3 .\" Author: Jason Evans
4 .\" Generator: DocBook XSL Stylesheets v1.76.1 <http://docbook.sf.net/>
6 .\" Manual: User Manual
7 .\" Source: jemalloc 5.0.0-4-g84f6c2cae0fb1399377ef6aea9368444c4987cc6
10 .TH "JEMALLOC" "3" "06/14/2017" "jemalloc 5.0.0-4-g84f6c2cae0fb" "User Manual"
11 .\" -----------------------------------------------------------------
12 .\" * Define some portability stuff
13 .\" -----------------------------------------------------------------
14 .\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
15 .\" http://bugs.debian.org/507673
16 .\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
17 .\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
20 .\" -----------------------------------------------------------------
21 .\" * set default formatting
22 .\" -----------------------------------------------------------------
23 .\" disable hyphenation
25 .\" disable justification (adjust text to left margin only)
27 .\" -----------------------------------------------------------------
28 .\" * MAIN CONTENT STARTS HERE *
29 .\" -----------------------------------------------------------------
31 jemalloc \- general purpose memory allocation functions
34 This manual describes jemalloc 5\&.0\&.0\-4\-g84f6c2cae0fb1399377ef6aea9368444c4987cc6\&. More information can be found at the
35 \m[blue]\fBjemalloc website\fR\m[]\&\s-2\u[1]\d\s+2\&.
37 The following configuration options are enabled in libc\*(Aqs built\-in jemalloc:
38 \fB\-\-enable\-fill\fR,
39 \fB\-\-enable\-lazy\-lock\fR,
40 \fB\-\-enable\-stats\fR,
41 \fB\-\-enable\-utrace\fR, and
42 \fB\-\-enable\-xmalloc\fR\&. Additionally,
43 \fB\-\-enable\-debug\fR
44 is enabled in development versions of FreeBSD (controlled by the
45 \fBMALLOC_PRODUCTION\fR
52 #include <malloc_np\&.h>
56 .HP \w'void\ *malloc('u
57 .BI "void *malloc(size_t\ " "size" ");"
58 .HP \w'void\ *calloc('u
59 .BI "void *calloc(size_t\ " "number" ", size_t\ " "size" ");"
60 .HP \w'int\ posix_memalign('u
61 .BI "int posix_memalign(void\ **" "ptr" ", size_t\ " "alignment" ", size_t\ " "size" ");"
62 .HP \w'void\ *aligned_alloc('u
63 .BI "void *aligned_alloc(size_t\ " "alignment" ", size_t\ " "size" ");"
64 .HP \w'void\ *realloc('u
65 .BI "void *realloc(void\ *" "ptr" ", size_t\ " "size" ");"
67 .BI "void free(void\ *" "ptr" ");"
68 .SS "Non\-standard API"
69 .HP \w'void\ *mallocx('u
70 .BI "void *mallocx(size_t\ " "size" ", int\ " "flags" ");"
71 .HP \w'void\ *rallocx('u
72 .BI "void *rallocx(void\ *" "ptr" ", size_t\ " "size" ", int\ " "flags" ");"
73 .HP \w'size_t\ xallocx('u
74 .BI "size_t xallocx(void\ *" "ptr" ", size_t\ " "size" ", size_t\ " "extra" ", int\ " "flags" ");"
75 .HP \w'size_t\ sallocx('u
76 .BI "size_t sallocx(void\ *" "ptr" ", int\ " "flags" ");"
77 .HP \w'void\ dallocx('u
78 .BI "void dallocx(void\ *" "ptr" ", int\ " "flags" ");"
79 .HP \w'void\ sdallocx('u
80 .BI "void sdallocx(void\ *" "ptr" ", size_t\ " "size" ", int\ " "flags" ");"
81 .HP \w'size_t\ nallocx('u
82 .BI "size_t nallocx(size_t\ " "size" ", int\ " "flags" ");"
83 .HP \w'int\ mallctl('u
84 .BI "int mallctl(const\ char\ *" "name" ", void\ *" "oldp" ", size_t\ *" "oldlenp" ", void\ *" "newp" ", size_t\ " "newlen" ");"
85 .HP \w'int\ mallctlnametomib('u
86 .BI "int mallctlnametomib(const\ char\ *" "name" ", size_t\ *" "mibp" ", size_t\ *" "miblenp" ");"
87 .HP \w'int\ mallctlbymib('u
88 .BI "int mallctlbymib(const\ size_t\ *" "mib" ", size_t\ " "miblen" ", void\ *" "oldp" ", size_t\ *" "oldlenp" ", void\ *" "newp" ", size_t\ " "newlen" ");"
89 .HP \w'void\ malloc_stats_print('u
90 .BI "void malloc_stats_print(void\ " "(*write_cb)" "\ (void\ *,\ const\ char\ *), void\ *" "cbopaque" ", const\ char\ *" "opts" ");"
91 .HP \w'size_t\ malloc_usable_size('u
92 .BI "size_t malloc_usable_size(const\ void\ *" "ptr" ");"
93 .HP \w'void\ (*malloc_message)('u
94 .BI "void (*malloc_message)(void\ *" "cbopaque" ", const\ char\ *" "s" ");"
96 const char *\fImalloc_conf\fR;
104 bytes of uninitialized memory\&. The allocated space is suitably aligned (after possible pointer coercion) for storage of any type of object\&.
108 function allocates space for
112 bytes in length\&. The result is identical to calling
117 \fIsize\fR, with the exception that the allocated memory is explicitly initialized to zero bytes\&.
123 bytes of memory such that the allocation\*(Aqs base address is a multiple of
124 \fIalignment\fR, and returns the allocation in the value pointed to by
125 \fIptr\fR\&. The requested
127 must be a power of 2 at least as large as
128 sizeof(\fBvoid *\fR)\&.
134 bytes of memory such that the allocation\*(Aqs base address is a multiple of
135 \fIalignment\fR\&. The requested
137 must be a power of 2\&. Behavior is undefined if
139 is not an integral multiple of
144 function changes the size of the previously allocated memory referenced by
148 bytes\&. The contents of the memory are unchanged up to the lesser of the new and old sizes\&. If the new size is larger, the contents of the newly allocated portion of the memory are undefined\&. Upon success, the memory referenced by
150 is freed and a pointer to the newly allocated memory is returned\&. Note that
152 may move the memory allocation, resulting in a different return value than
158 function behaves identically to
160 for the specified size\&.
164 function causes the allocated memory referenced by
166 to be made available for future allocations\&. If
169 \fBNULL\fR, no action occurs\&.
170 .SS "Non\-standard API"
182 argument that can be used to specify options\&. The functions only check the options that are contextually relevant\&. Use bitwise or (|) operations to specify one or more of the following:
184 \fBMALLOCX_LG_ALIGN(\fR\fB\fIla\fR\fR\fB) \fR
186 Align the memory allocation to start at an address that is a multiple of
187 (1 << \fIla\fR)\&. This macro does not validate that
189 is within the valid range\&.
192 \fBMALLOCX_ALIGN(\fR\fB\fIa\fR\fR\fB) \fR
194 Align the memory allocation to start at an address that is a multiple of
197 is a power of two\&. This macro does not validate that
204 Initialize newly allocated memory to contain zero bytes\&. In the growing reallocation case, the real size prior to reallocation defines the boundary between untouched bytes and those that are initialized to contain zero bytes\&. If this macro is absent, newly allocated memory is uninitialized\&.
207 \fBMALLOCX_TCACHE(\fR\fB\fItc\fR\fR\fB) \fR
209 Use the thread\-specific cache (tcache) specified by the identifier
210 \fItc\fR, which must have been acquired via the
212 mallctl\&. This macro does not validate that
214 specifies a valid identifier\&.
217 \fBMALLOCX_TCACHE_NONE\fR
219 Do not use a thread\-specific cache (tcache)\&. Unless
220 \fBMALLOCX_TCACHE(\fR\fB\fItc\fR\fR\fB)\fR
222 \fBMALLOCX_TCACHE_NONE\fR
223 is specified, an automatically managed tcache will be used under many circumstances\&. This macro cannot be used in the same
226 \fBMALLOCX_TCACHE(\fR\fB\fItc\fR\fR\fB)\fR\&.
229 \fBMALLOCX_ARENA(\fR\fB\fIa\fR\fR\fB) \fR
231 Use the arena specified by the index
232 \fIa\fR\&. This macro has no effect for regions that were allocated via an arena other than the one specified\&. This macro does not validate that
234 specifies an arena index in the valid range\&.
239 function allocates at least
241 bytes of memory, and returns a pointer to the base address of the allocation\&. Behavior is undefined if
248 function resizes the allocation at
252 bytes, and returns a pointer to the base address of the resulting allocation, which may or may not have moved from its original location\&. Behavior is undefined if
259 function resizes the allocation at
261 in place to be at least
263 bytes, and returns the real size of the allocation\&. If
265 is non\-zero, an attempt is made to resize the allocation to be at least
266 (\fIsize\fR + \fIextra\fR)
267 bytes, though inability to allocate the extra byte(s) will not by itself result in failure to resize\&. Behavior is undefined if
271 (\fIsize\fR + \fIextra\fR > \fBSIZE_T_MAX\fR)\&.
275 function returns the real size of the allocation at
280 function causes the memory referenced by
282 to be made available for future allocations\&.
