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 V1.75.2"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" title="JEMALLOC"><a name="id2783946"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>jemalloc — general purpose memory allocation functions</p></div><div class="refsect1" title="LIBRARY"><a name="library"></a><h2>LIBRARY</h2><p>This manual describes jemalloc 2.2.1-0-g5ef7abf6d846720fb3fb8c737861c99b5ad1d862. More information 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 <<code class="filename">stdlib.h</code>> 3#include <<code class="filename">jemalloc/jemalloc.h</code>></pre><div class="refsect2" title="Standard API"><a name="id2830421"></a><h3>Standard API</h3><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void *<b class="fsfunc">malloc</b>(</code></td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer">�</div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void *<b class="fsfunc">calloc</b>(</code></td><td>size_t <var class="pdparam">number</var>, </td></tr><tr><td>�</td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer">�</div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">posix_memalign</b>(</code></td><td>void **<var class="pdparam">ptr</var>, </td></tr><tr><td>�</td><td>size_t <var class="pdparam">alignment</var>, </td></tr><tr><td>�</td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer">�</div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void *<b class="fsfunc">realloc</b>(</code></td><td>void *<var class="pdparam">ptr</var>, </td></tr><tr><td>�</td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer">�</div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">free</b>(</code></td><td>void *<var class="pdparam">ptr</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer">�</div></div><div class="refsect2" title="Non-standard API"><a name="id2837717"></a><h3>Non-standard API</h3><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">size_t <b class="fsfunc">malloc_usable_size</b>(</code></td><td>const void *<var class="pdparam">ptr</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer">�</div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">malloc_stats_print</b>(</code></td><td>void <var class="pdparam">(*write_cb)</var> 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="id2830042"></a><h3>Experimental API</h3><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">allocm</b>(</code></td><td>void **<var class="pdparam">ptr</var>, </td></tr><tr><td>�</td><td>size_t *<var class="pdparam">rsize</var>, </td></tr><tr><td>�</td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td>�</td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer">�</div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">rallocm</b>(</code></td><td>void **<var class="pdparam">ptr</var>, </td></tr><tr><td>�</td><td>size_t *<var class="pdparam">rsize</var>, </td></tr><tr><td>�</td><td>size_t <var class="pdparam">size</var>, </td></tr><tr><td>�</td><td>size_t <var class="pdparam">extra</var>, </td></tr><tr><td>�</td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer">�</div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">sallocm</b>(</code></td><td>const void *<var class="pdparam">ptr</var>, </td></tr><tr><td>�</td><td>size_t *<var class="pdparam">rsize</var>, </td></tr><tr><td>�</td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer">�</div><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">dallocm</b>(</code></td><td>void *<var class="pdparam">ptr</var>, </td></tr><tr><td>�</td><td>int <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer">�</div></div></div></div><div class="refsect1" title="DESCRIPTION"><a name="description"></a><h2>DESCRIPTION</h2><div class="refsect2" title="Standard API"><a name="id2840968"></a><h3>Standard API</h3><p>The <code class="function">malloc</code>(<em class="parameter"><code></code></em>) function allocates 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">realloc</code>(<em class="parameter"><code></code></em>) function changes the 21 size of the previously allocated memory referenced by 22 <em class="parameter"><code>ptr</code></em> to <em class="parameter"><code>size</code></em> bytes. The 23 contents of the memory are unchanged up to the lesser of the new and old 24 sizes. If the new size is larger, the contents of the newly allocated 25 portion of the memory are undefined. Upon success, the memory referenced 26 by <em class="parameter"><code>ptr</code></em> is freed and a pointer to the newly 27 allocated memory is returned. Note that 28 <code class="function">realloc</code>(<em class="parameter"><code></code></em>) may move the memory allocation, 29 resulting in a different return value than <em class="parameter"><code>ptr</code></em>. 30 If <em class="parameter"><code>ptr</code></em> is <code class="constant">NULL</code>, the 31 <code class="function">realloc</code>(<em class="parameter"><code></code></em>) function behaves identically to 32 <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 33 allocated memory referenced by <em class="parameter"><code>ptr</code></em> to be made 34 available for future allocations. If <em class="parameter"><code>ptr</code></em> is 35 <code class="constant">NULL</code>, no action occurs.</p></div><div class="refsect2" title="Non-standard API"><a name="id2827225"></a><h3>Non-standard API</h3><p>The <code class="function">malloc_usable_size</code>(<em class="parameter"><code></code></em>) function 36 returns the usable size of the allocation pointed to by 37 <em class="parameter"><code>ptr</code></em>. The return value may be larger than the size 38 that was requested during allocation. The 39 <code class="function">malloc_usable_size</code>(<em class="parameter"><code></code></em>) function is not a 40 mechanism for in-place <code class="function">realloc</code>(<em class="parameter"><code></code></em>); rather 41 it is provided solely as a tool for introspection purposes. Any 42 discrepancy between the requested allocation size and the size reported 43 by <code class="function">malloc_usable_size</code>(<em class="parameter"><code></code></em>) should not be 44 depended on, since such behavior is entirely implementation-dependent. 45 </p><p>The <code class="function">malloc_stats_print</code>(<em class="parameter"><code></code></em>) function 46 writes human-readable summary statistics via the 47 <em class="parameter"><code>write_cb</code></em> callback function pointer and 48 <em class="parameter"><code>cbopaque</code></em> data passed to 49 <em class="parameter"><code>write_cb</code></em>, or 50 <code class="function">malloc_message</code>(<em class="parameter"><code></code></em>) if 51 <em class="parameter"><code>write_cb</code></em> is <code class="constant">NULL</code>. This 52 function can be called repeatedly. General information that never 53 changes during execution can be omitted by specifying "g" as a character 54 within the <em class="parameter"><code>opts</code></em> string. Note that 55 <code class="function">malloc_message</code>(<em class="parameter"><code></code></em>) uses the 56 <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) functions internally, so 57 inconsistent statistics can be reported if multiple threads use these 58 functions simultaneously. If <code class="option">--enable-stats</code> is 59 specified during configuration, “m” and “a” can 60 be specified to omit merged arena and per arena statistics, respectively; 61 “b” and “l” can be specified to omit per size 62 class statistics for bins and large objects, respectively. Unrecognized 63 characters are silently ignored. Note that thread caching may prevent 64 some statistics from being completely up to date, since extra locking 65 would be required to merge counters that track thread cache operations. 66 </p><p>The <code class="function">mallctl</code>(<em class="parameter"><code></code></em>) function provides a 67 general interface for introspecting the memory allocator, as well as 68 setting modifiable parameters and triggering actions. The 69 period-separated <em class="parameter"><code>name</code></em> argument specifies a 70 location in a tree-structured namespace; see the <a class="xref" href="#mallctl_namespace" title="MALLCTL NAMESPACE">MALLCTL NAMESPACE</a> section for 71 documentation on the tree contents. To read a value, pass a pointer via 72 <em class="parameter"><code>oldp</code></em> to adequate space to contain the value, and a 73 pointer to its length via <em class="parameter"><code>oldlenp</code></em>; otherwise pass 74 <code class="constant">NULL</code> and <code class="constant">NULL</code>. Similarly, to 75 write a value, pass a pointer to the value via 76 <em class="parameter"><code>newp</code></em>, and its length via 77 <em class="parameter"><code>newlen</code></em>; otherwise pass <code class="constant">NULL</code> 78 and <code class="constant">0</code>.</p><p>The <code class="function">mallctlnametomib</code>(<em class="parameter"><code></code></em>) function 79 provides a way to avoid repeated name lookups for applications that 80 repeatedly query the same portion of the namespace, by translating a name 81 to a “Management Information Base” (MIB) that can be passed 82 repeatedly to <code class="function">mallctlbymib</code>(<em class="parameter"><code></code></em>). Upon 83 successful return from <code class="function">mallctlnametomib</code>(<em class="parameter"><code></code></em>), 84 <em class="parameter"><code>mibp</code></em> contains an array of 85 <em class="parameter"><code>*miblenp</code></em> integers, where 86 <em class="parameter"><code>*miblenp</code></em> is the lesser of the number of components 87 in <em class="parameter"><code>name</code></em> and the input value of 88 <em class="parameter"><code>*miblenp</code></em>. Thus it is possible to pass a 89 <em class="parameter"><code>*miblenp</code></em> that is smaller than the number of 90 period-separated name components, which results in a partial MIB that can 91 be used as the basis for constructing a complete MIB. For name 92 components that are integers (e.g. the 2 in 93 <a class="link" href="#arenas.bin.i.size"> 94 "<code class="mallctl">arenas.bin.2.size</code>" 95 </a>), 96 the corresponding MIB component will always be that integer. Therefore, 97 it is legitimate to construct code like the following: </p><pre class="programlisting"> 98unsigned nbins, i; 99 100int mib[4]; 101size_t len, miblen; 102 103len = sizeof(nbins); 104mallctl("arenas.nbins", &nbins, &len, NULL, 0); 105 106miblen = 4; 107mallnametomib("arenas.bin.0.size", mib, &miblen); 108for (i = 0; i < nbins; i++) { 109 size_t bin_size; 110 111 mib[2] = i; 112 len = sizeof(bin_size); 113 mallctlbymib(mib, miblen, &bin_size, &len, NULL, 0); 114 /* Do something with bin_size... */ 115}</pre></div><div class="refsect2" title="Experimental API"><a name="id2807945"></a><h3>Experimental API</h3><p>The experimental API is subject to change or removal without regard 116 for backward compatibility.