deps/jemalloc/doc/jemalloc.html

   1 <html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>JEMALLOC</title><meta name="generator" content="DocBook XSL Stylesheets V1.76.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" title="JEMALLOC"><a name="id286949398"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>jemalloc &#8212; general purpose memory allocation functions</p></div><div class="refsect1" title="LIBRARY"><a name="library"></a><h2>LIBRARY</h2><p>This manual describes jemalloc 3.0.0-0-gfc9b1dbf69f59d7ecfc4ac68da9847e017e1d046.  More information
   2     can be found at the <a class="ulink" href="http://www.canonware.com/jemalloc/" target="_top">jemalloc website</a>.</p></div><div class="refsynopsisdiv" title="SYNOPSIS"><h2>SYNOPSIS</h2><div class="funcsynopsis"><pre class="funcsynopsisinfo">#include &lt;<code class="filename">stdlib.h</code>&gt;
   3 #include &lt;<code class="filename">jemalloc/jemalloc.h</code>&gt;</pre><div class="refsect2" title="Standard API"><a name="id286949667"></a><h3>Standard API</h3><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void *<b class="fsfunc">malloc</b>(</code></td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void *<b class="fsfunc">calloc</b>(</code></td><td>size_t <var class="pdparam">number</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">posix_memalign</b>(</code></td><td>void **<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">alignment</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void *<b class="fsfunc">aligned_alloc</b>(</code></td><td>size_t <var class="pdparam">alignment</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void *<b class="fsfunc">realloc</b>(</code></td><td>void *<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">free</b>(</code></td><td>void *<var class="pdparam">ptr</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="refsect2" title="Non-standard API"><a name="id286949803"></a><h3>Non-standard API</h3><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">size_t <b class="fsfunc">malloc_usable_size</b>(</code></td><td>const void *<var class="pdparam">ptr</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">malloc_stats_print</b>(</code></td><td>void <var class="pdparam">(*write_cb)</var>
   4             <code>(</code>void *, const char *<code>)</code>
   5           , </td></tr><tr><td> </td><td>void *<var class="pdparam">cbopaque</var>, </td></tr><tr><td> </td><td>const char *<var class="pdparam">opts</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">mallctl</b>(</code></td><td>const char *<var class="pdparam">name</var>, </td></tr><tr><td> </td><td>void *<var class="pdparam">oldp</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">oldlenp</var>, </td></tr><tr><td> </td><td>void *<var class="pdparam">newp</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">newlen</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">mallctlnametomib</b>(</code></td><td>const char *<var class="pdparam">name</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">mibp</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">miblenp</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">mallctlbymib</b>(</code></td><td>const size_t *<var class="pdparam">mib</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">miblen</var>, </td></tr><tr><td> </td><td>void *<var class="pdparam">oldp</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">oldlenp</var>, </td></tr><tr><td> </td><td>void *<var class="pdparam">newp</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">newlen</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">(*malloc_message)</b>(</code></td><td>void *<var class="pdparam">cbopaque</var>, </td></tr><tr><td> </td><td>const char *<var class="pdparam">s</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><p><span class="type">const char *</span><code class="varname">malloc_conf</code>;</p></div><div class="refsect2" title="Experimental API"><a name="id286950044"></a><h3>Experimental API</h3><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">allocm</b>(</code></td><td>void **<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">rsize</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">rallocm</b>(</code></td><td>void **<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">rsize</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">extra</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">sallocm</b>(</code></td><td>const void *<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>size_t *<var class="pdparam">rsize</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">dallocm</b>(</code></td><td>void *<var class="pdparam">ptr</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">nallocm</b>(</code></td><td>size_t *<var class="pdparam">rsize</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div></div><div class="refsect1" title="DESCRIPTION"><a name="description"></a><h2>DESCRIPTION</h2><div class="refsect2" title="Standard API"><a name="id286950218"></a><h3>Standard API</h3><p>The <code class="function">malloc</code>(<em class="parameter"><code></code></em>) function allocates
   6       <em class="parameter"><code>size</code></em> bytes of uninitialized memory.  The allocated
   7       space is suitably aligned (after possible pointer coercion) for storage
   8       of any type of object.</p><p>The <code class="function">calloc</code>(<em class="parameter"><code></code></em>) function allocates
   9       space for <em class="parameter"><code>number</code></em> objects, each
  10       <em class="parameter"><code>size</code></em> bytes in length.  The result is identical to
  11       calling <code class="function">malloc</code>(<em class="parameter"><code></code></em>) with an argument of
  12       <em class="parameter"><code>number</code></em> * <em class="parameter"><code>size</code></em>, with the
  13       exception that the allocated memory is explicitly initialized to zero
  14       bytes.</p><p>The <code class="function">posix_memalign</code>(<em class="parameter"><code></code></em>) function
  15       allocates <em class="parameter"><code>size</code></em> bytes of memory such that the
  16       allocation's base address is an even multiple of
  17       <em class="parameter"><code>alignment</code></em>, and returns the allocation in the value
  18       pointed to by <em class="parameter"><code>ptr</code></em>.  The requested
  19       <em class="parameter"><code>alignment</code></em> must be a power of 2 at least as large
  20       as <code class="code">sizeof(<span class="type">void *</span>)</code>.</p><p>The <code class="function">aligned_alloc</code>(<em class="parameter"><code></code></em>) function
  21       allocates <em class="parameter"><code>size</code></em> bytes of memory such that the
  22       allocation's base address is an even multiple of
  23       <em class="parameter"><code>alignment</code></em>.  The requested
  24       <em class="parameter"><code>alignment</code></em> must be a power of 2.  Behavior is
  25       undefined if <em class="parameter"><code>size</code></em> is not an integral multiple of
  26       <em class="parameter"><code>alignment</code></em>.</p><p>The <code class="function">realloc</code>(<em class="parameter"><code></code></em>) function changes the
  27       size of the previously allocated memory referenced by
  28       <em class="parameter"><code>ptr</code></em> to <em class="parameter"><code>size</code></em> bytes.  The
  29       contents of the memory are unchanged up to the lesser of the new and old
  30       sizes.  If the new size is larger, the contents of the newly allocated
  31       portion of the memory are undefined.  Upon success, the memory referenced
  32       by <em class="parameter"><code>ptr</code></em> is freed and a pointer to the newly
  33       allocated memory is returned.  Note that
  34       <code class="function">realloc</code>(<em class="parameter"><code></code></em>) may move the memory allocation,
  35       resulting in a different return value than <em class="parameter"><code>ptr</code></em>.
  36       If <em class="parameter"><code>ptr</code></em> is <code class="constant">NULL</code>, the
  37       <code class="function">realloc</code>(<em class="parameter"><code></code></em>) function behaves identically to
  38       <code class="function">malloc</code>(<em class="parameter"><code></code></em>) for the specified size.</p><p>The <code class="function">free</code>(<em class="parameter"><code></code></em>) function causes the
  39       allocated memory referenced by <em class="parameter"><code>ptr</code></em> to be made
  40       available for future allocations.  If <em class="parameter"><code>ptr</code></em> is
  41       <code class="constant">NULL</code>, no action occurs.</p></div><div class="refsect2" title="Non-standard API"><a name="id286950483"></a><h3>Non-standard API</h3><p>The <code class="function">malloc_usable_size</code>(<em class="parameter"><code></code></em>) function
  42       returns the usable size of the allocation pointed to by
  43       <em class="parameter"><code>ptr</code></em>.  The return value may be larger than the size
  44       that was requested during allocation.  The
  45       <code class="function">malloc_usable_size</code>(<em class="parameter"><code></code></em>) function is not a
  46       mechanism for in-place <code class="function">realloc</code>(<em class="parameter"><code></code></em>); rather
  47       it is provided solely as a tool for introspection purposes.  Any
  48       discrepancy between the requested allocation size and the size reported
  49       by <code class="function">malloc_usable_size</code>(<em class="parameter"><code></code></em>) should not be
  50       depended on, since such behavior is entirely implementation-dependent.
  51       </p><p>The <code class="function">malloc_stats_print</code>(<em class="parameter"><code></code></em>) function
  52       writes human-readable summary statistics via the
  53       <em class="parameter"><code>write_cb</code></em> callback function pointer and
  54       <em class="parameter"><code>cbopaque</code></em> data passed to
  55       <em class="parameter"><code>write_cb</code></em>, or
  56       <code class="function">malloc_message</code>(<em class="parameter"><code></code></em>) if
  57       <em class="parameter"><code>write_cb</code></em> is <code class="constant">NULL</code>.  This
  58       function can be called repeatedly.  General information that never
  59       changes during execution can be omitted by specifying "g" as a character
  60       within the <em class="parameter"><code>opts</code></em> string.  Note that
  61       <code class="function">malloc_message</code>(<em class="parameter"><code></code></em>) uses the
  62       <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) functions internally, so
  63       inconsistent statistics can be reported if multiple threads use these
  64       functions simultaneously.  If <code class="option">--enable-stats</code> is
  65       specified during configuration, &#8220;m&#8221; and &#8220;a&#8221; can
  66       be specified to omit merged arena and per arena statistics, respectively;
  67       &#8220;b&#8221; and &#8220;l&#8221; can be specified to omit per size
  68       class statistics for bins and large objects, respectively.  Unrecognized
  69       characters are silently ignored.  Note that thread caching may prevent
  70       some statistics from being completely up to date, since extra locking
  71       would be required to merge counters that track thread cache operations.