286 function is an extension of
290 parameter to allow the caller to pass in the allocation size as an optimization\&. The minimum valid input size is the original requested size of the allocation, and the maximum valid input size is the corresponding value returned by
297 function allocates no memory, but it performs the same size computation as the
299 function, and returns the real size of the allocation that would result from the equivalent
303 if the inputs exceed the maximum supported size class and/or alignment\&. Behavior is undefined if
310 function provides a general interface for introspecting the memory allocator, as well as setting modifiable parameters and triggering actions\&. The period\-separated
312 argument specifies a location in a tree\-structured namespace; see the
314 section for documentation on the tree contents\&. To read a value, pass a pointer via
316 to adequate space to contain the value, and a pointer to its length via
317 \fIoldlenp\fR; otherwise pass
320 \fBNULL\fR\&. Similarly, to write a value, pass a pointer to the value via
321 \fInewp\fR, and its length via
322 \fInewlen\fR; otherwise pass
329 function provides a way to avoid repeated name lookups for applications that repeatedly query the same portion of the namespace, by translating a name to a
330 \(lqManagement Information Base\(rq
331 (MIB) that can be passed repeatedly to
332 mallctlbymib()\&. Upon successful return from
339 is the lesser of the number of components in
341 and the input value of
342 \fI*miblenp\fR\&. Thus it is possible to pass a
344 that is smaller than the number of period\-separated name components, which results in a partial MIB that can be used as the basis for constructing a complete MIB\&. For name components that are integers (e\&.g\&. the 2 in
345 arenas\&.bin\&.2\&.size), the corresponding MIB component will always be that integer\&. Therefore, it is legitimate to construct code like the following:
356 mallctl("arenas\&.nbins", &nbins, &len, NULL, 0);
359 mallctlnametomib("arenas\&.bin\&.0\&.size", mib, &miblen);
360 for (i = 0; i < nbins; i++) {
364 len = sizeof(bin_size);
365 mallctlbymib(mib, miblen, (void *)&bin_size, &len, NULL, 0);
366 /* Do something with bin_size\&.\&.\&. */
378 function writes summary statistics via the
380 callback function pointer and
388 \fBNULL\fR\&. The statistics are presented in human\-readable form unless
390 is specified as a character within the
392 string, in which case the statistics are presented in
393 \m[blue]\fBJSON format\fR\m[]\&\s-2\u[2]\d\s+2\&. This function can be called repeatedly\&. General information that never changes during execution can be omitted by specifying
395 as a character within the
401 functions internally, so inconsistent statistics can be reported if multiple threads use these functions simultaneously\&. If
402 \fB\-\-enable\-stats\fR
403 is specified during configuration,
407 can be specified to omit merged arena, destroyed merged arena, and per arena statistics, respectively;
411 can be specified to omit per size class statistics for bins and large objects, respectively;
413 can be specified to omit all mutex statistics\&. Unrecognized characters are silently ignored\&. Note that thread caching may prevent some statistics from being completely up to date, since extra locking would be required to merge counters that track thread cache operations\&.
417 function returns the usable size of the allocation pointed to by
418 \fIptr\fR\&. The return value may be larger than the size that was requested during allocation\&. The
420 function is not a mechanism for in\-place
421 realloc(); rather it is provided solely as a tool for introspection purposes\&. Any discrepancy between the requested allocation size and the size reported by
423 should not be depended on, since such behavior is entirely implementation\-dependent\&.
426 Once, when the first call is made to one of the memory allocation routines, the allocator initializes its internals based in part on various options that can be specified at compile\- or run\-time\&.
428 The string specified via
429 \fB\-\-with\-malloc\-conf\fR, the string pointed to by the global variable
430 \fImalloc_conf\fR, the
432 of the file referenced by the symbolic link named
433 /etc/malloc\&.conf, and the value of the environment variable
434 \fBMALLOC_CONF\fR, will be interpreted, in that order, from left to right as options\&. Note that
438 is entered, so the declaration of
440 should specify an initializer that contains the final value to be read by jemalloc\&.
441 \fB\-\-with\-malloc\-conf\fR
444 are compile\-time mechanisms, whereas
448 can be safely set any time prior to program invocation\&.
450 An options string is a comma\-separated list of option:value pairs\&. There is one key corresponding to each
454 section for options documentation)\&. For example,
460 options\&. Some options have boolean values (true/false), others have integer values (base 8, 10, or 16, depending on prefix), and yet others have raw string values\&.
461 .SH "IMPLEMENTATION NOTES"
463 Traditionally, allocators have used
465 to obtain memory, which is suboptimal for several reasons, including race conditions, increased fragmentation, and artificial limitations on maximum usable memory\&. If
467 is supported by the operating system, this allocator uses both
470 \fBsbrk\fR(2), in that order of preference; otherwise only
474 This allocator uses multiple arenas in order to reduce lock contention for threaded programs on multi\-processor systems\&. This works well with regard to threading scalability, but incurs some costs\&. There is a small fixed per\-arena overhead, and additionally, arenas manage memory completely independently of each other, which means a small fixed increase in overall memory fragmentation\&. These overheads are not generally an issue, given the number of arenas normally used\&. Note that using substantially more arenas than the default is not likely to improve performance, mainly due to reduced cache performance\&. However, it may make sense to reduce the number of arenas if an application does not make much use of the allocation functions\&.
476 In addition to multiple arenas, this allocator supports thread\-specific caching, in order to make it possible to completely avoid synchronization for most allocation requests\&. Such caching allows very fast allocation in the common case, but it increases memory usage and fragmentation, since a bounded number of objects can remain allocated in each thread cache\&.
478 Memory is conceptually broken into extents\&. Extents are always aligned to multiples of the page size\&. This alignment makes it possible to find metadata for user objects quickly\&. User objects are broken into two categories according to size: small and large\&. Contiguous small objects comprise a slab, which resides within a single extent, whereas large objects each have their own extents backing them\&.
480 Small objects are managed in groups by slabs\&. Each slab maintains a bitmap to track which regions are in use\&. Allocation requests that are no more than half the quantum (8 or 16, depending on architecture) are rounded up to the nearest power of two that is at least
481 sizeof(\fBdouble\fR)\&. All other object size classes are multiples of the quantum, spaced such that there are four size classes for each doubling in size, which limits internal fragmentation to approximately 20% for all but the smallest size classes\&. Small size classes are smaller than four times the page size, and large size classes extend from four times the page size up to the largest size class that does not exceed
484 Allocations are packed tightly together, which can be an issue for multi\-threaded applications\&. If you need to assure that allocations do not suffer from cacheline sharing, round your allocation requests up to the nearest multiple of the cacheline size, or specify cacheline alignment when allocating\&.
490 functions may resize allocations without moving them under limited circumstances\&. Unlike the
492 API, the standard API does not officially round up the usable size of an allocation to the nearest size class, so technically it is necessary to call
494 to grow e\&.g\&. a 9\-byte allocation to 16 bytes, or shrink a 16\-byte allocation to 9 bytes\&. Growth and shrinkage trivially succeeds in place as long as the pre\-size and post\-size both round up to the same size class\&. No other API guarantees are made regarding in\-place resizing, but the current implementation also tries to resize large allocations in place, as long as the pre\-size and post\-size are both large\&. For shrinkage to succeed, the extent allocator must support splitting (see
495 arena\&.<i>\&.extent_hooks)\&. Growth only succeeds if the trailing memory is currently available, and the extent allocator supports merging\&.
497 Assuming 4 KiB pages and a 16\-byte quantum on a 64\-bit system, the size classes in each category are as shown in
501 .nr an-no-space-flag 1
504 .B Table\ \&1.\ \&Size classes
551 [16, 32, 48, 64, 80, 96, 112, 128]
566 [640, 768, 896, 1024]
571 [1280, 1536, 1792, 2048]
576 [2560, 3072, 3584, 4096]
581 [5 KiB, 6 KiB, 7 KiB, 8 KiB]
586 [10 KiB, 12 KiB, 14 KiB]
598 [20 KiB, 24 KiB, 28 KiB, 32 KiB]
603 [40 KiB, 48 KiB, 54 KiB, 64 KiB]
608 [80 KiB, 96 KiB, 112 KiB, 128 KiB]
613 [160 KiB, 192 KiB, 224 KiB, 256 KiB]
618 [320 KiB, 384 KiB, 448 KiB, 512 KiB]
623 [640 KiB, 768 KiB, 896 KiB, 1 MiB]
628 [1280 KiB, 1536 KiB, 1792 KiB, 2 MiB]
633 [2560 KiB, 3 MiB, 3584 KiB, 4 MiB]
638 [5 MiB, 6 MiB, 7 MiB, 8 MiB]
643 [10 MiB, 12 MiB, 14 MiB, 16 MiB]
648 [20 MiB, 24 MiB, 28 MiB, 32 MiB]
653 [40 MiB, 48 MiB, 56 MiB, 64 MiB]
663 [2560 PiB, 3 EiB, 3584 PiB, 4 EiB]
668 [5 EiB, 6 EiB, 7 EiB]
672 .SH "MALLCTL NAMESPACE"
674 The following names are defined in the namespace accessible via the
676 functions\&. Value types are specified in parentheses, their readable/writable statuses are encoded as
680 \-\-, and required build configuration flags follow, if any\&. A name element encoded as
684 indicates an integer component, where the integer varies from 0 to some upper value that must be determined via introspection\&. In the case of
685 stats\&.arenas\&.<i>\&.*
687 arena\&.<i>\&.{initialized,purge,decay,dss},
690 \fBMALLCTL_ARENAS_ALL\fR
691 can be used to operate on all arenas or access the summation of statistics from all arenas; similarly
694 \fBMALLCTL_ARENAS_DESTROYED\fR
695 can be used to access the summation of statistics from all destroyed arenas\&. These constants can be utilized either via
698 mallctlbymib(), or via code such as the following:
704 #define STRINGIFY_HELPER(x) #x
705 #define STRINGIFY(x) STRINGIFY_HELPER(x)
707 mallctl("arena\&." STRINGIFY(MALLCTL_ARENAS_ALL) "\&.decay",
708 NULL, NULL, NULL, 0);
714 Take special note of the
716 mallctl, which controls refreshing of cached dynamic statistics\&.
