallocx()</function> function allocates at
+ least <parameter>size</parameter> bytes of memory, and returns a pointer
+ to the base address of the allocation. Behavior is undefined if
+ <parameter>size</parameter> is <constant>0</constant>.</para>
+
+ <para>The <function>rallocx()</function> function resizes the
+ allocation at <parameter>ptr</parameter> to be at least
+ <parameter>size</parameter> 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
+ <parameter>size</parameter> is <constant>0</constant>.</para>
+
+ <para>The <function>xallocx()</function> function resizes the
+ allocation at <parameter>ptr</parameter> in place to be at least
+ <parameter>size</parameter> bytes, and returns the real size of the
+ allocation. If <parameter>extra</parameter> is non-zero, an attempt is
+ made to resize the allocation to be at least <code
+ language="C">(<parameter>size</parameter> +
+ <parameter>extra</parameter>)</code> bytes, though inability to allocate
+ the extra byte(s) will not by itself result in failure to resize.
+ Behavior is undefined if <parameter>size</parameter> is
+ <constant>0</constant>, or if <code
+ language="C">(<parameter>size</parameter> + <parameter>extra</parameter>
+ &gt; <constant>SIZE_T_MAX</constant>)</code>.</para>
+
+ <para>The <function>sallocx()</function> function returns the
+ real size of the allocation at <parameter>ptr</parameter>.</para>
+
+ <para>The <function>dallocx()</function> function causes the
+ memory referenced by <parameter>ptr</parameter> to be made available for
+ future allocations.</para>
+
+ <para>The <function>sdallocx()</function> function is an
+ extension of <function>dallocx()</function> with a
+ <parameter>size</parameter> 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
+ <function>nallocx()</function> or
+ <function>sallocx()</function>.</para>
+
+ <para>The <function>nallocx()</function> function allocates no
+ memory, but it performs the same size computation as the
+ <function>mallocx()</function> function, and returns the real
+ size of the allocation that would result from the equivalent
+ <function>mallocx()</function> function call, or
+ <constant>0</constant> if the inputs exceed the maximum supported size
+ class and/or alignment. Behavior is undefined if
+ <parameter>size</parameter> is <constant>0</constant>.</para>
+
+ <para>The <function>mallctl()</function> function provides a
+ general interface for introspecting the memory allocator, as well as
+ setting modifiable parameters and triggering actions. The
+ period-separated <parameter>name</parameter> argument specifies a
+ location in a tree-structured namespace; see the <xref
+ linkend="mallctl_namespace" xrefstyle="template:%t"/> section for
+ documentation on the tree contents. To read a value, pass a pointer via
+ <parameter>oldp</parameter> to adequate space to contain the value, and a
+ pointer to its length via <parameter>oldlenp</parameter>; otherwise pass
+ <constant>NULL</constant> and <constant>NULL</constant>. Similarly, to
+ write a value, pass a pointer to the value via
+ <parameter>newp</parameter>, and its length via
+ <parameter>newlen</parameter>; otherwise pass <constant>NULL</constant>
+ and <constant>0</constant>.</para>
+
+ <para>The <function>mallctlnametomib()</function> 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 <quote>Management Information Base</quote> (MIB) that can be passed
+ repeatedly to <function>mallctlbymib()</function>. Upon
+ successful return from <function>mallctlnametomib()</function>,
+ <parameter>mibp</parameter> contains an array of
+ <parameter>*miblenp</parameter> integers, where
+ <parameter>*miblenp</parameter> is the lesser of the number of components
+ in <parameter>name</parameter> and the input value of
+ <parameter>*miblenp</parameter>. Thus it is possible to pass a
+ <parameter>*miblenp</parameter> 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
+ <link
+ linkend="arenas.bin.i.size"><mallctl>arenas.bin.2.size</mallctl></link>),
+ the corresponding MIB component will always be that integer. Therefore,
+ it is legitimate to construct code like the following: <programlisting
+ language="C"><![CDATA[
+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... */
+}]]></programlisting></para>
+
+ <para>The <function>malloc_stats_print()</function> function writes
+ summary statistics via the <parameter>write_cb</parameter> callback
+ function pointer and <parameter>cbopaque</parameter> data passed to
+ <parameter>write_cb</parameter>, or <function>malloc_message()</function>
+ if <parameter>write_cb</parameter> is <constant>NULL</constant>. The
+ statistics are presented in human-readable form unless <quote>J</quote> is
+ specified as a character within the <parameter>opts</parameter> string, in
+ which case the statistics are presented in <ulink
+ url="http://www.json.org/">JSON format</ulink>. This function can be
+ called repeatedly. General information that never changes during
+ execution can be omitted by specifying <quote>g</quote> as a character
+ within the <parameter>opts</parameter> string. Note that
+ <function>malloc_message()</function> uses the
+ <function>mallctl*()</function> functions internally, so inconsistent
+ statistics can be reported if multiple threads use these functions
+ simultaneously. If <option>--enable-stats</option> is specified during
+ configuration, <quote>m</quote> and <quote>a</quote> can be specified to
+ omit merged arena and per arena statistics, respectively;
+ <quote>b</quote>, <quote>l</quote>, and <quote>h</quote> 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.</para>
+
+ <para>The <function>malloc_usable_size()</function> function
+ returns the usable size of the allocation pointed to by
+ <parameter>ptr</parameter>. The return value may be larger than the size
+ that was requested during allocation. The
+ <function>malloc_usable_size()</function> function is not a
+ mechanism for in-place <function>realloc()</function>; rather
+ it is provided solely as a tool for introspection purposes. Any
+ discrepancy between the requested allocation size and the size reported
+ by <function>malloc_usable_size()</function> should not be
+ depended on, since such behavior is entirely implementation-dependent.
+ </para>
+ </refsect2>
+ </refsect1>
+ <refsect1 id="tuning">
+ <title>TUNING</title>
+ <para>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.</para>
+
+ <para>The string specified via <option>--with-malloc-conf</option>, the
+ string pointed to by the global variable <varname>malloc_conf</varname>, the
+ <quote>name</quote> of the file referenced by the symbolic link named
+ <filename class="symlink">/etc/malloc.conf</filename>, and the value of the
+ environment variable <envar>MALLOC_CONF</envar>, will be interpreted, in
+ that order, from left to right as options. Note that
+ <varname>malloc_conf</varname> may be read before
+ <function>main()</function> is entered, so the declaration of
+ <varname>malloc_conf</varname> should specify an initializer that contains
+ the final value to be read by jemalloc. <option>--with-malloc-conf</option>
+ and <varname>malloc_conf</varname> are compile-time mechanisms, whereas
+ <filename class="symlink">/etc/malloc.conf</filename> and
+ <envar>MALLOC_CONF</envar> can be safely set any time prior to program
+ invocation.</para>
+
+ <para>An options string is a comma-separated list of option:value pairs.
+ There is one key corresponding to each <link
+ linkend="opt.abort"><mallctl>opt.*</mallctl></link> mallctl (see the <xref
+ linkend="mallctl_namespace" xrefstyle="template:%t"/> section for options
+ documentation). For example, <literal>abort:true,narenas:1</literal> sets
+ the <link linkend="opt.abort"><mallctl>opt.abort</mallctl></link> and <link
+ linkend="opt.narenas"><mallctl>opt.narenas</mallctl></link> 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.</para>
+ </refsect1>
+ <refsect1 id="implementation_notes">
+ <title>IMPLEMENTATION NOTES</title>
+ <para>Traditionally, allocators have used
+ <citerefentry><refentrytitle>sbrk</refentrytitle>
+ <manvolnum>2</manvolnum></citerefentry> to obtain memory, which is
+ suboptimal for several reasons, including race conditions, increased
+ fragmentation, and artificial limitations on maximum usable memory. If
+ <citerefentry><refentrytitle>sbrk</refentrytitle>
+ <manvolnum>2</manvolnum></citerefentry> is supported by the operating
+ system, this allocator uses both
+ <citerefentry><refentrytitle>mmap</refentrytitle>
+ <manvolnum>2</manvolnum></citerefentry> and
+ <citerefentry><refentrytitle>sbrk</refentrytitle>
+ <manvolnum>2</manvolnum></citerefentry>, in that order of preference;
+ otherwise only <citerefentry><refentrytitle>mmap</refentrytitle>
+ <manvolnum>2</manvolnum></citerefentry> is used.</para>
+
+ <para>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.</para>
+
+ <para>In addition to multiple arenas, unless
+ <option>--disable-tcache</option> 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.</para>
+
+ <para>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. User objects are
+ broken into three categories according to size: small, large, and huge.
+ Multiple small and large objects can reside within a single chunk, whereas
+ huge objects each have one or more chunks backing them. Each chunk that
+ contains small and/or large objects 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.</para>
+
+ <para>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
+ language="C">sizeof(<type>double</type>)</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 <link
+ linkend="opt.lg_chunk"><mallctl>opt.lg_chunk</mallctl></link> option), and
+ huge size classes extend from the chunk size up to the largest size class
+ that does not exceed <constant>PTRDIFF_MAX</constant>.</para>
+
+ <para>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.</para>
+
+ <para>The <function>realloc()</function>,
+ <function>rallocx()</function>, and
+ <function>xallocx()</function> functions may resize allocations
+ without moving them under limited circumstances. Unlike the
+ <function>*allocx()</function> 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
+ <function>realloc()</function> 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 <link
+ linkend="arena.i.chunk_hooks"><mallctl>arena.&lt;i&gt;.chunk_hooks</mallctl></link>).