  72       </p><p>The <code class="function">mallctl</code>(<em class="parameter"><code></code></em>) function provides a
  73       general interface for introspecting the memory allocator, as well as
  74       setting modifiable parameters and triggering actions.  The
  75       period-separated <em class="parameter"><code>name</code></em> argument specifies a
  76       location in a tree-structured namespace; see the <a class="xref" href="#mallctl_namespace" title="MALLCTL NAMESPACE">MALLCTL NAMESPACE</a> section for
  77       documentation on the tree contents.  To read a value, pass a pointer via
  78       <em class="parameter"><code>oldp</code></em> to adequate space to contain the value, and a
  79       pointer to its length via <em class="parameter"><code>oldlenp</code></em>; otherwise pass
  80       <code class="constant">NULL</code> and <code class="constant">NULL</code>.  Similarly, to
  81       write a value, pass a pointer to the value via
  82       <em class="parameter"><code>newp</code></em>, and its length via
  83       <em class="parameter"><code>newlen</code></em>; otherwise pass <code class="constant">NULL</code>
  84       and <code class="constant">0</code>.</p><p>The <code class="function">mallctlnametomib</code>(<em class="parameter"><code></code></em>) function
  85       provides a way to avoid repeated name lookups for applications that
  86       repeatedly query the same portion of the namespace, by translating a name
  87       to a &#8220;Management Information Base&#8221; (MIB) that can be passed
  88       repeatedly to <code class="function">mallctlbymib</code>(<em class="parameter"><code></code></em>).  Upon
  89       successful return from <code class="function">mallctlnametomib</code>(<em class="parameter"><code></code></em>),
  90       <em class="parameter"><code>mibp</code></em> contains an array of
  91       <em class="parameter"><code>*miblenp</code></em> integers, where
  92       <em class="parameter"><code>*miblenp</code></em> is the lesser of the number of components
  93       in <em class="parameter"><code>name</code></em> and the input value of
  94       <em class="parameter"><code>*miblenp</code></em>.  Thus it is possible to pass a
  95       <em class="parameter"><code>*miblenp</code></em> that is smaller than the number of
  96       period-separated name components, which results in a partial MIB that can
  97       be used as the basis for constructing a complete MIB.  For name
  98       components that are integers (e.g. the 2 in
  99       <a class="link" href="#arenas.bin.i.size">
 100     "<code class="mallctl">arenas.bin.2.size</code>"
 101   </a>),
 102       the corresponding MIB component will always be that integer.  Therefore,
 103       it is legitimate to construct code like the following: </p><pre class="programlisting">
 104 unsigned nbins, i;
 105
 106 int mib[4];
 107 size_t len, miblen;
 108
 109 len = sizeof(nbins);
 110 mallctl("arenas.nbins", &amp;nbins, &amp;len, NULL, 0);
 111
 112 miblen = 4;
 113 mallnametomib("arenas.bin.0.size", mib, &amp;miblen);
 114 for (i = 0; i &lt; nbins; i++) {
 115         size_t bin_size;
 116
 117         mib[2] = i;
 118         len = sizeof(bin_size);
 119         mallctlbymib(mib, miblen, &amp;bin_size, &amp;len, NULL, 0);
 120         /* Do something with bin_size... */
 121 }</pre></div><div class="refsect2" title="Experimental API"><a name="id286950724"></a><h3>Experimental API</h3><p>The experimental API is subject to change or removal without regard
 122       for backward compatibility.  If <code class="option">--disable-experimental</code>
 123       is specified during configuration, the experimental API is
 124       omitted.</p><p>The <code class="function">allocm</code>(<em class="parameter"><code></code></em>),
 125       <code class="function">rallocm</code>(<em class="parameter"><code></code></em>),
 126       <code class="function">sallocm</code>(<em class="parameter"><code></code></em>),
 127       <code class="function">dallocm</code>(<em class="parameter"><code></code></em>), and
 128       <code class="function">nallocm</code>(<em class="parameter"><code></code></em>) functions all have a
 129       <em class="parameter"><code>flags</code></em> argument that can be used to specify
 130       options.  The functions only check the options that are contextually
 131       relevant.  Use bitwise or (<code class="code">|</code>) operations to
 132       specify one or more of the following:
 133         </p><div class="variablelist"><dl><dt><span class="term"><code class="constant">ALLOCM_LG_ALIGN(<em class="parameter"><code>la</code></em>)
 134             </code></span></dt><dd><p>Align the memory allocation to start at an address
 135             that is a multiple of <code class="code">(1 &lt;&lt;
 136             <em class="parameter"><code>la</code></em>)</code>.  This macro does not validate
 137             that <em class="parameter"><code>la</code></em> is within the valid
 138             range.</p></dd><dt><span class="term"><code class="constant">ALLOCM_ALIGN(<em class="parameter"><code>a</code></em>)
 139             </code></span></dt><dd><p>Align the memory allocation to start at an address
 140             that is a multiple of <em class="parameter"><code>a</code></em>, where
 141             <em class="parameter"><code>a</code></em> is a power of two.  This macro does not
 142             validate that <em class="parameter"><code>a</code></em> is a power of 2.
 143             </p></dd><dt><span class="term"><code class="constant">ALLOCM_ZERO</code></span></dt><dd><p>Initialize newly allocated memory to contain zero
 144             bytes.  In the growing reallocation case, the real size prior to
 145             reallocation defines the boundary between untouched bytes and those
 146             that are initialized to contain zero bytes.  If this option is
 147             absent, newly allocated memory is uninitialized.</p></dd><dt><span class="term"><code class="constant">ALLOCM_NO_MOVE</code></span></dt><dd><p>For reallocation, fail rather than moving the
 148             object.  This constraint can apply to both growth and
 149             shrinkage.</p></dd></dl></div><p>
 150       </p><p>The <code class="function">allocm</code>(<em class="parameter"><code></code></em>) function allocates at
 151       least <em class="parameter"><code>size</code></em> bytes of memory, sets
 152       <em class="parameter"><code>*ptr</code></em> to the base address of the allocation, and
 153       sets <em class="parameter"><code>*rsize</code></em> to the real size of the allocation if
 154       <em class="parameter"><code>rsize</code></em> is not <code class="constant">NULL</code>.  Behavior
 155       is undefined if <em class="parameter"><code>size</code></em> is
 156       <code class="constant">0</code>.</p><p>The <code class="function">rallocm</code>(<em class="parameter"><code></code></em>) function resizes the
 157       allocation at <em class="parameter"><code>*ptr</code></em> to be at least
 158       <em class="parameter"><code>size</code></em> bytes, sets <em class="parameter"><code>*ptr</code></em> to
 159       the base address of the allocation if it moved, and sets
 160       <em class="parameter"><code>*rsize</code></em> to the real size of the allocation if
 161       <em class="parameter"><code>rsize</code></em> is not <code class="constant">NULL</code>.  If
 162       <em class="parameter"><code>extra</code></em> is non-zero, an attempt is made to resize
 163       the allocation to be at least <code class="code"><em class="parameter"><code>size</code></em> +
 164       <em class="parameter"><code>extra</code></em>)</code> bytes, though inability to allocate
 165       the extra byte(s) will not by itself result in failure.  Behavior is
 166       undefined if <em class="parameter"><code>size</code></em> is <code class="constant">0</code>, or if
 167       <code class="code">(<em class="parameter"><code>size</code></em> +
 168       <em class="parameter"><code>extra</code></em> &gt;
 169       <code class="constant">SIZE_T_MAX</code>)</code>.</p><p>The <code class="function">sallocm</code>(<em class="parameter"><code></code></em>) function sets
 170       <em class="parameter"><code>*rsize</code></em> to the real size of the allocation.</p><p>The <code class="function">dallocm</code>(<em class="parameter"><code></code></em>) function causes the
 171       memory referenced by <em class="parameter"><code>ptr</code></em> to be made available for
 172       future allocations.</p><p>The <code class="function">nallocm</code>(<em class="parameter"><code></code></em>) function allocates no
 173       memory, but it performs the same size computation as the
 174       <code class="function">allocm</code>(<em class="parameter"><code></code></em>) function, and if
 175       <em class="parameter"><code>rsize</code></em> is not <code class="constant">NULL</code> it sets
 176       <em class="parameter"><code>*rsize</code></em> to the real size of the allocation that
 177       would result from the equivalent <code class="function">allocm</code>(<em class="parameter"><code></code></em>)
 178       function call.  Behavior is undefined if
 179       <em class="parameter"><code>size</code></em> is <code class="constant">0</code>.</p></div></div><div class="refsect1" title="TUNING"><a name="tuning"></a><h2>TUNING</h2><p>Once, when the first call is made to one of the memory allocation
 180     routines, the allocator initializes its internals based in part on various
 181     options that can be specified at compile- or run-time.</p><p>The string pointed to by the global variable
 182     <code class="varname">malloc_conf</code>, the &#8220;name&#8221; of the file
 183     referenced by the symbolic link named <code class="filename">/etc/malloc.conf</code>, and the value of the
 184     environment variable <code class="envar">MALLOC_CONF</code>, will be interpreted, in
 185     that order, from left to right as options.</p><p>An options string is a comma-separated list of option:value pairs.
