1 <html><head><meta http-equiv=
"Content-Type" content=
"text/html; charset=ISO-8859-1"><title>JEMALLOC
</title><meta name=
"generator" content=
"DocBook XSL Stylesheets V1.76.1"></head><body bgcolor=
"white" text=
"black" link=
"#0000FF" vlink=
"#840084" alink=
"#0000FF"><div class=
"refentry" title=
"JEMALLOC"><a name=
"id286949159"></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
3.2.0-
0-g87499f6748ebe4817571e817e9f680ccb5bf54a9. 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=
"id286901505"></a><h3>Standard API
</h3><table border=
"0" summary=
"Function synopsis" cellspacing=
"0" cellpadding=
"0" class=
"funcprototype-table"><tr><td><code class=
"funcdef">void *
<b class=
"fsfunc">malloc
</b>(
</code></td><td>size_t
<var class=
"pdparam">size
</var><code>)
</code>;
</td></tr></table><div class=
"funcprototype-spacer"> </div><table border=
"0" summary=
"Function synopsis" cellspacing=
"0" cellpadding=
"0" class=
"funcprototype-table"><tr><td><code class=
"funcdef">void *
<b class=
"fsfunc">calloc
</b>(
</code></td><td>size_t
<var class=
"pdparam">number
</var>,
</td></tr><tr><td> </td><td>size_t
<var class=
"pdparam">size
</var><code>)
</code>;
</td></tr></table><div class=
"funcprototype-spacer"> </div><table border=
"0" summary=
"Function synopsis" cellspacing=
"0" cellpadding=
"0" class=
"funcprototype-table"><tr><td><code class=
"funcdef">int
<b class=
"fsfunc">posix_memalign
</b>(
</code></td><td>void **
<var class=
"pdparam">ptr
</var>,
</td></tr><tr><td> </td><td>size_t
<var class=
"pdparam">alignment
</var>,
</td></tr><tr><td> </td><td>size_t
<var class=
"pdparam">size
</var><code>)
</code>;
</td></tr></table><div class=
"funcprototype-spacer"> </div><table border=
"0" summary=
"Function synopsis" cellspacing=
"0" cellpadding=
"0" class=
"funcprototype-table"><tr><td><code class=
"funcdef">void *
<b class=
"fsfunc">aligned_alloc
</b>(
</code></td><td>size_t
<var class=
"pdparam">alignment
</var>,
</td></tr><tr><td> </td><td>size_t
<var class=
"pdparam">size
</var><code>)
</code>;
</td></tr></table><div class=
"funcprototype-spacer"> </div><table border=
"0" summary=
"Function synopsis" cellspacing=
"0" cellpadding=
"0" class=
"funcprototype-table"><tr><td><code class=
"funcdef">void *
<b class=
"fsfunc">realloc
</b>(
</code></td><td>void *
<var class=
"pdparam">ptr
</var>,
</td></tr><tr><td> </td><td>size_t
<var class=
"pdparam">size
</var><code>)
</code>;
</td></tr></table><div class=
"funcprototype-spacer"> </div><table border=
"0" summary=
"Function synopsis" cellspacing=
"0" cellpadding=
"0" class=
"funcprototype-table"><tr><td><code class=
"funcdef">void
<b class=
"fsfunc">free
</b>(
</code></td><td>void *
<var class=
"pdparam">ptr
</var><code>)
</code>;
</td></tr></table><div class=
"funcprototype-spacer"> </div></div><div class=
"refsect2" title=
"Non-standard API"><a name=
"id286900549"></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=
"id286900756"></a><h3>Experimental API
</h3><table border=
"0" summary=
"Function synopsis" cellspacing=
"0" cellpadding=
"0" class=
"funcprototype-table"><tr><td><code class=
"funcdef">int
<b class=
"fsfunc">allocm
</b>(
</code></td><td>void **
<var class=
"pdparam">ptr
</var>,
</td></tr><tr><td> </td><td>size_t *
<var class=
"pdparam">rsize
</var>,
</td></tr><tr><td> </td><td>size_t
<var class=
"pdparam">size
</var>,
</td></tr><tr><td> </td><td>int
<var class=
"pdparam">flags
</var><code>)
</code>;
</td></tr></table><div class=
"funcprototype-spacer"> </div><table border=
"0" summary=
"Function synopsis" cellspacing=
"0" cellpadding=
"0" class=
"funcprototype-table"><tr><td><code class=
"funcdef">int
<b class=
"fsfunc">rallocm
</b>(
</code></td><td>void **
<var class=
"pdparam">ptr
</var>,
</td></tr><tr><td> </td><td>size_t *
<var class=
"pdparam">rsize
</var>,
</td></tr><tr><td> </td><td>size_t
<var class=
"pdparam">size
</var>,
</td></tr><tr><td> </td><td>size_t
<var class=
"pdparam">extra
</var>,
</td></tr><tr><td> </td><td>int
<var class=
"pdparam">flags
</var><code>)
</code>;
</td></tr></table><div class=
"funcprototype-spacer"> </div><table border=
"0" summary=
"Function synopsis" cellspacing=
"0" cellpadding=
"0" class=
"funcprototype-table"><tr><td><code class=
"funcdef">int
<b class=
"fsfunc">sallocm
</b>(
</code></td><td>const void *
<var class=
"pdparam">ptr
</var>,
</td></tr><tr><td> </td><td>size_t *
<var class=
"pdparam">rsize
</var>,
</td></tr><tr><td> </td><td>int
<var class=
"pdparam">flags
</var><code>)
</code>;
</td></tr></table><div class=
"funcprototype-spacer"> </div><table border=
"0" summary=
"Function synopsis" cellspacing=
"0" cellpadding=
"0" class=
"funcprototype-table"><tr><td><code class=
"funcdef">int
<b class=
"fsfunc">dallocm
</b>(
</code></td><td>void *
<var class=
"pdparam">ptr
</var>,
</td></tr><tr><td> </td><td>int
<var class=
"pdparam">flags
</var><code>)
</code>;
</td></tr></table><div class=
"funcprototype-spacer"> </div><table border=
"0" summary=
"Function synopsis" cellspacing=
"0" cellpadding=
"0" class=
"funcprototype-table"><tr><td><code class=
"funcdef">int
<b class=
"fsfunc">nallocm
</b>(
</code></td><td>size_t *
<var class=
"pdparam">rsize
</var>,
</td></tr><tr><td> </td><td>size_t
<var class=
"pdparam">size
</var>,
</td></tr><tr><td> </td><td>int
<var class=
"pdparam">flags
</var><code>)
</code>;
</td></tr></table><div class=
"funcprototype-spacer"> </div></div></div></div><div class=
"refsect1" title=
"DESCRIPTION"><a name=
"description"></a><h2>DESCRIPTION
</h2><div class=
"refsect2" title=
"Standard API"><a name=
"id286949297"></a><h3>Standard API
</h3><p>The
<code class=
"function">malloc
</code>(
<em class=
"parameter"><code></code></em>) function allocates
6 <em class=
"parameter"><code>size
</code></em> bytes of uninitialized memory. The allocated
7 space is suitably aligned (after possible pointer coercion) for storage
8 of any type of object.
</p><p>The
<code class=
"function">calloc
</code>(
<em class=
"parameter"><code></code></em>) function allocates
9 space for
<em class=
"parameter"><code>number
</code></em> objects, each
10 <em class=
"parameter"><code>size
</code></em> bytes in length. The result is identical to
11 calling
<code class=
"function">malloc
</code>(
<em class=
"parameter"><code></code></em>) with an argument of
12 <em class=
"parameter"><code>number
</code></em> *
<em class=
"parameter"><code>size
</code></em>, with the
13 exception that the allocated memory is explicitly initialized to zero
14 bytes.
</p><p>The
<code class=
"function">posix_memalign
</code>(
<em class=
"parameter"><code></code></em>) function
15 allocates
<em class=
"parameter"><code>size
</code></em> bytes of memory such that the
16 allocation's base address is an even multiple of
17 <em class=
"parameter"><code>alignment
</code></em>, and returns the allocation in the value
18 pointed to by
<em class=
"parameter"><code>ptr
</code></em>. The requested
19 <em class=
"parameter"><code>alignment
</code></em> must be a power of
2 at least as large
20 as
<code class=
"code">sizeof(
<span class=
"type">void *
</span>)
</code>.
</p><p>The
<code class=
"function">aligned_alloc
</code>(
<em class=
"parameter"><code></code></em>) function
21 allocates
<em class=
"parameter"><code>size
</code></em> bytes of memory such that the
22 allocation's base address is an even multiple of
23 <em class=
"parameter"><code>alignment
</code></em>. The requested
24 <em class=
"parameter"><code>alignment
</code></em> must be a power of
2. Behavior is
25 undefined if
<em class=
"parameter"><code>size
</code></em> is not an integral multiple of
26 <em class=
"parameter"><code>alignment
</code></em>.
</p><p>The
<code class=
"function">realloc
</code>(
<em class=
"parameter"><code></code></em>) function changes the
27 size of the previously allocated memory referenced by
28 <em class=
"parameter"><code>ptr
</code></em> to
<em class=
"parameter"><code>size
</code></em> bytes. The
29 contents of the memory are unchanged up to the lesser of the new and old
30 sizes. If the new size is larger, the contents of the newly allocated
31 portion of the memory are undefined. Upon success, the memory referenced
32 by
<em class=
"parameter"><code>ptr
</code></em> is freed and a pointer to the newly
33 allocated memory is returned. Note that
34 <code class=
"function">realloc
</code>(
<em class=
"parameter"><code></code></em>) may move the memory allocation,
35 resulting in a different return value than
<em class=
"parameter"><code>ptr
</code></em>.
36 If
<em class=
"parameter"><code>ptr
</code></em> is
<code class=
"constant">NULL
</code>, the
37 <code class=
"function">realloc
</code>(
<em class=
"parameter"><code></code></em>) function behaves identically to
38 <code class=
"function">malloc
</code>(
<em class=
"parameter"><code></code></em>) for the specified size.
</p><p>The
<code class=
"function">free
</code>(
<em class=
"parameter"><code></code></em>) function causes the
39 allocated memory referenced by
<em class=
"parameter"><code>ptr
</code></em> to be made
40 available for future allocations. If
<em class=
"parameter"><code>ptr
</code></em> is
41 <code class=
"constant">NULL
</code>, no action occurs.
</p></div><div class=
"refsect2" title=
"Non-standard API"><a name=
"id286949561"></a><h3>Non-standard API
</h3><p>The
<code class=
"function">malloc_usable_size
</code>(
<em class=
"parameter"><code></code></em>) function
42 returns the usable size of the allocation pointed to by
43 <em class=
"parameter"><code>ptr
</code></em>. The return value may be larger than the size
44 that was requested during allocation. The
45 <code class=
"function">malloc_usable_size
</code>(
<em class=
"parameter"><code></code></em>) function is not a
46 mechanism for in-place
<code class=
"function">realloc
</code>(
<em class=
"parameter"><code></code></em>); rather
47 it is provided solely as a tool for introspection purposes. Any
48 discrepancy between the requested allocation size and the size reported
49 by
<code class=
"function">malloc_usable_size
</code>(
<em class=
"parameter"><code></code></em>) should not be
50 depended on, since such behavior is entirely implementation-dependent.
