35\m[blue]\fBjemalloc website\fR\m[]\&\s-2\u[1]\d\s+2\&.
36.PP
37The following configuration options are enabled in libc\*(Aqs built\-in jemalloc:
38\fB\-\-enable\-dss\fR,
39\fB\-\-enable\-experimental\fR,
40\fB\-\-enable\-fill\fR,
41\fB\-\-enable\-lazy\-lock\fR,
42\fB\-\-enable\-munmap\fR,
43\fB\-\-enable\-stats\fR,
44\fB\-\-enable\-tcache\fR,
45\fB\-\-enable\-tls\fR,
46\fB\-\-enable\-utrace\fR, and
47\fB\-\-enable\-xmalloc\fR\&. Additionally,
48\fB\-\-enable\-debug\fR
49is enabled in development versions of FreeBSD (controlled by the
50\fBMALLOC_PRODUCTION\fR
51make variable)\&.
52.SH "SYNOPSIS"
53.sp
54.ft B
55.nf
56#include <stdlib\&.h>
57#include <malloc_np\&.h>
58.fi
59.ft
60.SS "Standard API"
61.HP \w'void\ *malloc('u
62.BI "void *malloc(size_t\ " "size" ");"
63.HP \w'void\ *calloc('u
64.BI "void *calloc(size_t\ " "number" ", size_t\ " "size" ");"
65.HP \w'int\ posix_memalign('u
66.BI "int posix_memalign(void\ **" "ptr" ", size_t\ " "alignment" ", size_t\ " "size" ");"
67.HP \w'void\ *aligned_alloc('u
68.BI "void *aligned_alloc(size_t\ " "alignment" ", size_t\ " "size" ");"
69.HP \w'void\ *realloc('u
70.BI "void *realloc(void\ *" "ptr" ", size_t\ " "size" ");"
71.HP \w'void\ free('u
72.BI "void free(void\ *" "ptr" ");"
73.SS "Non\-standard API"
74.HP \w'size_t\ malloc_usable_size('u
75.BI "size_t malloc_usable_size(const\ void\ *" "ptr" ");"
76.HP \w'void\ malloc_stats_print('u
77.BI "void malloc_stats_print(void\ " "(*write_cb)" "\ (void\ *,\ const\ char\ *), void\ *" "cbopaque" ", const\ char\ *" "opts" ");"
78.HP \w'int\ mallctl('u
79.BI "int mallctl(const\ char\ *" "name" ", void\ *" "oldp" ", size_t\ *" "oldlenp" ", void\ *" "newp" ", size_t\ " "newlen" ");"
80.HP \w'int\ mallctlnametomib('u
81.BI "int mallctlnametomib(const\ char\ *" "name" ", size_t\ *" "mibp" ", size_t\ *" "miblenp" ");"
82.HP \w'int\ mallctlbymib('u
83.BI "int mallctlbymib(const\ size_t\ *" "mib" ", size_t\ " "miblen" ", void\ *" "oldp" ", size_t\ *" "oldlenp" ", void\ *" "newp" ", size_t\ " "newlen" ");"
84.HP \w'void\ (*malloc_message)('u
85.BI "void (*malloc_message)(void\ *" "cbopaque" ", const\ char\ *" "s" ");"
86.PP
87const char *\fImalloc_conf\fR;
88.SS "Experimental API"
89.HP \w'int\ allocm('u
90.BI "int allocm(void\ **" "ptr" ", size_t\ *" "rsize" ", size_t\ " "size" ", int\ " "flags" ");"
91.HP \w'int\ rallocm('u
92.BI "int rallocm(void\ **" "ptr" ", size_t\ *" "rsize" ", size_t\ " "size" ", size_t\ " "extra" ", int\ " "flags" ");"
93.HP \w'int\ sallocm('u
94.BI "int sallocm(const\ void\ *" "ptr" ", size_t\ *" "rsize" ", int\ " "flags" ");"
95.HP \w'int\ dallocm('u
96.BI "int dallocm(void\ *" "ptr" ", int\ " "flags" ");"
97.HP \w'int\ nallocm('u
98.BI "int nallocm(size_t\ *" "rsize" ", size_t\ " "size" ", int\ " "flags" ");"
99.SH "DESCRIPTION"
100.SS "Standard API"
101.PP
102The
103\fBmalloc\fR\fB\fR
104function allocates
105\fIsize\fR
106bytes of uninitialized memory\&. The allocated space is suitably aligned (after possible pointer coercion) for storage of any type of object\&.
107.PP
108The
109\fBcalloc\fR\fB\fR
110function allocates space for
111\fInumber\fR
112objects, each
113\fIsize\fR
114bytes in length\&. The result is identical to calling
115\fBmalloc\fR\fB\fR
116with an argument of
117\fInumber\fR
118*
119\fIsize\fR, with the exception that the allocated memory is explicitly initialized to zero bytes\&.
120.PP
121The
122\fBposix_memalign\fR\fB\fR
123function allocates
124\fIsize\fR
125bytes of memory such that the allocation\*(Aqs base address is an even multiple of
126\fIalignment\fR, and returns the allocation in the value pointed to by
127\fIptr\fR\&. The requested
128\fIalignment\fR
129must be a power of 2 at least as large as
130sizeof(\fBvoid *\fR)\&.
131.PP
132The
133\fBaligned_alloc\fR\fB\fR
134function allocates
135\fIsize\fR
136bytes of memory such that the allocation\*(Aqs base address is an even multiple of
137\fIalignment\fR\&. The requested
138\fIalignment\fR
139must be a power of 2\&. Behavior is undefined if
140\fIsize\fR
141is not an integral multiple of
142\fIalignment\fR\&.
143.PP
144The
145\fBrealloc\fR\fB\fR
146function changes the size of the previously allocated memory referenced by
147\fIptr\fR
148to
149\fIsize\fR
150bytes\&. 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
151\fIptr\fR
152is freed and a pointer to the newly allocated memory is returned\&. Note that
153\fBrealloc\fR\fB\fR
154may move the memory allocation, resulting in a different return value than
155\fIptr\fR\&. If
156\fIptr\fR
157is
158\fBNULL\fR, the
159\fBrealloc\fR\fB\fR
160function behaves identically to
161\fBmalloc\fR\fB\fR
162for the specified size\&.
163.PP
164The
165\fBfree\fR\fB\fR
166function causes the allocated memory referenced by
167\fIptr\fR
168to be made available for future allocations\&. If
169\fIptr\fR
170is
171\fBNULL\fR, no action occurs\&.