 186     There is one key corresponding to each <a class="link" href="#opt.abort">
 187     "<code class="mallctl">opt.*</code>"
 188   </a> mallctl (see the <a class="xref" href="#mallctl_namespace" title="MALLCTL NAMESPACE">MALLCTL NAMESPACE</a> section for options
 189     documentation).  For example, <code class="literal">abort:true,narenas:1</code> sets
 190     the <a class="link" href="#opt.abort">
 191     "<code class="mallctl">opt.abort</code>"
 192   </a> and <a class="link" href="#opt.narenas">
 193     "<code class="mallctl">opt.narenas</code>"
 194   </a> options.  Some
 195     options have boolean values (true/false), others have integer values (base
 196     8, 10, or 16, depending on prefix), and yet others have raw string
 197     values.</p></div><div class="refsect1" title="IMPLEMENTATION NOTES"><a name="implementation_notes"></a><h2>IMPLEMENTATION NOTES</h2><p>Traditionally, allocators have used
 198     <span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span> to obtain memory, which is
 199     suboptimal for several reasons, including race conditions, increased
 200     fragmentation, and artificial limitations on maximum usable memory.  If
 201     <code class="option">--enable-dss</code> is specified during configuration, this
 202     allocator uses both <span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span> and
 203     <span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span>, in that order of preference;
 204     otherwise only <span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span> is used.</p><p>This allocator uses multiple arenas in order to reduce lock
 205     contention for threaded programs on multi-processor systems.  This works
 206     well with regard to threading scalability, but incurs some costs.  There is
 207     a small fixed per-arena overhead, and additionally, arenas manage memory
 208     completely independently of each other, which means a small fixed increase
 209     in overall memory fragmentation.  These overheads are not generally an
 210     issue, given the number of arenas normally used.  Note that using
 211     substantially more arenas than the default is not likely to improve
 212     performance, mainly due to reduced cache performance.  However, it may make
 213     sense to reduce the number of arenas if an application does not make much
 214     use of the allocation functions.</p><p>In addition to multiple arenas, unless
 215     <code class="option">--disable-tcache</code> is specified during configuration, this
 216     allocator supports thread-specific caching for small and large objects, in
 217     order to make it possible to completely avoid synchronization for most
 218     allocation requests.  Such caching allows very fast allocation in the
 219     common case, but it increases memory usage and fragmentation, since a
 220     bounded number of objects can remain allocated in each thread cache.</p><p>Memory is conceptually broken into equal-sized chunks, where the
 221     chunk size is a power of two that is greater than the page size.  Chunks
 222     are always aligned to multiples of the chunk size.  This alignment makes it
 223     possible to find metadata for user objects very quickly.</p><p>User objects are broken into three categories according to size:
 224     small, large, and huge.  Small objects are smaller than one page.  Large
 225     objects are smaller than the chunk size.  Huge objects are a multiple of
 226     the chunk size.  Small and large objects are managed by arenas; huge
 227     objects are managed separately in a single data structure that is shared by
 228     all threads.  Huge objects are used by applications infrequently enough
 229     that this single data structure is not a scalability issue.</p><p>Each chunk that is managed by an arena tracks its contents as runs of
 230     contiguous pages (unused, backing a set of small objects, or backing one
 231     large object).  The combination of chunk alignment and chunk page maps
 232     makes it possible to determine all metadata regarding small and large
 233     allocations in constant time.</p><p>Small objects are managed in groups by page runs.  Each run maintains
 234     a frontier and free list to track which regions are in use.  Allocation
 235     requests that are no more than half the quantum (8 or 16, depending on
 236     architecture) are rounded up to the nearest power of two that is at least
 237     <code class="code">sizeof(<span class="type">double</span>)</code>.  All other small
 238     object size classes are multiples of the quantum, spaced such that internal
 239     fragmentation is limited to approximately 25% for all but the smallest size
 240     classes.  Allocation requests that are larger than the maximum small size
 241     class, but small enough to fit in an arena-managed chunk (see the <a class="link" href="#opt.lg_chunk">
 242     "<code class="mallctl">opt.lg_chunk</code>"
 243   </a> option), are
 244     rounded up to the nearest run size.  Allocation requests that are too large
 245     to fit in an arena-managed chunk are rounded up to the nearest multiple of
 246     the chunk size.</p><p>Allocations are packed tightly together, which can be an issue for
 247     multi-threaded applications.  If you need to assure that allocations do not
 248     suffer from cacheline sharing, round your allocation requests up to the
 249     nearest multiple of the cacheline size, or specify cacheline alignment when
 250     allocating.</p><p>Assuming 4 MiB chunks, 4 KiB pages, and a 16-byte quantum on a 64-bit
 251     system, the size classes in each category are as shown in <a class="xref" href="#size_classes" title="Table 1. Size classes">Table 1</a>.</p><div class="table"><a name="size_classes"></a><p class="title"><b>Table 1. Size classes</b></p><div class="table-contents"><table summary="Size classes" border="1"><colgroup><col align="left" class="c1"><col align="right" class="c2"><col align="left" class="c3"></colgroup><thead><tr><th align="left">Category</th><th align="right">Spacing</th><th align="left">Size</th></tr></thead><tbody><tr><td rowspan="7" align="left">Small</td><td align="right">lg</td><td align="left">[8]</td></tr><tr><td align="right">16</td><td align="left">[16, 32, 48, ..., 128]</td></tr><tr><td align="right">32</td><td align="left">[160, 192, 224, 256]</td></tr><tr><td align="right">64</td><td align="left">[320, 384, 448, 512]</td></tr><tr><td align="right">128</td><td align="left">[640, 768, 896, 1024]</td></tr><tr><td align="right">256</td><td align="left">[1280, 1536, 1792, 2048]</td></tr><tr><td align="right">512</td><td align="left">[2560, 3072, 3584]</td></tr><tr><td align="left">Large</td><td align="right">4 KiB</td><td align="left">[4 KiB, 8 KiB, 12 KiB, ..., 4072 KiB]</td></tr><tr><td align="left">Huge</td><td align="right">4 MiB</td><td align="left">[4 MiB, 8 MiB, 12 MiB, ...]</td></tr></tbody></table></div></div><br class="table-break"></div><div class="refsect1" title="MALLCTL NAMESPACE"><a name="mallctl_namespace"></a><h2>MALLCTL NAMESPACE</h2><p>The following names are defined in the namespace accessible via the
 252     <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) functions.  Value types are
 253     specified in parentheses, their readable/writable statuses are encoded as
 254     <code class="literal">rw</code>, <code class="literal">r-</code>, <code class="literal">-w</code>, or
 255     <code class="literal">--</code>, and required build configuration flags follow, if
 256     any.  A name element encoded as <code class="literal">&lt;i&gt;</code> or
 257     <code class="literal">&lt;j&gt;</code> indicates an integer component, where the
 258     integer varies from 0 to some upper value that must be determined via
 259     introspection.  In the case of
 260     "<code class="mallctl">stats.arenas.&lt;i&gt;.*</code>"
 261   ,
 262     <code class="literal">&lt;i&gt;</code> equal to <a class="link" href="#arenas.narenas">
 263     "<code class="mallctl">arenas.narenas</code>"
 264   </a> can be
 265     used to access the summation of statistics from all arenas.  Take special
 266     note of the <a class="link" href="#epoch">
 267     "<code class="mallctl">epoch</code>"
 268   </a> mallctl,
 269     which controls refreshing of cached dynamic statistics.</p><div class="variablelist"><dl><dt><span class="term">
 270
 271     "<code class="mallctl">version</code>"
 272
 273           (<span class="type">const char *</span>)
 274           <code class="literal">r-</code>
 275         </span></dt><dd><p>Return the jemalloc version string.</p></dd><dt><a name="epoch"></a><span class="term">
 276
 277     "<code class="mallctl">epoch</code>"
 278
 279           (<span class="type">uint64_t</span>)
 280           <code class="literal">rw</code>
 281         </span></dt><dd><p>If a value is passed in, refresh the data from which
 282         the <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) functions report values,
 283         and increment the epoch.  Return the current epoch.  This is useful for
 284         detecting whether another thread caused a refresh.</p></dd><dt><span class="term">
 285
 286     "<code class="mallctl">config.debug</code>"
 287
 288           (<span class="type">bool</span>)
 289           <code class="literal">r-</code>
 290         </span></dt><dd><p><code class="option">--enable-debug</code> was specified during
 291         build configuration.</p></dd><dt><span class="term">
 292
 293     "<code class="mallctl">config.dss</code>"
 294
 295           (<span class="type">bool</span>)
 296           <code class="literal">r-</code>
 297         </span></dt><dd><p><code class="option">--enable-dss</code> was specified during
 298         build configuration.</p></dd><dt><span class="term">
 299
 300     "<code class="mallctl">config.fill</code>"
 301
 302           (<span class="type">bool</span>)
 303           <code class="literal">r-</code>
 304         </span></dt><dd><p><code class="option">--enable-fill</code> was specified during
 305         build configuration.</p></dd><dt><span class="term">
 306
 307     "<code class="mallctl">config.lazy_lock</code>"
 308
 309           (<span class="type">bool</span>)
 310           <code class="literal">r-</code>
 311         </span></dt><dd><p><code class="option">--enable-lazy-lock</code> was specified
 312         during build configuration.</p></dd><dt><span class="term">
 313
 314     "<code class="mallctl">config.mremap</code>"
 315
 316           (<span class="type">bool</span>)
 317           <code class="literal">r-</code>
 318         </span></dt><dd><p><code class="option">--enable-mremap</code> was specified during
 319         build configuration.</p></dd><dt><span class="term">
 320
 321     "<code class="mallctl">config.munmap</code>"
 322
 323           (<span class="type">bool</span>)
 324           <code class="literal">r-</code>
 325         </span></dt><dd><p><code class="option">--enable-munmap</code> was specified during
 326         build configuration.</p></dd><dt><span class="term">
 327
 328     "<code class="mallctl">config.prof</code>"
 329
 330           (<span class="type">bool</span>)
 331           <code class="literal">r-</code>
 332         </span></dt><dd><p><code class="option">--enable-prof</code> was specified during
 333         build configuration.</p></dd><dt><span class="term">
 334
 335     "<code class="mallctl">config.prof_libgcc</code>"
 336
 337           (<span class="type">bool</span>)
 338           <code class="literal">r-</code>
 339         </span></dt><dd><p><code class="option">--disable-prof-libgcc</code> was not
 340         specified during build configuration.</p></dd><dt><span class="term">
 341
 342     "<code class="mallctl">config.prof_libunwind</code>"
 343
 344           (<span class="type">bool</span>)
 345           <code class="literal">r-</code>
 346         </span></dt><dd><p><code class="option">--enable-prof-libunwind</code> was specified
 347         during build configuration.</p></dd><dt><span class="term">
 348
 349     "<code class="mallctl">config.stats</code>"
 350
 351           (<span class="type">bool</span>)
 352           <code class="literal">r-</code>
 353         </span></dt><dd><p><code class="option">--enable-stats</code> was specified during
 354         build configuration.</p></dd><dt><span class="term">
 355
 356     "<code class="mallctl">config.tcache</code>"
 357
 358           (<span class="type">bool</span>)
 359           <code class="literal">r-</code>
 360         </span></dt><dd><p><code class="option">--disable-tcache</code> was not specified
 361         during build configuration.</p></dd><dt><span class="term">
 362
 363     "<code class="mallctl">config.tls</code>"
 364
 365           (<span class="type">bool</span>)
 366           <code class="literal">r-</code>
 367         </span></dt><dd><p><code class="option">--disable-tls</code> was not specified during
 368         build configuration.</p></dd><dt><span class="term">
 369
 370     "<code class="mallctl">config.utrace</code>"
 371
 372           (<span class="type">bool</span>)
 373           <code class="literal">r-</code>
 374         </span></dt><dd><p><code class="option">--enable-utrace</code> was specified during
 375         build configuration.</p></dd><dt><span class="term">
 376
 377     "<code class="mallctl">config.valgrind</code>"
 378
 379           (<span class="type">bool</span>)
 380           <code class="literal">r-</code>
 381         </span></dt><dd><p><code class="option">--enable-valgrind</code> was specified during
 382         build configuration.</p></dd><dt><span class="term">
 383
 384     "<code class="mallctl">config.xmalloc</code>"
 385
 386           (<span class="type">bool</span>)
 387           <code class="literal">r-</code>
 388         </span></dt><dd><p><code class="option">--enable-xmalloc</code> was specified during
 389         build configuration.</p></dd><dt><a name="opt.abort"></a><span class="term">
 390
 391     "<code class="mallctl">opt.abort</code>"
 392
 393           (<span class="type">bool</span>)
 394           <code class="literal">r-</code>
 395         </span></dt><dd><p>Abort-on-warning enabled/disabled.  If true, most
 396         warnings are fatal.  The process will call
 397         <span class="citerefentry"><span class="refentrytitle">abort</span>(3)</span> in these cases.  This option is
 398         disabled by default unless <code class="option">--enable-debug</code> is
 399         specified during configuration, in which case it is enabled by default.