51 </p><p>The
<code class=
"function">malloc_stats_print
</code>(
<em class=
"parameter"><code></code></em>) function
52 writes human-readable summary statistics via the
53 <em class=
"parameter"><code>write_cb
</code></em> callback function pointer and
54 <em class=
"parameter"><code>cbopaque
</code></em> data passed to
55 <em class=
"parameter"><code>write_cb
</code></em>, or
56 <code class=
"function">malloc_message
</code>(
<em class=
"parameter"><code></code></em>) if
57 <em class=
"parameter"><code>write_cb
</code></em> is
<code class=
"constant">NULL
</code>. This
58 function can be called repeatedly. General information that never
59 changes during execution can be omitted by specifying "g" as a character
60 within the
<em class=
"parameter"><code>opts
</code></em> string. Note that
61 <code class=
"function">malloc_message
</code>(
<em class=
"parameter"><code></code></em>) uses the
62 <code class=
"function">mallctl*
</code>(
<em class=
"parameter"><code></code></em>) functions internally, so
63 inconsistent statistics can be reported if multiple threads use these
64 functions simultaneously. If
<code class=
"option">--enable-stats
</code> is
65 specified during configuration,
“m
” and
“a
” can
66 be specified to omit merged arena and per arena statistics, respectively;
67 “b
” and
“l
” can be specified to omit per size
68 class statistics for bins and large objects, respectively. Unrecognized
69 characters are silently ignored. Note that thread caching may prevent
70 some statistics from being completely up to date, since extra locking
71 would be required to merge counters that track thread cache operations.
72 </p><p>The
<code class=
"function">mallctl
</code>(
<em class=
"parameter"><code></code></em>) function provides a
73 general interface for introspecting the memory allocator, as well as
74 setting modifiable parameters and triggering actions. The
75 period-separated
<em class=
"parameter"><code>name
</code></em> argument specifies a
76 location in a tree-structured namespace; see the
<a class=
"xref" href=
"#mallctl_namespace" title=
"MALLCTL NAMESPACE">MALLCTL NAMESPACE
</a> section for
77 documentation on the tree contents. To read a value, pass a pointer via
78 <em class=
"parameter"><code>oldp
</code></em> to adequate space to contain the value, and a
79 pointer to its length via
<em class=
"parameter"><code>oldlenp
</code></em>; otherwise pass
80 <code class=
"constant">NULL
</code> and
<code class=
"constant">NULL
</code>. Similarly, to
81 write a value, pass a pointer to the value via
82 <em class=
"parameter"><code>newp
</code></em>, and its length via
83 <em class=
"parameter"><code>newlen
</code></em>; otherwise pass
<code class=
"constant">NULL
</code>
84 and
<code class=
"constant">0</code>.
</p><p>The
<code class=
"function">mallctlnametomib
</code>(
<em class=
"parameter"><code></code></em>) function
85 provides a way to avoid repeated name lookups for applications that
86 repeatedly query the same portion of the namespace, by translating a name
87 to a
“Management Information Base
” (MIB) that can be passed
88 repeatedly to
<code class=
"function">mallctlbymib
</code>(
<em class=
"parameter"><code></code></em>). Upon
89 successful return from
<code class=
"function">mallctlnametomib
</code>(
<em class=
"parameter"><code></code></em>),
90 <em class=
"parameter"><code>mibp
</code></em> contains an array of
91 <em class=
"parameter"><code>*miblenp
</code></em> integers, where
92 <em class=
"parameter"><code>*miblenp
</code></em> is the lesser of the number of components
93 in
<em class=
"parameter"><code>name
</code></em> and the input value of
94 <em class=
"parameter"><code>*miblenp
</code></em>. Thus it is possible to pass a
95 <em class=
"parameter"><code>*miblenp
</code></em> that is smaller than the number of
96 period-separated name components, which results in a partial MIB that can
97 be used as the basis for constructing a complete MIB. For name
98 components that are integers (e.g. the
2 in
99 <a class=
"link" href=
"#arenas.bin.i.size">
100 "
<code class=
"mallctl">arenas.bin
.2.size
</code>"
102 the corresponding MIB component will always be that integer. Therefore,
103 it is legitimate to construct code like the following: </p><pre class="programlisting
">
110 mallctl("arenas.nbins",
&nbins,
&len, NULL,
0);
113 mallnametomib("arenas.bin
.0.size", mib,
&miblen);
114 for (i =
0; i
< nbins; i++) {
118 len = sizeof(bin_size);
119 mallctlbymib(mib, miblen,
&bin_size,
&len, NULL,
0);
120 /* Do something with bin_size... */
121 }
</pre></div><div class=
"refsect2" title=
"Experimental API"><a name=
"id286949870"></a><h3>Experimental API
</h3><p>The experimental API is subject to change or removal without regard
122 for backward compatibility. If
<code class=
"option">--disable-experimental
</code>
123 is specified during configuration, the experimental API is
124 omitted.
</p><p>The
<code class=
"function">allocm
</code>(
<em class=
"parameter"><code></code></em>),
125 <code class=
"function">rallocm
</code>(
<em class=
"parameter"><code></code></em>),
126 <code class=
"function">sallocm
</code>(
<em class=
"parameter"><code></code></em>),
127 <code class=
"function">dallocm
</code>(
<em class=
"parameter"><code></code></em>), and
128 <code class=
"function">nallocm
</code>(
<em class=
"parameter"><code></code></em>) functions all have a
129 <em class=
"parameter"><code>flags
</code></em> argument that can be used to specify
130 options. The functions only check the options that are contextually
131 relevant. Use bitwise or (
<code class=
"code">|
</code>) operations to
132 specify one or more of the following:
133 </p><div class=
"variablelist"><dl><dt><span class=
"term"><code class=
"constant">ALLOCM_LG_ALIGN(
<em class=
"parameter"><code>la
</code></em>)
134 </code></span></dt><dd><p>Align the memory allocation to start at an address
135 that is a multiple of
<code class=
"code">(
1 <<
136 <em class=
"parameter"><code>la
</code></em>)
</code>. This macro does not validate
137 that
<em class=
"parameter"><code>la
</code></em> is within the valid
138 range.
</p></dd><dt><span class=
"term"><code class=
"constant">ALLOCM_ALIGN(
<em class=
"parameter"><code>a
</code></em>)
139 </code></span></dt><dd><p>Align the memory allocation to start at an address
140 that is a multiple of
<em class=
"parameter"><code>a
</code></em>, where
141 <em class=
"parameter"><code>a
</code></em> is a power of two. This macro does not
142 validate that
<em class=
"parameter"><code>a
</code></em> is a power of
2.
143 </p></dd><dt><span class=
"term"><code class=
"constant">ALLOCM_ZERO
</code></span></dt><dd><p>Initialize newly allocated memory to contain zero
144 bytes. In the growing reallocation case, the real size prior to
145 reallocation defines the boundary between untouched bytes and those
146 that are initialized to contain zero bytes. If this option is
147 absent, newly allocated memory is uninitialized.
</p></dd><dt><span class=
"term"><code class=
"constant">ALLOCM_NO_MOVE
</code></span></dt><dd><p>For reallocation, fail rather than moving the
148 object. This constraint can apply to both growth and
149 shrinkage.
</p></dd><dt><span class=
"term"><code class=
"constant">ALLOCM_ARENA(
<em class=
"parameter"><code>a
</code></em>)
150 </code></span></dt><dd><p>Use the arena specified by the index
151 <em class=
"parameter"><code>a
</code></em>. This macro does not validate that
152 <em class=
"parameter"><code>a
</code></em> specifies an arena in the valid
153 range.
</p></dd></dl></div><p>
154 </p><p>The
<code class=
"function">allocm
</code>(
<em class=
"parameter"><code></code></em>) function allocates at
155 least
<em class=
"parameter"><code>size
</code></em> bytes of memory, sets
156 <em class=
"parameter"><code>*ptr
</code></em> to the base address of the allocation, and
157 sets
<em class=
"parameter"><code>*rsize
</code></em> to the real size of the allocation if
158 <em class=
"parameter"><code>rsize
</code></em> is not
<code class=
"constant">NULL
</code>. Behavior
159 is undefined if
<em class=
"parameter"><code>size
</code></em> is
160 <code class=
"constant">0</code>.
</p><p>The
<code class=
"function">rallocm
</code>(
<em class=
"parameter"><code></code></em>) function resizes the
161 allocation at
<em class=
"parameter"><code>*ptr
</code></em> to be at least
162 <em class=
"parameter"><code>size
</code></em> bytes, sets
<em class=
"parameter"><code>*ptr
</code></em> to
163 the base address of the allocation if it moved, and sets
164 <em class=
"parameter"><code>*rsize
</code></em> to the real size of the allocation if
165 <em class=
"parameter"><code>rsize
</code></em> is not
<code class=
"constant">NULL
</code>. If
166 <em class=
"parameter"><code>extra
</code></em> is non-zero, an attempt is made to resize
167 the allocation to be at least
<code class=
"code"><em class=
"parameter"><code>size
</code></em> +
168 <em class=
"parameter"><code>extra
</code></em>)
</code> bytes, though inability to allocate
169 the extra byte(s) will not by itself result in failure. Behavior is
170 undefined if
<em class=
"parameter"><code>size
</code></em> is
<code class=
"constant">0</code>, or if
171 <code class=
"code">(
<em class=
"parameter"><code>size
</code></em> +
172 <em class=
"parameter"><code>extra
</code></em> >
173 <code class=
"constant">SIZE_T_MAX
</code>)
</code>.
</p><p>The
<code class=
"function">sallocm
</code>(
<em class=
"parameter"><code></code></em>) function sets
174 <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
175 memory referenced by
<em class=
"parameter"><code>ptr
</code></em> to be made available for
176 future allocations.
</p><p>The
<code class=
"function">nallocm
</code>(
<em class=
"parameter"><code></code></em>) function allocates no
177 memory, but it performs the same size computation as the
178 <code class=
"function">allocm
</code>(
<em class=
"parameter"><code></code></em>) function, and if
179 <em class=
"parameter"><code>rsize
</code></em> is not
<code class=
"constant">NULL
</code> it sets
180 <em class=
"parameter"><code>*rsize
</code></em> to the real size of the allocation that
181 would result from the equivalent
<code class=
"function">allocm
</code>(
<em class=
"parameter"><code></code></em>)
182 function call. Behavior is undefined if
183 <em class=
"parameter"><code>size
</code></em> is
<code class=
"constant">0</code>.
</p></div></div><div class=
"refsect1" title=
"TUNING"><a name=
"tuning"></a><h2>TUNING
</h2><p>Once, when the first call is made to one of the memory allocation
184 routines, the allocator initializes its internals based in part on various
185 options that can be specified at compile- or run-time.
</p><p>The string pointed to by the global variable
186 <code class=
"varname">malloc_conf
</code>, the
“name
” of the file
187 referenced by the symbolic link named
<code class=
"filename">/etc/malloc.conf
</code>, and the value of the
188 environment variable
<code class=
"envar">MALLOC_CONF
</code>, will be interpreted, in
189 that order, from left to right as options.