</p><p>The <code class="function">allocm</code>(<em class="parameter"><code></code></em>), 117 <code class="function">rallocm</code>(<em class="parameter"><code></code></em>), 118 <code class="function">sallocm</code>(<em class="parameter"><code></code></em>), and 119 <code class="function">dallocm</code>(<em class="parameter"><code></code></em>) functions all have a 120 <em class="parameter"><code>flags</code></em> argument that can be used to specify 121 options. The functions only check the options that are contextually 122 relevant. Use bitwise or (<code class="code">|</code>) operations to 123 specify one or more of the following: 124 </p><div class="variablelist"><dl><dt><span class="term"><code class="constant">ALLOCM_LG_ALIGN(<em class="parameter"><code>la</code></em>) 125 </code></span></dt><dd><p>Align the memory allocation to start at an address 126 that is a multiple of <code class="code">(1 << 127 <em class="parameter"><code>la</code></em>)</code>. This macro does not validate 128 that <em class="parameter"><code>la</code></em> is within the valid 129 range.</p></dd><dt><span class="term"><code class="constant">ALLOCM_ALIGN(<em class="parameter"><code>a</code></em>) 130 </code></span></dt><dd><p>Align the memory allocation to start at an address 131 that is a multiple of <em class="parameter"><code>a</code></em>, where 132 <em class="parameter"><code>a</code></em> is a power of two. This macro does not 133 validate that <em class="parameter"><code>a</code></em> is a power of 2. 134 </p></dd><dt><span class="term"><code class="constant">ALLOCM_ZERO</code></span></dt><dd><p>Initialize newly allocated memory to contain zero 135 bytes. In the growing reallocation case, the real size prior to 136 reallocation defines the boundary between untouched bytes and those 137 that are initialized to contain zero bytes. If this option is 138 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 139 object. This constraint can apply to both growth and 140 shrinkage.</p></dd></dl></div><p> 141 </p><p>The <code class="function">allocm</code>(<em class="parameter"><code></code></em>) function allocates at 142 least <em class="parameter"><code>size</code></em> bytes of memory, sets 143 <em class="parameter"><code>*ptr</code></em> to the base address of the allocation, and 144 sets <em class="parameter"><code>*rsize</code></em> to the real size of the allocation if 145 <em class="parameter"><code>rsize</code></em> is not <code class="constant">NULL</code>.</p><p>The <code class="function">rallocm</code>(<em class="parameter"><code></code></em>) function resizes the 146 allocation at <em class="parameter"><code>*ptr</code></em> to be at least 147 <em class="parameter"><code>size</code></em> bytes, sets <em class="parameter"><code>*ptr</code></em> to 148 the base address of the allocation if it moved, and sets 149 <em class="parameter"><code>*rsize</code></em> to the real size of the allocation if 150 <em class="parameter"><code>rsize</code></em> is not <code class="constant">NULL</code>. If 151 <em class="parameter"><code>extra</code></em> is non-zero, an attempt is made to resize 152 the allocation to be at least <code class="code"><em class="parameter"><code>size</code></em> + 153 <em class="parameter"><code>extra</code></em>)</code> bytes, though inability to allocate 154 the extra byte(s) will not by itself result in failure. Behavior is 155 undefined if <code class="code">(<em class="parameter"><code>size</code></em> + 156 <em class="parameter"><code>extra</code></em> > 157 <code class="constant">SIZE_T_MAX</code>)</code>.</p><p>The <code class="function">sallocm</code>(<em class="parameter"><code></code></em>) function sets 158 <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 159 memory referenced by <em class="parameter"><code>ptr</code></em> to be made available for 160 future allocations.</p></div></div><div class="refsect1" title="TUNING"><a name="tuning"></a><h2>TUNING</h2><p>Once, when the first call is made to one of the memory allocation 161 routines, the allocator initializes its internals based in part on various 162 options that can be specified at compile- or run-time.</p><p>The string pointed to by the global variable 163 <code class="varname">malloc_conf</code>, the “name” of the file 164 referenced by the symbolic link named <code class="filename">/etc/malloc.conf</code>, and the value of the 165 environment variable <code class="envar">MALLOC_CONF</code>, will be interpreted, in 166 that order, from left to right as options.</p><p>An options string is a comma-separated list of option:value pairs. 167 There is one key corresponding to each <a class="link" href="#opt.abort"> 168 "<code class="mallctl">opt.*</code>" 169 </a> mallctl (see the <a class="xref" href="#mallctl_namespace" title="MALLCTL NAMESPACE">MALLCTL NAMESPACE</a> section for options 170 documentation). For example, <code class="literal">abort:true,narenas:1</code> sets 171 the <a class="link" href="#opt.abort"> 172 "<code class="mallctl">opt.abort</code>" 173 </a> and <a class="link" href="#opt.narenas"> 174 "<code class="mallctl">opt.narenas</code>" 175 </a> options. Some 176 options have boolean values (true/false), others have integer values (base 177 8, 10, or 16, depending on prefix), and yet others have raw string 178 values.</p></div><div class="refsect1" title="IMPLEMENTATION NOTES"><a name="implementation_notes"></a><h2>IMPLEMENTATION NOTES</h2><p>Traditionally, allocators have used 179 <span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span> to obtain memory, which is 180 suboptimal for several reasons, including race conditions, increased 181 fragmentation, and artificial limitations on maximum usable memory. If 182 <code class="option">--enable-dss</code> is specified during configuration, this 183 allocator uses both <span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span> and 184 <span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span>, in that order of preference; 185 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 186 contention for threaded programs on multi-processor systems. This works 187 well with regard to threading scalability, but incurs some costs. There is 188 a small fixed per-arena overhead, and additionally, arenas manage memory 189 completely independently of each other, which means a small fixed increase 190 in overall memory fragmentation. These overheads are not generally an 191 issue, given the number of arenas normally used. Note that using 192 substantially more arenas than the default is not likely to improve 193 performance, mainly due to reduced cache performance. However, it may make 194 sense to reduce the number of arenas if an application does not make much 195 use of the allocation functions.</p><p>In addition to multiple arenas, unless 196 <code class="option">--disable-tcache</code> is specified during configuration, this 197 allocator supports thread-specific caching for small and large objects, in 198 order to make it possible to completely avoid synchronization for most 199 allocation requests. Such caching allows very fast allocation in the 200 common case, but it increases memory usage and fragmentation, since a 201 bounded number of objects can remain allocated in each thread cache.</p><p>Memory is conceptually broken into equal-sized chunks, where the 202 chunk size is a power of two that is greater than the page size. Chunks 203 are always aligned to multiples of the chunk size. This alignment makes it 204 possible to find metadata for user objects very quickly.</p><p>User objects are broken into three categories according to size: 205 small, large, and huge. Small objects are smaller than one page. Large 206 objects are smaller than the chunk size. Huge objects are a multiple of 207 the chunk size. Small and large objects are managed by arenas; huge 208 objects are managed separately in a single data structure that is shared by 209 all threads. Huge objects are used by applications infrequently enough 210 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 211 contiguous pages (unused, backing a set of small objects, or backing one 212 large object). The combination of chunk alignment and chunk page maps 213 makes it possible to determine all metadata regarding small and large 214 allocations in constant time.</p><p>Small objects are managed in groups by page runs. Each run maintains 215 a frontier and free list to track which regions are in use. Unless 216 <code class="option">--disable-tiny</code> is specified during configuration, 217 allocation requests that are no more than half the quantum (8 or 16, 218 depending on architecture) are rounded up to the nearest power of two that 219 is at least <code class="code">sizeof(<span class="type">void *</span>)</code>. 220 Allocation requests that are more than half the quantum, but no more than 221 the minimum cacheline-multiple size class (see the <a class="link" href="#opt.lg_qspace_max"> 222 "<code class="mallctl">opt.lg_qspace_max</code>" 223 </a> 224 option) are rounded up to the nearest multiple of the quantum. Allocation 225 requests that are more than the minimum cacheline-multiple size class, but 226 no more than the minimum subpage-multiple size class (see the <a class="link" href="#opt.lg_cspace_max"> 227 "<code class="mallctl">opt.lg_cspace_max</code>" 228 </a> 229 option) are rounded up to the nearest multiple of the cacheline size (64). 230 Allocation requests that are more than the minimum subpage-multiple size 231 class, but no more than the maximum subpage-multiple size class are rounded 232 up to the nearest multiple of the subpage size (256). Allocation requests 233 that are more than the maximum subpage-multiple size class, but small 234 enough to fit in an arena-managed chunk (see the <a class="link" href="#opt.lg_chunk"> 235 "<code class="mallctl">opt.lg_chunk</code>" 236 </a> option), are 237 rounded up to the nearest run size. Allocation requests that are too large 238 to fit in an arena-managed chunk are rounded up to the nearest multiple of 239 the chunk size.