 400         </p></dd><dt><a name="opt.lg_chunk"></a><span class="term">
 401
 402     "<code class="mallctl">opt.lg_chunk</code>"
 403
 404           (<span class="type">size_t</span>)
 405           <code class="literal">r-</code>
 406         </span></dt><dd><p>Virtual memory chunk size (log base 2).  The default
 407         chunk size is 4 MiB (2^22).</p></dd><dt><a name="opt.narenas"></a><span class="term">
 408
 409     "<code class="mallctl">opt.narenas</code>"
 410
 411           (<span class="type">size_t</span>)
 412           <code class="literal">r-</code>
 413         </span></dt><dd><p>Maximum number of arenas to use.  The default maximum
 414         number of arenas is four times the number of CPUs, or one if there is a
 415         single CPU.</p></dd><dt><a name="opt.lg_dirty_mult"></a><span class="term">
 416
 417     "<code class="mallctl">opt.lg_dirty_mult</code>"
 418
 419           (<span class="type">ssize_t</span>)
 420           <code class="literal">r-</code>
 421         </span></dt><dd><p>Per-arena minimum ratio (log base 2) of active to dirty
 422         pages.  Some dirty unused pages may be allowed to accumulate, within
 423         the limit set by the ratio (or one chunk worth of dirty pages,
 424         whichever is greater), before informing the kernel about some of those
 425         pages via <span class="citerefentry"><span class="refentrytitle">madvise</span>(2)</span> or a similar system call.  This
 426         provides the kernel with sufficient information to recycle dirty pages
 427         if physical memory becomes scarce and the pages remain unused.  The
 428         default minimum ratio is 32:1 (2^5:1); an option value of -1 will
 429         disable dirty page purging.</p></dd><dt><a name="opt.stats_print"></a><span class="term">
 430
 431     "<code class="mallctl">opt.stats_print</code>"
 432
 433           (<span class="type">bool</span>)
 434           <code class="literal">r-</code>
 435         </span></dt><dd><p>Enable/disable statistics printing at exit.  If
 436         enabled, the <code class="function">malloc_stats_print</code>(<em class="parameter"><code></code></em>)
 437         function is called at program exit via an
 438         <span class="citerefentry"><span class="refentrytitle">atexit</span>(3)</span> function.  If
 439         <code class="option">--enable-stats</code> is specified during configuration, this
 440         has the potential to cause deadlock for a multi-threaded process that
 441         exits while one or more threads are executing in the memory allocation
 442         functions.  Therefore, this option should only be used with care; it is
 443         primarily intended as a performance tuning aid during application
 444         development.  This option is disabled by default.</p></dd><dt><a name="opt.junk"></a><span class="term">
 445
 446     "<code class="mallctl">opt.junk</code>"
 447
 448           (<span class="type">bool</span>)
 449           <code class="literal">r-</code>
 450           [<code class="option">--enable-fill</code>]
 451         </span></dt><dd><p>Junk filling enabled/disabled.  If enabled, each byte
 452         of uninitialized allocated memory will be initialized to
 453         <code class="literal">0xa5</code>.  All deallocated memory will be initialized to
 454         <code class="literal">0x5a</code>.  This is intended for debugging and will
 455         impact performance negatively.  This option is disabled by default
 456         unless <code class="option">--enable-debug</code> is specified during
 457         configuration, in which case it is enabled by default.</p></dd><dt><a name="opt.quarantine"></a><span class="term">
 458
 459     "<code class="mallctl">opt.quarantine</code>"
 460
 461           (<span class="type">size_t</span>)
 462           <code class="literal">r-</code>
 463           [<code class="option">--enable-fill</code>]
 464         </span></dt><dd><p>Per thread quarantine size in bytes.  If non-zero, each
 465         thread maintains a FIFO object quarantine that stores up to the
 466         specified number of bytes of memory.  The quarantined memory is not
 467         freed until it is released from quarantine, though it is immediately
 468         junk-filled if the <a class="link" href="#opt.junk">
 469     "<code class="mallctl">opt.junk</code>"
 470   </a> option is
 471         enabled.  This feature is of particular use in combination with <a class="ulink" href="http://valgrind.org/" target="_top">Valgrind</a>, which can detect attempts
 472         to access quarantined objects.  This is intended for debugging and will
 473         impact performance negatively.  The default quarantine size is
 474         0.</p></dd><dt><a name="opt.redzone"></a><span class="term">
 475
 476     "<code class="mallctl">opt.redzone</code>"
 477
 478           (<span class="type">bool</span>)
 479           <code class="literal">r-</code>
 480           [<code class="option">--enable-fill</code>]
 481         </span></dt><dd><p>Redzones enabled/disabled.  If enabled, small
 482         allocations have redzones before and after them.  Furthermore, if the
 483         <a class="link" href="#opt.junk">
 484     "<code class="mallctl">opt.junk</code>"
 485   </a> option is
 486         enabled, the redzones are checked for corruption during deallocation.
 487         However, the primary intended purpose of this feature is to be used in
 488         combination with <a class="ulink" href="http://valgrind.org/" target="_top">Valgrind</a>,
 489         which needs redzones in order to do effective buffer overflow/underflow
 490         detection.  This option is intended for debugging and will impact
 491         performance negatively.  This option is disabled by
 492         default.</p></dd><dt><a name="opt.zero"></a><span class="term">
 493
 494     "<code class="mallctl">opt.zero</code>"
 495
 496           (<span class="type">bool</span>)
 497           <code class="literal">r-</code>
 498           [<code class="option">--enable-fill</code>]
 499         </span></dt><dd><p>Zero filling enabled/disabled.  If enabled, each byte
 500         of uninitialized allocated memory will be initialized to 0.  Note that
 501         this initialization only happens once for each byte, so
 502         <code class="function">realloc</code>(<em class="parameter"><code></code></em>) and
 503         <code class="function">rallocm</code>(<em class="parameter"><code></code></em>) calls do not zero memory that
 504         was previously allocated.  This is intended for debugging and will
 505         impact performance negatively.  This option is disabled by default.
 506         </p></dd><dt><a name="opt.utrace"></a><span class="term">
 507
 508     "<code class="mallctl">opt.utrace</code>"
 509
 510           (<span class="type">bool</span>)
 511           <code class="literal">r-</code>
 512           [<code class="option">--enable-utrace</code>]
 513         </span></dt><dd><p>Allocation tracing based on
 514         <span class="citerefentry"><span class="refentrytitle">utrace</span>(2)</span> enabled/disabled.  This option
 515         is disabled by default.</p></dd><dt><a name="opt.valgrind"></a><span class="term">
 516
 517     "<code class="mallctl">opt.valgrind</code>"
 518
 519           (<span class="type">bool</span>)
 520           <code class="literal">r-</code>
 521           [<code class="option">--enable-valgrind</code>]
 522         </span></dt><dd><p><a class="ulink" href="http://valgrind.org/" target="_top">Valgrind</a>
 523         support enabled/disabled.  If enabled, several other options are
 524         automatically modified during options processing to work well with
 525         Valgrind: <a class="link" href="#opt.junk">
 526     "<code class="mallctl">opt.junk</code>"
 527   </a>
 528         and <a class="link" href="#opt.zero">
 529     "<code class="mallctl">opt.zero</code>"
 530   </a> are set
 531         to false, <a class="link" href="#opt.quarantine">
 532     "<code class="mallctl">opt.quarantine</code>"
 533   </a> is
 534         set to 16 MiB, and <a class="link" href="#opt.redzone">
 535     "<code class="mallctl">opt.redzone</code>"
 536   </a> is set to
 537         true.  This option is disabled by default.</p></dd><dt><a name="opt.xmalloc"></a><span class="term">
 538
 539     "<code class="mallctl">opt.xmalloc</code>"
 540
 541           (<span class="type">bool</span>)
 542           <code class="literal">r-</code>
 543           [<code class="option">--enable-xmalloc</code>]
 544         </span></dt><dd><p>Abort-on-out-of-memory enabled/disabled.  If enabled,
 545         rather than returning failure for any allocation function, display a
 546         diagnostic message on <code class="constant">STDERR_FILENO</code> and cause the
 547         program to drop core (using
 548         <span class="citerefentry"><span class="refentrytitle">abort</span>(3)</span>).  If an application is
 549         designed to depend on this behavior, set the option at compile time by
 550         including the following in the source code:
 551         </p><pre class="programlisting">
 552 malloc_conf = "xmalloc:true";</pre><p>
 553         This option is disabled by default.</p></dd><dt><a name="opt.tcache"></a><span class="term">
 554
 555     "<code class="mallctl">opt.tcache</code>"
 556
 557           (<span class="type">bool</span>)
 558           <code class="literal">r-</code>
 559           [<code class="option">--enable-tcache</code>]
 560         </span></dt><dd><p>Thread-specific caching enabled/disabled.  When there
 561         are multiple threads, each thread uses a thread-specific cache for
 562         objects up to a certain size.  Thread-specific caching allows many
 563         allocations to be satisfied without performing any thread
 564         synchronization, at the cost of increased memory use.  See the
 565         <a class="link" href="#opt.lg_tcache_max">
 566     "<code class="mallctl">opt.lg_tcache_max</code>"
 567   </a>
 568         option for related tuning information.  This option is enabled by
 569         default.</p></dd><dt><a name="opt.lg_tcache_max"></a><span class="term">
 570
 571     "<code class="mallctl">opt.lg_tcache_max</code>"
 572
 573           (<span class="type">size_t</span>)
 574           <code class="literal">r-</code>
 575           [<code class="option">--enable-tcache</code>]
 576         </span></dt><dd><p>Maximum size class (log base 2) to cache in the
 577         thread-specific cache.  At a minimum, all small size classes are
 578         cached, and at a maximum all large size classes are cached.  The
 579         default maximum is 32 KiB (2^15).</p></dd><dt><a name="opt.prof"></a><span class="term">
 580
 581     "<code class="mallctl">opt.prof</code>"
 582
 583           (<span class="type">bool</span>)
 584           <code class="literal">r-</code>
 585           [<code class="option">--enable-prof</code>]
 586         </span></dt><dd><p>Memory profiling enabled/disabled.  If enabled, profile
 587         memory allocation activity.  See the <a class="link" href="#opt.prof_active">
 588     "<code class="mallctl">opt.prof_active</code>"
 589   </a>
 590         option for on-the-fly activation/deactivation.  See the <a class="link" href="#opt.lg_prof_sample">
 591     "<code class="mallctl">opt.lg_prof_sample</code>"
 592   </a>
 593         option for probabilistic sampling control.  See the <a class="link" href="#opt.prof_accum">
 594     "<code class="mallctl">opt.prof_accum</code>"
 595   </a>
 596         option for control of cumulative sample reporting.  See the <a class="link" href="#opt.lg_prof_interval">
 597     "<code class="mallctl">opt.lg_prof_interval</code>"
 598   </a>
 599         option for information on interval-triggered profile dumping, the <a class="link" href="#opt.prof_gdump">
 600     "<code class="mallctl">opt.prof_gdump</code>"
 601   </a>
 602         option for information on high-water-triggered profile dumping, and the
 603         <a class="link" href="#opt.prof_final">
 604     "<code class="mallctl">opt.prof_final</code>"
 605   </a>
 606         option for final profile dumping.  Profile output is compatible with
 607         the included <span class="command"><strong>pprof</strong></span> Perl script, which originates
 608         from the <a class="ulink" href="http://code.google.com/p/gperftools/" target="_top">gperftools
 609         package</a>.</p></dd><dt><a name="opt.prof_prefix"></a><span class="term">
 610
 611     "<code class="mallctl">opt.prof_prefix</code>"
 612
 613           (<span class="type">const char *</span>)
 614           <code class="literal">r-</code>
 615           [<code class="option">--enable-prof</code>]
 616         </span></dt><dd><p>Filename prefix for profile dumps.  If the prefix is
 617         set to the empty string, no automatic dumps will occur; this is
 618         primarily useful for disabling the automatic final heap dump (which
 619         also disables leak reporting, if enabled).  The default prefix is
 620         <code class="filename">jeprof</code>.</p></dd><dt><a name="opt.prof_active"></a><span class="term">
 621
 622     "<code class="mallctl">opt.prof_active</code>"
 623
 624           (<span class="type">bool</span>)
 625           <code class="literal">r-</code>
 626           [<code class="option">--enable-prof</code>]
 627         </span></dt><dd><p>Profiling activated/deactivated.  This is a secondary
 628         control mechanism that makes it possible to start the application with
 629         profiling enabled (see the <a class="link" href="#opt.prof">
 630     "<code class="mallctl">opt.prof</code>"
 631   </a> option) but
 632         inactive, then toggle profiling at any time during program execution
 633         with the <a class="link" href="#prof.active">
 634     "<code class="mallctl">prof.active</code>"
 635   </a> mallctl.