+ Growth only succeeds if the trailing memory is currently available, and
+ additionally for huge size classes the chunk allocator must support
+ merging.</para>
+
+ <para>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 <xref
+ linkend="size_classes" xrefstyle="template:Table %n"/>.</para>
+
+ <table xml:id="size_classes" frame="all">
+ <title>Size classes</title>
+ <tgroup cols="3" colsep="1" rowsep="1">
+ <colspec colname="c1" align="left"/>
+ <colspec colname="c2" align="right"/>
+ <colspec colname="c3" align="left"/>
+ <thead>
+ <row>
+ <entry>Category</entry>
+ <entry>Spacing</entry>
+ <entry>Size</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry morerows="8">Small</entry>
+ <entry>lg</entry>
+ <entry>[8]</entry>
+ </row>
+ <row>
+ <entry>16</entry>
+ <entry>[16, 32, 48, 64, 80, 96, 112, 128]</entry>
+ </row>
+ <row>
+ <entry>32</entry>
+ <entry>[160, 192, 224, 256]</entry>
+ </row>
+ <row>
+ <entry>64</entry>
+ <entry>[320, 384, 448, 512]</entry>
+ </row>
+ <row>
+ <entry>128</entry>
+ <entry>[640, 768, 896, 1024]</entry>
+ </row>
+ <row>
+ <entry>256</entry>
+ <entry>[1280, 1536, 1792, 2048]</entry>
+ </row>
+ <row>
+ <entry>512</entry>
+ <entry>[2560, 3072, 3584, 4096]</entry>
+ </row>
+ <row>
+ <entry>1 KiB</entry>
+ <entry>[5 KiB, 6 KiB, 7 KiB, 8 KiB]</entry>
+ </row>
+ <row>
+ <entry>2 KiB</entry>
+ <entry>[10 KiB, 12 KiB, 14 KiB]</entry>
+ </row>
+ <row>
+ <entry morerows="7">Large</entry>
+ <entry>2 KiB</entry>
+ <entry>[16 KiB]</entry>
+ </row>
+ <row>
+ <entry>4 KiB</entry>
+ <entry>[20 KiB, 24 KiB, 28 KiB, 32 KiB]</entry>
+ </row>
+ <row>
+ <entry>8 KiB</entry>
+ <entry>[40 KiB, 48 KiB, 54 KiB, 64 KiB]</entry>
+ </row>
+ <row>
+ <entry>16 KiB</entry>
+ <entry>[80 KiB, 96 KiB, 112 KiB, 128 KiB]</entry>
+ </row>
+ <row>
+ <entry>32 KiB</entry>
+ <entry>[160 KiB, 192 KiB, 224 KiB, 256 KiB]</entry>
+ </row>
+ <row>
+ <entry>64 KiB</entry>
+ <entry>[320 KiB, 384 KiB, 448 KiB, 512 KiB]</entry>
+ </row>
+ <row>
+ <entry>128 KiB</entry>
+ <entry>[640 KiB, 768 KiB, 896 KiB, 1 MiB]</entry>
+ </row>
+ <row>
+ <entry>256 KiB</entry>
+ <entry>[1280 KiB, 1536 KiB, 1792 KiB]</entry>
+ </row>
+ <row>
+ <entry morerows="8">Huge</entry>
+ <entry>256 KiB</entry>
+ <entry>[2 MiB]</entry>
+ </row>
+ <row>
+ <entry>512 KiB</entry>
+ <entry>[2560 KiB, 3 MiB, 3584 KiB, 4 MiB]</entry>
+ </row>
+ <row>
+ <entry>1 MiB</entry>
+ <entry>[5 MiB, 6 MiB, 7 MiB, 8 MiB]</entry>
+ </row>
+ <row>
+ <entry>2 MiB</entry>
+ <entry>[10 MiB, 12 MiB, 14 MiB, 16 MiB]</entry>
+ </row>
+ <row>
+ <entry>4 MiB</entry>
+ <entry>[20 MiB, 24 MiB, 28 MiB, 32 MiB]</entry>
+ </row>
+ <row>
+ <entry>8 MiB</entry>
+ <entry>[40 MiB, 48 MiB, 56 MiB, 64 MiB]</entry>
+ </row>
+ <row>
+ <entry>...</entry>
+ <entry>...</entry>
+ </row>
+ <row>
+ <entry>512 PiB</entry>
+ <entry>[2560 PiB, 3 EiB, 3584 PiB, 4 EiB]</entry>
+ </row>
+ <row>
+ <entry>1 EiB</entry>
+ <entry>[5 EiB, 6 EiB, 7 EiB]</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+ </refsect1>
+ <refsect1 id="mallctl_namespace">
+ <title>MALLCTL NAMESPACE</title>
+ <para>The following names are defined in the namespace accessible via the
+ <function>mallctl*()</function> functions. Value types are
+ specified in parentheses, their readable/writable statuses are encoded as
+ <literal>rw</literal>, <literal>r-</literal>, <literal>-w</literal>, or
+ <literal>--</literal>, and required build configuration flags follow, if
+ any. A name element encoded as <literal>&lt;i&gt;</literal> or
+ <literal>&lt;j&gt;</literal> indicates an integer component, where the
+ integer varies from 0 to some upper value that must be determined via
+ introspection. In the case of <mallctl>stats.arenas.&lt;i&gt;.*</mallctl>,
+ <literal>&lt;i&gt;</literal> equal to <link
+ linkend="arenas.narenas"><mallctl>arenas.narenas</mallctl></link> can be
+ used to access the summation of statistics from all arenas. Take special
+ note of the <link linkend="epoch"><mallctl>epoch</mallctl></link> mallctl,
+ which controls refreshing of cached dynamic statistics.</para>
+
+ <variablelist>
+ <varlistentry id="version">
+ <term>
+ <mallctl>version</mallctl>
+ (<type>const char *</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>Return the jemalloc version string.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="epoch">
+ <term>
+ <mallctl>epoch</mallctl>
+ (<type>uint64_t</type>)
+ <literal>rw</literal>
+ </term>
+ <listitem><para>If a value is passed in, refresh the data from which
+ the <function>mallctl*()</function> functions report values,
+ and increment the epoch. Return the current epoch. This is useful for
+ detecting whether another thread caused a refresh.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="config.cache_oblivious">
+ <term>
+ <mallctl>config.cache_oblivious</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para><option>--enable-cache-oblivious</option> was specified
+ during build configuration.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="config.debug">
+ <term>
+ <mallctl>config.debug</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para><option>--enable-debug</option> was specified during
+ build configuration.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="config.fill">
+ <term>
+ <mallctl>config.fill</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para><option>--enable-fill</option> was specified during
+ build configuration.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="config.lazy_lock">
+ <term>
+ <mallctl>config.lazy_lock</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para><option>--enable-lazy-lock</option> was specified
+ during build configuration.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="config.malloc_conf">
+ <term>
+ <mallctl>config.malloc_conf</mallctl>
+ (<type>const char *</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>Embedded configure-time-specified run-time options
+ string, empty unless <option>--with-malloc-conf</option> was specified
+ during build configuration.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="config.munmap">
+ <term>
+ <mallctl>config.munmap</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para><option>--enable-munmap</option> was specified during
+ build configuration.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="config.prof">
+ <term>
+ <mallctl>config.prof</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para><option>--enable-prof</option> was specified during
+ build configuration.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="config.prof_libgcc">
+ <term>
+ <mallctl>config.prof_libgcc</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para><option>--disable-prof-libgcc</option> was not
+ specified during build configuration.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="config.prof_libunwind">
+ <term>
+ <mallctl>config.prof_libunwind</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para><option>--enable-prof-libunwind</option> was specified
+ during build configuration.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="config.stats">
+ <term>
+ <mallctl>config.stats</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para><option>--enable-stats</option> was specified during
+ build configuration.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="config.tcache">
+ <term>
+ <mallctl>config.tcache</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para><option>--disable-tcache</option> was not specified
+ during build configuration.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="config.tls">
+ <term>
+ <mallctl>config.tls</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para><option>--disable-tls</option> was not specified during
+ build configuration.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="config.utrace">
+ <term>
+ <mallctl>config.utrace</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para><option>--enable-utrace</option> was specified during
+ build configuration.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="config.valgrind">
+ <term>
+ <mallctl>config.valgrind</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para><option>--enable-valgrind</option> was specified during
+ build configuration.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="config.xmalloc">
+ <term>
+ <mallctl>config.xmalloc</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para><option>--enable-xmalloc</option> was specified during
+ build configuration.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="opt.abort">
+ <term>
+ <mallctl>opt.abort</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>Abort-on-warning enabled/disabled. If true, most
+ warnings are fatal. The process will call
+ <citerefentry><refentrytitle>abort</refentrytitle>
+ <manvolnum>3</manvolnum></citerefentry> in these cases. This option is
+ disabled by default unless <option>--enable-debug</option> is
+ specified during configuration, in which case it is enabled by default.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id="opt.dss">
+ <term>
+ <mallctl>opt.dss</mallctl>
+ (<type>const char *</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>dss (<citerefentry><refentrytitle>sbrk</refentrytitle>
+ <manvolnum>2</manvolnum></citerefentry>) allocation precedence as
+ related to <citerefentry><refentrytitle>mmap</refentrytitle>
+ <manvolnum>2</manvolnum></citerefentry> allocation. The following
+ settings are supported if
+ <citerefentry><refentrytitle>sbrk</refentrytitle>
+ <manvolnum>2</manvolnum></citerefentry> is supported by the operating
+ system: <quote>disabled</quote>, <quote>primary</quote>, and
+ <quote>secondary</quote>; otherwise only <quote>disabled</quote> is
+ supported. The default is <quote>secondary</quote> if
+ <citerefentry><refentrytitle>sbrk</refentrytitle>
+ <manvolnum>2</manvolnum></citerefentry> is supported by the operating
+ system; <quote>disabled</quote> otherwise.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id="opt.lg_chunk">
+ <term>
+ <mallctl>opt.lg_chunk</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>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).