</p><p>Allocations are packed tightly together, which can be an issue for 240 multi-threaded applications. If you need to assure that allocations do not 241 suffer from cacheline sharing, round your allocation requests up to the 242 nearest multiple of the cacheline size, or specify cacheline alignment when 243 allocating.</p><p>Assuming 4 MiB chunks, 4 KiB pages, and a 16-byte quantum on a 64-bit 244 system, the size classes in each category are as shown in <a class="xref" href="#size_classes" title="Table�1.�Size classes">Table 1</a>.</p><div class="table"><a name="size_classes"></a><p class="title"><b>Table�1.�Size classes</b></p><div class="table-contents"><table summary="Size classes" border="1"><colgroup><col align="left"><col align="left"><col align="left"></colgroup><thead><tr><th align="left">Category</th><th align="left">Subcategory</th><th align="left">Size</th></tr></thead><tbody><tr><td rowspan="4" align="left">Small</td><td align="left">Tiny</td><td align="left">[8]</td></tr><tr><td align="left">Quantum-spaced</td><td align="left">[16, 32, 48, ..., 128]</td></tr><tr><td align="left">Cacheline-spaced</td><td align="left">[192, 256, 320, ..., 512]</td></tr><tr><td align="left">Subpage-spaced</td><td align="left">[768, 1024, 1280, ..., 3840]</td></tr><tr><td colspan="2" align="left">Large</td><td align="left">[4 KiB, 8 KiB, 12 KiB, ..., 4072 KiB]</td></tr><tr><td colspan="2" align="left">Huge</td><td align="left">[4 MiB, 8 MiB, 12 MiB, ...]</td></tr></tbody></table></div></div><br class="table-break"></div><div class="refsect1" title="MALLCTL NAMESPACE"><a name="mallctl_namespace"></a><h2>MALLCTL NAMESPACE</h2><p>The following names are defined in the namespace accessible via the 245 <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) functions. Value types are 246 specified in parentheses, their readable/writable statuses are encoded as 247 <code class="literal">rw</code>, <code class="literal">r-</code>, <code class="literal">-w</code>, or 248 <code class="literal">--</code>, and required build configuration flags follow, if 249 any. A name element encoded as <code class="literal"><i></code> or 250 <code class="literal"><j></code> indicates an integer component, where the 251 integer varies from 0 to some upper value that must be determined via 252 introspection. In the case of 253 "<code class="mallctl">stats.arenas.<i>.*</code>" 254 , 255 <code class="literal"><i></code> equal to <a class="link" href="#arenas.narenas"> 256 "<code class="mallctl">arenas.narenas</code>" 257 </a> can be 258 used to access the summation of statistics from all arenas. Take special 259 note of the <a class="link" href="#epoch"> 260 "<code class="mallctl">epoch</code>" 261 </a> mallctl, 262 which controls refreshing of cached dynamic statistics.</p><div class="variablelist"><dl><dt><span class="term"> 263 264 "<code class="mallctl">version</code>" 265 266 (<span class="type">const char *</span>) 267 <code class="literal">r-</code> 268 </span></dt><dd><p>Return the jemalloc version string.</p></dd><dt><a name="epoch"></a><span class="term"> 269 270 "<code class="mallctl">epoch</code>" 271 272 (<span class="type">uint64_t</span>) 273 <code class="literal">rw</code> 274 </span></dt><dd><p>If a value is passed in, refresh the data from which 275 the <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) functions report values, 276 and increment the epoch. Return the current epoch. This is useful for 277 detecting whether another thread caused a refresh.</p></dd><dt><span class="term"> 278 279 "<code class="mallctl">config.debug</code>" 280 281 (<span class="type">bool</span>) 282 <code class="literal">r-</code> 283 </span></dt><dd><p><code class="option">--enable-debug</code> was specified during 284 build configuration.</p></dd><dt><span class="term"> 285 286 "<code class="mallctl">config.dss</code>" 287 288 (<span class="type">bool</span>) 289 <code class="literal">r-</code> 290 </span></dt><dd><p><code class="option">--enable-dss</code> was specified during 291 build configuration.</p></dd><dt><span class="term"> 292 293 "<code class="mallctl">config.dynamic_page_shift</code>" 294 295 (<span class="type">bool</span>) 296 <code class="literal">r-</code> 297 </span></dt><dd><p><code class="option">--enable-dynamic-page-shift</code> was 298 specified during 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.prof</code>" 315 316 (<span class="type">bool</span>) 317 <code class="literal">r-</code> 318 </span></dt><dd><p><code class="option">--enable-prof</code> was specified during 319 build configuration.</p></dd><dt><span class="term"> 320 321 "<code class="mallctl">config.prof_libgcc</code>" 322 323 (<span class="type">bool</span>) 324 <code class="literal">r-</code> 325 </span></dt><dd><p><code class="option">--disable-prof-libgcc</code> was not 326 specified during build configuration.</p></dd><dt><span class="term"> 327 328 "<code class="mallctl">config.prof_libunwind</code>" 329 330 (<span class="type">bool</span>) 331 <code class="literal">r-</code> 332 </span></dt><dd><p><code class="option">--enable-prof-libunwind</code> was specified 333 during build configuration.</p></dd><dt><span class="term"> 334 335 "<code class="mallctl">config.stats</code>" 336 337 (<span class="type">bool</span>) 338 <code class="literal">r-</code> 339 </span></dt><dd><p><code class="option">--enable-stats</code> was specified during 340 build configuration.</p></dd><dt><span class="term"> 341 342 "<code class="mallctl">config.swap</code>" 343 344 (<span class="type">bool</span>) 345 <code class="literal">r-</code> 346 </span></dt><dd><p><code class="option">--enable-swap</code> was specified during 347 build configuration.</p></dd><dt><span class="term"> 348 349 "<code class="mallctl">config.sysv</code>" 350 351 (<span class="type">bool</span>) 352 <code class="literal">r-</code> 353 </span></dt><dd><p><code class="option">--enable-sysv</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.tiny</code>" 364 365 (<span class="type">bool</span>) 366 <code class="literal">r-</code> 367 </span></dt><dd><p><code class="option">--disable-tiny</code> was not specified 368 during build configuration.</p></dd><dt><span class="term"> 369 370 "<code class="mallctl">config.tls</code>" 371 372 (<span class="type">bool</span>) 373 <code class="literal">r-</code> 374 </span></dt><dd><p><code class="option">--disable-tls</code> was not specified during 375 build configuration.</p></dd><dt><span class="term"> 376 377 "<code class="mallctl">config.xmalloc</code>" 378 379 (<span class="type">bool</span>) 380 <code class="literal">r-</code> 381 </span></dt><dd><p><code class="option">--enable-xmalloc</code> was specified during 382 build configuration.</p></dd><dt><a name="opt.abort"></a><span class="term"> 383 384 "<code class="mallctl">opt.abort</code>" 385 386 (<span class="type">bool</span>) 387 <code class="literal">r-</code> 388 </span></dt><dd><p>Abort-on-warning enabled/disabled. If true, most 389 warnings are fatal. The process will call 390 <span class="citerefentry"><span class="refentrytitle">abort</span>(3)</span> in these cases. This option is 391 disabled by default unless <code class="option">--enable-debug</code> is 392 specified during configuration, in which case it is enabled by default. 393 </p></dd><dt><a name="opt.lg_qspace_max"></a><span class="term"> 394 395 "<code class="mallctl">opt.lg_qspace_max</code>" 396 397 (<span class="type">size_t</span>) 398 <code class="literal">r-</code> 399 </span></dt><dd><p>Size (log base 2) of the maximum size class that is a 400 multiple of the quantum (8 or 16 bytes, depending on architecture). 401 Above this size, cacheline spacing is used for size classes. The 402 default value is 128 bytes (2^7).</p></dd><dt><a name="opt.lg_cspace_max"></a><span class="term"> 403 404 "<code class="mallctl">opt.lg_cspace_max</code>" 405 406 (<span class="type">size_t</span>) 407 <code class="literal">r-</code> 408 </span></dt><dd><p>Size (log base 2) of the maximum size class that is a 409 multiple of the cacheline size (64). Above this size, subpage spacing 410 (256 bytes) is used for size classes. The default value is 512 bytes 411 (2^9).</p></dd><dt><a name="opt.lg_chunk"></a><span class="term"> 412 413 "<code class="mallctl">opt.lg_chunk</code>" 414 415 (<span class="type">size_t</span>) 416 <code class="literal">r-</code> 417 </span></dt><dd><p>Virtual memory chunk size (log base 2). The default 418 chunk size is 4 MiB (2^22).</p></dd><dt><a name="opt.narenas"></a><span class="term"> 419 420 "<code class="mallctl">opt.narenas</code>" 421 422 (<span class="type">size_t</span>) 423 <code class="literal">r-</code> 424 </span></dt><dd><p>Maximum number of arenas to use. The default maximum 425 number of arenas is four times the number of CPUs, or one if there is a 426 single CPU.</p></dd><dt><a name="opt.lg_dirty_mult"></a><span class="term"> 427 428 "<code class="mallctl">opt.lg_dirty_mult</code>" 429 430 (<span class="type">ssize_t</span>) 431 <code class="literal">r-</code> 432 </span></dt><dd><p>Per-arena minimum ratio (log base 2) of active to dirty 433 pages. Some dirty unused pages may be allowed to accumulate, within 434 the limit set by the ratio (or one chunk worth of dirty pages, 435 whichever is greater), before informing the kernel about some of those 436 pages via <span class="citerefentry"><span class="refentrytitle">madvise</span>(2)</span> or a similar system call. This 437 provides the kernel with sufficient information to recycle dirty pages 438 if physical memory becomes scarce and the pages remain unused. The 439 default minimum ratio is 32:1 (2^5:1); an option value of -1 will 440 disable dirty page purging.</p></dd><dt><a name="opt.stats_print"></a><span class="term"> 441 442 "<code class="mallctl">opt.stats_print</code>" 443 444 (<span class="type">bool</span>) 445 <code class="literal">r-</code> 446 </span></dt><dd><p>Enable/disable statistics printing at exit. If 447 enabled, the <code class="function">malloc_stats_print</code>(<em class="parameter"><code></code></em>) 448 function is called at program exit via an 449 <span class="citerefentry"><span class="refentrytitle">atexit</span>(3)</span> function. If 450 <code class="option">--enable-stats</code> is specified during configuration, this 451 has the potential to cause deadlock for a multi-threaded process that 452 exits while one or more threads are executing in the memory allocation 453 functions. Therefore, this option should only be used with care; it is 454 primarily intended as a performance tuning aid during application 455 development. This option is disabled by default.