718 version (\fBconst char *\fR) r\-
720 Return the jemalloc version string\&.
723 epoch (\fBuint64_t\fR) rw
725 If a value is passed in, refresh the data from which the
727 functions report values, and increment the epoch\&. Return the current epoch\&. This is useful for detecting whether another thread caused a refresh\&.
730 background_thread (\fBbool\fR) rw
732 Enable/disable internal background worker threads\&. When set to true, background threads are created on demand (the number of background threads will be no more than the number of CPUs or active arenas)\&. Threads run periodically, and handle
734 asynchronously\&. When switching off, background threads are terminated synchronously\&. Note that after
736 function, the state in the child process will be disabled regardless the state in parent process\&. See
737 stats\&.background_thread
739 opt\&.background_thread
740 can be used to set the default option\&. This option is only available on selected pthread\-based platforms\&.
743 config\&.cache_oblivious (\fBbool\fR) r\-
745 \fB\-\-enable\-cache\-oblivious\fR
746 was specified during build configuration\&.
749 config\&.debug (\fBbool\fR) r\-
751 \fB\-\-enable\-debug\fR
752 was specified during build configuration\&.
755 config\&.fill (\fBbool\fR) r\-
757 \fB\-\-enable\-fill\fR
758 was specified during build configuration\&.
761 config\&.lazy_lock (\fBbool\fR) r\-
763 \fB\-\-enable\-lazy\-lock\fR
764 was specified during build configuration\&.
767 config\&.malloc_conf (\fBconst char *\fR) r\-
769 Embedded configure\-time\-specified run\-time options string, empty unless
770 \fB\-\-with\-malloc\-conf\fR
771 was specified during build configuration\&.
774 config\&.prof (\fBbool\fR) r\-
776 \fB\-\-enable\-prof\fR
777 was specified during build configuration\&.
780 config\&.prof_libgcc (\fBbool\fR) r\-
782 \fB\-\-disable\-prof\-libgcc\fR
783 was not specified during build configuration\&.
786 config\&.prof_libunwind (\fBbool\fR) r\-
788 \fB\-\-enable\-prof\-libunwind\fR
789 was specified during build configuration\&.
792 config\&.stats (\fBbool\fR) r\-
794 \fB\-\-enable\-stats\fR
795 was specified during build configuration\&.
798 config\&.thp (\fBbool\fR) r\-
800 \fB\-\-disable\-thp\fR
801 was not specified during build configuration, and the system supports transparent huge page manipulation\&.
804 config\&.utrace (\fBbool\fR) r\-
806 \fB\-\-enable\-utrace\fR
807 was specified during build configuration\&.
810 config\&.xmalloc (\fBbool\fR) r\-
812 \fB\-\-enable\-xmalloc\fR
813 was specified during build configuration\&.
816 opt\&.abort (\fBbool\fR) r\-
818 Abort\-on\-warning enabled/disabled\&. If true, most warnings are fatal\&. Note that runtime option warnings are not included (see
820 for that)\&. The process will call
822 in these cases\&. This option is disabled by default unless
823 \fB\-\-enable\-debug\fR
824 is specified during configuration, in which case it is enabled by default\&.
827 opt\&.abort_conf (\fBbool\fR) r\-
829 Abort\-on\-invalid\-configuration enabled/disabled\&. If true, invalid runtime options are fatal\&. The process will call
831 in these cases\&. This option is disabled by default unless
832 \fB\-\-enable\-debug\fR
833 is specified during configuration, in which case it is enabled by default\&.
836 opt\&.retain (\fBbool\fR) r\-
838 If true, retain unused virtual memory for later reuse rather than discarding it by calling
842 for related details)\&. This option is disabled by default unless discarding virtual memory is known to trigger platform\-specific performance problems, e\&.g\&. for [64\-bit] Linux, which has a quirk in its virtual memory allocation algorithm that causes semi\-permanent VM map holes under normal jemalloc operation\&. Although
844 causes issues on 32\-bit Linux as well, retaining virtual memory for 32\-bit Linux is disabled by default due to the practical possibility of address space exhaustion\&.
847 opt\&.dss (\fBconst char *\fR) r\-
849 dss (\fBsbrk\fR(2)) allocation precedence as related to
851 allocation\&. The following settings are supported if
853 is supported by the operating system:
856 \(lqsecondary\(rq; otherwise only
858 is supported\&. The default is
862 is supported by the operating system;
867 opt\&.narenas (\fBunsigned\fR) r\-
869 Maximum number of arenas to use for automatic multiplexing of threads and arenas\&. The default is four times the number of CPUs, or one if there is a single CPU\&.
872 opt\&.percpu_arena (\fBconst char *\fR) r\-
874 Per CPU arena mode\&. Use the
876 setting to enable this feature, which uses number of CPUs to determine number of arenas, and bind threads to arenas dynamically based on the CPU the thread runs on currently\&.
878 setting uses one arena per physical CPU, which means the two hyper threads on the same CPU share one arena\&. Note that no runtime checking regarding the availability of hyper threading is done at the moment\&. When set to
879 \(lqdisabled\(rq, narenas and thread to arena association will not be impacted by this option\&. The default is
883 opt\&.background_thread (\fBconst bool\fR) r\-
885 Internal background worker threads enabled/disabled\&. See
887 for dynamic control options and details\&. This option is disabled by default\&.
890 opt\&.dirty_decay_ms (\fBssize_t\fR) r\-
892 Approximate time in milliseconds from the creation of a set of unused dirty pages until an equivalent set of unused dirty pages is purged (i\&.e\&. converted to muzzy via e\&.g\&.
893 madvise(\fI\&.\&.\&.\fR\fI\fBMADV_FREE\fR\fR)
894 if supported by the operating system, or converted to clean otherwise) and/or reused\&. Dirty pages are defined as previously having been potentially written to by the application, and therefore consuming physical memory, yet having no current use\&. The pages are incrementally purged according to a sigmoidal decay curve that starts and ends with zero purge rate\&. A decay time of 0 causes all unused dirty pages to be purged immediately upon creation\&. A decay time of \-1 disables purging\&. The default decay time is 10 seconds\&. See
895 arenas\&.dirty_decay_ms
897 arena\&.<i>\&.muzzy_decay_ms
898 for related dynamic control options\&. See
900 for a description of muzzy pages\&.
903 opt\&.muzzy_decay_ms (\fBssize_t\fR) r\-
905 Approximate time in milliseconds from the creation of a set of unused muzzy pages until an equivalent set of unused muzzy pages is purged (i\&.e\&. converted to clean) and/or reused\&. Muzzy pages are defined as previously having been unused dirty pages that were subsequently purged in a manner that left them subject to the reclamation whims of the operating system (e\&.g\&.
906 madvise(\fI\&.\&.\&.\fR\fI\fBMADV_FREE\fR\fR)), and therefore in an indeterminate state\&. The pages are incrementally purged according to a sigmoidal decay curve that starts and ends with zero purge rate\&. A decay time of 0 causes all unused muzzy pages to be purged immediately upon creation\&. A decay time of \-1 disables purging\&. The default decay time is 10 seconds\&. See
907 arenas\&.muzzy_decay_ms
909 arena\&.<i>\&.muzzy_decay_ms
910 for related dynamic control options\&.
913 opt\&.stats_print (\fBbool\fR) r\-
915 Enable/disable statistics printing at exit\&. If enabled, the
917 function is called at program exit via an
920 opt\&.stats_print_opts
921 can be combined to specify output options\&. If
922 \fB\-\-enable\-stats\fR
923 is specified during configuration, this has the potential to cause deadlock for a multi\-threaded process that exits while one or more threads are executing in the memory allocation functions\&. Furthermore,
925 may allocate memory during application initialization and then deadlock internally when jemalloc in turn calls
926 atexit(), so this option is not universally usable (though the application can register its own
928 function with equivalent functionality)\&. Therefore, this option should only be used with care; it is primarily intended as a performance tuning aid during application development\&. This option is disabled by default\&.
931 opt\&.stats_print_opts (\fBconst char *\fR) r\-
935 string) to pass to the
937 at exit (enabled through
938 opt\&.stats_print)\&. See available options in
939 malloc_stats_print()\&. Has no effect unless
941 is enabled\&. The default is
945 opt\&.junk (\fBconst char *\fR) r\- [\fB\-\-enable\-fill\fR]
947 Junk filling\&. If set to
948 \(lqalloc\(rq, each byte of uninitialized allocated memory will be initialized to
950 \(lqfree\(rq, all deallocated memory will be initialized to
952 \(lqtrue\(rq, both allocated and deallocated memory will be initialized, and if set to
953 \(lqfalse\(rq, junk filling be disabled entirely\&. This is intended for debugging and will impact performance negatively\&. This option is
956 \fB\-\-enable\-debug\fR
957 is specified during configuration, in which case it is
962 opt\&.zero (\fBbool\fR) r\- [\fB\-\-enable\-fill\fR]
964 Zero filling enabled/disabled\&. If enabled, each byte of uninitialized allocated memory will be initialized to 0\&. Note that this initialization only happens once for each byte, so
968 calls do not zero memory that was previously allocated\&. This is intended for debugging and will impact performance negatively\&. This option is disabled by default\&.