</p><p>An options string is a comma-separated list of option:value pairs.
190 There is one key corresponding to each
<a class=
"link" href=
"#opt.abort">
191 "
<code class=
"mallctl">opt.*
</code>"
192 </a> mallctl (see the <a class="xref
" href="#mallctl_namespace
" title="MALLCTL NAMESPACE
">MALLCTL NAMESPACE</a> section for options
193 documentation). For example, <code class="literal
">abort:true,narenas:1</code> sets
194 the <a class="link
" href="#opt.abort
">
195 "<code class=
"mallctl">opt.abort
</code>"
196 </a> and <a class="link
" href="#opt.narenas
">
197 "<code class=
"mallctl">opt.narenas
</code>"
199 options have boolean values (true/false), others have integer values (base
200 8, 10, or 16, depending on prefix), and yet others have raw string
201 values.</p></div><div class="refsect1
" title="IMPLEMENTATION NOTES
"><a name="implementation_notes
"></a><h2>IMPLEMENTATION NOTES</h2><p>Traditionally, allocators have used
202 <span class="citerefentry
"><span class="refentrytitle
">sbrk</span>(2)</span> to obtain memory, which is
203 suboptimal for several reasons, including race conditions, increased
204 fragmentation, and artificial limitations on maximum usable memory. If
205 <code class="option
">--enable-dss</code> is specified during configuration, this
206 allocator uses both <span class="citerefentry
"><span class="refentrytitle
">mmap</span>(2)</span> and
207 <span class="citerefentry
"><span class="refentrytitle
">sbrk</span>(2)</span>, in that order of preference;
208 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
209 contention for threaded programs on multi-processor systems. This works
210 well with regard to threading scalability, but incurs some costs. There is
211 a small fixed per-arena overhead, and additionally, arenas manage memory
212 completely independently of each other, which means a small fixed increase
213 in overall memory fragmentation. These overheads are not generally an
214 issue, given the number of arenas normally used. Note that using
215 substantially more arenas than the default is not likely to improve
216 performance, mainly due to reduced cache performance. However, it may make
217 sense to reduce the number of arenas if an application does not make much
218 use of the allocation functions.</p><p>In addition to multiple arenas, unless
219 <code class="option
">--disable-tcache</code> is specified during configuration, this
220 allocator supports thread-specific caching for small and large objects, in
221 order to make it possible to completely avoid synchronization for most
222 allocation requests. Such caching allows very fast allocation in the
223 common case, but it increases memory usage and fragmentation, since a
224 bounded number of objects can remain allocated in each thread cache.</p><p>Memory is conceptually broken into equal-sized chunks, where the
225 chunk size is a power of two that is greater than the page size. Chunks
226 are always aligned to multiples of the chunk size. This alignment makes it
227 possible to find metadata for user objects very quickly.</p><p>User objects are broken into three categories according to size:
228 small, large, and huge. Small objects are smaller than one page. Large
229 objects are smaller than the chunk size. Huge objects are a multiple of
230 the chunk size. Small and large objects are managed by arenas; huge
231 objects are managed separately in a single data structure that is shared by
232 all threads. Huge objects are used by applications infrequently enough
233 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
234 contiguous pages (unused, backing a set of small objects, or backing one
235 large object). The combination of chunk alignment and chunk page maps
236 makes it possible to determine all metadata regarding small and large
237 allocations in constant time.</p><p>Small objects are managed in groups by page runs. Each run maintains
238 a frontier and free list to track which regions are in use. Allocation
239 requests that are no more than half the quantum (8 or 16, depending on
240 architecture) are rounded up to the nearest power of two that is at least
241 <code class="code
">sizeof(<span class="type
">double</span>)</code>. All other small
242 object size classes are multiples of the quantum, spaced such that internal
243 fragmentation is limited to approximately 25% for all but the smallest size
244 classes. Allocation requests that are larger than the maximum small size
245 class, but small enough to fit in an arena-managed chunk (see the <a class="link
" href="#opt.lg_chunk
">
246 "<code class=
"mallctl">opt.lg_chunk
</code>"
248 rounded up to the nearest run size. Allocation requests that are too large
249 to fit in an arena-managed chunk are rounded up to the nearest multiple of
250 the chunk size.</p><p>Allocations are packed tightly together, which can be an issue for
251 multi-threaded applications. If you need to assure that allocations do not
252 suffer from cacheline sharing, round your allocation requests up to the
253 nearest multiple of the cacheline size, or specify cacheline alignment when
254 allocating.</p><p>Assuming 4 MiB chunks, 4 KiB pages, and a 16-byte quantum on a 64-bit
255 system, the size classes in each category are as shown in <a class="xref
" href="#size_classes
" title="Table
1. Size classes
">Table 1</a>.</p><div class="table
"><a name="size_classes
"></a><p class="title
"><b>Table 1. Size classes</b></p><div class="table-contents
"><table summary="Size classes
" border="1"><colgroup><col align="left
" class="c1
"><col align="right
" class="c2
"><col align="left
" class="c3
"></colgroup><thead><tr><th align="left
">Category</th><th align="right
">Spacing</th><th align="left
">Size</th></tr></thead><tbody><tr><td rowspan="7" align="left
">Small</td><td align="right
">lg</td><td align="left
">[8]</td></tr><tr><td align="right
">16</td><td align="left
">[16, 32, 48, ..., 128]</td></tr><tr><td align="right
">32</td><td align="left
">[160, 192, 224, 256]</td></tr><tr><td align="right
">64</td><td align="left
">[320, 384, 448, 512]</td></tr><tr><td align="right
">128</td><td align="left
">[640, 768, 896, 1024]</td></tr><tr><td align="right
">256</td><td align="left
">[1280, 1536, 1792, 2048]</td></tr><tr><td align="right
">512</td><td align="left
">[2560, 3072, 3584]</td></tr><tr><td align="left
">Large</td><td align="right
">4 KiB</td><td align="left
">[4 KiB, 8 KiB, 12 KiB, ..., 4072 KiB]</td></tr><tr><td align="left
">Huge</td><td align="right
">4 MiB</td><td align="left
">[4 MiB, 8 MiB, 12 MiB, ...]</td></tr></tbody></table></div></div><br class="table-break
"></div><div class="refsect1
" title="MALLCTL NAMESPACE
"><a name="mallctl_namespace
"></a><h2>MALLCTL NAMESPACE</h2><p>The following names are defined in the namespace accessible via the
256 <code class="function
">mallctl*</code>(<em class="parameter
"><code></code></em>) functions. Value types are
257 specified in parentheses, their readable/writable statuses are encoded as
258 <code class="literal
">rw</code>, <code class="literal
">r-</code>, <code class="literal
">-w</code>, or
259 <code class="literal
">--</code>, and required build configuration flags follow, if
260 any. A name element encoded as <code class="literal
"><i></code> or
261 <code class="literal
"><j></code> indicates an integer component, where the
262 integer varies from 0 to some upper value that must be determined via
263 introspection. In the case of
264 "<code class=
"mallctl">stats.arenas.
<i
>.*
</code>"
266 <code class="literal
"><i></code> equal to <a class="link
" href="#arenas.narenas
">
267 "<code class=
"mallctl">arenas.narenas
</code>"
269 used to access the summation of statistics from all arenas. Take special
270 note of the <a class="link
" href="#epoch
">
271 "<code class=
"mallctl">epoch
</code>"
273 which controls refreshing of cached dynamic statistics.</p><div class="variablelist
"><dl><dt><span class="term
">
275 "<code class=
"mallctl">version
</code>"
277 (<span class="type
">const char *</span>)
278 <code class="literal
">r-</code>
279 </span></dt><dd><p>Return the jemalloc version string.</p></dd><dt><a name="epoch
"></a><span class="term
">
281 "<code class=
"mallctl">epoch
</code>"
283 (<span class="type
">uint64_t</span>)
284 <code class="literal
">rw</code>
285 </span></dt><dd><p>If a value is passed in, refresh the data from which
286 the <code class="function
">mallctl*</code>(<em class="parameter
"><code></code></em>) functions report values,
287 and increment the epoch. Return the current epoch. This is useful for
288 detecting whether another thread caused a refresh.</p></dd><dt><span class="term
">
290 "<code class=
"mallctl">config.debug
</code>"
292 (<span class="type
">bool</span>)
293 <code class="literal
">r-</code>
294 </span></dt><dd><p><code class="option
">--enable-debug</code> was specified during
295 build configuration.</p></dd><dt><span class="term
">
297 "<code class=
"mallctl">config.dss
</code>"
299 (<span class="type
">bool</span>)
300 <code class="literal
">r-</code>
301 </span></dt><dd><p><code class="option
">--enable-dss</code> was specified during
302 build configuration.</p></dd><dt><span class="term
">
304 "<code class=
"mallctl">config.fill
</code>"
306 (<span class="type
">bool</span>)
307 <code class="literal
">r-</code>
308 </span></dt><dd><p><code class="option
">--enable-fill</code> was specified during
309 build configuration.</p></dd><dt><span class="term
">
311 "<code class=
"mallctl">config.lazy_lock
</code>"
313 (<span class="type
">bool</span>)
314 <code class="literal
">r-</code>
315 </span></dt><dd><p><code class="option
">--enable-lazy-lock</code> was specified
316 during build configuration.</p></dd><dt><span class="term
">
318 "<code class=
"mallctl">config.mremap
</code>"
320 (<span class="type
">bool</span>)
321 <code class="literal
">r-</code>
322 </span></dt><dd><p><code class="option
">--enable-mremap</code> was specified during
323 build configuration.</p></dd><dt><span class="term
">
325 "<code class=
"mallctl">config.munmap
</code>"
327 (<span class="type
">bool</span>)
328 <code class="literal
">r-</code>
329 </span></dt><dd><p><code class="option
">--enable-munmap</code> was specified during
330 build configuration.</p></dd><dt><span class="term
">
332 "<code class=
"mallctl">config.prof
</code>"
334 (<span class="type
">bool</span>)
335 <code class="literal
">r-</code>
336 </span></dt><dd><p><code class="option
">--enable-prof</code> was specified during
337 build configuration.</p></dd><dt><span class="term
">
339 "<code class=
"mallctl">config.prof_libgcc
</code>"
341 (<span class="type
">bool</span>)
342 <code class="literal
">r-</code>
343 </span></dt><dd><p><code class="option
">--disable-prof-libgcc</code> was not
344 specified during build configuration.</p></dd><dt><span class="term
">
346 "<code class=
"mallctl">config.prof_libunwind
</code>"
348 (<span class="type
">bool</span>)
349 <code class="literal
">r-</code>
350 </span></dt><dd><p><code class="option
">--enable-prof-libunwind</code> was specified
351 during build configuration.</p></dd><dt><span class="term
">
353 "<code class=
"mallctl">config.stats
</code>"
355 (<span class="type
">bool</span>)
356 <code class="literal
">r-</code>
357 </span></dt><dd><p><code class="option
">--enable-stats</code> was specified during
358 build configuration.</p></dd><dt><span class="term
">
360 "<code class=
"mallctl">config.tcache
</code>"
362 (<span class="type
">bool</span>)
363 <code class="literal
">r-</code>
364 </span></dt><dd><p><code class="option
">--disable-tcache</code> was not specified
365 during build configuration.</p></dd><dt><span class="term
">
367 "<code class=
"mallctl">config.tls
</code>"
369 (<span class="type
">bool</span>)
370 <code class="literal
">r-</code>
371 </span></dt><dd><p><code class="option
">--disable-tls</code> was not specified during
372 build configuration.</p></dd><dt><span class="term
">
374 "<code class=
"mallctl">config.utrace
</code>"
376 (<span class="type
">bool</span>)
377 <code class="literal
">r-</code>
378 </span></dt><dd><p><code class="option
">--enable-utrace</code> was specified during
379 build configuration.</p></dd><dt><span class="term
">
381 "<code class=
"mallctl">config.valgrind
</code>"
383 (<span class="type
">bool</span>)
384 <code class="literal
">r-</code>
385 </span></dt><dd><p><code class="option
">--enable-valgrind</code> was specified during
386 build configuration.</p></dd><dt><span class="term
">
388 "<code class=
"mallctl">config.xmalloc
</code>"
390 (<span class="type
">bool</span>)
391 <code class="literal
">r-</code>
392 </span></dt><dd><p><code class="option
">--enable-xmalloc</code> was specified during
393 build configuration.</p></dd><dt><a name="opt.abort
"></a><span class="term
">
395 "<code class=
"mallctl">opt.abort
</code>"
397 (<span class="type
">bool</span>)
398 <code class="literal
">r-</code>
399 </span></dt><dd><p>Abort-on-warning enabled/disabled. If true, most
400 warnings are fatal. The process will call
401 <span class="citerefentry
"><span class="refentrytitle
">abort</span>(3)</span> in these cases. This option is
402 disabled by default unless <code class="option
">--enable-debug</code> is
403 specified during configuration, in which case it is enabled by default.