 636         This option is enabled by default.</p></dd><dt><a name="opt.lg_prof_sample"></a><span class="term">
 637
 638     "<code class="mallctl">opt.lg_prof_sample</code>"
 639
 640           (<span class="type">ssize_t</span>)
 641           <code class="literal">r-</code>
 642           [<code class="option">--enable-prof</code>]
 643         </span></dt><dd><p>Average interval (log base 2) between allocation
 644         samples, as measured in bytes of allocation activity.  Increasing the
 645         sampling interval decreases profile fidelity, but also decreases the
 646         computational overhead.  The default sample interval is 512 KiB (2^19
 647         B).</p></dd><dt><a name="opt.prof_accum"></a><span class="term">
 648
 649     "<code class="mallctl">opt.prof_accum</code>"
 650
 651           (<span class="type">bool</span>)
 652           <code class="literal">r-</code>
 653           [<code class="option">--enable-prof</code>]
 654         </span></dt><dd><p>Reporting of cumulative object/byte counts in profile
 655         dumps enabled/disabled.  If this option is enabled, every unique
 656         backtrace must be stored for the duration of execution.  Depending on
 657         the application, this can impose a large memory overhead, and the
 658         cumulative counts are not always of interest.  This option is disabled
 659         by default.</p></dd><dt><a name="opt.lg_prof_interval"></a><span class="term">
 660
 661     "<code class="mallctl">opt.lg_prof_interval</code>"
 662
 663           (<span class="type">ssize_t</span>)
 664           <code class="literal">r-</code>
 665           [<code class="option">--enable-prof</code>]
 666         </span></dt><dd><p>Average interval (log base 2) between memory profile
 667         dumps, as measured in bytes of allocation activity.  The actual
 668         interval between dumps may be sporadic because decentralized allocation
 669         counters are used to avoid synchronization bottlenecks.  Profiles are
 670         dumped to files named according to the pattern
 671         <code class="filename">&lt;prefix&gt;.&lt;pid&gt;.&lt;seq&gt;.i&lt;iseq&gt;.heap</code>,
 672         where <code class="literal">&lt;prefix&gt;</code> is controlled by the
 673         <a class="link" href="#opt.prof_prefix">
 674     "<code class="mallctl">opt.prof_prefix</code>"
 675   </a>
 676         option.  By default, interval-triggered profile dumping is disabled
 677         (encoded as -1).
 678         </p></dd><dt><a name="opt.prof_gdump"></a><span class="term">
 679
 680     "<code class="mallctl">opt.prof_gdump</code>"
 681
 682           (<span class="type">bool</span>)
 683           <code class="literal">r-</code>
 684           [<code class="option">--enable-prof</code>]
 685         </span></dt><dd><p>Trigger a memory profile dump every time the total
 686         virtual memory exceeds the previous maximum.  Profiles are dumped to
 687         files named according to the pattern
 688         <code class="filename">&lt;prefix&gt;.&lt;pid&gt;.&lt;seq&gt;.u&lt;useq&gt;.heap</code>,
 689         where <code class="literal">&lt;prefix&gt;</code> is controlled by the <a class="link" href="#opt.prof_prefix">
 690     "<code class="mallctl">opt.prof_prefix</code>"
 691   </a>
 692         option.  This option is disabled by default.</p></dd><dt><a name="opt.prof_final"></a><span class="term">
 693
 694     "<code class="mallctl">opt.prof_final</code>"
 695
 696           (<span class="type">bool</span>)
 697           <code class="literal">r-</code>
 698           [<code class="option">--enable-prof</code>]
 699         </span></dt><dd><p>Use an
 700         <span class="citerefentry"><span class="refentrytitle">atexit</span>(3)</span> function to dump final memory
 701         usage to a file named according to the pattern
 702         <code class="filename">&lt;prefix&gt;.&lt;pid&gt;.&lt;seq&gt;.f.heap</code>,
 703         where <code class="literal">&lt;prefix&gt;</code> is controlled by the <a class="link" href="#opt.prof_prefix">
 704     "<code class="mallctl">opt.prof_prefix</code>"
 705   </a>
 706         option.  This option is enabled by default.</p></dd><dt><a name="opt.prof_leak"></a><span class="term">
 707
 708     "<code class="mallctl">opt.prof_leak</code>"
 709
 710           (<span class="type">bool</span>)
 711           <code class="literal">r-</code>
 712           [<code class="option">--enable-prof</code>]
 713         </span></dt><dd><p>Leak reporting enabled/disabled.  If enabled, use an
 714         <span class="citerefentry"><span class="refentrytitle">atexit</span>(3)</span> function to report memory leaks
 715         detected by allocation sampling.  See the
 716         <a class="link" href="#opt.prof">
 717     "<code class="mallctl">opt.prof</code>"
 718   </a> option for
 719         information on analyzing heap profile output.  This option is disabled
 720         by default.</p></dd><dt><span class="term">
 721
 722     "<code class="mallctl">thread.arena</code>"
 723
 724           (<span class="type">unsigned</span>)
 725           <code class="literal">rw</code>
 726         </span></dt><dd><p>Get or set the arena associated with the calling
 727         thread.  The arena index must be less than the maximum number of arenas
 728         (see the <a class="link" href="#arenas.narenas">
 729     "<code class="mallctl">arenas.narenas</code>"
 730   </a>
 731         mallctl).  If the specified arena was not initialized beforehand (see
 732         the <a class="link" href="#arenas.initialized">
 733     "<code class="mallctl">arenas.initialized</code>"
 734   </a>
 735         mallctl), it will be automatically initialized as a side effect of
 736         calling this interface.</p></dd><dt><a name="thread.allocated"></a><span class="term">
 737
 738     "<code class="mallctl">thread.allocated</code>"
 739
 740           (<span class="type">uint64_t</span>)
 741           <code class="literal">r-</code>
 742           [<code class="option">--enable-stats</code>]
 743         </span></dt><dd><p>Get the total number of bytes ever allocated by the
 744         calling thread.  This counter has the potential to wrap around; it is
 745         up to the application to appropriately interpret the counter in such
 746         cases.</p></dd><dt><span class="term">
 747
 748     "<code class="mallctl">thread.allocatedp</code>"
 749
 750           (<span class="type">uint64_t *</span>)
 751           <code class="literal">r-</code>
 752           [<code class="option">--enable-stats</code>]
 753         </span></dt><dd><p>Get a pointer to the the value that is returned by the
 754         <a class="link" href="#thread.allocated">
 755     "<code class="mallctl">thread.allocated</code>"
 756   </a>
 757         mallctl.  This is useful for avoiding the overhead of repeated
 758         <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) calls.</p></dd><dt><a name="thread.deallocated"></a><span class="term">
 759
 760     "<code class="mallctl">thread.deallocated</code>"
 761
 762           (<span class="type">uint64_t</span>)
 763           <code class="literal">r-</code>
 764           [<code class="option">--enable-stats</code>]
 765         </span></dt><dd><p>Get the total number of bytes ever deallocated by the
 766         calling thread.  This counter has the potential to wrap around; it is
 767         up to the application to appropriately interpret the counter in such
 768         cases.</p></dd><dt><span class="term">
 769
 770     "<code class="mallctl">thread.deallocatedp</code>"
 771
 772           (<span class="type">uint64_t *</span>)
 773           <code class="literal">r-</code>
 774           [<code class="option">--enable-stats</code>]
 775         </span></dt><dd><p>Get a pointer to the the value that is returned by the
 776         <a class="link" href="#thread.deallocated">
 777     "<code class="mallctl">thread.deallocated</code>"
 778   </a>
 779         mallctl.  This is useful for avoiding the overhead of repeated
 780         <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) calls.</p></dd><dt><span class="term">
 781
 782     "<code class="mallctl">thread.tcache.enabled</code>"
 783
 784           (<span class="type">bool</span>)
 785           <code class="literal">rw</code>
 786           [<code class="option">--enable-tcache</code>]
 787         </span></dt><dd><p>Enable/disable calling thread's tcache.  The tcache is
 788         implicitly flushed as a side effect of becoming
 789         disabled (see
 790     "<code class="mallctl">thread.tcache.flush</code>"
 791   ).