</p></dd><dt><a name="opt.junk"></a><span class="term"> 456 457 "<code class="mallctl">opt.junk</code>" 458 459 (<span class="type">bool</span>) 460 <code class="literal">r-</code> 461 [<code class="option">--enable-fill</code>] 462 </span></dt><dd><p>Junk filling enabled/disabled. If enabled, each byte 463 of uninitialized allocated memory will be initialized to 464 <code class="literal">0xa5</code>. All deallocated memory will be initialized to 465 <code class="literal">0x5a</code>. This is intended for debugging and will 466 impact performance negatively. This option is disabled by default 467 unless <code class="option">--enable-debug</code> is specified during 468 configuration, in which case it is enabled by default.</p></dd><dt><a name="opt.zero"></a><span class="term"> 469 470 "<code class="mallctl">opt.zero</code>" 471 472 (<span class="type">bool</span>) 473 <code class="literal">r-</code> 474 [<code class="option">--enable-fill</code>] 475 </span></dt><dd><p>Zero filling enabled/disabled. If enabled, each byte 476 of uninitialized allocated memory will be initialized to 0. Note that 477 this initialization only happens once for each byte, so 478 <code class="function">realloc</code>(<em class="parameter"><code></code></em>) and 479 <code class="function">rallocm</code>(<em class="parameter"><code></code></em>) calls do not zero memory that 480 was previously allocated. This is intended for debugging and will 481 impact performance negatively. This option is disabled by default. 482 </p></dd><dt><a name="opt.sysv"></a><span class="term"> 483 484 "<code class="mallctl">opt.sysv</code>" 485 486 (<span class="type">bool</span>) 487 <code class="literal">r-</code> 488 [<code class="option">--enable-sysv</code>] 489 </span></dt><dd><p>If enabled, attempting to allocate zero bytes will 490 return a <code class="constant">NULL</code> pointer instead of a valid pointer. 491 (The default behavior is to make a minimal allocation and return a 492 pointer to it.) This option is provided for System V compatibility. 493 This option is incompatible with the <a class="link" href="#opt.xmalloc"> 494 "<code class="mallctl">opt.xmalloc</code>" 495 </a> option. 496 This option is disabled by default.</p></dd><dt><a name="opt.xmalloc"></a><span class="term"> 497 498 "<code class="mallctl">opt.xmalloc</code>" 499 500 (<span class="type">bool</span>) 501 <code class="literal">r-</code> 502 [<code class="option">--enable-xmalloc</code>] 503 </span></dt><dd><p>Abort-on-out-of-memory enabled/disabled. If enabled, 504 rather than returning failure for any allocation function, display a 505 diagnostic message on <code class="constant">STDERR_FILENO</code> and cause the 506 program to drop core (using 507 <span class="citerefentry"><span class="refentrytitle">abort</span>(3)</span>). If an application is 508 designed to depend on this behavior, set the option at compile time by 509 including the following in the source code: 510 </p><pre class="programlisting"> 511malloc_conf = "xmalloc:true";</pre><p> 512 This option is disabled by default.</p></dd><dt><a name="opt.tcache"></a><span class="term"> 513 514 "<code class="mallctl">opt.tcache</code>" 515 516 (<span class="type">bool</span>) 517 <code class="literal">r-</code> 518 [<code class="option">--enable-tcache</code>] 519 </span></dt><dd><p>Thread-specific caching enabled/disabled. When there 520 are multiple threads, each thread uses a thread-specific cache for 521 objects up to a certain size. Thread-specific caching allows many 522 allocations to be satisfied without performing any thread 523 synchronization, at the cost of increased memory use. See the 524 <a class="link" href="#opt.lg_tcache_gc_sweep"> 525 "<code class="mallctl">opt.lg_tcache_gc_sweep</code>" 526 </a> 527 and <a class="link" href="#opt.lg_tcache_max"> 528 "<code class="mallctl">opt.lg_tcache_max</code>" 529 </a> 530 options for related tuning information. This option is enabled by 531 default.</p></dd><dt><a name="opt.lg_tcache_gc_sweep"></a><span class="term"> 532 533 "<code class="mallctl">opt.lg_tcache_gc_sweep</code>" 534 535 (<span class="type">ssize_t</span>) 536 <code class="literal">r-</code> 537 [<code class="option">--enable-tcache</code>] 538 </span></dt><dd><p>Approximate interval (log base 2) between full 539 thread-specific cache garbage collection sweeps, counted in terms of 540 thread-specific cache allocation/deallocation events. Garbage 541 collection is actually performed incrementally, one size class at a 542 time, in order to avoid large collection pauses. The default sweep 543 interval is 8192 (2^13); setting this option to -1 will disable garbage 544 collection.</p></dd><dt><a name="opt.lg_tcache_max"></a><span class="term"> 545 546 "<code class="mallctl">opt.lg_tcache_max</code>" 547 548 (<span class="type">size_t</span>) 549 <code class="literal">r-</code> 550 [<code class="option">--enable-tcache</code>] 551 </span></dt><dd><p>Maximum size class (log base 2) to cache in the 552 thread-specific cache. At a minimum, all small size classes are 553 cached, and at a maximum all large size classes are cached. The 554 default maximum is 32 KiB (2^15).</p></dd><dt><a name="opt.prof"></a><span class="term"> 555 556 "<code class="mallctl">opt.prof</code>" 557 558 (<span class="type">bool</span>) 559 <code class="literal">r-</code> 560 [<code class="option">--enable-prof</code>] 561 </span></dt><dd><p>Memory profiling enabled/disabled. If enabled, profile 562 memory allocation activity, and use an 563 <span class="citerefentry"><span class="refentrytitle">atexit</span>(3)</span> function to dump final memory 564 usage to a file named according to the pattern 565 <code class="filename"><prefix>.<pid>.<seq>.f.heap</code>, 566 where <code class="literal"><prefix></code> is controlled by the <a class="link" href="#opt.prof_prefix"> 567 "<code class="mallctl">opt.prof_prefix</code>" 568 </a> 569 option. See the <a class="link" href="#opt.lg_prof_bt_max"> 570 "<code class="mallctl">opt.lg_prof_bt_max</code>" 571 </a> 572 option for backtrace depth control. See the <a class="link" href="#opt.prof_active"> 573 "<code class="mallctl">opt.prof_active</code>" 574 </a> 575 option for on-the-fly activation/deactivation. See the <a class="link" href="#opt.lg_prof_sample"> 576 "<code class="mallctl">opt.lg_prof_sample</code>" 577 </a> 578 option for probabilistic sampling control. See the <a class="link" href="#opt.prof_accum"> 579 "<code class="mallctl">opt.prof_accum</code>" 580 </a> 581 option for control of cumulative sample reporting. See the <a class="link" href="#opt.lg_prof_tcmax"> 582 "<code class="mallctl">opt.lg_prof_tcmax</code>" 583 </a> 584 option for control of per thread backtrace caching. See the <a class="link" href="#opt.lg_prof_interval"> 585 "<code class="mallctl">opt.lg_prof_interval</code>" 586 </a> 587 option for information on interval-triggered profile dumping, and the 588 <a class="link" href="#opt.prof_gdump"> 589 "<code class="mallctl">opt.prof_gdump</code>" 590 </a> 591 option for information on high-water-triggered profile dumping. 592 Profile output is compatible with the included <span class="command"><strong>pprof</strong></span> 593 Perl script, which originates from the <a class="ulink" href="http://code.google.com/p/google-perftools/" target="_top">google-perftools 594 package</a>.</p></dd><dt><a name="opt.prof_prefix"></a><span class="term"> 595 596 "<code class="mallctl">opt.prof_prefix</code>" 597 598 (<span class="type">const char *</span>) 599 <code class="literal">r-</code> 600 [<code class="option">--enable-prof</code>] 601 </span></dt><dd><p>Filename prefix for profile dumps. If the prefix is 602 set to the empty string, no automatic dumps will occur; this is 603 primarily useful for disabling the automatic final heap dump (which 604 also disables leak reporting, if enabled). The default prefix is 605 <code class="filename">jeprof</code>.</p></dd><dt><a name="opt.lg_prof_bt_max"></a><span class="term"> 606 607 "<code class="mallctl">opt.lg_prof_bt_max</code>" 608 609 (<span class="type">size_t</span>) 610 <code class="literal">r-</code> 611 [<code class="option">--enable-prof</code>] 612 </span></dt><dd><p>Maximum backtrace depth (log base 2) when profiling 613 memory allocation activity. The default is 128 (2^7).</p></dd><dt><a name="opt.prof_active"></a><span class="term"> 614 615 "<code class="mallctl">opt.prof_active</code>" 616 617 (<span class="type">bool</span>) 618 <code class="literal">r-</code> 619 [<code class="option">--enable-prof</code>] 620 </span></dt><dd><p>Profiling activated/deactivated. This is a secondary 621 control mechanism that makes it possible to start the application with 622 profiling enabled (see the <a class="link" href="#opt.prof"> 623 "<code class="mallctl">opt.prof</code>" 624 </a> option) but 625 inactive, then toggle profiling at any time during program execution 626 with the <a class="link" href="#prof.active"> 627 "<code class="mallctl">prof.active</code>" 628 </a> mallctl. 629 This option is enabled by default.</p></dd><dt><a name="opt.lg_prof_sample"></a><span class="term"> 630 631 "<code class="mallctl">opt.lg_prof_sample</code>" 632 633 (<span class="type">ssize_t</span>) 634 <code class="literal">r-</code> 635 [<code class="option">--enable-prof</code>] 636 </span></dt><dd><p>Average interval (log base 2) between allocation 637 samples, as measured in bytes of allocation activity. Increasing the 638 sampling interval decreases profile fidelity, but also decreases the 639 computational overhead. The default sample interval is 1 (2^0) (i.e. 640 all allocations are sampled).</p></dd><dt><a name="opt.prof_accum"></a><span class="term"> 641 642 "<code class="mallctl">opt.prof_accum</code>" 643 644 (<span class="type">bool</span>) 645 <code class="literal">r-</code> 646 [<code class="option">--enable-prof</code>] 647 </span></dt><dd><p>Reporting of cumulative object/byte counts in profile 648 dumps enabled/disabled. If this option is enabled, every unique 649 backtrace must be stored for the duration of execution. Depending on 650 the application, this can impose a large memory overhead, and the 651 cumulative counts are not always of interest. See the 652 <a class="link" href="#opt.lg_prof_tcmax"> 653 "<code class="mallctl">opt.lg_prof_tcmax</code>" 654 </a> 655 option for control of per thread backtrace caching, which has important 656 interactions. This option is enabled by default.