971 opt\&.utrace (\fBbool\fR) r\- [\fB\-\-enable\-utrace\fR]
973 Allocation tracing based on
975 enabled/disabled\&. This option is disabled by default\&.
978 opt\&.xmalloc (\fBbool\fR) r\- [\fB\-\-enable\-xmalloc\fR]
980 Abort\-on\-out\-of\-memory enabled/disabled\&. If enabled, rather than returning failure for any allocation function, display a diagnostic message on
982 and cause the program to drop core (using
983 \fBabort\fR(3))\&. If an application is designed to depend on this behavior, set the option at compile time by including the following in the source code:
989 malloc_conf = "xmalloc:true";
995 This option is disabled by default\&.
998 opt\&.tcache (\fBbool\fR) r\-
1000 Thread\-specific caching (tcache) enabled/disabled\&. When there are multiple threads, each thread uses a tcache for objects up to a certain size\&. Thread\-specific caching allows many allocations to be satisfied without performing any thread synchronization, at the cost of increased memory use\&. See the
1002 option for related tuning information\&. This option is enabled by default\&.
1005 opt\&.lg_tcache_max (\fBsize_t\fR) r\-
1007 Maximum size class (log base 2) to cache in the thread\-specific cache (tcache)\&. At a minimum, all small size classes are cached, and at a maximum all large size classes are cached\&. The default maximum is 32 KiB (2^15)\&.
1010 opt\&.prof (\fBbool\fR) r\- [\fB\-\-enable\-prof\fR]
1012 Memory profiling enabled/disabled\&. If enabled, profile memory allocation activity\&. See the
1014 option for on\-the\-fly activation/deactivation\&. See the
1015 opt\&.lg_prof_sample
1016 option for probabilistic sampling control\&. See the
1018 option for control of cumulative sample reporting\&. See the
1019 opt\&.lg_prof_interval
1020 option for information on interval\-triggered profile dumping, the
1022 option for information on high\-water\-triggered profile dumping, and the
1024 option for final profile dumping\&. Profile output is compatible with the
1026 command, which is based on the
1028 that is developed as part of the
1029 \m[blue]\fBgperftools package\fR\m[]\&\s-2\u[3]\d\s+2\&. See
1031 for heap profile format documentation\&.
1034 opt\&.prof_prefix (\fBconst char *\fR) r\- [\fB\-\-enable\-prof\fR]
1036 Filename prefix for profile dumps\&. If the prefix is set to the empty string, no automatic dumps will occur; this is primarily useful for disabling the automatic final heap dump (which also disables leak reporting, if enabled)\&. The default prefix is
1040 opt\&.prof_active (\fBbool\fR) r\- [\fB\-\-enable\-prof\fR]
1042 Profiling activated/deactivated\&. This is a secondary control mechanism that makes it possible to start the application with profiling enabled (see the
1044 option) but inactive, then toggle profiling at any time during program execution with the
1046 mallctl\&. This option is enabled by default\&.
1049 opt\&.prof_thread_active_init (\fBbool\fR) r\- [\fB\-\-enable\-prof\fR]
1052 thread\&.prof\&.active
1053 in newly created threads\&. The initial setting for newly created threads can also be changed during execution via the
1054 prof\&.thread_active_init
1055 mallctl\&. This option is enabled by default\&.
1058 opt\&.lg_prof_sample (\fBsize_t\fR) r\- [\fB\-\-enable\-prof\fR]
1060 Average interval (log base 2) between allocation samples, as measured in bytes of allocation activity\&. Increasing the sampling interval decreases profile fidelity, but also decreases the computational overhead\&. The default sample interval is 512 KiB (2^19 B)\&.
1063 opt\&.prof_accum (\fBbool\fR) r\- [\fB\-\-enable\-prof\fR]
1065 Reporting of cumulative object/byte counts in profile dumps enabled/disabled\&. If this option is enabled, every unique backtrace must be stored for the duration of execution\&. Depending on the application, this can impose a large memory overhead, and the cumulative counts are not always of interest\&. This option is disabled by default\&.
1068 opt\&.lg_prof_interval (\fBssize_t\fR) r\- [\fB\-\-enable\-prof\fR]
1070 Average interval (log base 2) between memory profile dumps, as measured in bytes of allocation activity\&. The actual interval between dumps may be sporadic because decentralized allocation counters are used to avoid synchronization bottlenecks\&. Profiles are dumped to files named according to the pattern
1071 <prefix>\&.<pid>\&.<seq>\&.i<iseq>\&.heap, where
1073 is controlled by the
1075 option\&. By default, interval\-triggered profile dumping is disabled (encoded as \-1)\&.
1078 opt\&.prof_gdump (\fBbool\fR) r\- [\fB\-\-enable\-prof\fR]
1080 Set the initial state of
1081 prof\&.gdump, which when enabled triggers a memory profile dump every time the total virtual memory exceeds the previous maximum\&. This option is disabled by default\&.
1084 opt\&.prof_final (\fBbool\fR) r\- [\fB\-\-enable\-prof\fR]
1088 function to dump final memory usage to a file named according to the pattern
1089 <prefix>\&.<pid>\&.<seq>\&.f\&.heap, where
1091 is controlled by the
1095 may allocate memory during application initialization and then deadlock internally when jemalloc in turn calls
1096 atexit(), so this option is not universally usable (though the application can register its own
1098 function with equivalent functionality)\&. This option is disabled by default\&.
1101 opt\&.prof_leak (\fBbool\fR) r\- [\fB\-\-enable\-prof\fR]
1103 Leak reporting enabled/disabled\&. If enabled, use an
1105 function to report memory leaks detected by allocation sampling\&. See the
1107 option for information on analyzing heap profile output\&. This option is disabled by default\&.
1110 thread\&.arena (\fBunsigned\fR) rw
1112 Get or set the arena associated with the calling thread\&. If the specified arena was not initialized beforehand (see the
1113 arena\&.i\&.initialized
1114 mallctl), it will be automatically initialized as a side effect of calling this interface\&.
1117 thread\&.allocated (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1119 Get the total number of bytes ever allocated by the calling thread\&. This counter has the potential to wrap around; it is up to the application to appropriately interpret the counter in such cases\&.
1122 thread\&.allocatedp (\fBuint64_t *\fR) r\- [\fB\-\-enable\-stats\fR]
1124 Get a pointer to the the value that is returned by the
1126 mallctl\&. This is useful for avoiding the overhead of repeated
1131 thread\&.deallocated (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1133 Get the total number of bytes ever deallocated by the calling thread\&. This counter has the potential to wrap around; it is up to the application to appropriately interpret the counter in such cases\&.
1136 thread\&.deallocatedp (\fBuint64_t *\fR) r\- [\fB\-\-enable\-stats\fR]
1138 Get a pointer to the the value that is returned by the
1139 thread\&.deallocated
1140 mallctl\&. This is useful for avoiding the overhead of repeated
1145 thread\&.tcache\&.enabled (\fBbool\fR) rw
1147 Enable/disable calling thread\*(Aqs tcache\&. The tcache is implicitly flushed as a side effect of becoming disabled (see
1148 thread\&.tcache\&.flush)\&.
1151 thread\&.tcache\&.flush (\fBvoid\fR) \-\-
1153 Flush calling thread\*(Aqs thread\-specific cache (tcache)\&. This interface releases all cached objects and internal data structures associated with the calling thread\*(Aqs tcache\&. Ordinarily, this interface need not be called, since automatic periodic incremental garbage collection occurs, and the thread cache is automatically discarded when a thread exits\&. However, garbage collection is triggered by allocation activity, so it is possible for a thread that stops allocating/deallocating to retain its cache indefinitely, in which case the developer may find manual flushing useful\&.
1156 thread\&.prof\&.name (\fBconst char *\fR) r\- or \-w [\fB\-\-enable\-prof\fR]
1158 Get/set the descriptive name associated with the calling thread in memory profile dumps\&. An internal copy of the name string is created, so the input string need not be maintained after this interface completes execution\&. The output string of this interface should be copied for non\-ephemeral uses, because multiple implementation details can cause asynchronous string deallocation\&. Furthermore, each invocation of this interface can only read or write; simultaneous read/write is not supported due to string lifetime limitations\&. The name string must be nil\-terminated and comprised only of characters in the sets recognized by
1164 thread\&.prof\&.active (\fBbool\fR) rw [\fB\-\-enable\-prof\fR]
1166 Control whether sampling is currently active for the calling thread\&. This is an activation mechanism in addition to
1167 prof\&.active; both must be active for the calling thread to sample\&. This flag is enabled by default\&.
1170 tcache\&.create (\fBunsigned\fR) r\-
1172 Create an explicit thread\-specific cache (tcache) and return an identifier that can be passed to the
1173 \fBMALLOCX_TCACHE(\fR\fB\fItc\fR\fR\fB)\fR
1174 macro to explicitly use the specified cache rather than the automatically managed one that is used by default\&. Each explicit cache can be used by only one thread at a time; the application must assure that this constraint holds\&.
1177 tcache\&.flush (\fBunsigned\fR) \-w
1179 Flush the specified thread\-specific cache (tcache)\&. The same considerations apply to this interface as to
1180 thread\&.tcache\&.flush, except that the tcache will never be automatically discarded\&.
1183 tcache\&.destroy (\fBunsigned\fR) \-w
1185 Flush the specified thread\-specific cache (tcache) and make the identifier available for use during a future tcache creation\&.
1188 arena\&.<i>\&.initialized (\fBbool\fR) r\-
1190 Get whether the specified arena\*(Aqs statistics are initialized (i\&.e\&. the arena was initialized prior to the current epoch)\&. This interface can also be nominally used to query whether the merged statistics corresponding to
1191 \fBMALLCTL_ARENAS_ALL\fR
1192 are initialized (always true)\&.