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id="opt.narenas">
+ <term>
+ <mallctl>opt.narenas</mallctl>
+ (<type>unsigned</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>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.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="opt.purge">
+ <term>
+ <mallctl>opt.purge</mallctl>
+ (<type>const char *</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>Purge mode is &ldquo;ratio&rdquo; (default) or
+ &ldquo;decay&rdquo;. See <link
+ linkend="opt.lg_dirty_mult"><mallctl>opt.lg_dirty_mult</mallctl></link>
+ for details of the ratio mode. See <link
+ linkend="opt.decay_time"><mallctl>opt.decay_time</mallctl></link> for
+ details of the decay mode.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="opt.lg_dirty_mult">
+ <term>
+ <mallctl>opt.lg_dirty_mult</mallctl>
+ (<type>ssize_t</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>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 <citerefentry><refentrytitle>madvise</refentrytitle>
+ <manvolnum>2</manvolnum></citerefentry> 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 <link
+ linkend="arenas.lg_dirty_mult"><mallctl>arenas.lg_dirty_mult</mallctl></link>
+ and <link
+ linkend="arena.i.lg_dirty_mult"><mallctl>arena.&lt;i&gt;.lg_dirty_mult</mallctl></link>
+ for related dynamic control options.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="opt.decay_time">
+ <term>
+ <mallctl>opt.decay_time</mallctl>
+ (<type>ssize_t</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>Approximate time in seconds from the creation of a set
+ of unused dirty pages until an equivalent set of unused dirty pages is
+ purged and/or reused. The pages are incrementally purged according to a
+ sigmoidal decay curve that starts and ends with zero purge rate. A
+ decay time of 0 causes all unused dirty pages to be purged immediately
+ upon creation. A decay time of -1 disables purging. The default decay
+ time is 10 seconds. See <link
+ linkend="arenas.decay_time"><mallctl>arenas.decay_time</mallctl></link>
+ and <link
+ linkend="arena.i.decay_time"><mallctl>arena.&lt;i&gt;.decay_time</mallctl></link>
+ for related dynamic control options.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id="opt.stats_print">
+ <term>
+ <mallctl>opt.stats_print</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>Enable/disable statistics printing at exit. If
+ enabled, the <function>malloc_stats_print()</function>
+ function is called at program exit via an
+ <citerefentry><refentrytitle>atexit</refentrytitle>
+ <manvolnum>3</manvolnum></citerefentry> function. If
+ <option>--enable-stats</option> 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, <function>atexit()</function> may
+ allocate memory during application initialization and then deadlock
+ internally when jemalloc in turn calls
+ <function>atexit()</function>, so this option is not
+ universally usable (though the application can register its own
+ <function>atexit()</function> 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.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="opt.junk">
+ <term>
+ <mallctl>opt.junk</mallctl>
+ (<type>const char *</type>)
+ <literal>r-</literal>
+ [<option>--enable-fill</option>]
+ </term>
+ <listitem><para>Junk filling. If set to <quote>alloc</quote>, each byte
+ of uninitialized allocated memory will be initialized to
+ <literal>0xa5</literal>. If set to <quote>free</quote>, all deallocated
+ memory will be initialized to <literal>0x5a</literal>. If set to
+ <quote>true</quote>, both allocated and deallocated memory will be
+ initialized, and if set to <quote>false</quote>, junk filling be
+ disabled entirely. This is intended for debugging and will impact
+ performance negatively. This option is <quote>false</quote> by default
+ unless <option>--enable-debug</option> is specified during
+ configuration, in which case it is <quote>true</quote> by default unless
+ running inside <ulink
+ url="http://valgrind.org/">Valgrind</ulink>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="opt.quarantine">
+ <term>
+ <mallctl>opt.quarantine</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-fill</option>]
+ </term>
+ <listitem><para>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 <link
+ linkend="opt.junk"><mallctl>opt.junk</mallctl></link> option is
+ enabled. This feature is of particular use in combination with <ulink
+ url="http://valgrind.org/">Valgrind</ulink>, 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.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="opt.redzone">
+ <term>
+ <mallctl>opt.redzone</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ [<option>--enable-fill</option>]
+ </term>
+ <listitem><para>Redzones enabled/disabled. If enabled, small
+ allocations have redzones before and after them. Furthermore, if the
+ <link linkend="opt.junk"><mallctl>opt.junk</mallctl></link> 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 <ulink url="http://valgrind.org/">Valgrind</ulink>,
+ 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.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="opt.zero">
+ <term>
+ <mallctl>opt.zero</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ [<option>--enable-fill</option>]
+ </term>
+ <listitem><para>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
+ <function>realloc()</function> and
+ <function>rallocx()</function> 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.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id="opt.utrace">
+ <term>
+ <mallctl>opt.utrace</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ [<option>--enable-utrace</option>]
+ </term>
+ <listitem><para>Allocation tracing based on
+ <citerefentry><refentrytitle>utrace</refentrytitle>
+ <manvolnum>2</manvolnum></citerefentry> enabled/disabled. This option
+ is disabled by default.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="opt.xmalloc">
+ <term>
+ <mallctl>opt.xmalloc</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ [<option>--enable-xmalloc</option>]
+ </term>
+ <listitem><para>Abort-on-out-of-memory enabled/disabled. If enabled,
+ rather than returning failure for any allocation function, display a
+ diagnostic message on <constant>STDERR_FILENO</constant> and cause the
+ program to drop core (using
+ <citerefentry><refentrytitle>abort</refentrytitle>
+ <manvolnum>3</manvolnum></citerefentry>). If an application is
+ designed to depend on this behavior, set the option at compile time by
+ including the following in the source code:
+ <programlisting language="C"><![CDATA[
+malloc_conf = "xmalloc:true";]]></programlisting>
+ This option is disabled by default.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="opt.tcache">
+ <term>
+ <mallctl>opt.tcache</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ [<option>--enable-tcache</option>]
+ </term>
+ <listitem><para>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 <link
+ linkend="opt.lg_tcache_max"><mallctl>opt.lg_tcache_max</mallctl></link>
+ option for related tuning information. This option is enabled by
+ default unless running inside <ulink
+ url="http://valgrind.org/">Valgrind</ulink>, in which case it is
+ forcefully disabled.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="opt.lg_tcache_max">
+ <term>
+ <mallctl>opt.lg_tcache_max</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-tcache</option>]
+ </term>
+ <listitem><para>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).</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="opt.prof">
+ <term>
+ <mallctl>opt.prof</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ [<option>--enable-prof</option>]
+ </term>
+ <listitem><para>Memory profiling enabled/disabled. If enabled, profile
+ memory allocation activity. See the <link
+ linkend="opt.prof_active"><mallctl>opt.prof_active</mallctl></link>
+ option for on-the-fly activation/deactivation. See the <link
+ linkend="opt.lg_prof_sample"><mallctl>opt.lg_prof_sample</mallctl></link>
+ option for probabilistic sampling control. See the <link
+ linkend="opt.prof_accum"><mallctl>opt.prof_accum</mallctl></link>
+ option for control of cumulative sample reporting. See the <link
+ linkend="opt.lg_prof_interval"><mallctl>opt.lg_prof_interval</mallctl></link>
+ option for information on interval-triggered profile dumping, the <link
+ linkend="opt.prof_gdump"><mallctl>opt.prof_gdump</mallctl></link>
+ option for information on high-water-triggered profile dumping, and the
+ <link linkend="opt.prof_final"><mallctl>opt.prof_final</mallctl></link>
+ option for final profile dumping. Profile output is compatible with
+ the <command>jeprof</command> command, which is based on the
+ <command>pprof</command> that is developed as part of the <ulink
+ url="http://code.google.com/p/gperftools/">gperftools
+ package</ulink>. See <link linkend="heap_profile_format">HEAP PROFILE
+ FORMAT</link> for heap profile format documentation.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="opt.prof_prefix">
+ <term>
+ <mallctl>opt.prof_prefix</mallctl>
+ (<type>const char *</type>)
+ <literal>r-</literal>
+ [<option>--enable-prof</option>]
+ </term>
+ <listitem><para>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
+ <filename>jeprof</filename>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="opt.prof_active">
+ <term>
+ <mallctl>opt.prof_active</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ [<option>--enable-prof</option>]
+ </term>
+ <listitem><para>Profiling activated/deactivated. This is a secondary
+ control mechanism that makes it possible to start the application with
+ profiling enabled (see the <link
+ linkend="opt.prof"><mallctl>opt.prof</mallctl></link> option) but
+ inactive, then toggle profiling at any time during program execution
+ with the <link
+ linkend="prof.active"><mallctl>prof.active</mallctl></link> mallctl.