404 </p></dd><dt><a name="opt.lg_chunk
"></a><span class="term
">
406 "<code class=
"mallctl">opt.lg_chunk
</code>"
408 (<span class="type
">size_t</span>)
409 <code class="literal
">r-</code>
410 </span></dt><dd><p>Virtual memory chunk size (log base 2). The default
411 chunk size is 4 MiB (2^22).</p></dd><dt><a name="opt.dss
"></a><span class="term
">
413 "<code class=
"mallctl">opt.dss
</code>"
415 (<span class="type
">const char *</span>)
416 <code class="literal
">r-</code>
417 </span></dt><dd><p>dss (<span class="citerefentry
"><span class="refentrytitle
">sbrk</span>(2)</span>) allocation precedence as
418 related to <span class="citerefentry
"><span class="refentrytitle
">mmap</span>(2)</span> allocation. The following
419 settings are supported: “disabled”, “primary”,
420 and “secondary” (default).</p></dd><dt><a name="opt.narenas
"></a><span class="term
">
422 "<code class=
"mallctl">opt.narenas
</code>"
424 (<span class="type
">size_t</span>)
425 <code class="literal
">r-</code>
426 </span></dt><dd><p>Maximum number of arenas to use for automatic
427 multiplexing of threads and arenas. The default is four times the
428 number of CPUs, or one if there is a single CPU.</p></dd><dt><a name="opt.lg_dirty_mult
"></a><span class="term
">
430 "<code class=
"mallctl">opt.lg_dirty_mult
</code>"
432 (<span class="type
">ssize_t</span>)
433 <code class="literal
">r-</code>
434 </span></dt><dd><p>Per-arena minimum ratio (log base 2) of active to dirty
435 pages. Some dirty unused pages may be allowed to accumulate, within
436 the limit set by the ratio (or one chunk worth of dirty pages,
437 whichever is greater), before informing the kernel about some of those
438 pages via <span class="citerefentry
"><span class="refentrytitle
">madvise</span>(2)</span> or a similar system call. This
439 provides the kernel with sufficient information to recycle dirty pages
440 if physical memory becomes scarce and the pages remain unused. The
441 default minimum ratio is 8:1 (2^3:1); an option value of -1 will
442 disable dirty page purging.</p></dd><dt><a name="opt.stats_print
"></a><span class="term
">
444 "<code class=
"mallctl">opt.stats_print
</code>"
446 (<span class="type
">bool</span>)
447 <code class="literal
">r-</code>
448 </span></dt><dd><p>Enable/disable statistics printing at exit. If
449 enabled, the <code class="function
">malloc_stats_print</code>(<em class="parameter
"><code></code></em>)
450 function is called at program exit via an
451 <span class="citerefentry
"><span class="refentrytitle
">atexit</span>(3)</span> function. If
452 <code class="option
">--enable-stats</code> is specified during configuration, this
453 has the potential to cause deadlock for a multi-threaded process that
454 exits while one or more threads are executing in the memory allocation
455 functions. Therefore, this option should only be used with care; it is
456 primarily intended as a performance tuning aid during application
457 development. This option is disabled by default.</p></dd><dt><a name="opt.junk
"></a><span class="term
">
459 "<code class=
"mallctl">opt.junk
</code>"
461 (<span class="type
">bool</span>)
462 <code class="literal
">r-</code>
463 [<code class="option
">--enable-fill</code>]
464 </span></dt><dd><p>Junk filling enabled/disabled. If enabled, each byte
465 of uninitialized allocated memory will be initialized to
466 <code class="literal
">0xa5</code>. All deallocated memory will be initialized to
467 <code class="literal
">0x5a</code>. This is intended for debugging and will
468 impact performance negatively. This option is disabled by default
469 unless <code class="option
">--enable-debug</code> is specified during
470 configuration, in which case it is enabled by default unless running
471 inside <a class="ulink
" href="http://valgrind.org/
" target="_top
">Valgrind</a>.</p></dd><dt><a name="opt.quarantine
"></a><span class="term
">
473 "<code class=
"mallctl">opt.quarantine
</code>"
475 (<span class="type
">size_t</span>)
476 <code class="literal
">r-</code>
477 [<code class="option
">--enable-fill</code>]
478 </span></dt><dd><p>Per thread quarantine size in bytes. If non-zero, each
479 thread maintains a FIFO object quarantine that stores up to the
480 specified number of bytes of memory. The quarantined memory is not
481 freed until it is released from quarantine, though it is immediately
482 junk-filled if the <a class="link
" href="#opt.junk
">
483 "<code class=
"mallctl">opt.junk
</code>"
485 enabled. This feature is of particular use in combination with <a class="ulink
" href="http://valgrind.org/
" target="_top
">Valgrind</a>, which can detect attempts
486 to access quarantined objects. This is intended for debugging and will
487 impact performance negatively. The default quarantine size is 0 unless
488 running inside Valgrind, in which case the default is 16
489 MiB.</p></dd><dt><a name="opt.redzone
"></a><span class="term
">
491 "<code class=
"mallctl">opt.redzone
</code>"
493 (<span class="type
">bool</span>)
494 <code class="literal
">r-</code>
495 [<code class="option
">--enable-fill</code>]
496 </span></dt><dd><p>Redzones enabled/disabled. If enabled, small
497 allocations have redzones before and after them. Furthermore, if the
498 <a class="link
" href="#opt.junk
">
499 "<code class=
"mallctl">opt.junk
</code>"
501 enabled, the redzones are checked for corruption during deallocation.
502 However, the primary intended purpose of this feature is to be used in
503 combination with <a class="ulink
" href="http://valgrind.org/
" target="_top
">Valgrind</a>,
504 which needs redzones in order to do effective buffer overflow/underflow
505 detection. This option is intended for debugging and will impact
506 performance negatively. This option is disabled by
507 default unless running inside Valgrind.</p></dd><dt><a name="opt.zero
"></a><span class="term
">
509 "<code class=
"mallctl">opt.zero
</code>"
511 (<span class="type
">bool</span>)
512 <code class="literal
">r-</code>
513 [<code class="option
">--enable-fill</code>]
514 </span></dt><dd><p>Zero filling enabled/disabled. If enabled, each byte
515 of uninitialized allocated memory will be initialized to 0. Note that
516 this initialization only happens once for each byte, so
517 <code class="function
">realloc</code>(<em class="parameter
"><code></code></em>) and
518 <code class="function
">rallocm</code>(<em class="parameter
"><code></code></em>) calls do not zero memory that
519 was previously allocated. This is intended for debugging and will
520 impact performance negatively. This option is disabled by default.
521 </p></dd><dt><a name="opt.utrace
"></a><span class="term
">
523 "<code class=
"mallctl">opt.utrace
</code>"
525 (<span class="type
">bool</span>)
526 <code class="literal
">r-</code>
527 [<code class="option
">--enable-utrace</code>]
528 </span></dt><dd><p>Allocation tracing based on
529 <span class="citerefentry
"><span class="refentrytitle
">utrace</span>(2)</span> enabled/disabled. This option
530 is disabled by default.</p></dd><dt><a name="opt.valgrind
"></a><span class="term
">
532 "<code class=
"mallctl">opt.valgrind
</code>"
534 (<span class="type
">bool</span>)
535 <code class="literal
">r-</code>
536 [<code class="option
">--enable-valgrind</code>]
537 </span></dt><dd><p><a class="ulink
" href="http://valgrind.org/
" target="_top
">Valgrind</a>
538 support enabled/disabled. This option is vestigal because jemalloc
539 auto-detects whether it is running inside Valgrind. This option is
540 disabled by default, unless running inside Valgrind.</p></dd><dt><a name="opt.xmalloc
"></a><span class="term
">
542 "<code class=
"mallctl">opt.xmalloc
</code>"
544 (<span class="type
">bool</span>)
545 <code class="literal
">r-</code>
546 [<code class="option
">--enable-xmalloc</code>]
547 </span></dt><dd><p>Abort-on-out-of-memory enabled/disabled. If enabled,
548 rather than returning failure for any allocation function, display a
549 diagnostic message on <code class="constant
">STDERR_FILENO</code> and cause the
550 program to drop core (using
551 <span class="citerefentry
"><span class="refentrytitle
">abort</span>(3)</span>). If an application is
552 designed to depend on this behavior, set the option at compile time by
553 including the following in the source code:
554 </p><pre class="programlisting
">
555 malloc_conf = "xmalloc:true";