 792         </p></dd><dt><span class="term">
 793
 794     "<code class="mallctl">thread.tcache.flush</code>"
 795
 796           (<span class="type">void</span>)
 797           <code class="literal">--</code>
 798           [<code class="option">--enable-tcache</code>]
 799         </span></dt><dd><p>Flush calling thread's tcache.  This interface releases
 800         all cached objects and internal data structures associated with the
 801         calling thread's thread-specific cache.  Ordinarily, this interface
 802         need not be called, since automatic periodic incremental garbage
 803         collection occurs, and the thread cache is automatically discarded when
 804         a thread exits.  However, garbage collection is triggered by allocation
 805         activity, so it is possible for a thread that stops
 806         allocating/deallocating to retain its cache indefinitely, in which case
 807         the developer may find manual flushing useful.</p></dd><dt><a name="arenas.narenas"></a><span class="term">
 808
 809     "<code class="mallctl">arenas.narenas</code>"
 810
 811           (<span class="type">unsigned</span>)
 812           <code class="literal">r-</code>
 813         </span></dt><dd><p>Maximum number of arenas.</p></dd><dt><a name="arenas.initialized"></a><span class="term">
 814
 815     "<code class="mallctl">arenas.initialized</code>"
 816
 817           (<span class="type">bool *</span>)
 818           <code class="literal">r-</code>
 819         </span></dt><dd><p>An array of <a class="link" href="#arenas.narenas">
 820     "<code class="mallctl">arenas.narenas</code>"
 821   </a>
 822         booleans.  Each boolean indicates whether the corresponding arena is
 823         initialized.</p></dd><dt><span class="term">
 824
 825     "<code class="mallctl">arenas.quantum</code>"
 826
 827           (<span class="type">size_t</span>)
 828           <code class="literal">r-</code>
 829         </span></dt><dd><p>Quantum size.</p></dd><dt><span class="term">
 830
 831     "<code class="mallctl">arenas.page</code>"
 832
 833           (<span class="type">size_t</span>)
 834           <code class="literal">r-</code>
 835         </span></dt><dd><p>Page size.</p></dd><dt><span class="term">
 836
 837     "<code class="mallctl">arenas.tcache_max</code>"
 838
 839           (<span class="type">size_t</span>)
 840           <code class="literal">r-</code>
 841           [<code class="option">--enable-tcache</code>]
 842         </span></dt><dd><p>Maximum thread-cached size class.</p></dd><dt><span class="term">
 843
 844     "<code class="mallctl">arenas.nbins</code>"
 845
 846           (<span class="type">unsigned</span>)
 847           <code class="literal">r-</code>
 848         </span></dt><dd><p>Number of bin size classes.</p></dd><dt><span class="term">
 849
 850     "<code class="mallctl">arenas.nhbins</code>"
 851
 852           (<span class="type">unsigned</span>)
 853           <code class="literal">r-</code>
 854           [<code class="option">--enable-tcache</code>]
 855         </span></dt><dd><p>Total number of thread cache bin size
 856         classes.</p></dd><dt><a name="arenas.bin.i.size"></a><span class="term">
 857
 858     "<code class="mallctl">arenas.bin.&lt;i&gt;.size</code>"
 859
 860           (<span class="type">size_t</span>)
 861           <code class="literal">r-</code>
 862         </span></dt><dd><p>Maximum size supported by size class.</p></dd><dt><span class="term">
 863
 864     "<code class="mallctl">arenas.bin.&lt;i&gt;.nregs</code>"
 865
 866           (<span class="type">uint32_t</span>)
 867           <code class="literal">r-</code>
 868         </span></dt><dd><p>Number of regions per page run.</p></dd><dt><span class="term">
 869
 870     "<code class="mallctl">arenas.bin.&lt;i&gt;.run_size</code>"
 871
 872           (<span class="type">size_t</span>)
 873           <code class="literal">r-</code>
 874         </span></dt><dd><p>Number of bytes per page run.</p></dd><dt><span class="term">
 875
 876     "<code class="mallctl">arenas.nlruns</code>"
 877
 878           (<span class="type">size_t</span>)
 879           <code class="literal">r-</code>
 880         </span></dt><dd><p>Total number of large size classes.</p></dd><dt><span class="term">
 881
 882     "<code class="mallctl">arenas.lrun.&lt;i&gt;.size</code>"
 883
 884           (<span class="type">size_t</span>)
 885           <code class="literal">r-</code>
 886         </span></dt><dd><p>Maximum size supported by this large size
 887         class.</p></dd><dt><span class="term">
 888
 889     "<code class="mallctl">arenas.purge</code>"
 890
 891           (<span class="type">unsigned</span>)
 892           <code class="literal">-w</code>
 893         </span></dt><dd><p>Purge unused dirty pages for the specified arena, or
 894         for all arenas if none is specified.</p></dd><dt><a name="prof.active"></a><span class="term">
 895
 896     "<code class="mallctl">prof.active</code>"
 897
 898           (<span class="type">bool</span>)
 899           <code class="literal">rw</code>
 900           [<code class="option">--enable-prof</code>]
 901         </span></dt><dd><p>Control whether sampling is currently active.  See the
 902         <a class="link" href="#opt.prof_active">
 903     "<code class="mallctl">opt.prof_active</code>"
 904   </a>
 905         option for additional information.
 906         </p></dd><dt><span class="term">
 907
 908     "<code class="mallctl">prof.dump</code>"
 909
 910           (<span class="type">const char *</span>)
 911           <code class="literal">-w</code>
 912           [<code class="option">--enable-prof</code>]
 913         </span></dt><dd><p>Dump a memory profile to the specified file, or if NULL
 914         is specified, to a file according to the pattern
 915         <code class="filename">&lt;prefix&gt;.&lt;pid&gt;.&lt;seq&gt;.m&lt;mseq&gt;.heap</code>,
 916         where <code class="literal">&lt;prefix&gt;</code> is controlled by the
 917         <a class="link" href="#opt.prof_prefix">
 918     "<code class="mallctl">opt.prof_prefix</code>"
 919   </a>
 920         option.</p></dd><dt><span class="term">
 921
 922     "<code class="mallctl">prof.interval</code>"
 923
 924           (<span class="type">uint64_t</span>)
 925           <code class="literal">r-</code>
 926           [<code class="option">--enable-prof</code>]
 927         </span></dt><dd><p>Average number of bytes allocated between
 928         inverval-based profile dumps.  See the
 929         <a class="link" href="#opt.lg_prof_interval">
 930     "<code class="mallctl">opt.lg_prof_interval</code>"
 931   </a>
 932         option for additional information.</p></dd><dt><a name="stats.cactive"></a><span class="term">
 933
 934     "<code class="mallctl">stats.cactive</code>"
 935
 936           (<span class="type">size_t *</span>)
 937           <code class="literal">r-</code>
 938           [<code class="option">--enable-stats</code>]
 939         </span></dt><dd><p>Pointer to a counter that contains an approximate count
 940         of the current number of bytes in active pages.  The estimate may be
 941         high, but never low, because each arena rounds up to the nearest
 942         multiple of the chunk size when computing its contribution to the
 943         counter.  Note that the <a class="link" href="#epoch">
 944     "<code class="mallctl">epoch</code>"
 945   </a> mallctl has no bearing
 946         on this counter.  Furthermore, counter consistency is maintained via
 947         atomic operations, so it is necessary to use an atomic operation in
 948         order to guarantee a consistent read when dereferencing the pointer.
 949         </p></dd><dt><a name="stats.allocated"></a><span class="term">
 950
 951     "<code class="mallctl">stats.allocated</code>"
 952
 953           (<span class="type">size_t</span>)
 954           <code class="literal">r-</code>
 955           [<code class="option">--enable-stats</code>]
 956         </span></dt><dd><p>Total number of bytes allocated by the
 957         application.</p></dd><dt><a name="stats.active"></a><span class="term">
 958
 959     "<code class="mallctl">stats.active</code>"
 960
 961           (<span class="type">size_t</span>)
 962           <code class="literal">r-</code>
 963           [<code class="option">--enable-stats</code>]
 964         </span></dt><dd><p>Total number of bytes in active pages allocated by the
 965         application.  This is a multiple of the page size, and greater than or
 966         equal to <a class="link" href="#stats.allocated">
 967     "<code class="mallctl">stats.allocated</code>"
 968   </a>.
 969         </p></dd><dt><span class="term">
 970
 971     "<code class="mallctl">stats.mapped</code>"
 972
 973           (<span class="type">size_t</span>)
 974           <code class="literal">r-</code>
 975           [<code class="option">--enable-stats</code>]
 976         </span></dt><dd><p>Total number of bytes in chunks mapped on behalf of the
 977         application.  This is a multiple of the chunk size, and is at least as
 978         large as <a class="link" href="#stats.active">
 979     "<code class="mallctl">stats.active</code>"
 980   </a>.  This
 981         does not include inactive chunks.</p></dd><dt><span class="term">
 982
 983     "<code class="mallctl">stats.chunks.current</code>"
 984
 985           (<span class="type">size_t</span>)
 986           <code class="literal">r-</code>
 987           [<code class="option">--enable-stats</code>]
 988         </span></dt><dd><p>Total number of chunks actively mapped on behalf of the
 989         application.  This does not include inactive chunks.
 990         </p></dd><dt><span class="term">
 991
 992     "<code class="mallctl">stats.chunks.total</code>"
 993
 994           (<span class="type">uint64_t</span>)
 995           <code class="literal">r-</code>
 996           [<code class="option">--enable-stats</code>]
 997         </span></dt><dd><p>Cumulative number of chunks allocated.</p></dd><dt><span class="term">
 998
 999     "<code class="mallctl">stats.chunks.high</code>"
1000
1001           (<span class="type">size_t</span>)
1002           <code class="literal">r-</code>
1003           [<code class="option">--enable-stats</code>]
1004         </span></dt><dd><p>Maximum number of active chunks at any time thus far.
1005         </p></dd><dt><span class="term">
1006
1007     "<code class="mallctl">stats.huge.allocated</code>"
1008
1009           (<span class="type">size_t</span>)
1010           <code class="literal">r-</code>
1011           [<code class="option">--enable-stats</code>]
1012         </span></dt><dd><p>Number of bytes currently allocated by huge objects.
1013         </p></dd><dt><span class="term">
1014
1015     "<code class="mallctl">stats.huge.nmalloc</code>"
1016
1017           (<span class="type">uint64_t</span>)
1018           <code class="literal">r-</code>
1019           [<code class="option">--enable-stats</code>]
1020         </span></dt><dd><p>Cumulative number of huge allocation requests.
1021         </p></dd><dt><span class="term">
1022
1023     "<code class="mallctl">stats.huge.ndalloc</code>"
1024
1025           (<span class="type">uint64_t</span>)
1026           <code class="literal">r-</code>
1027           [<code class="option">--enable-stats</code>]
1028         </span></dt><dd><p>Cumulative number of huge deallocation requests.
1029         </p></dd><dt><span class="term">
1030
1031     "<code class="mallctl">stats.arenas.&lt;i&gt;.nthreads</code>"
1032
1033           (<span class="type">unsigned</span>)
1034           <code class="literal">r-</code>
1035         </span></dt><dd><p>Number of threads currently assigned to
1036         arena.</p></dd><dt><span class="term">
1037
1038     "<code class="mallctl">stats.arenas.&lt;i&gt;.pactive</code>"
1039
1040           (<span class="type">size_t</span>)
1041           <code class="literal">r-</code>
1042         </span></dt><dd><p>Number of pages in active runs.</p></dd><dt><span class="term">
1043
1044     "<code class="mallctl">stats.arenas.&lt;i&gt;.pdirty</code>"
1045
1046           (<span class="type">size_t</span>)
1047           <code class="literal">r-</code>
1048         </span></dt><dd><p>Number of pages within unused runs that are potentially
1049         dirty, and for which <code class="function">madvise</code>(<em class="parameter"><code>...</code></em>,
1050         <em class="parameter"><code><code class="constant">MADV_DONTNEED</code></code></em>) or
1051         similar has not been called.</p></dd><dt><span class="term">
1052
1053     "<code class="mallctl">stats.arenas.&lt;i&gt;.mapped</code>"
1054
1055           (<span class="type">size_t</span>)
1056           <code class="literal">r-</code>
1057           [<code class="option">--enable-stats</code>]
1058         </span></dt><dd><p>Number of mapped bytes.</p></dd><dt><span class="term">
1059
1060     "<code class="mallctl">stats.arenas.&lt;i&gt;.npurge</code>"
1061
1062           (<span class="type">uint64_t</span>)
1063           <code class="literal">r-</code>
1064           [<code class="option">--enable-stats</code>]
1065         </span></dt><dd><p>Number of dirty page purge sweeps performed.