</p></dd><dt><a name="opt.lg_prof_tcmax"></a><span class="term"> 657 658 "<code class="mallctl">opt.lg_prof_tcmax</code>" 659 660 (<span class="type">ssize_t</span>) 661 <code class="literal">r-</code> 662 [<code class="option">--enable-prof</code>] 663 </span></dt><dd><p>Maximum per thread backtrace cache (log base 2) used 664 for heap profiling. A backtrace can only be discarded if the 665 <a class="link" href="#opt.prof_accum"> 666 "<code class="mallctl">opt.prof_accum</code>" 667 </a> 668 option is disabled, and no thread caches currently refer to the 669 backtrace. Therefore, a backtrace cache limit should be imposed if the 670 intention is to limit how much memory is used by backtraces. By 671 default, no limit is imposed (encoded as -1). 672 </p></dd><dt><a name="opt.lg_prof_interval"></a><span class="term"> 673 674 "<code class="mallctl">opt.lg_prof_interval</code>" 675 676 (<span class="type">ssize_t</span>) 677 <code class="literal">r-</code> 678 [<code class="option">--enable-prof</code>] 679 </span></dt><dd><p>Average interval (log base 2) between memory profile 680 dumps, as measured in bytes of allocation activity. The actual 681 interval between dumps may be sporadic because decentralized allocation 682 counters are used to avoid synchronization bottlenecks. Profiles are 683 dumped to files named according to the pattern 684 <code class="filename"><prefix>.<pid>.<seq>.i<iseq>.heap</code>, 685 where <code class="literal"><prefix></code> is controlled by the 686 <a class="link" href="#opt.prof_prefix"> 687 "<code class="mallctl">opt.prof_prefix</code>" 688 </a> 689 option. By default, interval-triggered profile dumping is disabled 690 (encoded as -1). 691 </p></dd><dt><a name="opt.prof_gdump"></a><span class="term"> 692 693 "<code class="mallctl">opt.prof_gdump</code>" 694 695 (<span class="type">bool</span>) 696 <code class="literal">r-</code> 697 [<code class="option">--enable-prof</code>] 698 </span></dt><dd><p>Trigger a memory profile dump every time the total 699 virtual memory exceeds the previous maximum. Profiles are dumped to 700 files named according to the pattern 701 <code class="filename"><prefix>.<pid>.<seq>.u<useq>.heap</code>, 702 where <code class="literal"><prefix></code> is controlled by the <a class="link" href="#opt.prof_prefix"> 703 "<code class="mallctl">opt.prof_prefix</code>" 704 </a> 705 option. This option is disabled by default.</p></dd><dt><a name="opt.prof_leak"></a><span class="term"> 706 707 "<code class="mallctl">opt.prof_leak</code>" 708 709 (<span class="type">bool</span>) 710 <code class="literal">r-</code> 711 [<code class="option">--enable-prof</code>] 712 </span></dt><dd><p>Leak reporting enabled/disabled. If enabled, use an 713 <span class="citerefentry"><span class="refentrytitle">atexit</span>(3)</span> function to report memory leaks 714 detected by allocation sampling. See the 715 <a class="link" href="#opt.lg_prof_bt_max"> 716 "<code class="mallctl">opt.lg_prof_bt_max</code>" 717 </a> 718 option for backtrace depth control. See the 719 <a class="link" href="#opt.prof"> 720 "<code class="mallctl">opt.prof</code>" 721 </a> option for 722 information on analyzing heap profile output. This option is disabled 723 by default.</p></dd><dt><a name="opt.overcommit"></a><span class="term"> 724 725 "<code class="mallctl">opt.overcommit</code>" 726 727 (<span class="type">bool</span>) 728 <code class="literal">r-</code> 729 [<code class="option">--enable-swap</code>] 730 </span></dt><dd><p>Over-commit enabled/disabled. If enabled, over-commit 731 memory as a side effect of using anonymous 732 <span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span> or 733 <span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span> for virtual memory allocation. 734 In order for overcommit to be disabled, the <a class="link" href="#swap.fds"> 735 "<code class="mallctl">swap.fds</code>" 736 </a> mallctl must have 737 been successfully written to. This option is enabled by 738 default.</p></dd><dt><span class="term"> 739 740 "<code class="mallctl">tcache.flush</code>" 741 742 (<span class="type">void</span>) 743 <code class="literal">--</code> 744 [<code class="option">--enable-tcache</code>] 745 </span></dt><dd><p>Flush calling thread's tcache. This interface releases 746 all cached objects and internal data structures associated with the 747 calling thread's thread-specific cache. Ordinarily, this interface 748 need not be called, since automatic periodic incremental garbage 749 collection occurs, and the thread cache is automatically discarded when 750 a thread exits. However, garbage collection is triggered by allocation 751 activity, so it is possible for a thread that stops 752 allocating/deallocating to retain its cache indefinitely, in which case 753 the developer may find manual flushing useful.</p></dd><dt><span class="term"> 754 755 "<code class="mallctl">thread.arena</code>" 756 757 (<span class="type">unsigned</span>) 758 <code class="literal">rw</code> 759 </span></dt><dd><p>Get or set the arena associated with the calling 760 thread. The arena index must be less than the maximum number of arenas 761 (see the <a class="link" href="#arenas.narenas"> 762 "<code class="mallctl">arenas.narenas</code>" 763 </a> 764 mallctl). If the specified arena was not initialized beforehand (see 765 the <a class="link" href="#arenas.initialized"> 766 "<code class="mallctl">arenas.initialized</code>" 767 </a> 768 mallctl), it will be automatically initialized as a side effect of 769 calling this interface.</p></dd><dt><a name="thread.allocated"></a><span class="term"> 770 771 "<code class="mallctl">thread.allocated</code>" 772 773 (<span class="type">uint64_t</span>) 774 <code class="literal">r-</code> 775 [<code class="option">--enable-stats</code>] 776 </span></dt><dd><p>Get the total number of bytes ever allocated by the 777 calling thread. This counter has the potential to wrap around; it is 778 up to the application to appropriately interpret the counter in such 779 cases.</p></dd><dt><span class="term"> 780 781 "<code class="mallctl">thread.allocatedp</code>" 782 783 (<span class="type">uint64_t *</span>) 784 <code class="literal">r-</code> 785 [<code class="option">--enable-stats</code>] 786 </span></dt><dd><p>Get a pointer to the the value that is returned by the 787 <a class="link" href="#thread.allocated"> 788 "<code class="mallctl">thread.allocated</code>" 789 </a> 790 mallctl. This is useful for avoiding the overhead of repeated 791 <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) calls.</p></dd><dt><a name="thread.deallocated"></a><span class="term"> 792 793 "<code class="mallctl">thread.deallocated</code>" 794 795 (<span class="type">uint64_t</span>) 796 <code class="literal">r-</code> 797 [<code class="option">--enable-stats</code>] 798 </span></dt><dd><p>Get the total number of bytes ever deallocated by the 799 calling thread. This counter has the potential to wrap around; it is 800 up to the application to appropriately interpret the counter in such 801 cases.</p></dd><dt><span class="term"> 802 803 "<code class="mallctl">thread.deallocatedp</code>" 804 805 (<span class="type">uint64_t *</span>) 806 <code class="literal">r-</code> 807 [<code class="option">--enable-stats</code>] 808 </span></dt><dd><p>Get a pointer to the the value that is returned by the 809 <a class="link" href="#thread.deallocated"> 810 "<code class="mallctl">thread.deallocated</code>" 811 </a> 812 mallctl. This is useful for avoiding the overhead of repeated 813 <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) calls.</p></dd><dt><a name="arenas.narenas"></a><span class="term"> 814 815 "<code class="mallctl">arenas.narenas</code>" 816 817 (<span class="type">unsigned</span>) 818 <code class="literal">r-</code> 819 </span></dt><dd><p>Maximum number of arenas.</p></dd><dt><a name="arenas.initialized"></a><span class="term"> 820 821 "<code class="mallctl">arenas.initialized</code>" 822 823 (<span class="type">bool *</span>) 824 <code class="literal">r-</code> 825 </span></dt><dd><p>An array of <a class="link" href="#arenas.narenas"> 826 "<code class="mallctl">arenas.narenas</code>" 827 </a> 828 booleans. Each boolean indicates whether the corresponding arena is 829 initialized.</p></dd><dt><span class="term"> 830 831 "<code class="mallctl">arenas.quantum</code>" 832 833 (<span class="type">size_t</span>) 834 <code class="literal">r-</code> 835 </span></dt><dd><p>Quantum size.</p></dd><dt><span class="term"> 836 837 "<code class="mallctl">arenas.cacheline</code>" 838 839 (<span class="type">size_t</span>) 840 <code class="literal">r-</code> 841 </span></dt><dd><p>Assumed cacheline size.</p></dd><dt><span class="term"> 842 843 "<code class="mallctl">arenas.subpage</code>" 844 845 (<span class="type">size_t</span>) 846 <code class="literal">r-</code> 847 </span></dt><dd><p>Subpage size class interval.</p></dd><dt><span class="term"> 848 849 "<code class="mallctl">arenas.pagesize</code>" 850 851 (<span class="type">size_t</span>) 852 <code class="literal">r-</code> 853 </span></dt><dd><p>Page size.</p></dd><dt><span class="term"> 854 855 "<code class="mallctl">arenas.chunksize</code>" 856 857 (<span class="type">size_t</span>) 858 <code class="literal">r-</code> 859 </span></dt><dd><p>Chunk size.</p></dd><dt><span class="term"> 860 861 "<code class="mallctl">arenas.tspace_min</code>" 862 863 (<span class="type">size_t</span>) 864 <code class="literal">r-</code> 865 </span></dt><dd><p>Minimum tiny size class. Tiny size classes are powers 866 of two.</p></dd><dt><span class="term"> 867 868 "<code class="mallctl">arenas.tspace_max</code>" 869 870 (<span class="type">size_t</span>) 871 <code class="literal">r-</code> 872 </span></dt><dd><p>Maximum tiny size class. Tiny size classes are powers 873 of two.</p></dd><dt><span class="term"> 874 875 "<code class="mallctl">arenas.qspace_min</code>" 876 877 (<span class="type">size_t</span>) 878 <code class="literal">r-</code> 879 </span></dt><dd><p>Minimum quantum-spaced size class.</p></dd><dt><span class="term"> 880 881 "<code class="mallctl">arenas.qspace_max</code>" 882 883 (<span class="type">size_t</span>) 884 <code class="literal">r-</code> 885 </span></dt><dd><p>Maximum quantum-spaced size class.</p></dd><dt><span class="term"> 886 887 "<code class="mallctl">arenas.cspace_min</code>" 888 889 (<span class="type">size_t</span>) 890 <code class="literal">r-</code> 891 </span></dt><dd><p>Minimum cacheline-spaced size class.