</pre><p>
556 This option is disabled by default.
</p></dd><dt><a name=
"opt.tcache"></a><span class=
"term">
558 "
<code class=
"mallctl">opt.tcache
</code>"
560 (<span class="type
">bool</span>)
561 <code class="literal
">r-</code>
562 [<code class="option
">--enable-tcache</code>]
563 </span></dt><dd><p>Thread-specific caching enabled/disabled. When there
564 are multiple threads, each thread uses a thread-specific cache for
565 objects up to a certain size. Thread-specific caching allows many
566 allocations to be satisfied without performing any thread
567 synchronization, at the cost of increased memory use. See the
568 <a class="link
" href="#opt.lg_tcache_max
">
569 "<code class=
"mallctl">opt.lg_tcache_max
</code>"
571 option for related tuning information. This option is enabled by
572 default unless running inside <a class="ulink
" href="http://valgrind.org/
" target="_top
">Valgrind</a>.</p></dd><dt><a name="opt.lg_tcache_max
"></a><span class="term
">
574 "<code class=
"mallctl">opt.lg_tcache_max
</code>"
576 (<span class="type
">size_t</span>)
577 <code class="literal
">r-</code>
578 [<code class="option
">--enable-tcache</code>]
579 </span></dt><dd><p>Maximum size class (log base 2) to cache in the
580 thread-specific cache. At a minimum, all small size classes are
581 cached, and at a maximum all large size classes are cached. The
582 default maximum is 32 KiB (2^15).</p></dd><dt><a name="opt.prof
"></a><span class="term
">
584 "<code class=
"mallctl">opt.prof
</code>"
586 (<span class="type
">bool</span>)
587 <code class="literal
">r-</code>
588 [<code class="option
">--enable-prof</code>]
589 </span></dt><dd><p>Memory profiling enabled/disabled. If enabled, profile
590 memory allocation activity. See the <a class="link
" href="#opt.prof_active
">
591 "<code class=
"mallctl">opt.prof_active
</code>"
593 option for on-the-fly activation/deactivation. See the <a class="link
" href="#opt.lg_prof_sample
">
594 "<code class=
"mallctl">opt.lg_prof_sample
</code>"
596 option for probabilistic sampling control. See the <a class="link
" href="#opt.prof_accum
">
597 "<code class=
"mallctl">opt.prof_accum
</code>"
599 option for control of cumulative sample reporting. See the <a class="link
" href="#opt.lg_prof_interval
">
600 "<code class=
"mallctl">opt.lg_prof_interval
</code>"
602 option for information on interval-triggered profile dumping, the <a class="link
" href="#opt.prof_gdump
">
603 "<code class=
"mallctl">opt.prof_gdump
</code>"
605 option for information on high-water-triggered profile dumping, and the
606 <a class="link
" href="#opt.prof_final
">
607 "<code class=
"mallctl">opt.prof_final
</code>"
609 option for final profile dumping. Profile output is compatible with
610 the included <span class="command
"><strong>pprof</strong></span> Perl script, which originates
611 from the <a class="ulink
" href="http://code.google.com/p/gperftools/
" target="_top
">gperftools
612 package</a>.</p></dd><dt><a name="opt.prof_prefix
"></a><span class="term
">
614 "<code class=
"mallctl">opt.prof_prefix
</code>"
616 (<span class="type
">const char *</span>)
617 <code class="literal
">r-</code>
618 [<code class="option
">--enable-prof</code>]
619 </span></dt><dd><p>Filename prefix for profile dumps. If the prefix is
620 set to the empty string, no automatic dumps will occur; this is
621 primarily useful for disabling the automatic final heap dump (which
622 also disables leak reporting, if enabled). The default prefix is
623 <code class="filename
">jeprof</code>.</p></dd><dt><a name="opt.prof_active
"></a><span class="term
">
625 "<code class=
"mallctl">opt.prof_active
</code>"
627 (<span class="type
">bool</span>)
628 <code class="literal
">r-</code>
629 [<code class="option
">--enable-prof</code>]
630 </span></dt><dd><p>Profiling activated/deactivated. This is a secondary
631 control mechanism that makes it possible to start the application with
632 profiling enabled (see the <a class="link
" href="#opt.prof
">
633 "<code class=
"mallctl">opt.prof
</code>"
635 inactive, then toggle profiling at any time during program execution
636 with the <a class="link
" href="#prof.active
">
637 "<code class=
"mallctl">prof.active
</code>"
639 This option is enabled by default.</p></dd><dt><a name="opt.lg_prof_sample
"></a><span class="term
">
641 "<code class=
"mallctl">opt.lg_prof_sample
</code>"
643 (<span class="type
">ssize_t</span>)
644 <code class="literal
">r-</code>
645 [<code class="option
">--enable-prof</code>]
646 </span></dt><dd><p>Average interval (log base 2) between allocation
647 samples, as measured in bytes of allocation activity. Increasing the
648 sampling interval decreases profile fidelity, but also decreases the
649 computational overhead. The default sample interval is 512 KiB (2^19
650 B).</p></dd><dt><a name="opt.prof_accum
"></a><span class="term
">
652 "<code class=
"mallctl">opt.prof_accum
</code>"
654 (<span class="type
">bool</span>)
655 <code class="literal
">r-</code>
656 [<code class="option
">--enable-prof</code>]
657 </span></dt><dd><p>Reporting of cumulative object/byte counts in profile
658 dumps enabled/disabled. If this option is enabled, every unique
659 backtrace must be stored for the duration of execution. Depending on
660 the application, this can impose a large memory overhead, and the
661 cumulative counts are not always of interest. This option is disabled
662 by default.</p></dd><dt><a name="opt.lg_prof_interval
"></a><span class="term
">
664 "<code class=
"mallctl">opt.lg_prof_interval
</code>"
666 (<span class="type
">ssize_t</span>)
667 <code class="literal
">r-</code>
668 [<code class="option
">--enable-prof</code>]
669 </span></dt><dd><p>Average interval (log base 2) between memory profile
670 dumps, as measured in bytes of allocation activity. The actual
671 interval between dumps may be sporadic because decentralized allocation
672 counters are used to avoid synchronization bottlenecks. Profiles are
673 dumped to files named according to the pattern
674 <code class="filename
"><prefix>.<pid>.<seq>.i<iseq>.heap</code>,
675 where <code class="literal
"><prefix></code> is controlled by the
676 <a class="link
" href="#opt.prof_prefix
">
677 "<code class=
"mallctl">opt.prof_prefix
</code>"
679 option. By default, interval-triggered profile dumping is disabled
681 </p></dd><dt><a name="opt.prof_gdump
"></a><span class="term
">
683 "<code class=
"mallctl">opt.prof_gdump
</code>"
685 (<span class="type
">bool</span>)
686 <code class="literal
">r-</code>
687 [<code class="option
">--enable-prof</code>]
688 </span></dt><dd><p>Trigger a memory profile dump every time the total
689 virtual memory exceeds the previous maximum. Profiles are dumped to
690 files named according to the pattern
691 <code class="filename
"><prefix>.<pid>.<seq>.u<useq>.heap</code>,
692 where <code class="literal
"><prefix></code> is controlled by the <a class="link
" href="#opt.prof_prefix
">
693 "<code class=
"mallctl">opt.prof_prefix
</code>"
695 option. This option is disabled by default.</p></dd><dt><a name="opt.prof_final
"></a><span class="term
">
697 "<code class=
"mallctl">opt.prof_final
</code>"
699 (<span class="type
">bool</span>)
700 <code class="literal
">r-</code>
701 [<code class="option
">--enable-prof</code>]
702 </span></dt><dd><p>Use an
703 <span class="citerefentry
"><span class="refentrytitle
">atexit</span>(3)</span> function to dump final memory
704 usage to a file named according to the pattern
705 <code class="filename
"><prefix>.<pid>.<seq>.f.heap</code>,
706 where <code class="literal
"><prefix></code> is controlled by the <a class="link
" href="#opt.prof_prefix
">
707 "<code class=
"mallctl">opt.prof_prefix
</code>"
709 option. This option is enabled by default.</p></dd><dt><a name="opt.prof_leak
"></a><span class="term
">
711 "<code class=
"mallctl">opt.prof_leak
</code>"
713 (<span class="type
">bool</span>)
714 <code class="literal
">r-</code>
715 [<code class="option
">--enable-prof</code>]
716 </span></dt><dd><p>Leak reporting enabled/disabled. If enabled, use an
717 <span class="citerefentry
"><span class="refentrytitle
">atexit</span>(3)</span> function to report memory leaks
718 detected by allocation sampling. See the
719 <a class="link
" href="#opt.prof
">
720 "<code class=
"mallctl">opt.prof
</code>"
722 information on analyzing heap profile output. This option is disabled
723 by default.</p></dd><dt><span class="term
">
725 "<code class=
"mallctl">thread.arena
</code>"
727 (<span class="type
">unsigned</span>)
728 <code class="literal
">rw</code>
729 </span></dt><dd><p>Get or set the arena associated with the calling
730 thread. If the specified arena was not initialized beforehand (see the
731 <a class="link
" href="#arenas.initialized
">
732 "<code class=
"mallctl">arenas.initialized
</code>"
734 mallctl), it will be automatically initialized as a side effect of
735 calling this interface.</p></dd><dt><a name="thread.allocated
"></a><span class="term
">
737 "<code class=
"mallctl">thread.allocated
</code>"
739 (<span class="type
">uint64_t</span>)
740 <code class="literal
">r-</code>
741 [<code class="option
">--enable-stats</code>]
742 </span></dt><dd><p>Get the total number of bytes ever allocated by the
743 calling thread. This counter has the potential to wrap around; it is
744 up to the application to appropriately interpret the counter in such
745 cases.</p></dd><dt><span class="term
">
747 "<code class=
"mallctl">thread.allocatedp
</code>"
749 (<span class="type
">uint64_t *</span>)
750 <code class="literal
">r-</code>
751 [<code class="option
">--enable-stats</code>]
752 </span></dt><dd><p>Get a pointer to the the value that is returned by the
753 <a class="link
" href="#thread.allocated
">
754 "<code class=
"mallctl">thread.allocated
</code>"
756 mallctl. This is useful for avoiding the overhead of repeated
757 <code class="function
">mallctl*</code>(<em class="parameter
"><code></code></em>) calls.</p></dd><dt><a name="thread.deallocated
"></a><span class="term
">
759 "<code class=
"mallctl">thread.deallocated
</code>"
761 (<span class="type
">uint64_t</span>)
762 <code class="literal
">r-</code>
763 [<code class="option
">--enable-stats</code>]
764 </span></dt><dd><p>Get the total number of bytes ever deallocated by the
765 calling thread. This counter has the potential to wrap around; it is
766 up to the application to appropriately interpret the counter in such
767 cases.</p></dd><dt><span class="term
">
769 "<code class=
"mallctl">thread.deallocatedp
</code>"
771 (<span class="type
">uint64_t *</span>)
772 <code class="literal
">r-</code>
773 [<code class="option
">--enable-stats</code>]
774 </span></dt><dd><p>Get a pointer to the the value that is returned by the
775 <a class="link
" href="#thread.deallocated
">
776 "<code class=
"mallctl">thread.deallocated
</code>"
778 mallctl. This is useful for avoiding the overhead of repeated
779 <code class="function
">mallctl*</code>(<em class="parameter
"><code></code></em>) calls.</p></dd><dt><span class="term
">
781 "<code class=
"mallctl">thread.tcache.enabled
</code>"
783 (<span class="type
">bool</span>)
784 <code class="literal
">rw</code>
785 [<code class="option
">--enable-tcache</code>]
786 </span></dt><dd><p>Enable/disable calling thread's tcache. The tcache is
787 implicitly flushed as a side effect of becoming
789 "<code class=
"mallctl">thread.tcache.flush
</code>"
791 </p></dd><dt><span class="term
">
793 "<code class=
"mallctl">thread.tcache.flush
</code>"
795 (<span class="type
">void</span>)
796 <code class="literal
">--</code>
797 [<code class="option
">--enable-tcache</code>]
798 </span></dt><dd><p>Flush calling thread's tcache. This interface releases
799 all cached objects and internal data structures associated with the
800 calling thread's thread-specific cache. Ordinarily, this interface
801 need not be called, since automatic periodic incremental garbage
802 collection occurs, and the thread cache is automatically discarded when
803 a thread exits. However, garbage collection is triggered by allocation
804 activity, so it is possible for a thread that stops
805 allocating/deallocating to retain its cache indefinitely, in which case
806 the developer may find manual flushing useful.</p></dd><dt><a name="arena.i.purge
"></a><span class="term
">
808 "<code class=
"mallctl">arena.