1195 arena\&.<i>\&.decay (\fBvoid\fR) \-\-
1197 Trigger decay\-based purging of unused dirty/muzzy pages for arena <i>, or for all arenas if <i> equals
1198 \fBMALLCTL_ARENAS_ALL\fR\&. The proportion of unused dirty/muzzy pages to be purged depends on the current time; see
1199 opt\&.dirty_decay_ms
1205 arena\&.<i>\&.purge (\fBvoid\fR) \-\-
1207 Purge all unused dirty pages for arena <i>, or for all arenas if <i> equals
1208 \fBMALLCTL_ARENAS_ALL\fR\&.
1211 arena\&.<i>\&.reset (\fBvoid\fR) \-\-
1213 Discard all of the arena\*(Aqs extant allocations\&. This interface can only be used with arenas explicitly created via
1214 arenas\&.create\&. None of the arena\*(Aqs discarded/cached allocations may accessed afterward\&. As part of this requirement, all thread caches which were used to allocate/deallocate in conjunction with the arena must be flushed beforehand\&.
1217 arena\&.<i>\&.destroy (\fBvoid\fR) \-\-
1219 Destroy the arena\&. Discard all of the arena\*(Aqs extant allocations using the same mechanism as for
1221 (with all the same constraints and side effects), merge the arena stats into those accessible at arena index
1222 \fBMALLCTL_ARENAS_DESTROYED\fR, and then completely discard all metadata associated with the arena\&. Future calls to
1224 may recycle the arena index\&. Destruction will fail if any threads are currently associated with the arena as a result of calls to
1228 arena\&.<i>\&.dss (\fBconst char *\fR) rw
1230 Set the precedence of dss allocation as related to mmap allocation for arena <i>, or for all arenas if <i> equals
1231 \fBMALLCTL_ARENAS_ALL\fR\&. See
1233 for supported settings\&.
1236 arena\&.<i>\&.dirty_decay_ms (\fBssize_t\fR) rw
1238 Current per\-arena approximate time in milliseconds from the creation of a set of unused dirty pages until an equivalent set of unused dirty pages is purged and/or reused\&. Each time this interface is set, all currently unused dirty pages are considered to have fully decayed, which causes immediate purging of all unused dirty pages unless the decay time is set to \-1 (i\&.e\&. purging disabled)\&. See
1239 opt\&.dirty_decay_ms
1240 for additional information\&.
1243 arena\&.<i>\&.muzzy_decay_ms (\fBssize_t\fR) rw
1245 Current per\-arena approximate time in milliseconds from the creation of a set of unused muzzy pages until an equivalent set of unused muzzy pages is purged and/or reused\&. Each time this interface is set, all currently unused muzzy pages are considered to have fully decayed, which causes immediate purging of all unused muzzy pages unless the decay time is set to \-1 (i\&.e\&. purging disabled)\&. See
1246 opt\&.muzzy_decay_ms
1247 for additional information\&.
1250 arena\&.<i>\&.extent_hooks (\fBextent_hooks_t *\fR) rw
1252 Get or set the extent management hook functions for arena <i>\&. The functions must be capable of operating on all extant extents associated with arena <i>, usually by passing unknown extents to the replaced functions\&. In practice, it is feasible to control allocation for arenas explicitly created via
1254 such that all extents originate from an application\-supplied extent allocator (by specifying the custom extent hook functions during arena creation), but the automatically created arenas will have already created extents prior to the application having an opportunity to take over extent allocation\&.
1260 typedef extent_hooks_s extent_hooks_t;
1261 struct extent_hooks_s {
1262 extent_alloc_t *alloc;
1263 extent_dalloc_t *dalloc;
1264 extent_destroy_t *destroy;
1265 extent_commit_t *commit;
1266 extent_decommit_t *decommit;
1267 extent_purge_t *purge_lazy;
1268 extent_purge_t *purge_forced;
1269 extent_split_t *split;
1270 extent_merge_t *merge;
1278 \fBextent_hooks_t\fR
1279 structure comprises function pointers which are described individually below\&. jemalloc uses these functions to manage extent lifetime, which starts off with allocation of mapped committed memory, in the simplest case followed by deallocation\&. However, there are performance and platform reasons to retain extents for later reuse\&. Cleanup attempts cascade from deallocation to decommit to forced purging to lazy purging, which gives the extent management functions opportunities to reject the most permanent cleanup operations in favor of less permanent (and often less costly) operations\&. All operations except allocation can be universally opted out of by setting the hook pointers to
1280 \fBNULL\fR, or selectively opted out of by returning failure\&.
1281 .HP \w'typedef\ void\ *(extent_alloc_t)('u
1282 .BI "typedef void *(extent_alloc_t)(extent_hooks_t\ *" "extent_hooks" ", void\ *" "new_addr" ", size_t\ " "size" ", size_t\ " "alignment" ", bool\ *" "zero" ", bool\ *" "commit" ", unsigned\ " "arena_ind" ");"
1293 An extent allocation function conforms to the
1294 \fBextent_alloc_t\fR
1295 type and upon success returns a pointer to
1297 bytes of mapped memory on behalf of arena
1299 such that the extent\*(Aqs base address is a multiple of
1300 \fIalignment\fR, as well as setting
1302 to indicate whether the extent is zeroed and
1304 to indicate whether the extent is committed\&. Upon error the function returns
1312 parameter is always a multiple of the page size\&. The
1314 parameter is always a power of two at least as large as the page size\&. Zeroing is mandatory if
1316 is true upon function entry\&. Committing is mandatory if
1318 is true upon function entry\&. If
1321 \fBNULL\fR, the returned pointer must be
1325 on error\&. Committed memory may be committed in absolute terms as on a system that does not overcommit, or in implicit terms as on a system that overcommits and satisfies physical memory needs on demand via soft page faults\&. Note that replacing the default extent allocation function makes the arena\*(Aqs
1327 setting irrelevant\&.
1328 .HP \w'typedef\ bool\ (extent_dalloc_t)('u
1329 .BI "typedef bool (extent_dalloc_t)(extent_hooks_t\ *" "extent_hooks" ", void\ *" "addr" ", size_t\ " "size" ", bool\ " "committed" ", unsigned\ " "arena_ind" ");"
1340 An extent deallocation function conforms to the
1341 \fBextent_dalloc_t\fR
1342 type and deallocates an extent at given
1347 \fIcommitted\fR/decommited memory as indicated, on behalf of arena
1348 \fIarena_ind\fR, returning false upon success\&. If the function returns true, this indicates opt\-out from deallocation; the virtual memory mapping associated with the extent remains mapped, in the same commit state, and available for future use, in which case it will be automatically retained for later reuse\&.
1349 .HP \w'typedef\ void\ (extent_destroy_t)('u
1350 .BI "typedef void (extent_destroy_t)(extent_hooks_t\ *" "extent_hooks" ", void\ *" "addr" ", size_t\ " "size" ", bool\ " "committed" ", unsigned\ " "arena_ind" ");"
1361 An extent destruction function conforms to the
1362 \fBextent_destroy_t\fR
1363 type and unconditionally destroys an extent at given
1368 \fIcommitted\fR/decommited memory as indicated, on behalf of arena
1369 \fIarena_ind\fR\&. This function may be called to destroy retained extents during arena destruction (see
1370 arena\&.<i>\&.destroy)\&.
1371 .HP \w'typedef\ bool\ (extent_commit_t)('u
1372 .BI "typedef bool (extent_commit_t)(extent_hooks_t\ *" "extent_hooks" ", void\ *" "addr" ", size_t\ " "size" ", size_t\ " "offset" ", size_t\ " "length" ", unsigned\ " "arena_ind" ");"
1383 An extent commit function conforms to the
1384 \fBextent_commit_t\fR
1385 type and commits zeroed physical memory to back pages within an extent at given
1391 bytes, extending for
1394 \fIarena_ind\fR, returning false upon success\&. Committed memory may be committed in absolute terms as on a system that does not overcommit, or in implicit terms as on a system that overcommits and satisfies physical memory needs on demand via soft page faults\&. If the function returns true, this indicates insufficient physical memory to satisfy the request\&.
1395 .HP \w'typedef\ bool\ (extent_decommit_t)('u
1396 .BI "typedef bool (extent_decommit_t)(extent_hooks_t\ *" "extent_hooks" ", void\ *" "addr" ", size_t\ " "size" ", size_t\ " "offset" ", size_t\ " "length" ", unsigned\ " "arena_ind" ");"
1407 An extent decommit function conforms to the
1408 \fBextent_decommit_t\fR
1409 type and decommits any physical memory that is backing pages within an extent at given
1415 bytes, extending for
1418 \fIarena_ind\fR, returning false upon success, in which case the pages will be committed via the extent commit function before being reused\&. If the function returns true, this indicates opt\-out from decommit; the memory remains committed and available for future use, in which case it will be automatically retained for later reuse\&.
1419 .HP \w'typedef\ bool\ (extent_purge_t)('u
1420 .BI "typedef bool (extent_purge_t)(extent_hooks_t\ *" "extent_hooks" ", void\ *" "addr" ", size_t\ " "size" ", size_t\ " "offset" ", size_t\ " "length" ", unsigned\ " "arena_ind" ");"
1431 An extent purge function conforms to the
1432 \fBextent_purge_t\fR
1433 type and discards physical pages within the virtual memory mapping associated with an extent at given
1439 bytes, extending for
1442 \fIarena_ind\fR\&. A lazy extent purge function (e\&.g\&. implemented via
1443 madvise(\fI\&.\&.\&.\fR\fI\fBMADV_FREE\fR\fR)) can delay purging indefinitely and leave the pages within the purged virtual memory range in an indeterminite state, whereas a forced extent purge function immediately purges, and the pages within the virtual memory range will be zero\-filled the next time they are accessed\&. If the function returns true, this indicates failure to purge\&.