172.SS "Non\-standard API"
173.PP
174The
175\fBmalloc_usable_size\fR\fB\fR
176function returns the usable size of the allocation pointed to by
177\fIptr\fR\&. The return value may be larger than the size that was requested during allocation\&. The
178\fBmalloc_usable_size\fR\fB\fR
179function is not a mechanism for in\-place
180\fBrealloc\fR\fB\fR; rather it is provided solely as a tool for introspection purposes\&. Any discrepancy between the requested allocation size and the size reported by
181\fBmalloc_usable_size\fR\fB\fR
182should not be depended on, since such behavior is entirely implementation\-dependent\&.
183.PP
184The
185\fBmalloc_stats_print\fR\fB\fR
186function writes human\-readable summary statistics via the
187\fIwrite_cb\fR
188callback function pointer and
189\fIcbopaque\fR
190data passed to
191\fIwrite_cb\fR, or
192\fBmalloc_message\fR\fB\fR
193if
194\fIwrite_cb\fR
195is
196\fBNULL\fR\&. This function can be called repeatedly\&. General information that never changes during execution can be omitted by specifying "g" as a character within the
197\fIopts\fR
198string\&. Note that
199\fBmalloc_message\fR\fB\fR
200uses the
201\fBmallctl*\fR\fB\fR
202functions internally, so inconsistent statistics can be reported if multiple threads use these functions simultaneously\&. If
203\fB\-\-enable\-stats\fR
204is specified during configuration, \(lqm\(rq and \(lqa\(rq can be specified to omit merged arena and per arena statistics, respectively; \(lqb\(rq and \(lql\(rq can be specified to omit per size class statistics for bins and large objects, respectively\&. Unrecognized characters are silently ignored\&. Note that thread caching may prevent some statistics from being completely up to date, since extra locking would be required to merge counters that track thread cache operations\&.
205.PP
206The
207\fBmallctl\fR\fB\fR
208function provides a general interface for introspecting the memory allocator, as well as setting modifiable parameters and triggering actions\&. The period\-separated
209\fIname\fR
210argument specifies a location in a tree\-structured namespace; see the
211MALLCTL NAMESPACE
212section for documentation on the tree contents\&. To read a value, pass a pointer via
213\fIoldp\fR
214to adequate space to contain the value, and a pointer to its length via
215\fIoldlenp\fR; otherwise pass
216\fBNULL\fR
217and
218\fBNULL\fR\&. Similarly, to write a value, pass a pointer to the value via
219\fInewp\fR, and its length via
220\fInewlen\fR; otherwise pass
221\fBNULL\fR
222and
223\fB0\fR\&.
224.PP
225The
226\fBmallctlnametomib\fR\fB\fR
227function 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 \(lqManagement Information Base\(rq (MIB) that can be passed repeatedly to
228\fBmallctlbymib\fR\fB\fR\&. Upon successful return from
229\fBmallctlnametomib\fR\fB\fR,
230\fImibp\fR
231contains an array of
232\fI*miblenp\fR
233integers, where
234\fI*miblenp\fR
235is the lesser of the number of components in
236\fIname\fR
237and the input value of
238\fI*miblenp\fR\&. Thus it is possible to pass a
239\fI*miblenp\fR
240that 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
241"arenas\&.bin\&.2\&.size"), the corresponding MIB component will always be that integer\&. Therefore, it is legitimate to construct code like the following:
242.sp
243.if n \{\
244.RS 4
245.\}
246.nf
247unsigned nbins, i;
248
249int mib[4];
250size_t len, miblen;
251
252len = sizeof(nbins);
253mallctl("arenas\&.nbins", &nbins, &len, NULL, 0);
254
255miblen = 4;
256mallnametomib("arenas\&.bin\&.0\&.size", mib, &miblen);
257for (i = 0; i < nbins; i++) {
258 size_t bin_size;
259
260 mib[2] = i;
261 len = sizeof(bin_size);
262 mallctlbymib(mib, miblen, &bin_size, &len, NULL, 0);
263 /* Do something with bin_size\&.\&.\&. */
264}
265.fi
266.if n \{\
267.RE
268.\}
269.SS "Experimental API"
270.PP
271The experimental API is subject to change or removal without regard for backward compatibility\&. If
272\fB\-\-disable\-experimental\fR
273is specified during configuration, the experimental API is omitted\&.
274.PP
275The
276\fBallocm\fR\fB\fR,
277\fBrallocm\fR\fB\fR,
278\fBsallocm\fR\fB\fR,
279\fBdallocm\fR\fB\fR, and
280\fBnallocm\fR\fB\fR
281functions all have a
282\fIflags\fR
283argument 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:
284.PP
285\fBALLOCM_LG_ALIGN(\fR\fB\fIla\fR\fR\fB) \fR
286.RS 4
287Align the memory allocation to start at an address that is a multiple of
288(1 << \fIla\fR)\&. This macro does not validate that
289\fIla\fR
290is within the valid range\&.
291.RE
292.PP
293\fBALLOCM_ALIGN(\fR\fB\fIa\fR\fR\fB) \fR
294.RS 4
295Align the memory allocation to start at an address that is a multiple of
296\fIa\fR, where
297\fIa\fR
298is a power of two\&. This macro does not validate that
299\fIa\fR
300is a power of 2\&.
301.RE
302.PP
303\fBALLOCM_ZERO\fR
304.RS 4
305Initialize 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 option is absent, newly allocated memory is uninitialized\&.
306.RE
307.PP
308\fBALLOCM_NO_MOVE\fR
309.RS 4
310For reallocation, fail rather than moving the object\&. This constraint can apply to both growth and shrinkage\&.
311.RE
312.PP
313\fBALLOCM_ARENA(\fR\fB\fIa\fR\fR\fB) \fR
314.RS 4
315Use the arena specified by the index
316\fIa\fR\&. This macro does not validate that
317\fIa\fR
318specifies an arena in the valid range\&.
319.RE
320.PP
321The
322\fBallocm\fR\fB\fR
323function allocates at least
324\fIsize\fR
325bytes of memory, sets
326\fI*ptr\fR
327to the base address of the allocation, and sets
328\fI*rsize\fR
329to the real size of the allocation if
330\fIrsize\fR
331is not
332\fBNULL\fR\&. Behavior is undefined if
333\fIsize\fR
334is
335\fB0\fR\&.