+ This option is enabled by default.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="opt.prof_thread_active_init">
+ <term>
+ <mallctl>opt.prof_thread_active_init</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ [<option>--enable-prof</option>]
+ </term>
+ <listitem><para>Initial setting for <link
+ linkend="thread.prof.active"><mallctl>thread.prof.active</mallctl></link>
+ in newly created threads. The initial setting for newly created threads
+ can also be changed during execution via the <link
+ linkend="prof.thread_active_init"><mallctl>prof.thread_active_init</mallctl></link>
+ mallctl. This option is enabled by default.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="opt.lg_prof_sample">
+ <term>
+ <mallctl>opt.lg_prof_sample</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-prof</option>]
+ </term>
+ <listitem><para>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).</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="opt.prof_accum">
+ <term>
+ <mallctl>opt.prof_accum</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ [<option>--enable-prof</option>]
+ </term>
+ <listitem><para>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.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="opt.lg_prof_interval">
+ <term>
+ <mallctl>opt.lg_prof_interval</mallctl>
+ (<type>ssize_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-prof</option>]
+ </term>
+ <listitem><para>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
+ <filename>&lt;prefix&gt;.&lt;pid&gt;.&lt;seq&gt;.i&lt;iseq&gt;.heap</filename>,
+ where <literal>&lt;prefix&gt;</literal> is controlled by the
+ <link
+ linkend="opt.prof_prefix"><mallctl>opt.prof_prefix</mallctl></link>
+ option. By default, interval-triggered profile dumping is disabled
+ (encoded as -1).
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id="opt.prof_gdump">
+ <term>
+ <mallctl>opt.prof_gdump</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ [<option>--enable-prof</option>]
+ </term>
+ <listitem><para>Set the initial state of <link
+ linkend="prof.gdump"><mallctl>prof.gdump</mallctl></link>, which when
+ enabled triggers a memory profile dump every time the total virtual
+ memory exceeds the previous maximum. This option is disabled by
+ default.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="opt.prof_final">
+ <term>
+ <mallctl>opt.prof_final</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ [<option>--enable-prof</option>]
+ </term>
+ <listitem><para>Use an
+ <citerefentry><refentrytitle>atexit</refentrytitle>
+ <manvolnum>3</manvolnum></citerefentry> function to dump final memory
+ usage to a file named according to the pattern
+ <filename>&lt;prefix&gt;.&lt;pid&gt;.&lt;seq&gt;.f.heap</filename>,
+ where <literal>&lt;prefix&gt;</literal> is controlled by the <link
+ linkend="opt.prof_prefix"><mallctl>opt.prof_prefix</mallctl></link>
+ option. Note that <function>atexit()</function> may allocate
+ memory during application initialization and then deadlock internally
+ when jemalloc in turn calls <function>atexit()</function>, so
+ this option is not universally usable (though the application can
+ register its own <function>atexit()</function> function with
+ equivalent functionality). This option is disabled by
+ default.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="opt.prof_leak">
+ <term>
+ <mallctl>opt.prof_leak</mallctl>
+ (<type>bool</type>)
+ <literal>r-</literal>
+ [<option>--enable-prof</option>]
+ </term>
+ <listitem><para>Leak reporting enabled/disabled. If enabled, use an
+ <citerefentry><refentrytitle>atexit</refentrytitle>
+ <manvolnum>3</manvolnum></citerefentry> function to report memory leaks
+ detected by allocation sampling. See the
+ <link linkend="opt.prof"><mallctl>opt.prof</mallctl></link> option for
+ information on analyzing heap profile output. This option is disabled
+ by default.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="thread.arena">
+ <term>
+ <mallctl>thread.arena</mallctl>
+ (<type>unsigned</type>)
+ <literal>rw</literal>
+ </term>
+ <listitem><para>Get or set the arena associated with the calling
+ thread. If the specified arena was not initialized beforehand (see the
+ <link
+ linkend="arenas.initialized"><mallctl>arenas.initialized</mallctl></link>
+ mallctl), it will be automatically initialized as a side effect of
+ calling this interface.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="thread.allocated">
+ <term>
+ <mallctl>thread.allocated</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>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.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="thread.allocatedp">
+ <term>
+ <mallctl>thread.allocatedp</mallctl>
+ (<type>uint64_t *</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Get a pointer to the the value that is returned by the
+ <link
+ linkend="thread.allocated"><mallctl>thread.allocated</mallctl></link>
+ mallctl. This is useful for avoiding the overhead of repeated
+ <function>mallctl*()</function> calls.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="thread.deallocated">
+ <term>
+ <mallctl>thread.deallocated</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>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.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="thread.deallocatedp">
+ <term>
+ <mallctl>thread.deallocatedp</mallctl>
+ (<type>uint64_t *</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Get a pointer to the the value that is returned by the
+ <link
+ linkend="thread.deallocated"><mallctl>thread.deallocated</mallctl></link>
+ mallctl. This is useful for avoiding the overhead of repeated
+ <function>mallctl*()</function> calls.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="thread.tcache.enabled">
+ <term>
+ <mallctl>thread.tcache.enabled</mallctl>
+ (<type>bool</type>)
+ <literal>rw</literal>
+ [<option>--enable-tcache</option>]
+ </term>
+ <listitem><para>Enable/disable calling thread's tcache. The tcache is
+ implicitly flushed as a side effect of becoming
+ disabled (see <link
+ linkend="thread.tcache.flush"><mallctl>thread.tcache.flush</mallctl></link>).
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id="thread.tcache.flush">
+ <term>
+ <mallctl>thread.tcache.flush</mallctl>
+ (<type>void</type>)
+ <literal>--</literal>
+ [<option>--enable-tcache</option>]
+ </term>
+ <listitem><para>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.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="thread.prof.name">
+ <term>
+ <mallctl>thread.prof.name</mallctl>
+ (<type>const char *</type>)
+ <literal>r-</literal> or
+ <literal>-w</literal>
+ [<option>--enable-prof</option>]
+ </term>
+ <listitem><para>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 be nil-terminated and comprised only of characters in
+ the sets recognized
+ by <citerefentry><refentrytitle>isgraph</refentrytitle>
+ <manvolnum>3</manvolnum></citerefentry> and
+ <citerefentry><refentrytitle>isblank</refentrytitle>
+ <manvolnum>3</manvolnum></citerefentry>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="thread.prof.active">
+ <term>
+ <mallctl>thread.prof.active</mallctl>
+ (<type>bool</type>)
+ <literal>rw</literal>
+ [<option>--enable-prof</option>]
+ </term>
+ <listitem><para>Control whether sampling is currently active for the
+ calling thread. This is an activation mechanism in addition to <link
+ linkend="prof.active"><mallctl>prof.active</mallctl></link>; both must
+ be active for the calling thread to sample. This flag is enabled by
+ default.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="tcache.create">
+ <term>
+ <mallctl>tcache.create</mallctl>
+ (<type>unsigned</type>)
+ <literal>r-</literal>
+ [<option>--enable-tcache</option>]
+ </term>
+ <listitem><para>Create an explicit thread-specific cache (tcache) and
+ return an identifier that can be passed to the <link
+ linkend="MALLOCX_TCACHE"><constant>MALLOCX_TCACHE(<parameter>tc</parameter>)</constant></link>
+ 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.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id="tcache.flush">
+ <term>
+ <mallctl>tcache.flush</mallctl>
+ (<type>unsigned</type>)
+ <literal>-w</literal>
+ [<option>--enable-tcache</option>]
+ </term>
+ <listitem><para>Flush the specified thread-specific cache (tcache). The
+ same considerations apply to this interface as to <link
+ linkend="thread.tcache.flush"><mallctl>thread.tcache.flush</mallctl></link>,
+ except that the tcache will never be automatically discarded.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id="tcache.destroy">
+ <term>
+ <mallctl>tcache.destroy</mallctl>
+ (<type>unsigned</type>)
+ <literal>-w</literal>
+ [<option>--enable-tcache</option>]
+ </term>
+ <listitem><para>Flush the specified thread-specific cache (tcache) and
+ make the identifier available for use during a future tcache creation.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id="arena.i.purge">
+ <term>
+ <mallctl>arena.&lt;i&gt;.purge</mallctl>
+ (<type>void</type>)
+ <literal>--</literal>
+ </term>
+ <listitem><para>Purge all unused dirty pages for arena &lt;i&gt;, or for
+ all arenas if &lt;i&gt; equals <link
+ linkend="arenas.narenas"><mallctl>arenas.narenas</mallctl></link>.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id="arena.i.decay">
+ <term>
+ <mallctl>arena.&lt;i&gt;.decay</mallctl>
+ (<type>void</type>)
+ <literal>--</literal>
+ </term>
+ <listitem><para>Trigger decay-based purging of unused dirty pages for
+ arena &lt;i&gt;, or for all arenas if &lt;i&gt; equals <link
+ linkend="arenas.narenas"><mallctl>arenas.narenas</mallctl></link>.