1444 .HP \w'typedef\ bool\ (extent_split_t)('u
1445 .BI "typedef bool (extent_split_t)(extent_hooks_t\ *" "extent_hooks" ", void\ *" "addr" ", size_t\ " "size" ", size_t\ " "size_a" ", size_t\ " "size_b" ", bool\ " "committed" ", unsigned\ " "arena_ind" ");"
1456 An extent split function conforms to the
1457 \fBextent_split_t\fR
1458 type and optionally splits an extent at given
1462 into two adjacent extents, the first of
1464 bytes, and the second of
1467 \fIcommitted\fR/decommitted memory as indicated, on behalf of arena
1468 \fIarena_ind\fR, returning false upon success\&. If the function returns true, this indicates that the extent remains unsplit and therefore should continue to be operated on as a whole\&.
1469 .HP \w'typedef\ bool\ (extent_merge_t)('u
1470 .BI "typedef bool (extent_merge_t)(extent_hooks_t\ *" "extent_hooks" ", void\ *" "addr_a" ", size_t\ " "size_a" ", void\ *" "addr_b" ", size_t\ " "size_b" ", bool\ " "committed" ", unsigned\ " "arena_ind" ");"
1481 An extent merge function conforms to the
1482 \fBextent_merge_t\fR
1483 type and optionally merges adjacent extents, at given
1491 into one contiguous extent, operating on
1492 \fIcommitted\fR/decommitted memory as indicated, on behalf of arena
1493 \fIarena_ind\fR, returning false upon success\&. If the function returns true, this indicates that the extents remain distinct mappings and therefore should continue to be operated on independently\&.
1496 arenas\&.narenas (\fBunsigned\fR) r\-
1498 Current limit on number of arenas\&.
1501 arenas\&.dirty_decay_ms (\fBssize_t\fR) rw
1503 Current default per\-arena approximate time in milliseconds from the creation of a set of unused dirty pages until an equivalent set of unused dirty pages is purged and/or reused, used to initialize
1504 arena\&.<i>\&.dirty_decay_ms
1505 during arena creation\&. See
1506 opt\&.dirty_decay_ms
1507 for additional information\&.
1510 arenas\&.muzzy_decay_ms (\fBssize_t\fR) rw
1512 Current default per\-arena approximate time in milliseconds from the creation of a set of unused muzzy pages until an equivalent set of unused muzzy pages is purged and/or reused, used to initialize
1513 arena\&.<i>\&.muzzy_decay_ms
1514 during arena creation\&. See
1515 opt\&.muzzy_decay_ms
1516 for additional information\&.
1519 arenas\&.quantum (\fBsize_t\fR) r\-
1524 arenas\&.page (\fBsize_t\fR) r\-
1529 arenas\&.tcache_max (\fBsize_t\fR) r\-
1531 Maximum thread\-cached size class\&.
1534 arenas\&.nbins (\fBunsigned\fR) r\-
1536 Number of bin size classes\&.
1539 arenas\&.nhbins (\fBunsigned\fR) r\-
1541 Total number of thread cache bin size classes\&.
1544 arenas\&.bin\&.<i>\&.size (\fBsize_t\fR) r\-
1546 Maximum size supported by size class\&.
1549 arenas\&.bin\&.<i>\&.nregs (\fBuint32_t\fR) r\-
1551 Number of regions per slab\&.
1554 arenas\&.bin\&.<i>\&.slab_size (\fBsize_t\fR) r\-
1556 Number of bytes per slab\&.
1559 arenas\&.nlextents (\fBunsigned\fR) r\-
1561 Total number of large size classes\&.
1564 arenas\&.lextent\&.<i>\&.size (\fBsize_t\fR) r\-
1566 Maximum size supported by this large size class\&.
1569 arenas\&.create (\fBunsigned\fR, \fBextent_hooks_t *\fR) rw
1571 Explicitly create a new arena outside the range of automatically managed arenas, with optionally specified extent hooks, and return the new arena index\&.
1574 prof\&.thread_active_init (\fBbool\fR) rw [\fB\-\-enable\-prof\fR]
1576 Control the initial setting for
1577 thread\&.prof\&.active
1578 in newly created threads\&. See the
1579 opt\&.prof_thread_active_init
1580 option for additional information\&.
1583 prof\&.active (\fBbool\fR) rw [\fB\-\-enable\-prof\fR]
1585 Control whether sampling is currently active\&. See the
1587 option for additional information, as well as the interrelated
1588 thread\&.prof\&.active
1592 prof\&.dump (\fBconst char *\fR) \-w [\fB\-\-enable\-prof\fR]
1594 Dump a memory profile to the specified file, or if NULL is specified, to a file according to the pattern
1595 <prefix>\&.<pid>\&.<seq>\&.m<mseq>\&.heap, where
1597 is controlled by the
1602 prof\&.gdump (\fBbool\fR) rw [\fB\-\-enable\-prof\fR]
1604 When enabled, trigger a memory profile dump every time the total virtual memory exceeds the previous maximum\&. Profiles are dumped to files named according to the pattern
1605 <prefix>\&.<pid>\&.<seq>\&.u<useq>\&.heap, where
1607 is controlled by the
1612 prof\&.reset (\fBsize_t\fR) \-w [\fB\-\-enable\-prof\fR]
1614 Reset all memory profile statistics, and optionally update the sample rate (see
1615 opt\&.lg_prof_sample
1617 prof\&.lg_sample)\&.
1620 prof\&.lg_sample (\fBsize_t\fR) r\- [\fB\-\-enable\-prof\fR]
1622 Get the current sample rate (see
1623 opt\&.lg_prof_sample)\&.
1626 prof\&.interval (\fBuint64_t\fR) r\- [\fB\-\-enable\-prof\fR]
1628 Average number of bytes allocated between interval\-based profile dumps\&. See the
1629 opt\&.lg_prof_interval
1630 option for additional information\&.
1633 stats\&.allocated (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1635 Total number of bytes allocated by the application\&.
1638 stats\&.active (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1640 Total number of bytes in active pages allocated by the application\&. This is a multiple of the page size, and greater than or equal to
1641 stats\&.allocated\&. This does not include
1642 stats\&.arenas\&.<i>\&.pdirty,
1643 stats\&.arenas\&.<i>\&.pmuzzy, nor pages entirely devoted to allocator metadata\&.
1646 stats\&.metadata (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1648 Total number of bytes dedicated to metadata, which comprise base allocations used for bootstrap\-sensitive allocator metadata structures (see
1649 stats\&.arenas\&.<i>\&.base) and internal allocations (see
1650 stats\&.arenas\&.<i>\&.internal)\&.
1653 stats\&.resident (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1655 Maximum number of bytes in physically resident data pages mapped by the allocator, comprising all pages dedicated to allocator metadata, pages backing active allocations, and unused dirty pages\&. This is a maximum rather than precise because pages may not actually be physically resident if they correspond to demand\-zeroed virtual memory that has not yet been touched\&. This is a multiple of the page size, and is larger than
1659 stats\&.mapped (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1661 Total number of bytes in active extents mapped by the allocator\&. This is larger than
1662 stats\&.active\&. This does not include inactive extents, even those that contain unused dirty pages, which means that there is no strict ordering between this and
1666 stats\&.retained (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1668 Total number of bytes in virtual memory mappings that were retained rather than being returned to the operating system via e\&.g\&.
1670 or similar\&. Retained virtual memory is typically untouched, decommitted, or purged, so it has no strongly associated physical memory (see
1672 for details)\&. Retained memory is excluded from mapped memory statistics, e\&.g\&.
1676 stats\&.background_thread\&.num_threads (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1680 running currently\&.
1683 stats\&.background_thread\&.num_runs (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1685 Total number of runs from all
1686 background threads\&.
1689 stats\&.background_thread\&.run_interval (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1691 Average run interval in nanoseconds of
1692 background threads\&.
1695 stats\&.mutexes\&.ctl\&.{counter}; (\fBcounter specific type\fR) r\- [\fB\-\-enable\-stats\fR]
1699 mutex (global scope; mallctl related)\&.
1701 is one of the counters below:
1705 (\fBuint64_t\fR): Total number of lock acquisition operations on this mutex\&.
1708 (\fBuint64_t\fR): Number of times the mutex was spin\-acquired\&. When the mutex is currently locked and cannot be acquired immediately, a short period of spin\-retry within jemalloc will be performed\&. Acquired through spin generally means the contention was lightweight and not causing context switches\&.
1711 (\fBuint64_t\fR): Number of times the mutex was wait\-acquired, which means the mutex contention was not solved by spin\-retry, and blocking operation was likely involved in order to acquire the mutex\&. This event generally implies higher cost / longer delay, and should be investigated if it happens often\&.
1714 (\fBuint64_t\fR): Maximum length of time in nanoseconds spent on a single wait\-acquired lock operation\&. Note that to avoid profiling overhead on the common path, this does not consider spin\-acquired cases\&.
1716 \fItotal_wait_time\fR
1717 (\fBuint64_t\fR): Cumulative time in nanoseconds spent on wait\-acquired lock operations\&. Similarly, spin\-acquired cases are not considered\&.