336.PP
337The
338\fBrallocm\fR\fB\fR
339function resizes the allocation at
340\fI*ptr\fR
341to be at least
342\fIsize\fR
343bytes, sets
344\fI*ptr\fR
345to the base address of the allocation if it moved, and sets
346\fI*rsize\fR
347to the real size of the allocation if
348\fIrsize\fR
349is not
350\fBNULL\fR\&. If
351\fIextra\fR
352is non\-zero, an attempt is made to resize the allocation to be at least
353\fIsize\fR + \fIextra\fR)
354bytes, though inability to allocate the extra byte(s) will not by itself result in failure\&. Behavior is undefined if
355\fIsize\fR
356is
357\fB0\fR, or if
358(\fIsize\fR + \fIextra\fR > \fBSIZE_T_MAX\fR)\&.
359.PP
360The
361\fBsallocm\fR\fB\fR
362function sets
363\fI*rsize\fR
364to the real size of the allocation\&.
365.PP
366The
367\fBdallocm\fR\fB\fR
368function causes the memory referenced by
369\fIptr\fR
370to be made available for future allocations\&.
371.PP
372The
373\fBnallocm\fR\fB\fR
374function allocates no memory, but it performs the same size computation as the
375\fBallocm\fR\fB\fR
376function, and if
377\fIrsize\fR
378is not
379\fBNULL\fR
380it sets
381\fI*rsize\fR
382to the real size of the allocation that would result from the equivalent
383\fBallocm\fR\fB\fR
384function call\&. Behavior is undefined if
385\fIsize\fR
386is
387\fB0\fR\&.
388.SH "TUNING"
389.PP
390Once, 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\&.
391.PP
392The string pointed to by the global variable
393\fImalloc_conf\fR, the \(lqname\(rq of the file referenced by the symbolic link named
394/etc/malloc\&.conf, and the value of the environment variable
395\fBMALLOC_CONF\fR, will be interpreted, in that order, from left to right as options\&.
396.PP
397An options string is a comma\-separated list of option:value pairs\&. There is one key corresponding to each
398"opt\&.*"
399mallctl (see the
400MALLCTL NAMESPACE
401section for options documentation)\&. For example,
402abort:true,narenas:1
403sets the
404"opt\&.abort"
405and
406"opt\&.narenas"
407options\&. 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\&.
408.SH "IMPLEMENTATION NOTES"
409.PP
410Traditionally, allocators have used
411\fBsbrk\fR(2)
412to obtain memory, which is suboptimal for several reasons, including race conditions, increased fragmentation, and artificial limitations on maximum usable memory\&. If
413\fB\-\-enable\-dss\fR
414is specified during configuration, this allocator uses both
415\fBmmap\fR(2)
416and
417\fBsbrk\fR(2), in that order of preference; otherwise only
418\fBmmap\fR(2)
419is used\&.
420.PP
421This 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\&.
422.PP
423In addition to multiple arenas, unless
424\fB\-\-disable\-tcache\fR
425is specified during configuration, this allocator supports thread\-specific caching for small and large objects, in order to make it possible to completely avoid synchronization for most allocation requests\&. Such caching allows very fast allocation in the common case, but it increases memory usage and fragmentation, since a bounded number of objects can remain allocated in each thread cache\&.
426.PP
427Memory is conceptually broken into equal\-sized chunks, where the chunk size is a power of two that is greater than the page size\&. Chunks are always aligned to multiples of the chunk size\&. This alignment makes it possible to find metadata for user objects very quickly\&.
428.PP
429User objects are broken into three categories according to size: small, large, and huge\&. Small objects are smaller than one page\&. Large objects are smaller than the chunk size\&. Huge objects are a multiple of the chunk size\&. Small and large objects are managed by arenas; huge objects are managed separately in a single data structure that is shared by all threads\&. Huge objects are used by applications infrequently enough that this single data structure is not a scalability issue\&.
430.PP
431Each chunk that is managed by an arena tracks its contents as runs of contiguous pages (unused, backing a set of small objects, or backing one large object)\&. The combination of chunk alignment and chunk page maps makes it possible to determine all metadata regarding small and large allocations in constant time\&.
432.PP
433Small objects are managed in groups by page runs\&. Each run maintains a frontier and free list 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
434sizeof(\fBdouble\fR)\&. All other small object size classes are multiples of the quantum, spaced such that internal fragmentation is limited to approximately 25% for all but the smallest size classes\&. Allocation requests that are larger than the maximum small size class, but small enough to fit in an arena\-managed chunk (see the
435"opt\&.lg_chunk"
436option), are rounded up to the nearest run size\&. Allocation requests that are too large to fit in an arena\-managed chunk are rounded up to the nearest multiple of the chunk size\&.
437.PP
438Allocations 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\&.
439.PP
440Assuming 4 MiB chunks, 4 KiB pages, and a 16\-byte quantum on a 64\-bit system, the size classes in each category are as shown in
441Table 1\&.
442.sp
443.it 1 an-trap
444.nr an-no-space-flag 1
445.nr an-break-flag 1
446.br
447.B Table\ \&1.\ \&Size classes
448.TS
449allbox tab(:);
450lB rB lB.
451T{
452Category
453T}:T{
454Spacing
455T}:T{
456Size
457T}
458.T&
459l r l
460^ r l
461^ r l
462^ r l
463^ r l
464^ r l
465^ r l
466l r l
467l r l.
468T{
469Small
470T}:T{
471lg
472T}:T{
473[8]
474T}
475:T{
47616
477T}:T{
478[16, 32, 48, \&.\&.\&., 128]
479T}
480:T{
48132
482T}:T{
483[160, 192, 224, 256]
484T}
485:T{
48664
487T}:T{
488[320, 384, 448, 512]
489T}
490:T{
491128
492T}:T{
493[640, 768, 896, 1024]
494T}
495:T{
496256
497T}:T{
498[1280, 1536, 1792, 2048]
499T}
500:T{
501512
502T}:T{
503[2560, 3072, 3584]
504T}
505T{
506Large
507T}:T{
5084 KiB
509T}:T{
510[4 KiB, 8 KiB, 12 KiB, \&.\&.\&., 4072 KiB]
511T}
512T{
513Huge
514T}:T{
5154 MiB
516T}:T{
517[4 MiB, 8 MiB, 12 MiB, \&.\&.\&.]
518T}
519.TE
520.sp 1
521.SH "MALLCTL NAMESPACE"
522.PP
523The following names are defined in the namespace accessible via the
524\fBmallctl*\fR\fB\fR
525functions\&. Value types are specified in parentheses, their readable/writable statuses are encoded as
526rw,
527r\-,
528\-w, or
529\-\-, and required build configuration flags follow, if any\&. A name element encoded as
530<i>
531or
532<j>
533indicates an integer component, where the integer varies from 0 to some upper value that must be determined via introspection\&. In the case of
534"stats\&.arenas\&.<i>\&.*",
535<i>
536equal to
537"arenas\&.narenas"
538can be used to access the summation of statistics from all arenas\&. Take special note of the
539"epoch"
540mallctl, which controls refreshing of cached dynamic statistics\&.