</p></dd><dt><span class="term"> 892 893 "<code class="mallctl">arenas.cspace_max</code>" 894 895 (<span class="type">size_t</span>) 896 <code class="literal">r-</code> 897 </span></dt><dd><p>Maximum cacheline-spaced size class.</p></dd><dt><span class="term"> 898 899 "<code class="mallctl">arenas.sspace_min</code>" 900 901 (<span class="type">size_t</span>) 902 <code class="literal">r-</code> 903 </span></dt><dd><p>Minimum subpage-spaced size class.</p></dd><dt><span class="term"> 904 905 "<code class="mallctl">arenas.sspace_max</code>" 906 907 (<span class="type">size_t</span>) 908 <code class="literal">r-</code> 909 </span></dt><dd><p>Maximum subpage-spaced size class.</p></dd><dt><span class="term"> 910 911 "<code class="mallctl">arenas.tcache_max</code>" 912 913 (<span class="type">size_t</span>) 914 <code class="literal">r-</code> 915 [<code class="option">--enable-tcache</code>] 916 </span></dt><dd><p>Maximum thread-cached size class.</p></dd><dt><span class="term"> 917 918 "<code class="mallctl">arenas.ntbins</code>" 919 920 (<span class="type">unsigned</span>) 921 <code class="literal">r-</code> 922 </span></dt><dd><p>Number of tiny bin size classes.</p></dd><dt><span class="term"> 923 924 "<code class="mallctl">arenas.nqbins</code>" 925 926 (<span class="type">unsigned</span>) 927 <code class="literal">r-</code> 928 </span></dt><dd><p>Number of quantum-spaced bin size 929 classes.</p></dd><dt><span class="term"> 930 931 "<code class="mallctl">arenas.ncbins</code>" 932 933 (<span class="type">unsigned</span>) 934 <code class="literal">r-</code> 935 </span></dt><dd><p>Number of cacheline-spaced bin size 936 classes.</p></dd><dt><span class="term"> 937 938 "<code class="mallctl">arenas.nsbins</code>" 939 940 (<span class="type">unsigned</span>) 941 <code class="literal">r-</code> 942 </span></dt><dd><p>Number of subpage-spaced bin size 943 classes.</p></dd><dt><span class="term"> 944 945 "<code class="mallctl">arenas.nbins</code>" 946 947 (<span class="type">unsigned</span>) 948 <code class="literal">r-</code> 949 </span></dt><dd><p>Total number of bin size classes.</p></dd><dt><span class="term"> 950 951 "<code class="mallctl">arenas.nhbins</code>" 952 953 (<span class="type">unsigned</span>) 954 <code class="literal">r-</code> 955 [<code class="option">--enable-tcache</code>] 956 </span></dt><dd><p>Total number of thread cache bin size 957 classes.</p></dd><dt><a name="arenas.bin.i.size"></a><span class="term"> 958 959 "<code class="mallctl">arenas.bin.<i>.size</code>" 960 961 (<span class="type">size_t</span>) 962 <code class="literal">r-</code> 963 </span></dt><dd><p>Maximum size supported by size class.</p></dd><dt><span class="term"> 964 965 "<code class="mallctl">arenas.bin.<i>.nregs</code>" 966 967 (<span class="type">uint32_t</span>) 968 <code class="literal">r-</code> 969 </span></dt><dd><p>Number of regions per page run.</p></dd><dt><span class="term"> 970 971 "<code class="mallctl">arenas.bin.<i>.run_size</code>" 972 973 (<span class="type">size_t</span>) 974 <code class="literal">r-</code> 975 </span></dt><dd><p>Number of bytes per page run.</p></dd><dt><span class="term"> 976 977 "<code class="mallctl">arenas.nlruns</code>" 978 979 (<span class="type">size_t</span>) 980 <code class="literal">r-</code> 981 </span></dt><dd><p>Total number of large size classes.</p></dd><dt><span class="term"> 982 983 "<code class="mallctl">arenas.lrun.<i>.size</code>" 984 985 (<span class="type">size_t</span>) 986 <code class="literal">r-</code> 987 </span></dt><dd><p>Maximum size supported by this large size 988 class.</p></dd><dt><span class="term"> 989 990 "<code class="mallctl">arenas.purge</code>" 991 992 (<span class="type">unsigned</span>) 993 <code class="literal">-w</code> 994 </span></dt><dd><p>Purge unused dirty pages for the specified arena, or 995 for all arenas if none is specified.</p></dd><dt><a name="prof.active"></a><span class="term"> 996 997 "<code class="mallctl">prof.active</code>" 998 999 (<span class="type">bool</span>) 1000 <code class="literal">rw</code> 1001 [<code class="option">--enable-prof</code>] 1002 </span></dt><dd><p>Control whether sampling is currently active. See the 1003 <a class="link" href="#opt.prof_active"> 1004 "<code class="mallctl">opt.prof_active</code>" 1005 </a> 1006 option for additional information. 1007 </p></dd><dt><span class="term"> 1008 1009 "<code class="mallctl">prof.dump</code>" 1010 1011 (<span class="type">const char *</span>) 1012 <code class="literal">-w</code> 1013 [<code class="option">--enable-prof</code>] 1014 </span></dt><dd><p>Dump a memory profile to the specified file, or if NULL 1015 is specified, to a file according to the pattern 1016 <code class="filename"><prefix>.<pid>.<seq>.m<mseq>.heap</code>, 1017 where <code class="literal"><prefix></code> is controlled by the 1018 <a class="link" href="#opt.prof_prefix"> 1019 "<code class="mallctl">opt.prof_prefix</code>" 1020 </a> 1021 option.</p></dd><dt><span class="term"> 1022 1023 "<code class="mallctl">prof.interval</code>" 1024 1025 (<span class="type">uint64_t</span>) 1026 <code class="literal">r-</code> 1027 [<code class="option">--enable-prof</code>] 1028 </span></dt><dd><p>Average number of bytes allocated between 1029 inverval-based profile dumps. See the 1030 <a class="link" href="#opt.lg_prof_interval"> 1031 "<code class="mallctl">opt.lg_prof_interval</code>" 1032 </a> 1033 option for additional information.</p></dd><dt><a name="stats.cactive"></a><span class="term"> 1034 1035 "<code class="mallctl">stats.cactive</code>" 1036 1037 (<span class="type">size_t *</span>) 1038 <code class="literal">r-</code> 1039 [<code class="option">--enable-stats</code>] 1040 </span></dt><dd><p>Pointer to a counter that contains an approximate count 1041 of the current number of bytes in active pages. The estimate may be 1042 high, but never low, because each arena rounds up to the nearest 1043 multiple of the chunk size when computing its contribution to the 1044 counter. Note that the <a class="link" href="#epoch"> 1045 "<code class="mallctl">epoch</code>" 1046 </a> mallctl has no bearing 1047 on this counter. Furthermore, counter consistency is maintained via 1048 atomic operations, so it is necessary to use an atomic operation in 1049 order to guarantee a consistent read when dereferencing the pointer. 1050 </p></dd><dt><a name="stats.allocated"></a><span class="term"> 1051 1052 "<code class="mallctl">stats.allocated</code>" 1053 1054 (<span class="type">size_t</span>) 1055 <code class="literal">r-</code> 1056 [<code class="option">--enable-stats</code>] 1057 </span></dt><dd><p>Total number of bytes allocated by the 1058 application.</p></dd><dt><a name="stats.active"></a><span class="term"> 1059 1060 "<code class="mallctl">stats.active</code>" 1061 1062 (<span class="type">size_t</span>) 1063 <code class="literal">r-</code> 1064 [<code class="option">--enable-stats</code>] 1065 </span></dt><dd><p>Total number of bytes in active pages allocated by the 1066 application. This is a multiple of the page size, and greater than or 1067 equal to <a class="link" href="#stats.allocated"> 1068 "<code class="mallctl">stats.allocated</code>" 1069 </a>. 1070 </p></dd><dt><span class="term"> 1071 1072 "<code class="mallctl">stats.mapped</code>" 1073 1074 (<span class="type">size_t</span>) 1075 <code class="literal">r-</code> 1076 [<code class="option">--enable-stats</code>] 1077 </span></dt><dd><p>Total number of bytes in chunks mapped on behalf of the 1078 application. This is a multiple of the chunk size, and is at least as 1079 large as <a class="link" href="#stats.active"> 1080 "<code class="mallctl">stats.active</code>" 1081 </a>. This 1082 does not include inactive chunks backed by swap files. his does not 1083 include inactive chunks embedded in the DSS.</p></dd><dt><span class="term"> 1084 1085 "<code class="mallctl">stats.chunks.current</code>" 1086 1087 (<span class="type">size_t</span>) 1088 <code class="literal">r-</code> 1089 [<code class="option">--enable-stats</code>] 1090 </span></dt><dd><p>Total number of chunks actively mapped on behalf of the 1091 application. This does not include inactive chunks backed by swap 1092 files. This does not include inactive chunks embedded in the DSS. 1093 </p></dd><dt><span class="term"> 1094 1095 "<code class="mallctl">stats.chunks.total</code>" 1096 1097 (<span class="type">uint64_t</span>) 1098 <code class="literal">r-</code> 1099 [<code class="option">--enable-stats</code>] 1100 </span></dt><dd><p>Cumulative number of chunks allocated.</p></dd><dt><span class="term"> 1101 1102 "<code class="mallctl">stats.chunks.high</code>" 1103 1104 (<span class="type">size_t</span>) 1105 <code class="literal">r-</code> 1106 [<code class="option">--enable-stats</code>] 1107 </span></dt><dd><p>Maximum number of active chunks at any time thus far. 1108 </p></dd><dt><span class="term"> 1109 1110 "<code class="mallctl">stats.huge.allocated</code>" 1111 1112 (<span class="type">size_t</span>) 1113 <code class="literal">r-</code> 1114 [<code class="option">--enable-stats</code>] 1115 </span></dt><dd><p>Number of bytes currently allocated by huge objects. 1116 </p></dd><dt><span class="term"> 1117 1118 "<code class="mallctl">stats.huge.nmalloc</code>" 1119 1120 (<span class="type">uint64_t</span>) 1121 <code class="literal">r-</code> 1122 [<code class="option">--enable-stats</code>] 1123 </span></dt><dd><p>Cumulative number of huge allocation requests. 1124 </p></dd><dt><span class="term"> 1125 1126 "<code class="mallctl">stats.huge.ndalloc</code>" 1127 1128 (<span class="type">uint64_t</span>) 1129 <code class="literal">r-</code> 1130 [<code class="option">--enable-stats</code>] 1131 </span></dt><dd><p>Cumulative number of huge deallocation requests. 1132 </p></dd><dt><span class="term"> 1133 1134 "<code class="mallctl">stats.arenas.<i>.nthreads</code>" 1135 1136 (<span class="type">unsigned</span>) 1137 <code class="literal">r-</code> 1138 </span></dt><dd><p>Number of threads currently assigned to 1139 arena.</p></dd><dt><span class="term"> 1140 1141 "<code class="mallctl">stats.arenas.<i>.pactive</code>" 1142 1143 (<span class="type">size_t</span>) 1144 <code class="literal">r-</code> 1145 </span></dt><dd><p>Number of pages in active runs.</p></dd><dt><span class="term"> 1146 1147 "<code class="mallctl">stats.arenas.<i>.pdirty</code>" 1148 1149 (<span class="type">size_t</span>) 1150 <code class="literal">r-</code> 1151 </span></dt><dd><p>Number of pages within unused runs that are potentially 1152 dirty, and for which <code class="function">madvise</code>(<em class="parameter"><code>...