<i
>.purge
</code>"
810 (<span class="type
">unsigned</span>)
811 <code class="literal
">--</code>
812 </span></dt><dd><p>Purge unused dirty pages for arena <i>, or for
813 all arenas if <i> equals <a class="link
" href="#arenas.narenas
">
814 "<code class=
"mallctl">arenas.narenas
</code>"
816 </p></dd><dt><a name="arena.i.dss
"></a><span class="term
">
818 "<code class=
"mallctl">arena.
<i
>.dss
</code>"
820 (<span class="type
">const char *</span>)
821 <code class="literal
">rw</code>
822 </span></dt><dd><p>Set the precedence of dss allocation as related to mmap
823 allocation for arena <i>, or for all arenas if <i> equals
824 <a class="link
" href="#arenas.narenas
">
825 "<code class=
"mallctl">arenas.narenas
</code>"
827 <a class="link
" href="#opt.dss
">
828 "<code class=
"mallctl">opt.dss
</code>"
831 </p></dd><dt><a name="arenas.narenas
"></a><span class="term
">
833 "<code class=
"mallctl">arenas.narenas
</code>"
835 (<span class="type
">unsigned</span>)
836 <code class="literal
">r-</code>
837 </span></dt><dd><p>Current limit on number of arenas.</p></dd><dt><a name="arenas.initialized
"></a><span class="term
">
839 "<code class=
"mallctl">arenas.initialized
</code>"
841 (<span class="type
">bool *</span>)
842 <code class="literal
">r-</code>
843 </span></dt><dd><p>An array of <a class="link
" href="#arenas.narenas
">
844 "<code class=
"mallctl">arenas.narenas
</code>"
846 booleans. Each boolean indicates whether the corresponding arena is
847 initialized.</p></dd><dt><span class="term
">
849 "<code class=
"mallctl">arenas.quantum
</code>"
851 (<span class="type
">size_t</span>)
852 <code class="literal
">r-</code>
853 </span></dt><dd><p>Quantum size.</p></dd><dt><span class="term
">
855 "<code class=
"mallctl">arenas.page
</code>"
857 (<span class="type
">size_t</span>)
858 <code class="literal
">r-</code>
859 </span></dt><dd><p>Page size.</p></dd><dt><span class="term
">
861 "<code class=
"mallctl">arenas.tcache_max
</code>"
863 (<span class="type
">size_t</span>)
864 <code class="literal
">r-</code>
865 [<code class="option
">--enable-tcache</code>]
866 </span></dt><dd><p>Maximum thread-cached size class.</p></dd><dt><span class="term
">
868 "<code class=
"mallctl">arenas.nbins
</code>"
870 (<span class="type
">unsigned</span>)
871 <code class="literal
">r-</code>
872 </span></dt><dd><p>Number of bin size classes.</p></dd><dt><span class="term
">
874 "<code class=
"mallctl">arenas.nhbins
</code>"
876 (<span class="type
">unsigned</span>)
877 <code class="literal
">r-</code>
878 [<code class="option
">--enable-tcache</code>]
879 </span></dt><dd><p>Total number of thread cache bin size
880 classes.</p></dd><dt><a name="arenas.bin.i.size
"></a><span class="term
">
882 "<code class=
"mallctl">arenas.bin.
<i
>.size
</code>"
884 (<span class="type
">size_t</span>)
885 <code class="literal
">r-</code>
886 </span></dt><dd><p>Maximum size supported by size class.</p></dd><dt><span class="term
">
888 "<code class=
"mallctl">arenas.bin.
<i
>.nregs
</code>"
890 (<span class="type
">uint32_t</span>)
891 <code class="literal
">r-</code>
892 </span></dt><dd><p>Number of regions per page run.</p></dd><dt><span class="term
">
894 "<code class=
"mallctl">arenas.bin.
<i
>.run_size
</code>"
896 (<span class="type
">size_t</span>)
897 <code class="literal
">r-</code>
898 </span></dt><dd><p>Number of bytes per page run.</p></dd><dt><span class="term
">
900 "<code class=
"mallctl">arenas.nlruns
</code>"
902 (<span class="type
">size_t</span>)
903 <code class="literal
">r-</code>
904 </span></dt><dd><p>Total number of large size classes.</p></dd><dt><span class="term
">
906 "<code class=
"mallctl">arenas.lrun.
<i
>.size
</code>"
908 (<span class="type
">size_t</span>)
909 <code class="literal
">r-</code>
910 </span></dt><dd><p>Maximum size supported by this large size
911 class.</p></dd><dt><span class="term
">
913 "<code class=
"mallctl">arenas.purge
</code>"
915 (<span class="type
">unsigned</span>)
916 <code class="literal
">-w</code>
917 </span></dt><dd><p>Purge unused dirty pages for the specified arena, or
918 for all arenas if none is specified.</p></dd><dt><span class="term
">
920 "<code class=
"mallctl">arenas.extend
</code>"
922 (<span class="type
">unsigned</span>)
923 <code class="literal
">r-</code>
924 </span></dt><dd><p>Extend the array of arenas by appending a new arena,
925 and returning the new arena index.</p></dd><dt><a name="prof.active
"></a><span class="term
">
927 "<code class=
"mallctl">prof.active
</code>"
929 (<span class="type
">bool</span>)
930 <code class="literal
">rw</code>
931 [<code class="option
">--enable-prof</code>]
932 </span></dt><dd><p>Control whether sampling is currently active. See the
933 <a class="link
" href="#opt.prof_active
">
934 "<code class=
"mallctl">opt.prof_active
</code>"
936 option for additional information.
937 </p></dd><dt><span class="term
">
939 "<code class=
"mallctl">prof.dump
</code>"
941 (<span class="type
">const char *</span>)
942 <code class="literal
">-w</code>
943 [<code class="option
">--enable-prof</code>]
944 </span></dt><dd><p>Dump a memory profile to the specified file, or if NULL
945 is specified, to a file according to the pattern
946 <code class="filename
"><prefix>.<pid>.<seq>.m<mseq>.heap</code>,
947 where <code class="literal
"><prefix></code> is controlled by the
948 <a class="link
" href="#opt.prof_prefix
">
949 "<code class=
"mallctl">opt.prof_prefix
</code>"
951 option.</p></dd><dt><span class="term
">
953 "<code class=
"mallctl">prof.interval
</code>"
955 (<span class="type
">uint64_t</span>)
956 <code class="literal
">r-</code>
957 [<code class="option
">--enable-prof</code>]
958 </span></dt><dd><p>Average number of bytes allocated between
959 inverval-based profile dumps. See the
960 <a class="link
" href="#opt.lg_prof_interval
">
961 "<code class=
"mallctl">opt.lg_prof_interval
</code>"
963 option for additional information.</p></dd><dt><a name="stats.cactive
"></a><span class="term
">
965 "<code class=
"mallctl">stats.cactive
</code>"
967 (<span class="type
">size_t *</span>)
968 <code class="literal
">r-</code>
969 [<code class="option
">--enable-stats</code>]
970 </span></dt><dd><p>Pointer to a counter that contains an approximate count
971 of the current number of bytes in active pages. The estimate may be
972 high, but never low, because each arena rounds up to the nearest
973 multiple of the chunk size when computing its contribution to the
974 counter. Note that the <a class="link
" href="#epoch
">
975 "<code class=
"mallctl">epoch
</code>"
976 </a> mallctl has no bearing
977 on this counter. Furthermore, counter consistency is maintained via
978 atomic operations, so it is necessary to use an atomic operation in
979 order to guarantee a consistent read when dereferencing the pointer.
980 </p></dd><dt><a name="stats.allocated
"></a><span class="term
">
982 "<code class=
"mallctl">stats.allocated
</code>"
984 (<span class="type
">size_t</span>)
985 <code class="literal
">r-</code>
986 [<code class="option
">--enable-stats</code>]
987 </span></dt><dd><p>Total number of bytes allocated by the
988 application.</p></dd><dt><a name="stats.active
"></a><span class="term
">
990 "<code class=
"mallctl">stats.active
</code>"
992 (<span class="type
">size_t</span>)
993 <code class="literal
">r-</code>
994 [<code class="option
">--enable-stats</code>]
995 </span></dt><dd><p>Total number of bytes in active pages allocated by the
996 application. This is a multiple of the page size, and greater than or
997 equal to <a class="link
" href="#stats.allocated
">
998 "<code class=
"mallctl">stats.allocated
</code>"
1000 This does not include <a class="link
" href="#stats.arenas.i.pdirty
">
1002 "<code class=
"mallctl">stats.arenas.
<i
>.pdirty
</code>"
1004 entirely devoted to allocator metadata.</p></dd><dt><span class="term
">
1006 "<code class=
"mallctl">stats.mapped
</code>"
1008 (<span class="type
">size_t</span>)
1009 <code class="literal
">r-</code>
1010 [<code class="option
">--enable-stats</code>]
1011 </span></dt><dd><p>Total number of bytes in chunks mapped on behalf of the
1012 application. This is a multiple of the chunk size, and is at least as
1013 large as <a class="link
" href="#stats.active
">
1014 "<code class=
"mallctl">stats.active
</code>"
1016 does not include inactive chunks.</p></dd><dt><span class="term
">
1018 "<code class=
"mallctl">stats.chunks.current
</code>"
1020 (<span class="type
">size_t</span>)
1021 <code class="literal
">r-</code>
1022 [<code class="option
">--enable-stats</code>]
1023 </span></dt><dd><p>Total number of chunks actively mapped on behalf of the
1024 application. This does not include inactive chunks.
1025 </p></dd><dt><span class="term
">
1027 "<code class=
"mallctl">stats.chunks.total
</code>"
1029 (<span class="type
">uint64_t</span>)
1030 <code class="literal
">r-</code>
1031 [<code class="option
">--enable-stats</code>]
1032 </span></dt><dd><p>Cumulative number of chunks allocated.</p></dd><dt><span class="term
">
1034 "<code class=
"mallctl">stats.chunks.high
</code>"
1036 (<span class="type
">size_t</span>)
1037 <code class="literal
">r-</code>
1038 [<code class="option
">--enable-stats</code>]
1039 </span></dt><dd><p>Maximum number of active chunks at any time thus far.
1040 </p></dd><dt><span class="term
">
1042 "<code class=
"mallctl">stats.huge.allocated
</code>"
1044 (<span class="type
">size_t</span>)
1045 <code class="literal
">r-</code>
1046 [<code class="option
">--enable-stats</code>]
1047 </span></dt><dd><p>Number of bytes currently allocated by huge objects.