541.PP
542"version" (\fBconst char *\fR) r\-
543.RS 4
544Return the jemalloc version string\&.
545.RE
546.PP
547"epoch" (\fBuint64_t\fR) rw
548.RS 4
549If a value is passed in, refresh the data from which the
550\fBmallctl*\fR\fB\fR
551functions report values, and increment the epoch\&. Return the current epoch\&. This is useful for detecting whether another thread caused a refresh\&.
552.RE
553.PP
554"config\&.debug" (\fBbool\fR) r\-
555.RS 4
556\fB\-\-enable\-debug\fR
557was specified during build configuration\&.
558.RE
559.PP
560"config\&.dss" (\fBbool\fR) r\-
561.RS 4
562\fB\-\-enable\-dss\fR
563was specified during build configuration\&.
564.RE
565.PP
566"config\&.fill" (\fBbool\fR) r\-
567.RS 4
568\fB\-\-enable\-fill\fR
569was specified during build configuration\&.
570.RE
571.PP
572"config\&.lazy_lock" (\fBbool\fR) r\-
573.RS 4
574\fB\-\-enable\-lazy\-lock\fR
575was specified during build configuration\&.
576.RE
577.PP
578"config\&.mremap" (\fBbool\fR) r\-
579.RS 4
580\fB\-\-enable\-mremap\fR
581was specified during build configuration\&.
582.RE
583.PP
584"config\&.munmap" (\fBbool\fR) r\-
585.RS 4
586\fB\-\-enable\-munmap\fR
587was specified during build configuration\&.
588.RE
589.PP
590"config\&.prof" (\fBbool\fR) r\-
591.RS 4
592\fB\-\-enable\-prof\fR
593was specified during build configuration\&.
594.RE
595.PP
596"config\&.prof_libgcc" (\fBbool\fR) r\-
597.RS 4
598\fB\-\-disable\-prof\-libgcc\fR
599was not specified during build configuration\&.
600.RE
601.PP
602"config\&.prof_libunwind" (\fBbool\fR) r\-
603.RS 4
604\fB\-\-enable\-prof\-libunwind\fR
605was specified during build configuration\&.
606.RE
607.PP
608"config\&.stats" (\fBbool\fR) r\-
609.RS 4
610\fB\-\-enable\-stats\fR
611was specified during build configuration\&.
612.RE
613.PP
614"config\&.tcache" (\fBbool\fR) r\-
615.RS 4
616\fB\-\-disable\-tcache\fR
617was not specified during build configuration\&.
618.RE
619.PP
620"config\&.tls" (\fBbool\fR) r\-
621.RS 4
622\fB\-\-disable\-tls\fR
623was not specified during build configuration\&.
624.RE
625.PP
626"config\&.utrace" (\fBbool\fR) r\-
627.RS 4
628\fB\-\-enable\-utrace\fR
629was specified during build configuration\&.
630.RE
631.PP
632"config\&.valgrind" (\fBbool\fR) r\-
633.RS 4
634\fB\-\-enable\-valgrind\fR
635was specified during build configuration\&.
636.RE
637.PP
638"config\&.xmalloc" (\fBbool\fR) r\-
639.RS 4
640\fB\-\-enable\-xmalloc\fR
641was specified during build configuration\&.
642.RE
643.PP
644"opt\&.abort" (\fBbool\fR) r\-
645.RS 4
646Abort\-on\-warning enabled/disabled\&. If true, most warnings are fatal\&. The process will call
647\fBabort\fR(3)
648in these cases\&. This option is disabled by default unless
649\fB\-\-enable\-debug\fR
650is specified during configuration, in which case it is enabled by default\&.
651.RE
652.PP
653"opt\&.lg_chunk" (\fBsize_t\fR) r\-
654.RS 4
|
656.RE
657.PP
658"opt\&.dss" (\fBconst char *\fR) r\-
659.RS 4
660dss (\fBsbrk\fR(2)) allocation precedence as related to
661\fBmmap\fR(2)
662allocation\&. The following settings are supported: \(lqdisabled\(rq, \(lqprimary\(rq, and \(lqsecondary\(rq (default)\&.
663.RE
664.PP
665"opt\&.narenas" (\fBsize_t\fR) r\-
666.RS 4
667Maximum 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\&.
668.RE
669.PP
670"opt\&.lg_dirty_mult" (\fBssize_t\fR) r\-
671.RS 4
672Per\-arena minimum ratio (log base 2) of active to dirty pages\&. Some dirty unused pages may be allowed to accumulate, within the limit set by the ratio (or one chunk worth of dirty pages, whichever is greater), before informing the kernel about some of those pages via
673\fBmadvise\fR(2)
674or a similar system call\&. This provides the kernel with sufficient information to recycle dirty pages if physical memory becomes scarce and the pages remain unused\&. The default minimum ratio is 8:1 (2^3:1); an option value of \-1 will disable dirty page purging\&.
675.RE
676.PP
677"opt\&.stats_print" (\fBbool\fR) r\-
678.RS 4
679Enable/disable statistics printing at exit\&. If enabled, the
680\fBmalloc_stats_print\fR\fB\fR
681function is called at program exit via an
682\fBatexit\fR(3)
683function\&. If
684\fB\-\-enable\-stats\fR
685is 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\&. 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\&.
686.RE
687.PP
688"opt\&.junk" (\fBbool\fR) r\- [\fB\-\-enable\-fill\fR]
689.RS 4
690Junk filling enabled/disabled\&. If enabled, each byte of uninitialized allocated memory will be initialized to
6910xa5\&. All deallocated memory will be initialized to
6920x5a\&. This is intended for debugging and will impact performance negatively\&. This option is disabled by default unless
693\fB\-\-enable\-debug\fR
694is specified during configuration, in which case it is enabled by default unless running inside
695\m[blue]\fBValgrind\fR\m[]\&\s-2\u[2]\d\s+2\&.
696.RE
697.PP
698"opt\&.quarantine" (\fBsize_t\fR) r\- [\fB\-\-enable\-fill\fR]
699.RS 4
700Per thread quarantine size in bytes\&. If non\-zero, each thread maintains a FIFO object quarantine that stores up to the specified number of bytes of memory\&. The quarantined memory is not freed until it is released from quarantine, though it is immediately junk\-filled if the
701"opt\&.junk"
702option is enabled\&. This feature is of particular use in combination with
703\m[blue]\fBValgrind\fR\m[]\&\s-2\u[2]\d\s+2, which can detect attempts to access quarantined objects\&. This is intended for debugging and will impact performance negatively\&. The default quarantine size is 0 unless running inside Valgrind, in which case the default is 16 MiB\&.