1720 (\fBuint32_t\fR): Maximum number of threads waiting on this mutex simultaneously\&. Similarly, spin\-acquired cases are not considered\&.
1722 \fInum_owner_switch\fR
1723 (\fBuint64_t\fR): Number of times the current mutex owner is different from the previous one\&. This event does not generally imply an issue; rather it is an indicator of how often the protected data are accessed by different threads\&.
1727 stats\&.mutexes\&.background_thread\&.{counter} (\fBcounter specific type\fR) r\- [\fB\-\-enable\-stats\fR]
1730 \fIbackground_thread\fR
1731 mutex (global scope;
1735 is one of the counters in
1736 mutex profiling counters\&.
1739 stats\&.mutexes\&.prof\&.{counter} (\fBcounter specific type\fR) r\- [\fB\-\-enable\-stats\fR]
1743 mutex (global scope; profiling related)\&.
1745 is one of the counters in
1746 mutex profiling counters\&.
1749 stats\&.mutexes\&.reset (\fBvoid\fR) \-\- [\fB\-\-enable\-stats\fR]
1751 Reset all mutex profile statistics, including global mutexes, arena mutexes and bin mutexes\&.
1754 stats\&.arenas\&.<i>\&.dss (\fBconst char *\fR) r\-
1756 dss (\fBsbrk\fR(2)) allocation precedence as related to
1763 stats\&.arenas\&.<i>\&.dirty_decay_ms (\fBssize_t\fR) r\-
1765 Approximate time in milliseconds from the creation of a set of unused dirty pages until an equivalent set of unused dirty pages is purged and/or reused\&. See
1766 opt\&.dirty_decay_ms
1770 stats\&.arenas\&.<i>\&.muzzy_decay_ms (\fBssize_t\fR) r\-
1772 Approximate time in milliseconds from the creation of a set of unused muzzy pages until an equivalent set of unused muzzy pages is purged and/or reused\&. See
1773 opt\&.muzzy_decay_ms
1777 stats\&.arenas\&.<i>\&.nthreads (\fBunsigned\fR) r\-
1779 Number of threads currently assigned to arena\&.
1782 stats\&.arenas\&.<i>\&.uptime (\fBuint64_t\fR) r\-
1784 Time elapsed (in nanoseconds) since the arena was created\&. If <i> equals
1787 \fBMALLCTL_ARENAS_ALL\fR, this is the uptime since malloc initialization\&.
1790 stats\&.arenas\&.<i>\&.pactive (\fBsize_t\fR) r\-
1792 Number of pages in active extents\&.
1795 stats\&.arenas\&.<i>\&.pdirty (\fBsize_t\fR) r\-
1797 Number of pages within unused extents that are potentially dirty, and for which
1799 or similar has not been called\&. See
1800 opt\&.dirty_decay_ms
1801 for a description of dirty pages\&.
1804 stats\&.arenas\&.<i>\&.pmuzzy (\fBsize_t\fR) r\-
1806 Number of pages within unused extents that are muzzy\&. See
1807 opt\&.muzzy_decay_ms
1808 for a description of muzzy pages\&.
1811 stats\&.arenas\&.<i>\&.mapped (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1813 Number of mapped bytes\&.
1816 stats\&.arenas\&.<i>\&.retained (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1818 Number of retained bytes\&. See
1823 stats\&.arenas\&.<i>\&.base (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1825 Number of bytes dedicated to bootstrap\-sensitive allocator metadata structures\&.
1828 stats\&.arenas\&.<i>\&.internal (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1830 Number of bytes dedicated to internal allocations\&. Internal allocations differ from application\-originated allocations in that they are for internal use, and that they are omitted from heap profiles\&.
1833 stats\&.arenas\&.<i>\&.resident (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1835 Maximum number of bytes in physically resident data pages mapped by the arena, comprising all pages dedicated to allocator metadata, pages backing active allocations, and unused dirty pages\&. This is a maximum rather than precise because pages may not actually be physically resident if they correspond to demand\-zeroed virtual memory that has not yet been touched\&. This is a multiple of the page size\&.
1838 stats\&.arenas\&.<i>\&.dirty_npurge (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1840 Number of dirty page purge sweeps performed\&.
1843 stats\&.arenas\&.<i>\&.dirty_nmadvise (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1847 or similar calls made to purge dirty pages\&.
1850 stats\&.arenas\&.<i>\&.dirty_purged (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1852 Number of dirty pages purged\&.
1855 stats\&.arenas\&.<i>\&.muzzy_npurge (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1857 Number of muzzy page purge sweeps performed\&.
1860 stats\&.arenas\&.<i>\&.muzzy_nmadvise (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1864 or similar calls made to purge muzzy pages\&.
1867 stats\&.arenas\&.<i>\&.muzzy_purged (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1869 Number of muzzy pages purged\&.
1872 stats\&.arenas\&.<i>\&.small\&.allocated (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1874 Number of bytes currently allocated by small objects\&.
1877 stats\&.arenas\&.<i>\&.small\&.nmalloc (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1879 Cumulative number of times a small allocation was requested from the arena\*(Aqs bins, whether to fill the relevant tcache if
1881 is enabled, or to directly satisfy an allocation request otherwise\&.
1884 stats\&.arenas\&.<i>\&.small\&.ndalloc (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1886 Cumulative number of times a small allocation was returned to the arena\*(Aqs bins, whether to flush the relevant tcache if
1888 is enabled, or to directly deallocate an allocation otherwise\&.
1891 stats\&.arenas\&.<i>\&.small\&.nrequests (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1893 Cumulative number of allocation requests satisfied by all bin size classes\&.
1896 stats\&.arenas\&.<i>\&.large\&.allocated (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1898 Number of bytes currently allocated by large objects\&.
1901 stats\&.arenas\&.<i>\&.large\&.nmalloc (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1903 Cumulative number of times a large extent was allocated from the arena, whether to fill the relevant tcache if
1905 is enabled and the size class is within the range being cached, or to directly satisfy an allocation request otherwise\&.
1908 stats\&.arenas\&.<i>\&.large\&.ndalloc (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1910 Cumulative number of times a large extent was returned to the arena, whether to flush the relevant tcache if
1912 is enabled and the size class is within the range being cached, or to directly deallocate an allocation otherwise\&.
1915 stats\&.arenas\&.<i>\&.large\&.nrequests (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1917 Cumulative number of allocation requests satisfied by all large size classes\&.
1920 stats\&.arenas\&.<i>\&.bins\&.<j>\&.nmalloc (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1922 Cumulative number of times a bin region of the corresponding size class was allocated from the arena, whether to fill the relevant tcache if
1924 is enabled, or to directly satisfy an allocation request otherwise\&.
1927 stats\&.arenas\&.<i>\&.bins\&.<j>\&.ndalloc (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1929 Cumulative number of times a bin region of the corresponding size class was returned to the arena, whether to flush the relevant tcache if
1931 is enabled, or to directly deallocate an allocation otherwise\&.
1934 stats\&.arenas\&.<i>\&.bins\&.<j>\&.nrequests (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1936 Cumulative number of allocation requests satisfied by bin regions of the corresponding size class\&.
1939 stats\&.arenas\&.<i>\&.bins\&.<j>\&.curregs (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1941 Current number of regions for this size class\&.
1944 stats\&.arenas\&.<i>\&.bins\&.<j>\&.nfills (\fBuint64_t\fR) r\-
1946 Cumulative number of tcache fills\&.
1949 stats\&.arenas\&.<i>\&.bins\&.<j>\&.nflushes (\fBuint64_t\fR) r\-
1951 Cumulative number of tcache flushes\&.
1954 stats\&.arenas\&.<i>\&.bins\&.<j>\&.nslabs (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1956 Cumulative number of slabs created\&.
1959 stats\&.arenas\&.<i>\&.bins\&.<j>\&.nreslabs (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1961 Cumulative number of times the current slab from which to allocate changed\&.
1964 stats\&.arenas\&.<i>\&.bins\&.<j>\&.curslabs (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1966 Current number of slabs\&.
1969 stats\&.arenas\&.<i>\&.bins\&.<j>\&.mutex\&.{counter} (\fBcounter specific type\fR) r\- [\fB\-\-enable\-stats\fR]
1972 \fIarena\&.<i>\&.bins\&.<j>\fR
1973 mutex (arena bin scope; bin operation related)\&.
1975 is one of the counters in
1976 mutex profiling counters\&.
1979 stats\&.arenas\&.<i>\&.lextents\&.<j>\&.nmalloc (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1981 Cumulative number of times a large extent of the corresponding size class was allocated from the arena, whether to fill the relevant tcache if
1983 is enabled and the size class is within the range being cached, or to directly satisfy an allocation request otherwise\&.
1986 stats\&.arenas\&.<i>\&.lextents\&.<j>\&.ndalloc (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1988 Cumulative number of times a large extent of the corresponding size class was returned to the arena, whether to flush the relevant tcache if
1990 is enabled and the size class is within the range being cached, or to directly deallocate an allocation otherwise\&.
1993 stats\&.arenas\&.<i>\&.lextents\&.<j>\&.nrequests (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1995 Cumulative number of allocation requests satisfied by large extents of the corresponding size class\&.
1998 stats\&.arenas\&.<i>\&.lextents\&.<j>\&.curlextents (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
2000 Current number of large allocations for this size class\&.
2003 stats\&.arenas\&.<i>\&.mutexes\&.large\&.{counter} (\fBcounter specific type\fR) r\- [\fB\-\-enable\-stats\fR]
2006 \fIarena\&.<i>\&.large\fR
2007 mutex (arena scope; large allocation related)\&.
2009 is one of the counters in
2010 mutex profiling counters\&.