1048 </p></dd><dt><span class="term
">
1050 "<code class=
"mallctl">stats.huge.nmalloc
</code>"
1052 (<span class="type
">uint64_t</span>)
1053 <code class="literal
">r-</code>
1054 [<code class="option
">--enable-stats</code>]
1055 </span></dt><dd><p>Cumulative number of huge allocation requests.
1056 </p></dd><dt><span class="term
">
1058 "<code class=
"mallctl">stats.huge.ndalloc
</code>"
1060 (<span class="type
">uint64_t</span>)
1061 <code class="literal
">r-</code>
1062 [<code class="option
">--enable-stats</code>]
1063 </span></dt><dd><p>Cumulative number of huge deallocation requests.
1064 </p></dd><dt><span class="term
">
1066 "<code class=
"mallctl">stats.arenas.
<i
>.dss
</code>"
1068 (<span class="type
">const char *</span>)
1069 <code class="literal
">r-</code>
1070 </span></dt><dd><p>dss (<span class="citerefentry
"><span class="refentrytitle
">sbrk</span>(2)</span>) allocation precedence as
1071 related to <span class="citerefentry
"><span class="refentrytitle
">mmap</span>(2)</span> allocation. See <a class="link
" href="#opt.dss
">
1072 "<code class=
"mallctl">opt.dss
</code>"
1074 </p></dd><dt><span class="term
">
1076 "<code class=
"mallctl">stats.arenas.
<i
>.nthreads
</code>"
1078 (<span class="type
">unsigned</span>)
1079 <code class="literal
">r-</code>
1080 </span></dt><dd><p>Number of threads currently assigned to
1081 arena.</p></dd><dt><span class="term
">
1083 "<code class=
"mallctl">stats.arenas.
<i
>.pactive
</code>"
1085 (<span class="type
">size_t</span>)
1086 <code class="literal
">r-</code>
1087 </span></dt><dd><p>Number of pages in active runs.</p></dd><dt><a name="stats.arenas.i.pdirty
"></a><span class="term
">
1089 "<code class=
"mallctl">stats.arenas.
<i
>.pdirty
</code>"
1091 (<span class="type
">size_t</span>)
1092 <code class="literal
">r-</code>
1093 </span></dt><dd><p>Number of pages within unused runs that are potentially
1094 dirty, and for which <code class="function
">madvise</code>(<em class="parameter
"><code>...</code></em>,
1095 <em class="parameter
"><code><code class="constant
">MADV_DONTNEED</code></code></em>) or
1096 similar has not been called.</p></dd><dt><span class="term
">
1098 "<code class=
"mallctl">stats.arenas.
<i
>.mapped
</code>"
1100 (<span class="type
">size_t</span>)
1101 <code class="literal
">r-</code>
1102 [<code class="option
">--enable-stats</code>]
1103 </span></dt><dd><p>Number of mapped bytes.</p></dd><dt><span class="term
">
1105 "<code class=
"mallctl">stats.arenas.
<i
>.npurge
</code>"
1107 (<span class="type
">uint64_t</span>)
1108 <code class="literal
">r-</code>
1109 [<code class="option
">--enable-stats</code>]
1110 </span></dt><dd><p>Number of dirty page purge sweeps performed.
1111 </p></dd><dt><span class="term
">
1113 "<code class=
"mallctl">stats.arenas.
<i
>.nmadvise
</code>"
1115 (<span class="type
">uint64_t</span>)
1116 <code class="literal
">r-</code>
1117 [<code class="option
">--enable-stats</code>]
1118 </span></dt><dd><p>Number of <code class="function
">madvise</code>(<em class="parameter
"><code>...</code></em>,
1119 <em class="parameter
"><code><code class="constant
">MADV_DONTNEED</code></code></em>) or
1120 similar calls made to purge dirty pages.</p></dd><dt><span class="term
">
1122 "<code class=
"mallctl">stats.arenas.
<i
>.npurged
</code>"
1124 (<span class="type
">uint64_t</span>)
1125 <code class="literal
">r-</code>
1126 [<code class="option
">--enable-stats</code>]
1127 </span></dt><dd><p>Number of pages purged.</p></dd><dt><span class="term
">
1129 "<code class=
"mallctl">stats.arenas.
<i
>.small.allocated
</code>"
1131 (<span class="type
">size_t</span>)
1132 <code class="literal
">r-</code>
1133 [<code class="option
">--enable-stats</code>]
1134 </span></dt><dd><p>Number of bytes currently allocated by small objects.
1135 </p></dd><dt><span class="term
">
1137 "<code class=
"mallctl">stats.arenas.
<i
>.small.nmalloc
</code>"
1139 (<span class="type
">uint64_t</span>)
1140 <code class="literal
">r-</code>
1141 [<code class="option
">--enable-stats</code>]
1142 </span></dt><dd><p>Cumulative number of allocation requests served by
1143 small bins.</p></dd><dt><span class="term
">
1145 "<code class=
"mallctl">stats.arenas.
<i
>.small.ndalloc
</code>"
1147 (<span class="type
">uint64_t</span>)
1148 <code class="literal
">r-</code>
1149 [<code class="option
">--enable-stats</code>]
1150 </span></dt><dd><p>Cumulative number of small objects returned to bins.
1151 </p></dd><dt><span class="term
">
1153 "<code class=
"mallctl">stats.arenas.
<i
>.small.nrequests
</code>"
1155 (<span class="type
">uint64_t</span>)
1156 <code class="literal
">r-</code>
1157 [<code class="option
">--enable-stats</code>]
1158 </span></dt><dd><p>Cumulative number of small allocation requests.
1159 </p></dd><dt><span class="term
">
1161 "<code class=
"mallctl">stats.arenas.
<i
>.large.allocated
</code>"
1163 (<span class="type
">size_t</span>)
1164 <code class="literal
">r-</code>
1165 [<code class="option
">--enable-stats</code>]
1166 </span></dt><dd><p>Number of bytes currently allocated by large objects.
1167 </p></dd><dt><span class="term
">
1169 "<code class=
"mallctl">stats.arenas.
<i
>.large.nmalloc
</code>"
1171 (<span class="type
">uint64_t</span>)
1172 <code class="literal
">r-</code>
1173 [<code class="option
">--enable-stats</code>]
1174 </span></dt><dd><p>Cumulative number of large allocation requests served
1175 directly by the arena.</p></dd><dt><span class="term
">
1177 "<code class=
"mallctl">stats.arenas.
<i
>.large.ndalloc
</code>"
1179 (<span class="type
">uint64_t</span>)
1180 <code class="literal
">r-</code>
1181 [<code class="option
">--enable-stats</code>]
1182 </span></dt><dd><p>Cumulative number of large deallocation requests served
1183 directly by the arena.</p></dd><dt><span class="term
">
1185 "<code class=
"mallctl">stats.arenas.
<i
>.large.nrequests
</code>"
1187 (<span class="type
">uint64_t</span>)
1188 <code class="literal
">r-</code>
1189 [<code class="option
">--enable-stats</code>]
1190 </span></dt><dd><p>Cumulative number of large allocation requests.
1191 </p></dd><dt><span class="term
">
1193 "<code class=
"mallctl">stats.arenas.
<i
>.bins.
<j
>.allocated
</code>"
1195 (<span class="type
">size_t</span>)
1196 <code class="literal
">r-</code>
1197 [<code class="option
">--enable-stats</code>]
1198 </span></dt><dd><p>Current number of bytes allocated by
1199 bin.</p></dd><dt><span class="term
">
1201 "<code class=
"mallctl">stats.arenas.
<i
>.bins.
<j
>.nmalloc
</code>"
1203 (<span class="type
">uint64_t</span>)
1204 <code class="literal
">r-</code>
1205 [<code class="option
">--enable-stats</code>]
1206 </span></dt><dd><p>Cumulative number of allocations served by bin.
1207 </p></dd><dt><span class="term
">
1209 "<code class=
"mallctl">stats.arenas.
<i
>.bins.
<j
>.ndalloc
</code>"
1211 (<span class="type
">uint64_t</span>)
1212 <code class="literal
">r-</code>
1213 [<code class="option
">--enable-stats</code>]
1214 </span></dt><dd><p>Cumulative number of allocations returned to bin.
1215 </p></dd><dt><span class="term
">
1217 "<code class=
"mallctl">stats.arenas.
<i
>.bins.
<j
>.nrequests
</code>"
1219 (<span class="type
">uint64_t</span>)
1220 <code class="literal
">r-</code>
1221 [<code class="option
">--enable-stats</code>]
1222 </span></dt><dd><p>Cumulative number of allocation
1223 requests.</p></dd><dt><span class="term
">
1225 "<code class=
"mallctl">stats.arenas.
<i
>.bins.
<j
>.nfills
</code>"
1227 (<span class="type
">uint64_t</span>)
1228 <code class="literal
">r-</code>
1229 [<code class="option
">--enable-stats</code> <code class="option
">--enable-tcache</code>]
1230 </span></dt><dd><p>Cumulative number of tcache fills.</p></dd><dt><span class="term
">
1232 "<code class=
"mallctl">stats.arenas.
<i
>.bins.
<j
>.nflushes
</code>"
1234 (<span class="type
">uint64_t</span>)
1235 <code class="literal
">r-</code>
1236 [<code class="option
">--enable-stats</code> <code class="option
">--enable-tcache</code>]
1237 </span></dt><dd><p>Cumulative number of tcache flushes.</p></dd><dt><span class="term
">
1239 "<code class=
"mallctl">stats.arenas.
<i
>.bins.
<j
>.nruns
</code>"
1241 (<span class="type
">uint64_t</span>)
1242 <code class="literal
">r-</code>
1243 [<code class="option
">--enable-stats</code>]
1244 </span></dt><dd><p>Cumulative number of runs created.</p></dd><dt><span class="term
">
1246 "<code class=
"mallctl">stats.arenas.
<i
>.bins.
<j
>.nreruns
</code>"
1248 (<span class="type
">uint64_t</span>)
1249 <code class="literal
">r-</code>
1250 [<code class="option
">--enable-stats</code>]
1251 </span></dt><dd><p>Cumulative number of times the current run from which
1252 to allocate changed.</p></dd><dt><span class="term
">
1254 "<code class=
"mallctl">stats.arenas.
<i
>.bins.
<j
>.curruns
</code>"
1256 (<span class="type
">size_t</span>)
1257 <code class="literal
">r-</code>
1258 [<code class="option
">--enable-stats</code>]
1259 </span></dt><dd><p>Current number of runs.</p></dd><dt><span class="term
">
1261 "<code class=
"mallctl">stats.arenas.
<i
>.lruns.
<j
>.nmalloc
</code>"
1263 (<span class="type
">uint64_t</span>)
1264 <code class="literal
">r-</code>
1265 [<code class="option
">--enable-stats</code>]
1266 </span></dt><dd><p>Cumulative number of allocation requests for this size
1267 class served directly by the arena.</p></dd><dt><span class="term
">
1269 "<code class=
"mallctl">stats.arenas.
<i
>.lruns.