704.RE
705.PP
706"opt\&.redzone" (\fBbool\fR) r\- [\fB\-\-enable\-fill\fR]
707.RS 4
708Redzones enabled/disabled\&. If enabled, small allocations have redzones before and after them\&. Furthermore, if the
709"opt\&.junk"
710option is enabled, the redzones are checked for corruption during deallocation\&. However, the primary intended purpose of this feature is to be used in combination with
711\m[blue]\fBValgrind\fR\m[]\&\s-2\u[2]\d\s+2, which needs redzones in order to do effective buffer overflow/underflow detection\&. This option is intended for debugging and will impact performance negatively\&. This option is disabled by default unless running inside Valgrind\&.
712.RE
713.PP
714"opt\&.zero" (\fBbool\fR) r\- [\fB\-\-enable\-fill\fR]
715.RS 4
716Zero 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
717\fBrealloc\fR\fB\fR
718and
719\fBrallocm\fR\fB\fR
720calls do not zero memory that was previously allocated\&. This is intended for debugging and will impact performance negatively\&. This option is disabled by default\&.
721.RE
722.PP
723"opt\&.utrace" (\fBbool\fR) r\- [\fB\-\-enable\-utrace\fR]
724.RS 4
725Allocation tracing based on
726\fButrace\fR(2)
727enabled/disabled\&. This option is disabled by default\&.
728.RE
729.PP
730"opt\&.valgrind" (\fBbool\fR) r\- [\fB\-\-enable\-valgrind\fR]
731.RS 4
732\m[blue]\fBValgrind\fR\m[]\&\s-2\u[2]\d\s+2
733support enabled/disabled\&. This option is vestigal because jemalloc auto\-detects whether it is running inside Valgrind\&. This option is disabled by default, unless running inside Valgrind\&.
734.RE
735.PP
736"opt\&.xmalloc" (\fBbool\fR) r\- [\fB\-\-enable\-xmalloc\fR]
737.RS 4
738Abort\-on\-out\-of\-memory enabled/disabled\&. If enabled, rather than returning failure for any allocation function, display a diagnostic message on
739\fBSTDERR_FILENO\fR
740and cause the program to drop core (using
741\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:
742.sp
743.if n \{\
744.RS 4
745.\}
746.nf
747malloc_conf = "xmalloc:true";
748.fi
749.if n \{\
750.RE
751.\}
752.sp
753This option is disabled by default\&.
754.RE
755.PP
756"opt\&.tcache" (\fBbool\fR) r\- [\fB\-\-enable\-tcache\fR]
757.RS 4
758Thread\-specific caching enabled/disabled\&. When there are multiple threads, each thread uses a thread\-specific cache 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
759"opt\&.lg_tcache_max"
760option for related tuning information\&. This option is enabled by default unless running inside
761\m[blue]\fBValgrind\fR\m[]\&\s-2\u[2]\d\s+2\&.
762.RE
763.PP
764"opt\&.lg_tcache_max" (\fBsize_t\fR) r\- [\fB\-\-enable\-tcache\fR]
765.RS 4
766Maximum size class (log base 2) to cache in the thread\-specific cache\&. 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)\&.
767.RE
768.PP
769"opt\&.prof" (\fBbool\fR) r\- [\fB\-\-enable\-prof\fR]
770.RS 4
771Memory profiling enabled/disabled\&. If enabled, profile memory allocation activity\&. See the
772"opt\&.prof_active"
773option for on\-the\-fly activation/deactivation\&. See the
774"opt\&.lg_prof_sample"
775option for probabilistic sampling control\&. See the
776"opt\&.prof_accum"
777option for control of cumulative sample reporting\&. See the
778"opt\&.lg_prof_interval"
779option for information on interval\-triggered profile dumping, the
780"opt\&.prof_gdump"
781option for information on high\-water\-triggered profile dumping, and the
782"opt\&.prof_final"
783option for final profile dumping\&. Profile output is compatible with the included
784\fBpprof\fR
785Perl script, which originates from the
786\m[blue]\fBgperftools package\fR\m[]\&\s-2\u[3]\d\s+2\&.
787.RE
788.PP
789"opt\&.prof_prefix" (\fBconst char *\fR) r\- [\fB\-\-enable\-prof\fR]
790.RS 4
791Filename 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
792jeprof\&.
793.RE
794.PP
795"opt\&.prof_active" (\fBbool\fR) r\- [\fB\-\-enable\-prof\fR]
796.RS 4
797Profiling activated/deactivated\&. This is a secondary control mechanism that makes it possible to start the application with profiling enabled (see the
798"opt\&.prof"
799option) but inactive, then toggle profiling at any time during program execution with the
800"prof\&.active"
801mallctl\&. This option is enabled by default\&.
802.RE
803.PP
804"opt\&.lg_prof_sample" (\fBssize_t\fR) r\- [\fB\-\-enable\-prof\fR]
805.RS 4
806Average 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)\&.
807.RE
808.PP
809"opt\&.prof_accum" (\fBbool\fR) r\- [\fB\-\-enable\-prof\fR]
810.RS 4
811Reporting 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\&.
812.RE
813.PP
814"opt\&.lg_prof_interval" (\fBssize_t\fR) r\- [\fB\-\-enable\-prof\fR]
815.RS 4
816Average 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
817<prefix>\&.<pid>\&.<seq>\&.i<iseq>\&.heap, where
818<prefix>
819is controlled by the
820"opt\&.prof_prefix"
821option\&. By default, interval\-triggered profile dumping is disabled (encoded as \-1)\&.
822.RE
823.PP
824"opt\&.prof_gdump" (\fBbool\fR) r\- [\fB\-\-enable\-prof\fR]
825.RS 4
826Trigger a memory profile dump every time the total virtual memory exceeds the previous maximum\&. Profiles are dumped to files named according to the pattern
827<prefix>\&.<pid>\&.<seq>\&.u<useq>\&.heap, where
828<prefix>
829is controlled by the
830"opt\&.prof_prefix"
831option\&. This option is disabled by default\&.