2013 stats\&.arenas\&.<i>\&.mutexes\&.extent_avail\&.{counter} (\fBcounter specific type\fR) r\- [\fB\-\-enable\-stats\fR]
2016 \fIarena\&.<i>\&.extent_avail \fR
2017 mutex (arena scope; extent avail related)\&.
2019 is one of the counters in
2020 mutex profiling counters\&.
2023 stats\&.arenas\&.<i>\&.mutexes\&.extents_dirty\&.{counter} (\fBcounter specific type\fR) r\- [\fB\-\-enable\-stats\fR]
2026 \fIarena\&.<i>\&.extents_dirty \fR
2027 mutex (arena scope; dirty extents related)\&.
2029 is one of the counters in
2030 mutex profiling counters\&.
2033 stats\&.arenas\&.<i>\&.mutexes\&.extents_muzzy\&.{counter} (\fBcounter specific type\fR) r\- [\fB\-\-enable\-stats\fR]
2036 \fIarena\&.<i>\&.extents_muzzy \fR
2037 mutex (arena scope; muzzy extents related)\&.
2039 is one of the counters in
2040 mutex profiling counters\&.
2043 stats\&.arenas\&.<i>\&.mutexes\&.extents_retained\&.{counter} (\fBcounter specific type\fR) r\- [\fB\-\-enable\-stats\fR]
2046 \fIarena\&.<i>\&.extents_retained \fR
2047 mutex (arena scope; retained extents related)\&.
2049 is one of the counters in
2050 mutex profiling counters\&.
2053 stats\&.arenas\&.<i>\&.mutexes\&.decay_dirty\&.{counter} (\fBcounter specific type\fR) r\- [\fB\-\-enable\-stats\fR]
2056 \fIarena\&.<i>\&.decay_dirty \fR
2057 mutex (arena scope; decay for dirty pages related)\&.
2059 is one of the counters in
2060 mutex profiling counters\&.
2063 stats\&.arenas\&.<i>\&.mutexes\&.decay_muzzy\&.{counter} (\fBcounter specific type\fR) r\- [\fB\-\-enable\-stats\fR]
2066 \fIarena\&.<i>\&.decay_muzzy \fR
2067 mutex (arena scope; decay for muzzy pages related)\&.
2069 is one of the counters in
2070 mutex profiling counters\&.
2073 stats\&.arenas\&.<i>\&.mutexes\&.base\&.{counter} (\fBcounter specific type\fR) r\- [\fB\-\-enable\-stats\fR]
2076 \fIarena\&.<i>\&.base\fR
2077 mutex (arena scope; base allocator related)\&.
2079 is one of the counters in
2080 mutex profiling counters\&.
2083 stats\&.arenas\&.<i>\&.mutexes\&.tcache_list\&.{counter} (\fBcounter specific type\fR) r\- [\fB\-\-enable\-stats\fR]
2086 \fIarena\&.<i>\&.tcache_list\fR
2087 mutex (arena scope; tcache to arena association related)\&. This mutex is expected to be accessed less often\&.
2089 is one of the counters in
2090 mutex profiling counters\&.
2092 .SH "HEAP PROFILE FORMAT"
2094 Although the heap profiling functionality was originally designed to be compatible with the
2096 command that is developed as part of the
2097 \m[blue]\fBgperftools package\fR\m[]\&\s-2\u[3]\d\s+2, the addition of per thread heap profiling functionality required a different heap profile format\&. The
2099 command is derived from
2100 \fBpprof\fR, with enhancements to support the heap profile format described here\&.
2102 In the following hypothetical heap profile,
2104 indicates elision for the sake of compactness\&.
2111 t*: 28106: 56637512 [0: 0]
2113 t3: 352: 16777344 [0: 0]
2115 t99: 17754: 29341640 [0: 0]
2117 @ 0x5f86da8 0x5f5a1dc [\&.\&.\&.] 0x29e4d4e 0xa200316 0xabb2988 [\&.\&.\&.]
2130 The following matches the above heap profile, but most tokens are replaced with
2132 to indicate descriptions of the corresponding fields\&.
2138 <heap_profile_format_version>/<mean_sample_interval>
2139 <aggregate>: <curobjs>: <curbytes> [<cumobjs>: <cumbytes>]
2141 <thread_3_aggregate>: <curobjs>: <curbytes>[<cumobjs>: <cumbytes>]
2143 <thread_99_aggregate>: <curobjs>: <curbytes>[<cumobjs>: <cumbytes>]
2145 @ <top_frame> <frame> [\&.\&.\&.] <frame> <frame> <frame> [\&.\&.\&.]
2146 <backtrace_aggregate>: <curobjs>: <curbytes> [<cumobjs>: <cumbytes>]
2147 <backtrace_thread_3>: <curobjs>: <curbytes> [<cumobjs>: <cumbytes>]
2148 <backtrace_thread_99>: <curobjs>: <curbytes> [<cumobjs>: <cumbytes>]
2157 .SH "DEBUGGING MALLOC PROBLEMS"
2159 When debugging, it is a good idea to configure/build jemalloc with the
2160 \fB\-\-enable\-debug\fR
2162 \fB\-\-enable\-fill\fR
2163 options, and recompile the program with suitable options and symbols for debugger support\&. When so configured, jemalloc incorporates a wide variety of run\-time assertions that catch application errors such as double\-free, write\-after\-free, etc\&.
2165 Programs often accidentally depend on
2166 \(lquninitialized\(rq
2167 memory actually being filled with zero bytes\&. Junk filling (see the
2169 option) tends to expose such bugs in the form of obviously incorrect results and/or coredumps\&. Conversely, zero filling (see the
2171 option) eliminates the symptoms of such bugs\&. Between these two options, it is usually possible to quickly detect, diagnose, and eliminate such bugs\&.
2173 This implementation does not provide much detail about the problems it detects, because the performance impact for storing such information would be prohibitive\&.
2174 .SH "DIAGNOSTIC MESSAGES"
2176 If any of the memory allocation/deallocation functions detect an error or warning condition, a message will be printed to file descriptor
2177 \fBSTDERR_FILENO\fR\&. Errors will result in the process dumping core\&. If the
2179 option is set, most warnings are treated as errors\&.
2182 \fImalloc_message\fR
2183 variable allows the programmer to override the function which emits the text strings forming the errors and warnings if for some reason the
2185 file descriptor is not suitable for this\&.
2189 pointer argument that is
2191 unless overridden by the arguments in a call to
2192 malloc_stats_print(), followed by a string pointer\&. Please note that doing anything which tries to allocate memory in this function is likely to result in a crash or deadlock\&.
2194 All messages are prefixed by
2195 \(lq<jemalloc>: \(rq\&.
2203 functions return a pointer to the allocated memory if successful; otherwise a
2205 pointer is returned and
2212 function returns the value 0 if successful; otherwise it returns an error value\&. The
2214 function will fail if:
2220 parameter is not a power of 2 at least as large as
2221 sizeof(\fBvoid *\fR)\&.
2226 Memory allocation error\&.
2231 function returns a pointer to the allocated memory if successful; otherwise a
2233 pointer is returned and
2237 function will fail if:
2243 parameter is not a power of 2\&.
2248 Memory allocation error\&.
2253 function returns a pointer, possibly identical to
2254 \fIptr\fR, to the allocated memory if successful; otherwise a
2256 pointer is returned, and
2260 if the error was the result of an allocation failure\&. The
2262 function always leaves the original buffer intact when an error occurs\&.
2266 function returns no value\&.
2267 .SS "Non\-standard API"
2273 functions return a pointer to the allocated memory if successful; otherwise a
2275 pointer is returned to indicate insufficient contiguous memory was available to service the allocation request\&.
2279 function returns the real size of the resulting resized allocation pointed to by
2280 \fIptr\fR, which is a value less than
2282 if the allocation could not be adequately grown in place\&.
2286 function returns the real size of the allocation pointed to by
2291 returns the real size that would result from a successful equivalent
2293 function call, or zero if insufficient memory is available to perform the size computation\&.
2297 mallctlnametomib(), and
2299 functions return 0 on success; otherwise they return an error value\&. The functions will fail if:
2307 is too large or too small\&. Alternatively,
2309 is too large or too small; in this case as much data as possible are read despite the error\&.
2317 specifies an unknown/invalid value\&.
2322 Attempt to read or write void value, or attempt to write read\-only value\&.
2327 A memory allocation failure occurred\&.
2332 An interface with side effects failed in some way not directly related to
2334 read/write processing\&.
2338 malloc_usable_size()
2339 function returns the usable size of the allocation pointed to by
2343 The following environment variable affects the execution of the allocation functions:
2347 If the environment variable
2349 is set, the characters it contains will be interpreted as options\&.
2353 To dump core whenever a problem occurs:
2359 ln \-s \*(Aqabort:true\*(Aq /etc/malloc\&.conf
2365 To specify in the source that only one arena should be automatically created:
2371 malloc_conf = "narenas:1";
2384 \fBgetpagesize\fR(3)
2392 functions conform to ISO/IEC 9899:1990 (\(lqISO C90\(rq)\&.
2396 function conforms to IEEE Std 1003\&.1\-2001 (\(lqPOSIX\&.1\(rq)\&.
2400 malloc_usable_size()
2403 functions first appeared in FreeBSD 7\&.0\&.
2407 malloc_stats_print(), and
2409 functions first appeared in FreeBSD 10\&.0\&.
2413 functions first appeared in FreeBSD 11\&.0\&.
2423 \%http://jemalloc.net/
2428 \%http://www.json.org/
2433 \%http://code.google.com/p/gperftools/