</code></em>, 1153 <em class="parameter"><code><code class="constant">MADV_DONTNEED</code></code></em>) or 1154 similar has not been called.</p></dd><dt><span class="term"> 1155 1156 "<code class="mallctl">stats.arenas.<i>.mapped</code>" 1157 1158 (<span class="type">size_t</span>) 1159 <code class="literal">r-</code> 1160 [<code class="option">--enable-stats</code>] 1161 </span></dt><dd><p>Number of mapped bytes.</p></dd><dt><span class="term"> 1162 1163 "<code class="mallctl">stats.arenas.<i>.npurge</code>" 1164 1165 (<span class="type">uint64_t</span>) 1166 <code class="literal">r-</code> 1167 [<code class="option">--enable-stats</code>] 1168 </span></dt><dd><p>Number of dirty page purge sweeps performed. 1169 </p></dd><dt><span class="term"> 1170 1171 "<code class="mallctl">stats.arenas.<i>.nmadvise</code>" 1172 1173 (<span class="type">uint64_t</span>) 1174 <code class="literal">r-</code> 1175 [<code class="option">--enable-stats</code>] 1176 </span></dt><dd><p>Number of <code class="function">madvise</code>(<em class="parameter"><code>...</code></em>, 1177 <em class="parameter"><code><code class="constant">MADV_DONTNEED</code></code></em>) or 1178 similar calls made to purge dirty pages.</p></dd><dt><span class="term"> 1179 1180 "<code class="mallctl">stats.arenas.<i>.npurged</code>" 1181 1182 (<span class="type">uint64_t</span>) 1183 <code class="literal">r-</code> 1184 [<code class="option">--enable-stats</code>] 1185 </span></dt><dd><p>Number of pages purged.</p></dd><dt><span class="term"> 1186 1187 "<code class="mallctl">stats.arenas.<i>.small.allocated</code>" 1188 1189 (<span class="type">size_t</span>) 1190 <code class="literal">r-</code> 1191 [<code class="option">--enable-stats</code>] 1192 </span></dt><dd><p>Number of bytes currently allocated by small objects. 1193 </p></dd><dt><span class="term"> 1194 1195 "<code class="mallctl">stats.arenas.<i>.small.nmalloc</code>" 1196 1197 (<span class="type">uint64_t</span>) 1198 <code class="literal">r-</code> 1199 [<code class="option">--enable-stats</code>] 1200 </span></dt><dd><p>Cumulative number of allocation requests served by 1201 small bins.</p></dd><dt><span class="term"> 1202 1203 "<code class="mallctl">stats.arenas.<i>.small.ndalloc</code>" 1204 1205 (<span class="type">uint64_t</span>) 1206 <code class="literal">r-</code> 1207 [<code class="option">--enable-stats</code>] 1208 </span></dt><dd><p>Cumulative number of small objects returned to bins. 1209 </p></dd><dt><span class="term"> 1210 1211 "<code class="mallctl">stats.arenas.<i>.small.nrequests</code>" 1212 1213 (<span class="type">uint64_t</span>) 1214 <code class="literal">r-</code> 1215 [<code class="option">--enable-stats</code>] 1216 </span></dt><dd><p>Cumulative number of small allocation requests. 1217 </p></dd><dt><span class="term"> 1218 1219 "<code class="mallctl">stats.arenas.<i>.large.allocated</code>" 1220 1221 (<span class="type">size_t</span>) 1222 <code class="literal">r-</code> 1223 [<code class="option">--enable-stats</code>] 1224 </span></dt><dd><p>Number of bytes currently allocated by large objects. 1225 </p></dd><dt><span class="term"> 1226 1227 "<code class="mallctl">stats.arenas.<i>.large.nmalloc</code>" 1228 1229 (<span class="type">uint64_t</span>) 1230 <code class="literal">r-</code> 1231 [<code class="option">--enable-stats</code>] 1232 </span></dt><dd><p>Cumulative number of large allocation requests served 1233 directly by the arena.</p></dd><dt><span class="term"> 1234 1235 "<code class="mallctl">stats.arenas.<i>.large.ndalloc</code>" 1236 1237 (<span class="type">uint64_t</span>) 1238 <code class="literal">r-</code> 1239 [<code class="option">--enable-stats</code>] 1240 </span></dt><dd><p>Cumulative number of large deallocation requests served 1241 directly by the arena.</p></dd><dt><span class="term"> 1242 1243 "<code class="mallctl">stats.arenas.<i>.large.nrequests</code>" 1244 1245 (<span class="type">uint64_t</span>) 1246 <code class="literal">r-</code> 1247 [<code class="option">--enable-stats</code>] 1248 </span></dt><dd><p>Cumulative number of large allocation requests. 1249 </p></dd><dt><span class="term"> 1250 1251 "<code class="mallctl">stats.arenas.<i>.bins.<j>.allocated</code>" 1252 1253 (<span class="type">size_t</span>) 1254 <code class="literal">r-</code> 1255 [<code class="option">--enable-stats</code>] 1256 </span></dt><dd><p>Current number of bytes allocated by 1257 bin.</p></dd><dt><span class="term"> 1258 1259 "<code class="mallctl">stats.arenas.<i>.bins.<j>.nmalloc</code>" 1260 1261 (<span class="type">uint64_t</span>) 1262 <code class="literal">r-</code> 1263 [<code class="option">--enable-stats</code>] 1264 </span></dt><dd><p>Cumulative number of allocations served by bin. 1265 </p></dd><dt><span class="term"> 1266 1267 "<code class="mallctl">stats.arenas.<i>.bins.<j>.ndalloc</code>" 1268 1269 (<span class="type">uint64_t</span>) 1270 <code class="literal">r-</code> 1271 [<code class="option">--enable-stats</code>] 1272 </span></dt><dd><p>Cumulative number of allocations returned to bin. 1273 </p></dd><dt><span class="term"> 1274 1275 "<code class="mallctl">stats.arenas.<i>.bins.<j>.nrequests</code>" 1276 1277 (<span class="type">uint64_t</span>) 1278 <code class="literal">r-</code> 1279 [<code class="option">--enable-stats</code>] 1280 </span></dt><dd><p>Cumulative number of allocation 1281 requests.</p></dd><dt><span class="term"> 1282 1283 "<code class="mallctl">stats.arenas.<i>.bins.<j>.nfills</code>" 1284 1285 (<span class="type">uint64_t</span>) 1286 <code class="literal">r-</code> 1287 [<code class="option">--enable-stats</code> <code class="option">--enable-tcache</code>] 1288 </span></dt><dd><p>Cumulative number of tcache fills.</p></dd><dt><span class="term"> 1289 1290 "<code class="mallctl">stats.arenas.<i>.bins.<j>.nflushes</code>" 1291 1292 (<span class="type">uint64_t</span>) 1293 <code class="literal">r-</code> 1294 [<code class="option">--enable-stats</code> <code class="option">--enable-tcache</code>] 1295 </span></dt><dd><p>Cumulative number of tcache flushes.</p></dd><dt><span class="term"> 1296 1297 "<code class="mallctl">stats.arenas.<i>.bins.<j>.nruns</code>" 1298 1299 (<span class="type">uint64_t</span>) 1300 <code class="literal">r-</code> 1301 [<code class="option">--enable-stats</code>] 1302 </span></dt><dd><p>Cumulative number of runs created.</p></dd><dt><span class="term"> 1303 1304 "<code class="mallctl">stats.arenas.<i>.bins.<j>.nreruns</code>" 1305 1306 (<span class="type">uint64_t</span>) 1307 <code class="literal">r-</code> 1308 [<code class="option">--enable-stats</code>] 1309 </span></dt><dd><p>Cumulative number of times the current run from which 1310 to allocate changed.</p></dd><dt><span class="term"> 1311 1312 "<code class="mallctl">stats.arenas.<i>.bins.<j>.highruns</code>" 1313 1314 (<span class="type">size_t</span>) 1315 <code class="literal">r-</code> 1316 [<code class="option">--enable-stats</code>] 1317 </span></dt><dd><p>Maximum number of runs at any time thus far. 1318 </p></dd><dt><span class="term"> 1319 1320 "<code class="mallctl">stats.arenas.<i>.bins.<j>.curruns</code>" 1321 1322 (<span class="type">size_t</span>) 1323 <code class="literal">r-</code> 1324 [<code class="option">--enable-stats</code>] 1325 </span></dt><dd><p>Current number of runs.</p></dd><dt><span class="term"> 1326 1327 "<code class="mallctl">stats.arenas.<i>.lruns.<j>.nmalloc</code>" 1328 1329 (<span class="type">uint64_t</span>) 1330 <code class="literal">r-</code> 1331 [<code class="option">--enable-stats</code>] 1332 </span></dt><dd><p>Cumulative number of allocation requests for this size 1333 class served directly by the arena.</p></dd><dt><span class="term"> 1334 1335 "<code class="mallctl">stats.arenas.<i>.lruns.<j>.ndalloc</code>" 1336 1337 (<span class="type">uint64_t</span>) 1338 <code class="literal">r-</code> 1339 [<code class="option">--enable-stats</code>] 1340 </span></dt><dd><p>Cumulative number of deallocation requests for this 1341 size class served directly by the arena.</p></dd><dt><span class="term"> 1342 1343 "<code class="mallctl">stats.arenas.<i>.lruns.<j>.nrequests</code>" 1344 1345 (<span class="type">uint64_t</span>) 1346 <code class="literal">r-</code> 1347 [<code class="option">--enable-stats</code>] 1348 </span></dt><dd><p>Cumulative number of allocation requests for this size 1349 class.</p></dd><dt><span class="term"> 1350 1351 "<code class="mallctl">stats.arenas.<i>.lruns.<j>.highruns</code>" 1352 1353 (<span class="type">size_t</span>) 1354 <code class="literal">r-</code> 1355 [<code class="option">--enable-stats</code>] 1356 </span></dt><dd><p>Maximum number of runs at any time thus far for this 1357 size class.</p></dd><dt><span class="term"> 1358 1359 "<code class="mallctl">stats.arenas.<i>.lruns.<j>.curruns</code>" 1360 1361 (<span class="type">size_t</span>) 1362 <code class="literal">r-</code> 1363 [<code class="option">--enable-stats</code>] 1364 </span></dt><dd><p>Current number of runs for this size class. 1365 </p></dd><dt><span class="term"> 1366 1367 "<code class="mallctl">swap.avail</code>" 1368 1369 (<span class="type">size_t</span>) 1370 <code class="literal">r-</code> 1371 [<code class="option">--enable-stats --enable-swap</code>] 1372 </span></dt><dd><p>Number of swap file bytes that are currently not 1373 associated with any chunk (i.e. mapped, but otherwise completely 1374 unmanaged).</p></dd><dt><a name="swap.prezeroed"></a><span class="term"> 1375 1376 "<code class="mallctl">swap.prezeroed</code>" 1377 1378 (<span class="type">bool</span>) 1379 <code class="literal">rw</code> 1380 [<code class="option">--enable-swap</code>] 1381 </span></dt><dd><p>If true, the allocator assumes that the swap file(s) 1382 contain nothing but nil bytes. If this assumption is violated, 1383 allocator behavior is undefined. This value becomes read-only after 1384 <a class="link" href="#swap.fds"> 1385 "<code class="mallctl">swap.fds</code>" 1386 </a> is 1387 successfully written to.