<j
>.ndalloc
</code>"
1271 (<span class="type
">uint64_t</span>)
1272 <code class="literal
">r-</code>
1273 [<code class="option
">--enable-stats</code>]
1274 </span></dt><dd><p>Cumulative number of deallocation requests for this
1275 size class served directly by the arena.</p></dd><dt><span class="term
">
1277 "<code class=
"mallctl">stats.arenas.
<i
>.lruns.
<j
>.nrequests
</code>"
1279 (<span class="type
">uint64_t</span>)
1280 <code class="literal
">r-</code>
1281 [<code class="option
">--enable-stats</code>]
1282 </span></dt><dd><p>Cumulative number of allocation requests for this size
1283 class.</p></dd><dt><span class="term
">
1285 "<code class=
"mallctl">stats.arenas.
<i
>.lruns.
<j
>.curruns
</code>"
1287 (<span class="type
">size_t</span>)
1288 <code class="literal
">r-</code>
1289 [<code class="option
">--enable-stats</code>]
1290 </span></dt><dd><p>Current number of runs for this size class.
1291 </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
1292 the <code class="option
">--enable-debug</code> and <code class="option
">--enable-fill</code>
1293 options, and recompile the program with suitable options and symbols for
1294 debugger support. When so configured, jemalloc incorporates a wide variety
1295 of run-time assertions that catch application errors such as double-free,
1296 write-after-free, etc.</p><p>Programs often accidentally depend on “uninitialized”
1297 memory actually being filled with zero bytes. Junk filling
1298 (see the <a class="link
" href="#opt.junk
">
1299 "<code class=
"mallctl">opt.junk
</code>"
1301 option) tends to expose such bugs in the form of obviously incorrect
1302 results and/or coredumps. Conversely, zero
1303 filling (see the <a class="link
" href="#opt.zero
">
1304 "<code class=
"mallctl">opt.zero
</code>"
1305 </a> option) eliminates
1306 the symptoms of such bugs. Between these two options, it is usually
1307 possible to quickly detect, diagnose, and eliminate such bugs.</p><p>This implementation does not provide much detail about the problems
1308 it detects, because the performance impact for storing such information
1309 would be prohibitive. However, jemalloc does integrate with the most
1310 excellent <a class="ulink
" href="http://valgrind.org/
" target="_top
">Valgrind</a> tool if the
1311 <code class="option
">--enable-valgrind</code> configuration option is enabled.</p></div><div class="refsect1
" title="DIAGNOSTIC MESSAGES
"><a name="diagnostic_messages
"></a><h2>DIAGNOSTIC MESSAGES</h2><p>If any of the memory allocation/deallocation functions detect an
1312 error or warning condition, a message will be printed to file descriptor
1313 <code class="constant
">STDERR_FILENO</code>. Errors will result in the process
1314 dumping core. If the <a class="link
" href="#opt.abort
">
1315 "<code class=
"mallctl">opt.abort
</code>"
1316 </a> option is set, most
1317 warnings are treated as errors.</p><p>The <code class="varname
">malloc_message</code> variable allows the programmer
1318 to override the function which emits the text strings forming the errors
1319 and warnings if for some reason the <code class="constant
">STDERR_FILENO</code> file
1320 descriptor is not suitable for this.
1321 <code class="function
">malloc_message</code>(<em class="parameter
"><code></code></em>) takes the
1322 <em class="parameter
"><code>cbopaque</code></em> pointer argument that is
1323 <code class="constant
">NULL</code> unless overridden by the arguments in a call to
1324 <code class="function
">malloc_stats_print</code>(<em class="parameter
"><code></code></em>), followed by a string
1325 pointer. Please note that doing anything which tries to allocate memory in
1326 this function is likely to result in a crash or deadlock.</p><p>All messages are prefixed by
1327 “<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="id286954473
"></a><h3>Standard API</h3><p>The <code class="function
">malloc</code>(<em class="parameter
"><code></code></em>) and
1328 <code class="function
">calloc</code>(<em class="parameter
"><code></code></em>) functions return a pointer to the
1329 allocated memory if successful; otherwise a <code class="constant
">NULL</code>
1330 pointer is returned and <code class="varname
">errno</code> is set to
1331 <span class="errorname
">ENOMEM</span>.</p><p>The <code class="function
">posix_memalign</code>(<em class="parameter
"><code></code></em>) function
1332 returns the value 0 if successful; otherwise it returns an error value.
1333 The <code class="function
">posix_memalign</code>(<em class="parameter
"><code></code></em>) function will fail
1335 </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
1336 not a power of 2 at least as large as
1337 <code class="code
">sizeof(<span class="type
">void *</span>)</code>.
1338 </p></dd><dt><span class="term
"><span class="errorname
">ENOMEM</span></span></dt><dd><p>Memory allocation error.</p></dd></dl></div><p>
1339 </p><p>The <code class="function
">aligned_alloc</code>(<em class="parameter
"><code></code></em>) function returns
1340 a pointer to the allocated memory if successful; otherwise a
1341 <code class="constant
">NULL</code> pointer is returned and
1342 <code class="varname
">errno</code> is set. The
1343 <code class="function
">aligned_alloc</code>(<em class="parameter
"><code></code></em>) function will fail if:
1344 </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
1346 </p></dd><dt><span class="term
"><span class="errorname
">ENOMEM</span></span></dt><dd><p>Memory allocation error.</p></dd></dl></div><p>
1347 </p><p>The <code class="function
">realloc</code>(<em class="parameter
"><code></code></em>) function returns a
1348 pointer, possibly identical to <em class="parameter
"><code>ptr</code></em>, to the
1349 allocated memory if successful; otherwise a <code class="constant
">NULL</code>
1350 pointer is returned, and <code class="varname
">errno</code> is set to
1351 <span class="errorname
">ENOMEM</span> if the error was the result of an
1352 allocation failure. The <code class="function
">realloc</code>(<em class="parameter
"><code></code></em>)
1353 function always leaves the original buffer intact when an error occurs.
1354 </p><p>The <code class="function
">free</code>(<em class="parameter
"><code></code></em>) function returns no
1355 value.</p></div><div class="refsect2
" title="Non-standard API
"><a name="id286954690
"></a><h3>Non-standard API</h3><p>The <code class="function
">malloc_usable_size</code>(<em class="parameter
"><code></code></em>) function
1356 returns the usable size of the allocation pointed to by
1357 <em class="parameter
"><code>ptr</code></em>. </p><p>The <code class="function
">mallctl</code>(<em class="parameter
"><code></code></em>),
1358 <code class="function
">mallctlnametomib</code>(<em class="parameter
"><code></code></em>), and
1359 <code class="function
">mallctlbymib</code>(<em class="parameter
"><code></code></em>) functions return 0 on
1360 success; otherwise they return an error value. The functions will fail
1362 </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
1363 <code class="constant
">NULL</code>, and <em class="parameter
"><code>newlen</code></em> is too
1364 large or too small. Alternatively, <em class="parameter
"><code>*oldlenp</code></em>
1365 is too large or too small; in this case as much data as possible
1366 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
1367 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
1368 <em class="parameter
"><code>mib</code></em> specifies an unknown/invalid
1369 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
1370 write read-only value.</p></dd><dt><span class="term
"><span class="errorname
">EAGAIN</span></span></dt><dd><p>A memory allocation failure
1371 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
1372 not directly related to <code class="function
">mallctl*</code>(<em class="parameter
"><code></code></em>)
1373 read/write processing.</p></dd></dl></div><p>
1374 </p></div><div class="refsect2
" title="Experimental API
"><a name="id286954842
"></a><h3>Experimental API</h3><p>The <code class="function
">allocm</code>(<em class="parameter
"><code></code></em>),
1375 <code class="function
">rallocm</code>(<em class="parameter
"><code></code></em>),
1376 <code class="function
">sallocm</code>(<em class="parameter
"><code></code></em>),
1377 <code class="function
">dallocm</code>(<em class="parameter
"><code></code></em>), and
1378 <code class="function
">nallocm</code>(<em class="parameter
"><code></code></em>) functions return
1379 <code class="constant
">ALLOCM_SUCCESS</code> on success; otherwise they return an
1380 error value. The <code class="function
">allocm</code>(<em class="parameter
"><code></code></em>),
1381 <code class="function
">rallocm</code>(<em class="parameter
"><code></code></em>), and
1382 <code class="function
">nallocm</code>(<em class="parameter
"><code></code></em>) functions will fail if:
1383 </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
1384 available to service the allocation request. The
1385 <code class="function
">allocm</code>(<em class="parameter
"><code></code></em>) function additionally sets
1386 <em class="parameter
"><code>*ptr</code></em> to <code class="constant
">NULL</code>, whereas
1387 the <code class="function
">rallocm</code>(<em class="parameter
"><code></code></em>) function leaves
1388 <code class="constant
">*ptr</code> unmodified.</p></dd></dl></div><p>
1389 The <code class="function
">rallocm</code>(<em class="parameter
"><code></code></em>) function will also
1391 </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,
1392 but the reallocation request could not be serviced without moving
1393 the object.</p></dd></dl></div><p>
1394 </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
1395 allocation functions:
1396 </p><div class="variablelist
"><dl><dt><span class="term
"><code class="envar
">MALLOC_CONF</code></span></dt><dd><p>If the environment variable
1397 <code class="envar
">MALLOC_CONF</code> is set, the characters it contains
1398 will be interpreted as options.</p></dd></dl></div><p>
1399 </p></div><div class="refsect1
" title="EXAMPLES
"><a name="examples
"></a><h2>EXAMPLES</h2><p>To dump core whenever a problem occurs:
1400 </p><pre class="screen
">ln -s 'abort:true' /etc/malloc.conf</pre><p>
1401 </p><p>To specify in the source a chunk size that is 16 MiB:
1402 </p><pre class="programlisting
">
1403 malloc_conf = "lg_chunk:
24";
</pre></div><div class=
"refsect1" title=
"SEE ALSO"><a name=
"see_also"></a><h2>SEE ALSO
</h2><p><span class=
"citerefentry"><span class=
"refentrytitle">madvise
</span>(
2)
</span>,
1404 <span class=
"citerefentry"><span class=
"refentrytitle">mmap
</span>(
2)
</span>,
1405 <span class=
"citerefentry"><span class=
"refentrytitle">sbrk
</span>(
2)
</span>,
1406 <span class=
"citerefentry"><span class=
"refentrytitle">utrace
</span>(
2)
</span>,
1407 <span class=
"citerefentry"><span class=
"refentrytitle">alloca
</span>(
3)
</span>,
1408 <span class=
"citerefentry"><span class=
"refentrytitle">atexit
</span>(
3)
</span>,
1409 <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>),
1410 <code class=
"function">calloc
</code>(
<em class=
"parameter"><code></code></em>),
1411 <code class=
"function">realloc
</code>(
<em class=
"parameter"><code></code></em>), and
1412 <code class=
"function">free
</code>(
<em class=
"parameter"><code></code></em>) functions conform to ISO/IEC
1413 9899:
1990 (
“ISO C90
”).
</p><p>The
<code class=
"function">posix_memalign
</code>(
<em class=
"parameter"><code></code></em>) function conforms
1414 to IEEE Std
1003.1-
2001 (
“POSIX
.1”).
</p></div></div></body></html>
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