+ The proportion of unused dirty pages to be purged depends on the current
+ time; see <link
+ linkend="opt.decay_time"><mallctl>opt.decay_time</mallctl></link> for
+ details.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="arena.i.reset">
+ <term>
+ <mallctl>arena.&lt;i&gt;.reset</mallctl>
+ (<type>void</type>)
+ <literal>--</literal>
+ </term>
+ <listitem><para>Discard all of the arena's extant allocations. This
+ interface can only be used with arenas created via <link
+ linkend="arenas.extend"><mallctl>arenas.extend</mallctl></link>. None
+ of the arena's discarded/cached allocations may accessed afterward. As
+ part of this requirement, all thread caches which were used to
+ allocate/deallocate in conjunction with the arena must be flushed
+ beforehand. This interface cannot be used if running inside Valgrind,
+ nor if the <link linkend="opt.quarantine">quarantine</link> size is
+ non-zero.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="arena.i.dss">
+ <term>
+ <mallctl>arena.&lt;i&gt;.dss</mallctl>
+ (<type>const char *</type>)
+ <literal>rw</literal>
+ </term>
+ <listitem><para>Set the precedence of dss allocation as related to mmap
+ allocation for arena &lt;i&gt;, or for all arenas if &lt;i&gt; equals
+ <link
+ linkend="arenas.narenas"><mallctl>arenas.narenas</mallctl></link>. See
+ <link linkend="opt.dss"><mallctl>opt.dss</mallctl></link> for supported
+ settings.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="arena.i.lg_dirty_mult">
+ <term>
+ <mallctl>arena.&lt;i&gt;.lg_dirty_mult</mallctl>
+ (<type>ssize_t</type>)
+ <literal>rw</literal>
+ </term>
+ <listitem><para>Current per-arena minimum ratio (log base 2) of active
+ to dirty pages for arena &lt;i&gt;. Each time this interface is set and
+ the ratio is increased, pages are synchronously purged as necessary to
+ impose the new ratio. See <link
+ linkend="opt.lg_dirty_mult"><mallctl>opt.lg_dirty_mult</mallctl></link>
+ for additional information.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="arena.i.decay_time">
+ <term>
+ <mallctl>arena.&lt;i&gt;.decay_time</mallctl>
+ (<type>ssize_t</type>)
+ <literal>rw</literal>
+ </term>
+ <listitem><para>Current per-arena approximate time in seconds from the
+ creation of a set of unused dirty pages until an equivalent set of
+ unused dirty pages is purged and/or reused. Each time this interface is
+ set, all currently unused dirty pages are considered to have fully
+ decayed, which causes immediate purging of all unused dirty pages unless
+ the decay time is set to -1 (i.e. purging disabled). See <link
+ linkend="opt.decay_time"><mallctl>opt.decay_time</mallctl></link> for
+ additional information.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="arena.i.chunk_hooks">
+ <term>
+ <mallctl>arena.&lt;i&gt;.chunk_hooks</mallctl>
+ (<type>chunk_hooks_t</type>)
+ <literal>rw</literal>
+ </term>
+ <listitem><para>Get or set the chunk management hook functions for arena
+ &lt;i&gt;. The functions must be capable of operating on all extant
+ chunks associated with arena &lt;i&gt;, usually by passing unknown
+ chunks to the replaced functions. In practice, it is feasible to
+ control allocation for arenas created via <link
+ linkend="arenas.extend"><mallctl>arenas.extend</mallctl></link> 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.</para>
+
+ <programlisting language="C"><![CDATA[
+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;]]></programlisting>
+ <para>The <type>chunk_hooks_t</type> 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.</para>
+
+ <funcsynopsis><funcprototype>
+ <funcdef>typedef void *<function>(chunk_alloc_t)</function></funcdef>
+ <paramdef>void *<parameter>chunk</parameter></paramdef>
+ <paramdef>size_t <parameter>size</parameter></paramdef>
+ <paramdef>size_t <parameter>alignment</parameter></paramdef>
+ <paramdef>bool *<parameter>zero</parameter></paramdef>
+ <paramdef>bool *<parameter>commit</parameter></paramdef>
+ <paramdef>unsigned <parameter>arena_ind</parameter></paramdef>
+ </funcprototype></funcsynopsis>
+ <literallayout></literallayout>
+ <para>A chunk allocation function conforms to the
+ <type>chunk_alloc_t</type> type and upon success returns a pointer to
+ <parameter>size</parameter> bytes of mapped memory on behalf of arena
+ <parameter>arena_ind</parameter> such that the chunk's base address is a
+ multiple of <parameter>alignment</parameter>, as well as setting
+ <parameter>*zero</parameter> to indicate whether the chunk is zeroed and
+ <parameter>*commit</parameter> to indicate whether the chunk is
+ committed. Upon error the function returns <constant>NULL</constant>
+ and leaves <parameter>*zero</parameter> and
+ <parameter>*commit</parameter> unmodified. The
+ <parameter>size</parameter> parameter is always a multiple of the chunk
+ size. The <parameter>alignment</parameter> parameter is always a power
+ of two at least as large as the chunk size. Zeroing is mandatory if
+ <parameter>*zero</parameter> is true upon function entry. Committing is
+ mandatory if <parameter>*commit</parameter> is true upon function entry.
+ If <parameter>chunk</parameter> is not <constant>NULL</constant>, the
+ returned pointer must be <parameter>chunk</parameter> on success or
+ <constant>NULL</constant> 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 <link
+ linkend="arena.i.dss"><mallctl>arena.&lt;i&gt;.dss</mallctl></link>
+ setting irrelevant.</para>
+
+ <funcsynopsis><funcprototype>
+ <funcdef>typedef bool <function>(chunk_dalloc_t)</function></funcdef>
+ <paramdef>void *<parameter>chunk</parameter></paramdef>
+ <paramdef>size_t <parameter>size</parameter></paramdef>
+ <paramdef>bool <parameter>committed</parameter></paramdef>
+ <paramdef>unsigned <parameter>arena_ind</parameter></paramdef>
+ </funcprototype></funcsynopsis>
+ <literallayout></literallayout>
+ <para>
+ A chunk deallocation function conforms to the
+ <type>chunk_dalloc_t</type> type and deallocates a
+ <parameter>chunk</parameter> of given <parameter>size</parameter> with
+ <parameter>committed</parameter>/decommited memory as indicated, on
+ behalf of arena <parameter>arena_ind</parameter>, 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.</para>
+
+ <funcsynopsis><funcprototype>
+ <funcdef>typedef bool <function>(chunk_commit_t)</function></funcdef>
+ <paramdef>void *<parameter>chunk</parameter></paramdef>
+ <paramdef>size_t <parameter>size</parameter></paramdef>
+ <paramdef>size_t <parameter>offset</parameter></paramdef>
+ <paramdef>size_t <parameter>length</parameter></paramdef>
+ <paramdef>unsigned <parameter>arena_ind</parameter></paramdef>
+ </funcprototype></funcsynopsis>
+ <literallayout></literallayout>
+ <para>A chunk commit function conforms to the
+ <type>chunk_commit_t</type> type and commits zeroed physical memory to
+ back pages within a <parameter>chunk</parameter> of given
+ <parameter>size</parameter> at <parameter>offset</parameter> bytes,
+ extending for <parameter>length</parameter> on behalf of arena
+ <parameter>arena_ind</parameter>, 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.</para>
+
+ <funcsynopsis><funcprototype>
+ <funcdef>typedef bool <function>(chunk_decommit_t)</function></funcdef>
+ <paramdef>void *<parameter>chunk</parameter></paramdef>
+ <paramdef>size_t <parameter>size</parameter></paramdef>
+ <paramdef>size_t <parameter>offset</parameter></paramdef>
+ <paramdef>size_t <parameter>length</parameter></paramdef>
+ <paramdef>unsigned <parameter>arena_ind</parameter></paramdef>
+ </funcprototype></funcsynopsis>
+ <literallayout></literallayout>
+ <para>A chunk decommit function conforms to the
+ <type>chunk_decommit_t</type> type and decommits any physical memory
+ that is backing pages within a <parameter>chunk</parameter> of given
+ <parameter>size</parameter> at <parameter>offset</parameter> bytes,
+ extending for <parameter>length</parameter> on behalf of arena
+ <parameter>arena_ind</parameter>, 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.</para>
+
+ <funcsynopsis><funcprototype>
+ <funcdef>typedef bool <function>(chunk_purge_t)</function></funcdef>
+ <paramdef>void *<parameter>chunk</parameter></paramdef>
+ <paramdef>size_t<parameter>size</parameter></paramdef>
+ <paramdef>size_t <parameter>offset</parameter></paramdef>
+ <paramdef>size_t <parameter>length</parameter></paramdef>
+ <paramdef>unsigned <parameter>arena_ind</parameter></paramdef>
+ </funcprototype></funcsynopsis>
+ <literallayout></literallayout>
+ <para>A chunk purge function conforms to the <type>chunk_purge_t</type>
+ type and optionally discards physical pages within the virtual memory
+ mapping associated with <parameter>chunk</parameter> of given
+ <parameter>size</parameter> at <parameter>offset</parameter> bytes,
+ extending for <parameter>length</parameter> on behalf of arena
+ <parameter>arena_ind</parameter>, returning false if pages within the
+ purged virtual memory range will be zero-filled the next time they are
+ accessed.</para>
+
+ <funcsynopsis><funcprototype>
+ <funcdef>typedef bool <function>(chunk_split_t)</function></funcdef>
+ <paramdef>void *<parameter>chunk</parameter></paramdef>
+ <paramdef>size_t <parameter>size</parameter></paramdef>
+ <paramdef>size_t <parameter>size_a</parameter></paramdef>
+ <paramdef>size_t <parameter>size_b</parameter></paramdef>
+ <paramdef>bool <parameter>committed</parameter></paramdef>
+ <paramdef>unsigned <parameter>arena_ind</parameter></paramdef>
+ </funcprototype></funcsynopsis>
+ <literallayout></literallayout>
+ <para>A chunk split function conforms to the <type>chunk_split_t</type>
+ type and optionally splits <parameter>chunk</parameter> of given
+ <parameter>size</parameter> into two adjacent chunks, the first of
+ <parameter>size_a</parameter> bytes, and the second of
+ <parameter>size_b</parameter> bytes, operating on
+ <parameter>committed</parameter>/decommitted memory as indicated, on
+ behalf of arena <parameter>arena_ind</parameter>, 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.</para>
+
+ <funcsynopsis><funcprototype>
+ <funcdef>typedef bool <function>(chunk_merge_t)</function></funcdef>
+ <paramdef>void *<parameter>chunk_a</parameter></paramdef>
+ <paramdef>size_t <parameter>size_a</parameter></paramdef>
+ <paramdef>void *<parameter>chunk_b</parameter></paramdef>
+ <paramdef>size_t <parameter>size_b</parameter></paramdef>
+ <paramdef>bool <parameter>committed</parameter></paramdef>
+ <paramdef>unsigned <parameter>arena_ind</parameter></paramdef>
+ </funcprototype></funcsynopsis>
+ <literallayout></literallayout>
+ <para>A chunk merge function conforms to the <type>chunk_merge_t</type>