</p></dd><dt><span class="term"> 1388 1389 "<code class="mallctl">swap.nfds</code>" 1390 1391 (<span class="type">size_t</span>) 1392 <code class="literal">r-</code> 1393 [<code class="option">--enable-swap</code>] 1394 </span></dt><dd><p>Number of file descriptors in use for swap. 1395 </p></dd><dt><a name="swap.fds"></a><span class="term"> 1396 1397 "<code class="mallctl">swap.fds</code>" 1398 1399 (<span class="type">int *</span>) 1400 <code class="literal">r-</code> 1401 [<code class="option">--enable-swap</code>] 1402 </span></dt><dd><p>When written to, the files associated with the 1403 specified file descriptors are contiguously mapped via 1404 <span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span>. The resulting virtual memory 1405 region is preferred over anonymous 1406 <span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span> and 1407 <span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span> memory. Note that if a file's 1408 size is not a multiple of the page size, it is automatically truncated 1409 to the nearest page size multiple. See the 1410 <a class="link" href="#swap.prezeroed"> 1411 "<code class="mallctl">swap.prezeroed</code>" 1412 </a> 1413 mallctl for specifying that the files are pre-zeroed.</p></dd></dl></div></div><div class="refsect1" title="DEBUGGING MALLOC PROBLEMS"><a name="debugging_malloc_problems"></a><h2>DEBUGGING MALLOC PROBLEMS</h2><p>When debugging, it is a good idea to configure/build jemalloc with 1414 the <code class="option">--enable-debug</code> and <code class="option">--enable-fill</code> 1415 options, and recompile the program with suitable options and symbols for 1416 debugger support. When so configured, jemalloc incorporates a wide variety 1417 of run-time assertions that catch application errors such as double-free, 1418 write-after-free, etc.</p><p>Programs often accidentally depend on “uninitialized” 1419 memory actually being filled with zero bytes. Junk filling 1420 (see the <a class="link" href="#opt.junk"> 1421 "<code class="mallctl">opt.junk</code>" 1422 </a> 1423 option) tends to expose such bugs in the form of obviously incorrect 1424 results and/or coredumps. Conversely, zero 1425 filling (see the <a class="link" href="#opt.zero"> 1426 "<code class="mallctl">opt.zero</code>" 1427 </a> option) eliminates 1428 the symptoms of such bugs. Between these two options, it is usually 1429 possible to quickly detect, diagnose, and eliminate such bugs.</p><p>This implementation does not provide much detail about the problems 1430 it detects, because the performance impact for storing such information 1431 would be prohibitive. There are a number of allocator implementations 1432 available on the Internet which focus on detecting and pinpointing problems 1433 by trading performance for extra sanity checks and detailed 1434 diagnostics.</p></div><div class="refsect1" title="DIAGNOSTIC MESSAGES"><a name="diagnostic_messages"></a><h2>DIAGNOSTIC MESSAGES</h2><p>If any of the memory allocation/deallocation functions detect an 1435 error or warning condition, a message will be printed to file descriptor 1436 <code class="constant">STDERR_FILENO</code>. Errors will result in the process 1437 dumping core. If the <a class="link" href="#opt.abort"> 1438 "<code class="mallctl">opt.abort</code>" 1439 </a> option is set, most 1440 warnings are treated as errors.</p><p>The <code class="varname">malloc_message</code> variable allows the programmer 1441 to override the function which emits the text strings forming the errors 1442 and warnings if for some reason the <code class="constant">STDERR_FILENO</code> file 1443 descriptor is not suitable for this. 1444 <code class="function">malloc_message</code>(<em class="parameter"><code></code></em>) takes the 1445 <em class="parameter"><code>cbopaque</code></em> pointer argument that is 1446 <code class="constant">NULL</code> unless overridden by the arguments in a call to 1447 <code class="function">malloc_stats_print</code>(<em class="parameter"><code></code></em>), followed by a string 1448 pointer. Please note that doing anything which tries to allocate memory in 1449 this function is likely to result in a crash or deadlock.</p><p>All messages are prefixed by 1450 “<code class="computeroutput"><jemalloc>: </code>”.</p></div><div class="refsect1" title="RETURN VALUES"><a name="return_values"></a><h2>RETURN VALUES</h2><div class="refsect2" title="Standard API"><a name="id2844722"></a><h3>Standard API</h3><p>The <code class="function">malloc</code>(<em class="parameter"><code></code></em>) and 1451 <code class="function">calloc</code>(<em class="parameter"><code></code></em>) functions return a pointer to the 1452 allocated memory if successful; otherwise a <code class="constant">NULL</code> 1453 pointer is returned and <code class="varname">errno</code> is set to 1454 <span class="errorname">ENOMEM</span>.</p><p>The <code class="function">posix_memalign</code>(<em class="parameter"><code></code></em>) function 1455 returns the value 0 if successful; otherwise it returns an error value. 1456 The <code class="function">posix_memalign</code>(<em class="parameter"><code></code></em>) function will fail 1457 if: 1458 </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 1459 not a power of 2 at least as large as 1460 <code class="code">sizeof(<span class="type">void *</span>)</code>. 1461 </p></dd><dt><span class="term"><span class="errorname">ENOMEM</span></span></dt><dd><p>Memory allocation error.</p></dd></dl></div><p> 1462 </p><p>The <code class="function">realloc</code>(<em class="parameter"><code></code></em>) function returns a 1463 pointer, possibly identical to <em class="parameter"><code>ptr</code></em>, to the 1464 allocated memory if successful; otherwise a <code class="constant">NULL</code> 1465 pointer is returned, and <code class="varname">errno</code> is set to 1466 <span class="errorname">ENOMEM</span> if the error was the result of an 1467 allocation failure. The <code class="function">realloc</code>(<em class="parameter"><code></code></em>) 1468 function always leaves the original buffer intact when an error occurs. 1469 </p><p>The <code class="function">free</code>(<em class="parameter"><code></code></em>) function returns no 1470 value.</p></div><div class="refsect2" title="Non-standard API"><a name="id2844875"></a><h3>Non-standard API</h3><p>The <code class="function">malloc_usable_size</code>(<em class="parameter"><code></code></em>) function 1471 returns the usable size of the allocation pointed to by 1472 <em class="parameter"><code>ptr</code></em>. </p><p>The <code class="function">mallctl</code>(<em class="parameter"><code></code></em>), 1473 <code class="function">mallctlnametomib</code>(<em class="parameter"><code></code></em>), and 1474 <code class="function">mallctlbymib</code>(<em class="parameter"><code></code></em>) functions return 0 on 1475 success; otherwise they return an error value. The functions will fail 1476 if: 1477 </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 1478 <code class="constant">NULL</code>, and <em class="parameter"><code>newlen</code></em> is too 1479 large or too small. Alternatively, <em class="parameter"><code>*oldlenp</code></em> 1480 is too large or too small; in this case as much data as possible 1481 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 1482 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 1483 <em class="parameter"><code>mib</code></em> specifies an unknown/invalid 1484 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 1485 write read-only value.</p></dd><dt><span class="term"><span class="errorname">EAGAIN</span></span></dt><dd><p>A memory allocation failure 1486 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 1487 not directly related to <code class="function">mallctl*</code>(<em class="parameter"><code></code></em>) 1488 read/write processing.</p></dd></dl></div><p> 1489 </p></div><div class="refsect2" title="Experimental API"><a name="id2845053"></a><h3>Experimental API</h3><p>The <code class="function">allocm</code>(<em class="parameter"><code></code></em>), 1490 <code class="function">rallocm</code>(<em class="parameter"><code></code></em>), 1491 <code class="function">sallocm</code>(<em class="parameter"><code></code></em>), and 1492 <code class="function">dallocm</code>(<em class="parameter"><code></code></em>) functions return 1493 <code class="constant">ALLOCM_SUCCESS</code> on success; otherwise they return an 1494 error value. The <code class="function">allocm</code>(<em class="parameter"><code></code></em>) and 1495 <code class="function">rallocm</code>(<em class="parameter"><code></code></em>) functions will fail if: 1496 </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 1497 available to service the allocation request. The 1498 <code class="function">allocm</code>(<em class="parameter"><code></code></em>) function additionally sets 1499 <em class="parameter"><code>*ptr</code></em> to <code class="constant">NULL</code>, whereas 1500 the <code class="function">rallocm</code>(<em class="parameter"><code></code></em>) function leaves 1501 <code class="constant">*ptr</code> unmodified.</p></dd></dl></div><p> 1502 The <code class="function">rallocm</code>(<em class="parameter"><code></code></em>) function will also 1503 fail if: 1504 </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, 1505 but the reallocation request could not be serviced without moving 1506 the object.</p></dd></dl></div><p> 1507 </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 1508 allocation functions: 1509 </p><div class="variablelist"><dl><dt><span class="term"><code class="envar">MALLOC_CONF</code></span></dt><dd><p>If the environment variable 1510 <code class="envar">MALLOC_CONF</code> is set, the characters it contains 1511 will be interpreted as options.</p></dd></dl></div><p> 1512 </p></div><div class="refsect1" title="EXAMPLES"><a name="examples"></a><h2>EXAMPLES</h2><p>To dump core whenever a problem occurs: 1513 </p><pre class="screen">ln -s 'abort:true' /etc/malloc.conf</pre><p> 1514 </p><p>To specify in the source a chunk size that is 16 MiB: 1515 </p><pre class="programlisting"> 1516malloc_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>, 1517 <span class="citerefentry"><span class="refentrytitle">mmap</span>(2)</span>, 1518 <span class="citerefentry"><span class="refentrytitle">sbrk</span>(2)</span>, 1519 <span class="citerefentry"><span class="refentrytitle">alloca</span>(3)</span>, 1520 <span class="citerefentry"><span class="refentrytitle">atexit</span>(3)</span>, 1521 <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>), 1522 <code class="function">calloc</code>(<em class="parameter"><code></code></em>), 1523 <code class="function">realloc</code>(<em class="parameter"><code></code></em>), and 1524 <code class="function">free</code>(<em class="parameter"><code></code></em>) functions conform to ISO/IEC 1525 9899:1990 (“ISO C90”).</p><p>The <code class="function">posix_memalign</code>(<em class="parameter"><code></code></em>) function conforms 1526 to IEEE Std 1003.1-2001 (“POSIX.1”).</p></div></div></body></html> 1527