832.RE
833.PP
834"opt\&.prof_final" (\fBbool\fR) r\- [\fB\-\-enable\-prof\fR]
835.RS 4
836Use an
837\fBatexit\fR(3)
838function to dump final memory usage to a file named according to the pattern
839<prefix>\&.<pid>\&.<seq>\&.f\&.heap, where
840<prefix>
841is controlled by the
842"opt\&.prof_prefix"
843option\&. This option is enabled by default\&.
844.RE
845.PP
846"opt\&.prof_leak" (\fBbool\fR) r\- [\fB\-\-enable\-prof\fR]
847.RS 4
848Leak reporting enabled/disabled\&. If enabled, use an
849\fBatexit\fR(3)
850function to report memory leaks detected by allocation sampling\&. See the
851"opt\&.prof"
852option for information on analyzing heap profile output\&. This option is disabled by default\&.
853.RE
854.PP
855"thread\&.arena" (\fBunsigned\fR) rw
856.RS 4
857Get or set the arena associated with the calling thread\&. If the specified arena was not initialized beforehand (see the
858"arenas\&.initialized"
859mallctl), it will be automatically initialized as a side effect of calling this interface\&.
860.RE
861.PP
862"thread\&.allocated" (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
863.RS 4
864Get 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\&.
865.RE
866.PP
867"thread\&.allocatedp" (\fBuint64_t *\fR) r\- [\fB\-\-enable\-stats\fR]
868.RS 4
869Get a pointer to the the value that is returned by the
870"thread\&.allocated"
871mallctl\&. This is useful for avoiding the overhead of repeated
872\fBmallctl*\fR\fB\fR
873calls\&.
874.RE
875.PP
876"thread\&.deallocated" (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
877.RS 4
878Get 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\&.
879.RE
880.PP
881"thread\&.deallocatedp" (\fBuint64_t *\fR) r\- [\fB\-\-enable\-stats\fR]
882.RS 4
883Get a pointer to the the value that is returned by the
884"thread\&.deallocated"
885mallctl\&. This is useful for avoiding the overhead of repeated
886\fBmallctl*\fR\fB\fR
887calls\&.
888.RE
889.PP
890"thread\&.tcache\&.enabled" (\fBbool\fR) rw [\fB\-\-enable\-tcache\fR]
891.RS 4
892Enable/disable calling thread\*(Aqs tcache\&. The tcache is implicitly flushed as a side effect of becoming disabled (see
893"thread\&.tcache\&.flush")\&.
894.RE
895.PP
896"thread\&.tcache\&.flush" (\fBvoid\fR) \-\- [\fB\-\-enable\-tcache\fR]
897.RS 4
898Flush calling thread\*(Aqs tcache\&. This interface releases all cached objects and internal data structures associated with the calling thread\*(Aqs thread\-specific cache\&. 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\&.
899.RE
900.PP
901"arena\&.<i>\&.purge" (\fBunsigned\fR) \-\-
902.RS 4
903Purge unused dirty pages for arena <i>, or for all arenas if <i> equals
904"arenas\&.narenas"\&.
905.RE
906.PP
907"arena\&.<i>\&.dss" (\fBconst char *\fR) rw
908.RS 4
909Set the precedence of dss allocation as related to mmap allocation for arena <i>, or for all arenas if <i> equals
910"arenas\&.narenas"\&. See
911"opt\&.dss"
912for supported settings\&.
913.RE
914.PP
915"arenas\&.narenas" (\fBunsigned\fR) r\-
916.RS 4
917Current limit on number of arenas\&.
918.RE
919.PP
920"arenas\&.initialized" (\fBbool *\fR) r\-
921.RS 4
922An array of
923"arenas\&.narenas"
924booleans\&. Each boolean indicates whether the corresponding arena is initialized\&.
925.RE
926.PP
927"arenas\&.quantum" (\fBsize_t\fR) r\-
928.RS 4
929Quantum size\&.
930.RE
931.PP
932"arenas\&.page" (\fBsize_t\fR) r\-
933.RS 4
934Page size\&.
935.RE
936.PP
937"arenas\&.tcache_max" (\fBsize_t\fR) r\- [\fB\-\-enable\-tcache\fR]
938.RS 4
939Maximum thread\-cached size class\&.
940.RE
941.PP
942"arenas\&.nbins" (\fBunsigned\fR) r\-
943.RS 4
944Number of bin size classes\&.
945.RE
946.PP
947"arenas\&.nhbins" (\fBunsigned\fR) r\- [\fB\-\-enable\-tcache\fR]
948.RS 4
949Total number of thread cache bin size classes\&.
950.RE
951.PP
952"arenas\&.bin\&.<i>\&.size" (\fBsize_t\fR) r\-
953.RS 4
954Maximum size supported by size class\&.
955.RE
956.PP
957"arenas\&.bin\&.<i>\&.nregs" (\fBuint32_t\fR) r\-
958.RS 4
959Number of regions per page run\&.
960.RE
961.PP
962"arenas\&.bin\&.<i>\&.run_size" (\fBsize_t\fR) r\-
963.RS 4
964Number of bytes per page run\&.
965.RE
966.PP
967"arenas\&.nlruns" (\fBsize_t\fR) r\-
968.RS 4
969Total number of large size classes\&.
970.RE
971.PP
972"arenas\&.lrun\&.<i>\&.size" (\fBsize_t\fR) r\-
973.RS 4
974Maximum size supported by this large size class\&.
975.RE
976.PP
977"arenas\&.purge" (\fBunsigned\fR) \-w
978.RS 4
979Purge unused dirty pages for the specified arena, or for all arenas if none is specified\&.
980.RE
981.PP
982"arenas\&.extend" (\fBunsigned\fR) r\-
983.RS 4
984Extend the array of arenas by appending a new arena, and returning the new arena index\&.
985.RE
986.PP
987"prof\&.active" (\fBbool\fR) rw [\fB\-\-enable\-prof\fR]
988.RS 4
989Control whether sampling is currently active\&. See the
990"opt\&.prof_active"
991option for additional information\&.
992.RE
993.PP
994"prof\&.dump" (\fBconst char *\fR) \-w [\fB\-\-enable\-prof\fR]
995.RS 4
996Dump a memory profile to the specified file, or if NULL is specified, to a file according to the pattern
997<prefix>\&.<pid>\&.<seq>\&.m<mseq>\&.heap, where
998<prefix>
999is controlled by the
1000"opt\&.prof_prefix"
1001option\&.
1002.RE
1003.PP
1004"prof\&.interval" (\fBuint64_t\fR) r\- [\fB\-\-enable\-prof\fR]
1005.RS 4
1006Average number of bytes allocated between inverval\-based profile dumps\&. See the
1007"opt\&.lg_prof_interval"
1008option for additional information\&.