+ type and optionally merges adjacent chunks,
+ <parameter>chunk_a</parameter> of given <parameter>size_a</parameter>
+ and <parameter>chunk_b</parameter> of given
+ <parameter>size_b</parameter> into one contiguous chunk, operating on
+ <parameter>committed</parameter>/decommitted memory as indicated, on
+ behalf of arena <parameter>arena_ind</parameter>, 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.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id="arenas.narenas">
+ <term>
+ <mallctl>arenas.narenas</mallctl>
+ (<type>unsigned</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>Current limit on number of arenas.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="arenas.initialized">
+ <term>
+ <mallctl>arenas.initialized</mallctl>
+ (<type>bool *</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>An array of <link
+ linkend="arenas.narenas"><mallctl>arenas.narenas</mallctl></link>
+ booleans. Each boolean indicates whether the corresponding arena is
+ initialized.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="arenas.lg_dirty_mult">
+ <term>
+ <mallctl>arenas.lg_dirty_mult</mallctl>
+ (<type>ssize_t</type>)
+ <literal>rw</literal>
+ </term>
+ <listitem><para>Current default per-arena minimum ratio (log base 2) of
+ active to dirty pages, used to initialize <link
+ linkend="arena.i.lg_dirty_mult"><mallctl>arena.&lt;i&gt;.lg_dirty_mult</mallctl></link>
+ during arena creation. See <link
+ linkend="opt.lg_dirty_mult"><mallctl>opt.lg_dirty_mult</mallctl></link>
+ for additional information.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="arenas.decay_time">
+ <term>
+ <mallctl>arenas.decay_time</mallctl>
+ (<type>ssize_t</type>)
+ <literal>rw</literal>
+ </term>
+ <listitem><para>Current default per-arena approximate time in seconds
+ from the creation of a set of unused dirty pages until an equivalent set
+ of unused dirty pages is purged and/or reused, used to initialize <link
+ linkend="arena.i.decay_time"><mallctl>arena.&lt;i&gt;.decay_time</mallctl></link>
+ during arena creation. See <link
+ linkend="opt.decay_time"><mallctl>opt.decay_time</mallctl></link> for
+ additional information.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="arenas.quantum">
+ <term>
+ <mallctl>arenas.quantum</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>Quantum size.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="arenas.page">
+ <term>
+ <mallctl>arenas.page</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>Page size.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="arenas.tcache_max">
+ <term>
+ <mallctl>arenas.tcache_max</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-tcache</option>]
+ </term>
+ <listitem><para>Maximum thread-cached size class.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="arenas.nbins">
+ <term>
+ <mallctl>arenas.nbins</mallctl>
+ (<type>unsigned</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>Number of bin size classes.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="arenas.nhbins">
+ <term>
+ <mallctl>arenas.nhbins</mallctl>
+ (<type>unsigned</type>)
+ <literal>r-</literal>
+ [<option>--enable-tcache</option>]
+ </term>
+ <listitem><para>Total number of thread cache bin size
+ classes.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="arenas.bin.i.size">
+ <term>
+ <mallctl>arenas.bin.&lt;i&gt;.size</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>Maximum size supported by size class.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="arenas.bin.i.nregs">
+ <term>
+ <mallctl>arenas.bin.&lt;i&gt;.nregs</mallctl>
+ (<type>uint32_t</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>Number of regions per page run.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="arenas.bin.i.run_size">
+ <term>
+ <mallctl>arenas.bin.&lt;i&gt;.run_size</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>Number of bytes per page run.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="arenas.nlruns">
+ <term>
+ <mallctl>arenas.nlruns</mallctl>
+ (<type>unsigned</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>Total number of large size classes.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="arenas.lrun.i.size">
+ <term>
+ <mallctl>arenas.lrun.&lt;i&gt;.size</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>Maximum size supported by this large size
+ class.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="arenas.nhchunks">
+ <term>
+ <mallctl>arenas.nhchunks</mallctl>
+ (<type>unsigned</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>Total number of huge size classes.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="arenas.hchunk.i.size">
+ <term>
+ <mallctl>arenas.hchunk.&lt;i&gt;.size</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>Maximum size supported by this huge size
+ class.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="arenas.extend">
+ <term>
+ <mallctl>arenas.extend</mallctl>
+ (<type>unsigned</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>Extend the array of arenas by appending a new arena,
+ and returning the new arena index.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="prof.thread_active_init">
+ <term>
+ <mallctl>prof.thread_active_init</mallctl>
+ (<type>bool</type>)
+ <literal>rw</literal>
+ [<option>--enable-prof</option>]
+ </term>
+ <listitem><para>Control the initial setting for <link
+ linkend="thread.prof.active"><mallctl>thread.prof.active</mallctl></link>
+ in newly created threads. See the <link
+ linkend="opt.prof_thread_active_init"><mallctl>opt.prof_thread_active_init</mallctl></link>
+ option for additional information.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="prof.active">
+ <term>
+ <mallctl>prof.active</mallctl>
+ (<type>bool</type>)
+ <literal>rw</literal>
+ [<option>--enable-prof</option>]
+ </term>
+ <listitem><para>Control whether sampling is currently active. See the
+ <link
+ linkend="opt.prof_active"><mallctl>opt.prof_active</mallctl></link>
+ option for additional information, as well as the interrelated <link
+ linkend="thread.prof.active"><mallctl>thread.prof.active</mallctl></link>
+ mallctl.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="prof.dump">
+ <term>
+ <mallctl>prof.dump</mallctl>
+ (<type>const char *</type>)
+ <literal>-w</literal>
+ [<option>--enable-prof</option>]
+ </term>
+ <listitem><para>Dump a memory profile to the specified file, or if NULL
+ is specified, to a file according to the pattern
+ <filename>&lt;prefix&gt;.&lt;pid&gt;.&lt;seq&gt;.m&lt;mseq&gt;.heap</filename>,
+ where <literal>&lt;prefix&gt;</literal> is controlled by the
+ <link
+ linkend="opt.prof_prefix"><mallctl>opt.prof_prefix</mallctl></link>
+ option.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="prof.gdump">
+ <term>
+ <mallctl>prof.gdump</mallctl>
+ (<type>bool</type>)
+ <literal>rw</literal>
+ [<option>--enable-prof</option>]
+ </term>
+ <listitem><para>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
+ <filename>&lt;prefix&gt;.&lt;pid&gt;.&lt;seq&gt;.u&lt;useq&gt;.heap</filename>,
+ where <literal>&lt;prefix&gt;</literal> is controlled by the <link
+ linkend="opt.prof_prefix"><mallctl>opt.prof_prefix</mallctl></link>
+ option.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="prof.reset">
+ <term>
+ <mallctl>prof.reset</mallctl>
+ (<type>size_t</type>)
+ <literal>-w</literal>
+ [<option>--enable-prof</option>]
+ </term>
+ <listitem><para>Reset all memory profile statistics, and optionally
+ update the sample rate (see <link
+ linkend="opt.lg_prof_sample"><mallctl>opt.lg_prof_sample</mallctl></link>
+ and <link
+ linkend="prof.lg_sample"><mallctl>prof.lg_sample</mallctl></link>).
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id="prof.lg_sample">
+ <term>
+ <mallctl>prof.lg_sample</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-prof</option>]
+ </term>
+ <listitem><para>Get the current sample rate (see <link
+ linkend="opt.lg_prof_sample"><mallctl>opt.lg_prof_sample</mallctl></link>).
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id="prof.interval">
+ <term>
+ <mallctl>prof.interval</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-prof</option>]
+ </term>
+ <listitem><para>Average number of bytes allocated between
+ interval-based profile dumps. See the
+ <link
+ linkend="opt.lg_prof_interval"><mallctl>opt.lg_prof_interval</mallctl></link>
+ option for additional information.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.cactive">
+ <term>
+ <mallctl>stats.cactive</mallctl>
+ (<type>size_t *</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>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 <link
+ linkend="epoch"><mallctl>epoch</mallctl></link> 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.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.allocated">
+ <term>
+ <mallctl>stats.allocated</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Total number of bytes allocated by the
+ application.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.active">
+ <term>
+ <mallctl>stats.active</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>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 <link
+ linkend="stats.allocated"><mallctl>stats.allocated</mallctl></link>.
+ This does not include <link linkend="stats.arenas.i.pdirty">
+ <mallctl>stats.arenas.&lt;i&gt;.pdirty</mallctl></link>, nor pages
+ entirely devoted to allocator metadata.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.metadata">
+ <term>
+ <mallctl>stats.metadata</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Total number of bytes dedicated to metadata, which
+ comprise base allocations used for bootstrap-sensitive internal
+ allocator data structures, arena chunk headers (see <link
+ linkend="stats.arenas.i.metadata.mapped"><mallctl>stats.arenas.&lt;i&gt;.metadata.mapped</mallctl></link>),
+ and internal allocations (see <link
+ linkend="stats.arenas.i.metadata.allocated"><mallctl>stats.arenas.&lt;i&gt;.metadata.allocated</mallctl></link>).</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.resident">
+ <term>
+ <mallctl>stats.resident</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>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 <link
+ linkend="stats.active"><mallctl>stats.active</mallctl></link>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.mapped">
+ <term>
+ <mallctl>stats.mapped</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Total number of bytes in active chunks mapped by the
+ allocator. This is a multiple of the chunk size, and is larger than
+ <link linkend="stats.active"><mallctl>stats.active</mallctl></link>.