1066         </p></dd><dt><span class="term">
1067
1068     "<code class="mallctl">stats.arenas.&lt;i&gt;.nmadvise</code>"
1069
1070           (<span class="type">uint64_t</span>)
1071           <code class="literal">r-</code>
1072           [<code class="option">--enable-stats</code>]
1073         </span></dt><dd><p>Number of <code class="function">madvise</code>(<em class="parameter"><code>...</code></em>,
1074         <em class="parameter"><code><code class="constant">MADV_DONTNEED</code></code></em>) or
1075         similar calls made to purge dirty pages.</p></dd><dt><span class="term">
1076
1077     "<code class="mallctl">stats.arenas.&lt;i&gt;.npurged</code>"
1078
1079           (<span class="type">uint64_t</span>)
1080           <code class="literal">r-</code>
1081           [<code class="option">--enable-stats</code>]
1082         </span></dt><dd><p>Number of pages purged.</p></dd><dt><span class="term">
1083
1084     "<code class="mallctl">stats.arenas.&lt;i&gt;.small.allocated</code>"
1085
1086           (<span class="type">size_t</span>)
1087           <code class="literal">r-</code>
1088           [<code class="option">--enable-stats</code>]
1089         </span></dt><dd><p>Number of bytes currently allocated by small objects.
1090         </p></dd><dt><span class="term">
1091
1092     "<code class="mallctl">stats.arenas.&lt;i&gt;.small.nmalloc</code>"
1093
1094           (<span class="type">uint64_t</span>)
1095           <code class="literal">r-</code>
1096           [<code class="option">--enable-stats</code>]
1097         </span></dt><dd><p>Cumulative number of allocation requests served by
1098         small bins.</p></dd><dt><span class="term">
1099
1100     "<code class="mallctl">stats.arenas.&lt;i&gt;.small.ndalloc</code>"
1101
1102           (<span class="type">uint64_t</span>)
1103           <code class="literal">r-</code>
1104           [<code class="option">--enable-stats</code>]
1105         </span></dt><dd><p>Cumulative number of small objects returned to bins.
1106         </p></dd><dt><span class="term">
1107
1108     "<code class="mallctl">stats.arenas.&lt;i&gt;.small.nrequests</code>"
1109
1110           (<span class="type">uint64_t</span>)
1111           <code class="literal">r-</code>
1112           [<code class="option">--enable-stats</code>]
1113         </span></dt><dd><p>Cumulative number of small allocation requests.
1114         </p></dd><dt><span class="term">
1115
1116     "<code class="mallctl">stats.arenas.&lt;i&gt;.large.allocated</code>"
1117
1118           (<span class="type">size_t</span>)
1119           <code class="literal">r-</code>
1120           [<code class="option">--enable-stats</code>]
1121         </span></dt><dd><p>Number of bytes currently allocated by large objects.
1122         </p></dd><dt><span class="term">
1123
1124     "<code class="mallctl">stats.arenas.&lt;i&gt;.large.nmalloc</code>"
1125
1126           (<span class="type">uint64_t</span>)
1127           <code class="literal">r-</code>
1128           [<code class="option">--enable-stats</code>]
1129         </span></dt><dd><p>Cumulative number of large allocation requests served
1130         directly by the arena.</p></dd><dt><span class="term">
1131
1132     "<code class="mallctl">stats.arenas.&lt;i&gt;.large.ndalloc</code>"
1133
1134           (<span class="type">uint64_t</span>)
1135           <code class="literal">r-</code>
1136           [<code class="option">--enable-stats</code>]
1137         </span></dt><dd><p>Cumulative number of large deallocation requests served
1138         directly by the arena.</p></dd><dt><span class="term">
1139
1140     "<code class="mallctl">stats.arenas.&lt;i&gt;.large.nrequests</code>"
1141
1142           (<span class="type">uint64_t</span>)
1143           <code class="literal">r-</code>
1144           [<code class="option">--enable-stats</code>]
1145         </span></dt><dd><p>Cumulative number of large allocation requests.
1146         </p></dd><dt><span class="term">
1147
1148     "<code class="mallctl">stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.allocated</code>"
1149
1150           (<span class="type">size_t</span>)
1151           <code class="literal">r-</code>
1152           [<code class="option">--enable-stats</code>]
1153         </span></dt><dd><p>Current number of bytes allocated by
1154         bin.</p></dd><dt><span class="term">
1155
1156     "<code class="mallctl">stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.nmalloc</code>"
1157
1158           (<span class="type">uint64_t</span>)
1159           <code class="literal">r-</code>
1160           [<code class="option">--enable-stats</code>]
1161         </span></dt><dd><p>Cumulative number of allocations served by bin.
1162         </p></dd><dt><span class="term">
1163
1164     "<code class="mallctl">stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.ndalloc</code>"
1165
1166           (<span class="type">uint64_t</span>)
1167           <code class="literal">r-</code>
1168           [<code class="option">--enable-stats</code>]
1169         </span></dt><dd><p>Cumulative number of allocations returned to bin.
1170         </p></dd><dt><span class="term">
1171
1172     "<code class="mallctl">stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.nrequests</code>"
1173
1174           (<span class="type">uint64_t</span>)
1175           <code class="literal">r-</code>
1176           [<code class="option">--enable-stats</code>]
1177         </span></dt><dd><p>Cumulative number of allocation
1178         requests.</p></dd><dt><span class="term">
1179
1180     "<code class="mallctl">stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.nfills</code>"
1181
1182           (<span class="type">uint64_t</span>)
1183           <code class="literal">r-</code>
1184           [<code class="option">--enable-stats</code> <code class="option">--enable-tcache</code>]
1185         </span></dt><dd><p>Cumulative number of tcache fills.</p></dd><dt><span class="term">
1186
1187     "<code class="mallctl">stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.nflushes</code>"
1188
1189           (<span class="type">uint64_t</span>)
1190           <code class="literal">r-</code>
1191           [<code class="option">--enable-stats</code> <code class="option">--enable-tcache</code>]
1192         </span></dt><dd><p>Cumulative number of tcache flushes.</p></dd><dt><span class="term">
1193
1194     "<code class="mallctl">stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.nruns</code>"
1195
1196           (<span class="type">uint64_t</span>)
1197           <code class="literal">r-</code>
1198           [<code class="option">--enable-stats</code>]
1199         </span></dt><dd><p>Cumulative number of runs created.</p></dd><dt><span class="term">
1200
1201     "<code class="mallctl">stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.nreruns</code>"
1202
1203           (<span class="type">uint64_t</span>)
1204           <code class="literal">r-</code>
1205           [<code class="option">--enable-stats</code>]
1206         </span></dt><dd><p>Cumulative number of times the current run from which
1207         to allocate changed.</p></dd><dt><span class="term">
1208
1209     "<code class="mallctl">stats.arenas.&lt;i&gt;.bins.&lt;j&gt;.curruns</code>"
1210
1211           (<span class="type">size_t</span>)
1212           <code class="literal">r-</code>
1213           [<code class="option">--enable-stats</code>]
1214         </span></dt><dd><p>Current number of runs.</p></dd><dt><span class="term">
1215
1216     "<code class="mallctl">stats.arenas.&lt;i&gt;.lruns.&lt;j&gt;.nmalloc</code>"
1217
1218           (<span class="type">uint64_t</span>)
1219           <code class="literal">r-</code>
1220           [<code class="option">--enable-stats</code>]
1221         </span></dt><dd><p>Cumulative number of allocation requests for this size
1222         class served directly by the arena.</p></dd><dt><span class="term">
1223
1224     "<code class="mallctl">stats.arenas.&lt;i&gt;.lruns.&lt;j&gt;.ndalloc</code>"
1225
1226           (<span class="type">uint64_t</span>)
1227           <code class="literal">r-</code>
1228           [<code class="option">--enable-stats</code>]
1229         </span></dt><dd><p>Cumulative number of deallocation requests for this
1230         size class served directly by the arena.</p></dd><dt><span class="term">
1231
1232     "<code class="mallctl">stats.arenas.&lt;i&gt;.lruns.&lt;j&gt;.nrequests</code>"
1233
1234           (<span class="type">uint64_t</span>)
1235           <code class="literal">r-</code>
1236           [<code class="option">--enable-stats</code>]
1237         </span></dt><dd><p>Cumulative number of allocation requests for this size
1238         class.</p></dd><dt><span class="term">
1239
1240     "<code class="mallctl">stats.arenas.&lt;i&gt;.lruns.&lt;j&gt;.curruns</code>"
1241
1242           (<span class="type">size_t</span>)
1243           <code class="literal">r-</code>
1244           [<code class="option">--enable-stats</code>]
1245         </span></dt><dd><p>Current number of runs for this size class.
1246         </p></dd></dl></div></div><div class="refsect1" title="DEBUGGING MALLOC PROBLEMS"><a name="debugging_malloc_problems"></a><h2>DEBUGGING MALLOC PROBLEMS</h2><p>When debugging, it is a good idea to configure/build jemalloc with
1247     the <code class="option">--enable-debug</code> and <code class="option">--enable-fill</code>
1248     options, and recompile the program with suitable options and symbols for
1249     debugger support.  When so configured, jemalloc incorporates a wide variety
1250     of run-time assertions that catch application errors such as double-free,
1251     write-after-free, etc.</p><p>Programs often accidentally depend on &#8220;uninitialized&#8221;
1252     memory actually being filled with zero bytes.  Junk filling
1253     (see the <a class="link" href="#opt.junk">
1254     "<code class="mallctl">opt.junk</code>"
1255   </a>
1256     option) tends to expose such bugs in the form of obviously incorrect
1257     results and/or coredumps.  Conversely, zero
1258     filling (see the <a class="link" href="#opt.zero">
1259     "<code class="mallctl">opt.zero</code>"
1260   </a> option) eliminates
1261     the symptoms of such bugs.  Between these two options, it is usually
1262     possible to quickly detect, diagnose, and eliminate such bugs.</p><p>This implementation does not provide much detail about the problems
1263     it detects, because the performance impact for storing such information
1264     would be prohibitive.  However, jemalloc does integrate with the most
1265     excellent <a class="ulink" href="http://valgrind.org/" target="_top">Valgrind</a> tool if the
1266     <code class="option">--enable-valgrind</code> configuration option is enabled and the
1267     <a class="link" href="#opt.valgrind">
1268     "<code class="mallctl">opt.valgrind</code>"
1269   </a> option
1270     is enabled.</p></div><div class="refsect1" title="DIAGNOSTIC MESSAGES"><a name="diagnostic_messages"></a><h2>DIAGNOSTIC MESSAGES</h2><p>If any of the memory allocation/deallocation functions detect an
1271     error or warning condition, a message will be printed to file descriptor
1272     <code class="constant">STDERR_FILENO</code>.  Errors will result in the process
1273     dumping core.  If the <a class="link" href="#opt.abort">
1274     "<code class="mallctl">opt.abort</code>"
1275   </a> option is set, most
1276     warnings are treated as errors.</p><p>The <code class="varname">malloc_message</code> variable allows the programmer
1277     to override the function which emits the text strings forming the errors
1278     and warnings if for some reason the <code class="constant">STDERR_FILENO</code> file
1279     descriptor is not suitable for this.