1009.RE
1010.PP
1011"stats\&.cactive" (\fBsize_t *\fR) r\- [\fB\-\-enable\-stats\fR]
1012.RS 4
1013Pointer to a counter that contains an approximate count of the current number of bytes in active pages\&. The estimate may be high, but never low, because each arena rounds up to the nearest multiple of the chunk size when computing its contribution to the counter\&. Note that the
1014"epoch"
1015mallctl has no bearing on this counter\&. Furthermore, counter consistency is maintained via atomic operations, so it is necessary to use an atomic operation in order to guarantee a consistent read when dereferencing the pointer\&.
1016.RE
1017.PP
1018"stats\&.allocated" (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1019.RS 4
1020Total number of bytes allocated by the application\&.
1021.RE
1022.PP
1023"stats\&.active" (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1024.RS 4
1025Total number of bytes in active pages allocated by the application\&. This is a multiple of the page size, and greater than or equal to
1026"stats\&.allocated"\&. This does not include
1027"stats\&.arenas\&.<i>\&.pdirty"
1028and pages entirely devoted to allocator metadata\&.
1029.RE
1030.PP
1031"stats\&.mapped" (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1032.RS 4
1033Total number of bytes in chunks mapped on behalf of the application\&. This is a multiple of the chunk size, and is at least as large as
1034"stats\&.active"\&. This does not include inactive chunks\&.
1035.RE
1036.PP
1037"stats\&.chunks\&.current" (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1038.RS 4
1039Total number of chunks actively mapped on behalf of the application\&. This does not include inactive chunks\&.
1040.RE
1041.PP
1042"stats\&.chunks\&.total" (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1043.RS 4
1044Cumulative number of chunks allocated\&.
1045.RE
1046.PP
1047"stats\&.chunks\&.high" (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1048.RS 4
1049Maximum number of active chunks at any time thus far\&.
1050.RE
1051.PP
1052"stats\&.huge\&.allocated" (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1053.RS 4
1054Number of bytes currently allocated by huge objects\&.
1055.RE
1056.PP
1057"stats\&.huge\&.nmalloc" (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1058.RS 4
1059Cumulative number of huge allocation requests\&.
1060.RE
1061.PP
1062"stats\&.huge\&.ndalloc" (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1063.RS 4
1064Cumulative number of huge deallocation requests\&.
1065.RE
1066.PP
1067"stats\&.arenas\&.<i>\&.dss" (\fBconst char *\fR) r\-
1068.RS 4
1069dss (\fBsbrk\fR(2)) allocation precedence as related to
1070\fBmmap\fR(2)
1071allocation\&. See
1072"opt\&.dss"
1073for details\&.
1074.RE
1075.PP
1076"stats\&.arenas\&.<i>\&.nthreads" (\fBunsigned\fR) r\-
1077.RS 4
1078Number of threads currently assigned to arena\&.
1079.RE
1080.PP
1081"stats\&.arenas\&.<i>\&.pactive" (\fBsize_t\fR) r\-
1082.RS 4
1083Number of pages in active runs\&.
1084.RE
1085.PP
1086"stats\&.arenas\&.<i>\&.pdirty" (\fBsize_t\fR) r\-
1087.RS 4
1088Number of pages within unused runs that are potentially dirty, and for which
1089\fBmadvise\fR\fB\fI\&.\&.\&.\fR\fR\fB \fR\fB\fI\fBMADV_DONTNEED\fR\fR\fR
1090or similar has not been called\&.
1091.RE
1092.PP
1093"stats\&.arenas\&.<i>\&.mapped" (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1094.RS 4
1095Number of mapped bytes\&.
1096.RE
1097.PP
1098"stats\&.arenas\&.<i>\&.npurge" (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1099.RS 4
1100Number of dirty page purge sweeps performed\&.
1101.RE
1102.PP
1103"stats\&.arenas\&.<i>\&.nmadvise" (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1104.RS 4
1105Number of
1106\fBmadvise\fR\fB\fI\&.\&.\&.\fR\fR\fB \fR\fB\fI\fBMADV_DONTNEED\fR\fR\fR
1107or similar calls made to purge dirty pages\&.
1108.RE
1109.PP
1110"stats\&.arenas\&.<i>\&.npurged" (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1111.RS 4
1112Number of pages purged\&.
1113.RE
1114.PP
1115"stats\&.arenas\&.<i>\&.small\&.allocated" (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1116.RS 4
1117Number of bytes currently allocated by small objects\&.
1118.RE
1119.PP
1120"stats\&.arenas\&.<i>\&.small\&.nmalloc" (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1121.RS 4
1122Cumulative number of allocation requests served by small bins\&.
1123.RE
1124.PP
1125"stats\&.arenas\&.<i>\&.small\&.ndalloc" (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1126.RS 4
1127Cumulative number of small objects returned to bins\&.
1128.RE
1129.PP
1130"stats\&.arenas\&.<i>\&.small\&.nrequests" (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1131.RS 4
1132Cumulative number of small allocation requests\&.
1133.RE
1134.PP
1135"stats\&.arenas\&.<i>\&.large\&.allocated" (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1136.RS 4
1137Number of bytes currently allocated by large objects\&.
1138.RE
1139.PP
1140"stats\&.arenas\&.<i>\&.large\&.nmalloc" (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1141.RS 4
1142Cumulative number of large allocation requests served directly by the arena\&.
1143.RE
1144.PP
1145"stats\&.arenas\&.<i>\&.large\&.ndalloc" (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1146.RS 4
1147Cumulative number of large deallocation requests served directly by the arena\&.
1148.RE
1149.PP
1150"stats\&.arenas\&.<i>\&.large\&.nrequests" (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1151.RS 4
1152Cumulative number of large allocation requests\&.
1153.RE
1154.PP
1155"stats\&.arenas\&.<i>\&.bins\&.<j>\&.allocated" (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1156.RS 4
1157Current number of bytes allocated by bin\&.
1158.RE
1159.PP
1160"stats\&.arenas\&.<i>\&.bins\&.<j>\&.nmalloc" (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1161.RS 4
1162Cumulative number of allocations served by bin\&.
1163.RE
1164.PP
1165"stats\&.arenas\&.<i>\&.bins\&.<j>\&.ndalloc" (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1166.RS 4
1167Cumulative number of allocations returned to bin\&.
1168.RE
1169.PP
1170"stats\&.arenas\&.<i>\&.bins\&.<j>\&.nrequests" (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1171.RS 4
1172Cumulative number of allocation requests\&.