+ This does not include inactive chunks, even those that contain unused
+ dirty pages, which means that there is no strict ordering between this
+ and <link
+ linkend="stats.resident"><mallctl>stats.resident</mallctl></link>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.retained">
+ <term>
+ <mallctl>stats.retained</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Total number of bytes in virtual memory mappings that
+ were retained rather than being returned to the operating system via
+ e.g. <citerefentry><refentrytitle>munmap</refentrytitle>
+ <manvolnum>2</manvolnum></citerefentry>. Retained virtual memory is
+ typically untouched, decommitted, or purged, so it has no strongly
+ associated physical memory (see <link
+ linkend="arena.i.chunk_hooks">chunk hooks</link> for details). Retained
+ memory is excluded from mapped memory statistics, e.g. <link
+ linkend="stats.mapped"><mallctl>stats.mapped</mallctl></link>.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.dss">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.dss</mallctl>
+ (<type>const char *</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>dss (<citerefentry><refentrytitle>sbrk</refentrytitle>
+ <manvolnum>2</manvolnum></citerefentry>) allocation precedence as
+ related to <citerefentry><refentrytitle>mmap</refentrytitle>
+ <manvolnum>2</manvolnum></citerefentry> allocation. See <link
+ linkend="opt.dss"><mallctl>opt.dss</mallctl></link> for details.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.lg_dirty_mult">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.lg_dirty_mult</mallctl>
+ (<type>ssize_t</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>Minimum ratio (log base 2) of active to dirty pages.
+ See <link
+ linkend="opt.lg_dirty_mult"><mallctl>opt.lg_dirty_mult</mallctl></link>
+ for details.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.decay_time">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.decay_time</mallctl>
+ (<type>ssize_t</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>Approximate time in seconds from the creation of a set
+ of unused dirty pages until an equivalent set of unused dirty pages is
+ purged and/or reused. See <link
+ linkend="opt.decay_time"><mallctl>opt.decay_time</mallctl></link>
+ for details.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.nthreads">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.nthreads</mallctl>
+ (<type>unsigned</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>Number of threads currently assigned to
+ arena.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.pactive">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.pactive</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>Number of pages in active runs.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.pdirty">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.pdirty</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ </term>
+ <listitem><para>Number of pages within unused runs that are potentially
+ dirty, and for which <function>madvise<parameter>...</parameter>
+ <parameter><constant>MADV_DONTNEED</constant></parameter></function> or
+ similar has not been called.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.mapped">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.mapped</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Number of mapped bytes.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.retained">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.retained</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Number of retained bytes. See <link
+ linkend="stats.retained"><mallctl>stats.retained</mallctl></link> for
+ details.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.metadata.mapped">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.metadata.mapped</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Number of mapped bytes in arena chunk headers, which
+ track the states of the non-metadata pages.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.metadata.allocated">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.metadata.allocated</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>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 <link
+ linkend="stats.metadata"><mallctl>stats.metadata</mallctl></link> and
+ <link
+ linkend="stats.arenas.i.metadata.mapped"><mallctl>stats.arenas.&lt;i&gt;.metadata.mapped</mallctl></link>
+ because it overlaps with e.g. the <link
+ linkend="stats.allocated"><mallctl>stats.allocated</mallctl></link> and
+ <link linkend="stats.active"><mallctl>stats.active</mallctl></link>
+ statistics, whereas the other metadata statistics do
+ not.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.npurge">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.npurge</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Number of dirty page purge sweeps performed.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.nmadvise">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.nmadvise</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Number of <function>madvise<parameter>...</parameter>
+ <parameter><constant>MADV_DONTNEED</constant></parameter></function> or
+ similar calls made to purge dirty pages.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.purged">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.purged</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Number of pages purged.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.small.allocated">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.small.allocated</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Number of bytes currently allocated by small objects.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.small.nmalloc">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.small.nmalloc</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Cumulative number of allocation requests served by
+ small bins.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.small.ndalloc">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.small.ndalloc</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Cumulative number of small objects returned to bins.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.small.nrequests">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.small.nrequests</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Cumulative number of small allocation requests.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.large.allocated">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.large.allocated</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Number of bytes currently allocated by large objects.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.large.nmalloc">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.large.nmalloc</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Cumulative number of large allocation requests served
+ directly by the arena.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.large.ndalloc">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.large.ndalloc</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Cumulative number of large deallocation requests served
+ directly by the arena.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.large.nrequests">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.large.nrequests</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Cumulative number of large allocation requests.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.huge.allocated">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.huge.allocated</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Number of bytes currently allocated by huge objects.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.huge.nmalloc">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.huge.nmalloc</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Cumulative number of huge allocation requests served
+ directly by the arena.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.huge.ndalloc">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.huge.ndalloc</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Cumulative number of huge deallocation requests served
+ directly by the arena.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.huge.nrequests">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.huge.nrequests</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Cumulative number of huge allocation requests.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.bins.j.nmalloc">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.nmalloc</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Cumulative number of allocations served by bin.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.bins.j.ndalloc">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.ndalloc</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Cumulative number of allocations returned to bin.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.bins.j.nrequests">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.nrequests</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Cumulative number of allocation
+ requests.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.bins.j.curregs">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.curregs</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Current number of regions for this size
+ class.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.bins.j.nfills">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.nfills</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option> <option>--enable-tcache</option>]
+ </term>
+ <listitem><para>Cumulative number of tcache fills.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.bins.j.nflushes">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.nflushes</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option> <option>--enable-tcache</option>]
+ </term>
+ <listitem><para>Cumulative number of tcache flushes.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.bins.j.nruns">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.nruns</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Cumulative number of runs created.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.bins.j.nreruns">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.nreruns</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Cumulative number of times the current run from which
+ to allocate changed.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.bins.j.curruns">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.curruns</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Current number of runs.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.lruns.j.nmalloc">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.lruns.&lt;j&gt;.nmalloc</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Cumulative number of allocation requests for this size
+ class served directly by the arena.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.lruns.j.ndalloc">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.lruns.&lt;j&gt;.ndalloc</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Cumulative number of deallocation requests for this
+ size class served directly by the arena.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.lruns.j.nrequests">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.lruns.&lt;j&gt;.nrequests</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Cumulative number of allocation requests for this size
+ class.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.lruns.j.curruns">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.lruns.&lt;j&gt;.curruns</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Current number of runs for this size class.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.hchunks.j.nmalloc">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.hchunks.&lt;j&gt;.nmalloc</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Cumulative number of allocation requests for this size
+ class served directly by the arena.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.hchunks.j.ndalloc">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.hchunks.&lt;j&gt;.ndalloc</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Cumulative number of deallocation requests for this
+ size class served directly by the arena.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.hchunks.j.nrequests">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.hchunks.&lt;j&gt;.nrequests</mallctl>
+ (<type>uint64_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Cumulative number of allocation requests for this size
+ class.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id="stats.arenas.i.hchunks.j.curhchunks">
+ <term>
+ <mallctl>stats.arenas.&lt;i&gt;.hchunks.&lt;j&gt;.curhchunks</mallctl>
+ (<type>size_t</type>)
+ <literal>r-</literal>
+ [<option>--enable-stats</option>]
+ </term>
+ <listitem><para>Current number of huge allocations for this size class.
+ </para></listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+ <refsect1 id="heap_profile_format">
+ <title>HEAP PROFILE FORMAT</title>
+ <para>Although the heap profiling functionality was originally designed to
+ be compatible with the
+ <command>pprof</command> command that is developed as part of the <ulink
+ url="http://code.google.com/p/gperftools/">gperftools
+ package</ulink>, the addition of per thread heap profiling functionality
+ required a different heap profile format. The <command>jeprof</command>
+ command is derived from <command>pprof</command>, with enhancements to
+ support the heap profile format described here.</para>
+
+ <para>In the following hypothetical heap profile, <constant>[...]</constant>
+ indicates elision for the sake of compactness. <programlisting><![CDATA[
+heap_v2/524288
+ t*: 28106: 56637512 [0: 0]
+ [...]
+ t3: 352: 16777344 [0: 0]
+ [...]
+ t99: 17754: 29341640 [0: 0]
+ [...]
+@ 0x5f86da8 0x5f5a1dc [...] 0x29e4d4e 0xa200316 0xabb2988 [...]
+ t*: 13: 6688 [0: 0]
+ t3: 12: 6496 [0: ]
+ t99: 1: 192 [0: 0]
+[...]
+
+MAPPED_LIBRARIES:
+[...]]]></programlisting> The following matches the above heap profile, but most
+tokens are replaced with <constant>&lt;description&gt;</constant> to indicate
+descriptions of the corresponding fields. <programlisting><![CDATA[
+<heap_profile_format_version>/<mean_sample_interval>
+ <aggregate>: <curobjs>: <curbytes> [<cumobjs>: <cumbytes>]
+ [...]
+ <thread_3_aggregate>: <curobjs>: <curbytes>[<cumobjs>: <cumbytes>]
+ [...]
+ <thread_99_aggregate>: <curobjs>: <curbytes>[<cumobjs>: <cumbytes>]
+ [...]