1280     <code class="function">malloc_message</code>(<em class="parameter"><code></code></em>) takes the
1281     <em class="parameter"><code>cbopaque</code></em> pointer argument that is
1282     <code class="constant">NULL</code> unless overridden by the arguments in a call to
1283     <code class="function">malloc_stats_print</code>(<em class="parameter"><code></code></em>), followed by a string
1284     pointer.  Please note that doing anything which tries to allocate memory in
1285     this function is likely to result in a crash or deadlock.</p><p>All messages are prefixed by
1286     &#8220;<code class="computeroutput">&lt;jemalloc&gt;: </code>&#8221;.</p></div><div class="refsect1" title="RETURN VALUES"><a name="return_values"></a><h2>RETURN VALUES</h2><div class="refsect2" title="Standard API"><a name="id286955289"></a><h3>Standard API</h3><p>The <code class="function">malloc</code>(<em class="parameter"><code></code></em>) and
1287       <code class="function">calloc</code>(<em class="parameter"><code></code></em>) functions return a pointer to the
1288       allocated memory if successful; otherwise a <code class="constant">NULL</code>
1289       pointer is returned and <code class="varname">errno</code> is set to
1290       <span class="errorname">ENOMEM</span>.</p><p>The <code class="function">posix_memalign</code>(<em class="parameter"><code></code></em>) function
1291       returns the value 0 if successful; otherwise it returns an error value.
1292       The <code class="function">posix_memalign</code>(<em class="parameter"><code></code></em>) function will fail
1293       if:
1294         </p><div class="variablelist"><dl><dt><span class="term"><span class="errorname">EINVAL</span></span></dt><dd><p>The <em class="parameter"><code>alignment</code></em> parameter is
1295             not a power of 2 at least as large as
1296             <code class="code">sizeof(<span class="type">void *</span>)</code>.
1297             </p></dd><dt><span class="term"><span class="errorname">ENOMEM</span></span></dt><dd><p>Memory allocation error.</p></dd></dl></div><p>
1298       </p><p>The <code class="function">aligned_alloc</code>(<em class="parameter"><code></code></em>) function returns
1299       a pointer to the allocated memory if successful; otherwise a
1300       <code class="constant">NULL</code> pointer is returned and
1301       <code class="varname">errno</code> is set.  The
1302       <code class="function">aligned_alloc</code>(<em class="parameter"><code></code></em>) function will fail if:
1303         </p><div class="variablelist"><dl><dt><span class="term"><span class="errorname">EINVAL</span></span></dt><dd><p>The <em class="parameter"><code>alignment</code></em> parameter is
1304             not a power of 2.
1305             </p></dd><dt><span class="term"><span class="errorname">ENOMEM</span></span></dt><dd><p>Memory allocation error.</p></dd></dl></div><p>
1306       </p><p>The <code class="function">realloc</code>(<em class="parameter"><code></code></em>) function returns a
1307       pointer, possibly identical to <em class="parameter"><code>ptr</code></em>, to the
1308       allocated memory if successful; otherwise a <code class="constant">NULL</code>
1309       pointer is returned, and <code class="varname">errno</code> is set to
1310       <span class="errorname">ENOMEM</span> if the error was the result of an
1311       allocation failure.  The <code class="function">realloc</code>(<em class="parameter"><code></code></em>)
1312       function always leaves the original buffer intact when an error occurs.
1313       </p><p>The <code class="function">free</code>(<em class="parameter"><code></code></em>) function returns no
1314       value.</p></div><div class="refsect2" title="Non-standard API"><a name="id286955505"></a><h3>Non-standard API</h3><p>The <code class="function">malloc_usable_size</code>(<em class="parameter"><code></code></em>) function
1315       returns the usable size of the allocation pointed to by
1316       <em class="parameter"><code>ptr</code></em>.  </p><p>The <code class="function">mallctl</code>(<em class="parameter"><code></code></em>),
1317       <code class="function">mallctlnametomib</code>(<em class="parameter"><code></code></em>), and
1318       <code class="function">mallctlbymib</code>(<em class="parameter"><code></code></em>) functions return 0 on
1319       success; otherwise they return an error value.  The functions will fail
1320       if:
1321         </p><div class="variablelist"><dl><dt><span class="term"><span class="errorname">EINVAL</span></span></dt><dd><p><em class="parameter"><code>newp</code></em> is not
1322             <code class="constant">NULL</code>, and <em class="parameter"><code>newlen</code></em> is too
1323             large or too small.  Alternatively, <em class="parameter"><code>*oldlenp</code></em>
1324             is too large or too small; in this case as much data as possible
1325             are read despite the error.</p></dd><dt><span class="term"><span class="errorname">ENOMEM</span></span></dt><dd><p><em class="parameter"><code>*oldlenp</code></em> is too short to
1326             hold the requested value.</p></dd><dt><span class="term"><span class="errorname">ENOENT</span></span></dt><dd><p><em class="parameter"><code>name</code></em> or
1327             <em class="parameter"><code>mib</code></em> specifies an unknown/invalid
1328             value.</p></dd><dt><span class="term"><span class="errorname">EPERM</span></span></dt><dd><p>Attempt to read or write void value, or attempt to
1329             write read-only value.</p></dd><dt><span class="term"><span class="errorname">EAGAIN</span></span></dt><dd><p>A memory allocation failure
1330             occurred.</p></dd><dt><span class="term"><span class="errorname">EFAULT</span></span></dt><dd><p>An interface with side effects failed in some way
1331             not directly related to <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>)
1332             read/write processing.</p></dd></dl></div><p>
1333       </p></div><div class="refsect2" title="Experimental API"><a name="id286955658"></a><h3>Experimental API</h3><p>The <code class="function">allocm</code>(<em class="parameter"><code></code></em>),
1334       <code class="function">rallocm</code>(<em class="parameter"><code></code></em>),
1335       <code class="function">sallocm</code>(<em class="parameter"><code></code></em>),
1336       <code class="function">dallocm</code>(<em class="parameter"><code></code></em>), and
1337       <code class="function">nallocm</code>(<em class="parameter"><code></code></em>) functions return
1338       <code class="constant">ALLOCM_SUCCESS</code> on success; otherwise they return an
1339       error value.  The <code class="function">allocm</code>(<em class="parameter"><code></code></em>),
1340       <code class="function">rallocm</code>(<em class="parameter"><code></code></em>), and
1341       <code class="function">nallocm</code>(<em class="parameter"><code></code></em>) functions will fail if:
1342         </p><div class="variablelist"><dl><dt><span class="term"><span class="errorname">ALLOCM_ERR_OOM</span></span></dt><dd><p>Out of memory.  Insufficient contiguous memory was
1343             available to service the allocation request.  The
1344             <code class="function">allocm</code>(<em class="parameter"><code></code></em>) function additionally sets
1345             <em class="parameter"><code>*ptr</code></em> to <code class="constant">NULL</code>, whereas
1346             the <code class="function">rallocm</code>(<em class="parameter"><code></code></em>) function leaves
1347             <code class="constant">*ptr</code> unmodified.</p></dd></dl></div><p>
1348       The <code class="function">rallocm</code>(<em class="parameter"><code></code></em>) function will also
1349       fail if:
1350         </p><div class="variablelist"><dl><dt><span class="term"><span class="errorname">ALLOCM_ERR_NOT_MOVED</span></span></dt><dd><p><code class="constant">ALLOCM_NO_MOVE</code> was specified,
1351             but the reallocation request could not be serviced without moving
1352             the object.</p></dd></dl></div><p>
1353       </p></div></div><div class="refsect1" title="ENVIRONMENT"><a name="environment"></a><h2>ENVIRONMENT</h2><p>The following environment variable affects the execution of the
1354     allocation functions:
1355       </p><div class="variablelist"><dl><dt><span class="term"><code class="envar">MALLOC_CONF</code></span></dt><dd><p>If the environment variable
1356           <code class="envar">MALLOC_CONF</code> is set, the characters it contains
1357           will be interpreted as options.</p></dd></dl></div><p>
1358     </p></div><div class="refsect1" title="EXAMPLES"><a name="examples"></a><h2>EXAMPLES</h2><p>To dump core whenever a problem occurs:
1359       </p><pre class="screen">ln -s 'abort:true' /etc/malloc.conf</pre><p>
1360     </p><p>To specify in the source a chunk size that is 16 MiB:
1361       </p><pre class="programlisting">
1362 malloc_conf = "lg_chunk:24";</pre></div><div class="refsect1" title="SEE ALSO"><a name="see_also"></a><h2>SEE ALSO</h2><p><span class="citerefentry"><span class="refentrytitle">madvise</span>(2)</span>,
1363     <span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span>,
1364     <span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span>,
1365     <span class="citerefentry"><span class="refentrytitle">utrace</span>(2)</span>,
1366     <span class="citerefentry"><span class="refentrytitle">alloca</span>(3)</span>,
1367     <span class="citerefentry"><span class="refentrytitle">atexit</span>(3)</span>,
1368     <span class="citerefentry"><span class="refentrytitle">getpagesize</span>(3)</span></p></div><div class="refsect1" title="STANDARDS"><a name="standards"></a><h2>STANDARDS</h2><p>The <code class="function">malloc</code>(<em class="parameter"><code></code></em>),
1369     <code class="function">calloc</code>(<em class="parameter"><code></code></em>),
1370     <code class="function">realloc</code>(<em class="parameter"><code></code></em>), and
1371     <code class="function">free</code>(<em class="parameter"><code></code></em>) functions conform to ISO/IEC
1372     9899:1990 (&#8220;ISO C90&#8221;).</p><p>The <code class="function">posix_memalign</code>(<em class="parameter"><code></code></em>) function conforms
1373     to IEEE Std 1003.1-2001 (&#8220;POSIX.1&#8221;).</p></div></div></body></html>