+@ <top_frame> <frame> [...] <frame> <frame> <frame> [...]
+ <backtrace_aggregate>: <curobjs>: <curbytes> [<cumobjs>: <cumbytes>]
+ <backtrace_thread_3>: <curobjs>: <curbytes> [<cumobjs>: <cumbytes>]
+ <backtrace_thread_99>: <curobjs>: <curbytes> [<cumobjs>: <cumbytes>]
+[...]
+
+MAPPED_LIBRARIES:
+</proc/<pid>/maps>]]></programlisting></para>
+ </refsect1>
+
+ <refsect1 id="debugging_malloc_problems">
+ <title>DEBUGGING MALLOC PROBLEMS</title>
+ <para>When debugging, it is a good idea to configure/build jemalloc with
+ the <option>--enable-debug</option> and <option>--enable-fill</option>
+ 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.</para>
+
+ <para>Programs often accidentally depend on <quote>uninitialized</quote>
+ memory actually being filled with zero bytes. Junk filling
+ (see the <link linkend="opt.junk"><mallctl>opt.junk</mallctl></link>
+ option) tends to expose such bugs in the form of obviously incorrect
+ results and/or coredumps. Conversely, zero
+ filling (see the <link
+ linkend="opt.zero"><mallctl>opt.zero</mallctl></link> option) eliminates
+ the symptoms of such bugs. Between these two options, it is usually
+ possible to quickly detect, diagnose, and eliminate such bugs.</para>
+
+ <para>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 <ulink url="http://valgrind.org/">Valgrind</ulink> tool if the
+ <option>--enable-valgrind</option> configuration option is enabled.</para>
+ </refsect1>
+ <refsect1 id="diagnostic_messages">
+ <title>DIAGNOSTIC MESSAGES</title>
+ <para>If any of the memory allocation/deallocation functions detect an
+ error or warning condition, a message will be printed to file descriptor
+ <constant>STDERR_FILENO</constant>. Errors will result in the process
+ dumping core. If the <link
+ linkend="opt.abort"><mallctl>opt.abort</mallctl></link> option is set, most
+ warnings are treated as errors.</para>
+
+ <para>The <varname>malloc_message</varname> variable allows the programmer
+ to override the function which emits the text strings forming the errors
+ and warnings if for some reason the <constant>STDERR_FILENO</constant> file
+ descriptor is not suitable for this.
+ <function>malloc_message()</function> takes the
+ <parameter>cbopaque</parameter> pointer argument that is
+ <constant>NULL</constant> unless overridden by the arguments in a call to
+ <function>malloc_stats_print()</function>, 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.</para>
+
+ <para>All messages are prefixed by
+ <quote><computeroutput>&lt;jemalloc&gt;: </computeroutput></quote>.</para>
+ </refsect1>
+ <refsect1 id="return_values">
+ <title>RETURN VALUES</title>
+ <refsect2>
+ <title>Standard API</title>
+ <para>The <function>malloc()</function> and
+ <function>calloc()</function> functions return a pointer to the
+ allocated memory if successful; otherwise a <constant>NULL</constant>
+ pointer is returned and <varname>errno</varname> is set to
+ <errorname>ENOMEM</errorname>.</para>
+
+ <para>The <function>posix_memalign()</function> function
+ returns the value 0 if successful; otherwise it returns an error value.
+ The <function>posix_memalign()</function> function will fail
+ if:
+ <variablelist>
+ <varlistentry>
+ <term><errorname>EINVAL</errorname></term>
+
+ <listitem><para>The <parameter>alignment</parameter> parameter is
+ not a power of 2 at least as large as
+ <code language="C">sizeof(<type>void *</type>)</code>.
+ </para></listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><errorname>ENOMEM</errorname></term>
+
+ <listitem><para>Memory allocation error.</para></listitem>
+ </varlistentry>
+ </variablelist>
+ </para>
+
+ <para>The <function>aligned_alloc()</function> function returns
+ a pointer to the allocated memory if successful; otherwise a
+ <constant>NULL</constant> pointer is returned and
+ <varname>errno</varname> is set. The
+ <function>aligned_alloc()</function> function will fail if:
+ <variablelist>
+ <varlistentry>
+ <term><errorname>EINVAL</errorname></term>
+
+ <listitem><para>The <parameter>alignment</parameter> parameter is
+ not a power of 2.
+ </para></listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><errorname>ENOMEM</errorname></term>
+
+ <listitem><para>Memory allocation error.</para></listitem>
+ </varlistentry>
+ </variablelist>
+ </para>
+
+ <para>The <function>realloc()</function> function returns a
+ pointer, possibly identical to <parameter>ptr</parameter>, to the
+ allocated memory if successful; otherwise a <constant>NULL</constant>
+ pointer is returned, and <varname>errno</varname> is set to
+ <errorname>ENOMEM</errorname> if the error was the result of an
+ allocation failure. The <function>realloc()</function>
+ function always leaves the original buffer intact when an error occurs.
+ </para>
+
+ <para>The <function>free()</function> function returns no
+ value.</para>
+ </refsect2>
+ <refsect2>
+ <title>Non-standard API</title>
+ <para>The <function>mallocx()</function> and
+ <function>rallocx()</function> functions return a pointer to
+ the allocated memory if successful; otherwise a <constant>NULL</constant>
+ pointer is returned to indicate insufficient contiguous memory was
+ available to service the allocation request. </para>
+
+ <para>The <function>xallocx()</function> function returns the
+ real size of the resulting resized allocation pointed to by
+ <parameter>ptr</parameter>, which is a value less than
+ <parameter>size</parameter> if the allocation could not be adequately
+ grown in place. </para>
+
+ <para>The <function>sallocx()</function> function returns the
+ real size of the allocation pointed to by <parameter>ptr</parameter>.
+ </para>
+
+ <para>The <function>nallocx()</function> returns the real size
+ that would result from a successful equivalent
+ <function>mallocx()</function> function call, or zero if
+ insufficient memory is available to perform the size computation. </para>
+
+ <para>The <function>mallctl()</function>,
+ <function>mallctlnametomib()</function>, and
+ <function>mallctlbymib()</function> functions return 0 on
+ success; otherwise they return an error value. The functions will fail
+ if:
+ <variablelist>
+ <varlistentry>
+ <term><errorname>EINVAL</errorname></term>
+
+ <listitem><para><parameter>newp</parameter> is not
+ <constant>NULL</constant>, and <parameter>newlen</parameter> is too
+ large or too small. Alternatively, <parameter>*oldlenp</parameter>
+ is too large or too small; in this case as much data as possible
+ are read despite the error.</para></listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><errorname>ENOENT</errorname></term>
+
+ <listitem><para><parameter>name</parameter> or
+ <parameter>mib</parameter> specifies an unknown/invalid
+ value.</para></listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><errorname>EPERM</errorname></term>
+
+ <listitem><para>Attempt to read or write void value, or attempt to
+ write read-only value.</para></listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><errorname>EAGAIN</errorname></term>
+
+ <listitem><para>A memory allocation failure
+ occurred.</para></listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><errorname>EFAULT</errorname></term>
+
+ <listitem><para>An interface with side effects failed in some way
+ not directly related to <function>mallctl*()</function>
+ read/write processing.</para></listitem>
+ </varlistentry>
+ </variablelist>
+ </para>
+
+ <para>The <function>malloc_usable_size()</function> function
+ returns the usable size of the allocation pointed to by
+ <parameter>ptr</parameter>. </para>
+ </refsect2>
+ </refsect1>
+ <refsect1 id="environment">
+ <title>ENVIRONMENT</title>
+ <para>The following environment variable affects the execution of the
+ allocation functions:
+ <variablelist>
+ <varlistentry>
+ <term><envar>MALLOC_CONF</envar></term>
+
+ <listitem><para>If the environment variable
+ <envar>MALLOC_CONF</envar> is set, the characters it contains
+ will be interpreted as options.</para></listitem>
+ </varlistentry>
+ </variablelist>
+ </para>
+ </refsect1>
+ <refsect1 id="examples">
+ <title>EXAMPLES</title>
+ <para>To dump core whenever a problem occurs:
+ <screen>ln -s 'abort:true' /etc/malloc.conf</screen>
+ </para>
+ <para>To specify in the source a chunk size that is 16 MiB:
+ <programlisting language="C"><![CDATA[
+malloc_conf = "lg_chunk:24";]]></programlisting></para>
+ </refsect1>
+ <refsect1 id="see_also">
+ <title>SEE ALSO</title>
+ <para><citerefentry><refentrytitle>madvise</refentrytitle>
+ <manvolnum>2</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>mmap</refentrytitle>
+ <manvolnum>2</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sbrk</refentrytitle>
+ <manvolnum>2</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>utrace</refentrytitle>
+ <manvolnum>2</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>alloca</refentrytitle>
+ <manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>atexit</refentrytitle>
+ <manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>getpagesize</refentrytitle>
+ <manvolnum>3</manvolnum></citerefentry></para>
+ </refsect1>
+ <refsect1 id="standards">
+ <title>STANDARDS</title>
+ <para>The <function>malloc()</function>,
+ <function>calloc()</function>,
+ <function>realloc()</function>, and
+ <function>free()</function> functions conform to ISO/IEC
+ 9899:1990 (<quote>ISO C90</quote>).</para>
+
+ <para>The <function>posix_memalign()</function> function conforms
+ to IEEE Std 1003.1-2001 (<quote>POSIX.1</quote>).</para>
+ </refsect1>
+</refentry>