1173.RE
1174.PP
1175"stats\&.arenas\&.<i>\&.bins\&.<j>\&.nfills" (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR \fB\-\-enable\-tcache\fR]
1176.RS 4
1177Cumulative number of tcache fills\&.
1178.RE
1179.PP
1180"stats\&.arenas\&.<i>\&.bins\&.<j>\&.nflushes" (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR \fB\-\-enable\-tcache\fR]
1181.RS 4
1182Cumulative number of tcache flushes\&.
1183.RE
1184.PP
1185"stats\&.arenas\&.<i>\&.bins\&.<j>\&.nruns" (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1186.RS 4
1187Cumulative number of runs created\&.
1188.RE
1189.PP
1190"stats\&.arenas\&.<i>\&.bins\&.<j>\&.nreruns" (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1191.RS 4
1192Cumulative number of times the current run from which to allocate changed\&.
1193.RE
1194.PP
1195"stats\&.arenas\&.<i>\&.bins\&.<j>\&.curruns" (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1196.RS 4
1197Current number of runs\&.
1198.RE
1199.PP
1200"stats\&.arenas\&.<i>\&.lruns\&.<j>\&.nmalloc" (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1201.RS 4
1202Cumulative number of allocation requests for this size class served directly by the arena\&.
1203.RE
1204.PP
1205"stats\&.arenas\&.<i>\&.lruns\&.<j>\&.ndalloc" (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1206.RS 4
1207Cumulative number of deallocation requests for this size class served directly by the arena\&.
1208.RE
1209.PP
1210"stats\&.arenas\&.<i>\&.lruns\&.<j>\&.nrequests" (\fBuint64_t\fR) r\- [\fB\-\-enable\-stats\fR]
1211.RS 4
1212Cumulative number of allocation requests for this size class\&.
1213.RE
1214.PP
1215"stats\&.arenas\&.<i>\&.lruns\&.<j>\&.curruns" (\fBsize_t\fR) r\- [\fB\-\-enable\-stats\fR]
1216.RS 4
1217Current number of runs for this size class\&.
1218.RE
1219.SH "DEBUGGING MALLOC PROBLEMS"
1220.PP
1221When debugging, it is a good idea to configure/build jemalloc with the
1222\fB\-\-enable\-debug\fR
1223and
1224\fB\-\-enable\-fill\fR
1225options, 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\&.
1226.PP
1227Programs often accidentally depend on \(lquninitialized\(rq memory actually being filled with zero bytes\&. Junk filling (see the
1228"opt\&.junk"
1229option) tends to expose such bugs in the form of obviously incorrect results and/or coredumps\&. Conversely, zero filling (see the
1230"opt\&.zero"
1231option) eliminates the symptoms of such bugs\&. Between these two options, it is usually possible to quickly detect, diagnose, and eliminate such bugs\&.
1232.PP
1233This implementation does not provide much detail about the problems it detects, because the performance impact for storing such information would be prohibitive\&. However, jemalloc does integrate with the most excellent
1234\m[blue]\fBValgrind\fR\m[]\&\s-2\u[2]\d\s+2
1235tool if the
1236\fB\-\-enable\-valgrind\fR
1237configuration option is enabled\&.
1238.SH "DIAGNOSTIC MESSAGES"
1239.PP
1240If any of the memory allocation/deallocation functions detect an error or warning condition, a message will be printed to file descriptor
1241\fBSTDERR_FILENO\fR\&. Errors will result in the process dumping core\&. If the
1242"opt\&.abort"
1243option is set, most warnings are treated as errors\&.
1244.PP
1245The
1246\fImalloc_message\fR
1247variable allows the programmer to override the function which emits the text strings forming the errors and warnings if for some reason the
1248\fBSTDERR_FILENO\fR
1249file descriptor is not suitable for this\&.
1250\fBmalloc_message\fR\fB\fR
1251takes the
1252\fIcbopaque\fR
1253pointer argument that is
1254\fBNULL\fR
1255unless overridden by the arguments in a call to
1256\fBmalloc_stats_print\fR\fB\fR, 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\&.
1257.PP
1258All messages are prefixed by \(lq<jemalloc>:\(rq\&.
1259.SH "RETURN VALUES"
1260.SS "Standard API"
1261.PP
1262The
1263\fBmalloc\fR\fB\fR
1264and
1265\fBcalloc\fR\fB\fR
1266functions return a pointer to the allocated memory if successful; otherwise a
1267\fBNULL\fR
1268pointer is returned and
1269\fIerrno\fR
1270is set to
1271ENOMEM\&.
1272.PP
1273The
1274\fBposix_memalign\fR\fB\fR
1275function returns the value 0 if successful; otherwise it returns an error value\&. The
1276\fBposix_memalign\fR\fB\fR
1277function will fail if:
1278.PP
1279EINVAL
1280.RS 4
1281The
1282\fIalignment\fR
1283parameter is not a power of 2 at least as large as
1284sizeof(\fBvoid *\fR)\&.
1285.RE
1286.PP
1287ENOMEM
1288.RS 4
1289Memory allocation error\&.
1290.RE
1291.PP
1292The
1293\fBaligned_alloc\fR\fB\fR
1294function returns a pointer to the allocated memory if successful; otherwise a
1295\fBNULL\fR
1296pointer is returned and
1297\fIerrno\fR
1298is set\&. The
1299\fBaligned_alloc\fR\fB\fR
1300function will fail if:
1301.PP
1302EINVAL
1303.RS 4
1304The
1305\fIalignment\fR
1306parameter is not a power of 2\&.
1307.RE
1308.PP
1309ENOMEM
1310.RS 4
1311Memory allocation error\&.
1312.RE
1313.PP
1314The
1315\fBrealloc\fR\fB\fR
1316function returns a pointer, possibly identical to
1317\fIptr\fR, to the allocated memory if successful; otherwise a
1318\fBNULL\fR
1319pointer is returned, and
1320\fIerrno\fR
1321is set to
1322ENOMEM
1323if the error was the result of an allocation failure\&. The
1324\fBrealloc\fR\fB\fR
1325function always leaves the original buffer intact when an error occurs\&.
1326.PP
1327The
1328\fBfree\fR\fB\fR
1329function returns no value\&.
1330.SS "Non\-standard API"
1331.PP
1332The
1333\fBmalloc_usable_size\fR\fB\fR
1334function returns the usable size of the allocation pointed to by
1335\fIptr\fR\&.
1336.PP
1337The
1338\fBmallctl\fR\fB\fR,
1339\fBmallctlnametomib\fR\fB\fR, and
1340\fBmallctlbymib\fR\fB\fR
1341functions return 0 on success; otherwise they return an error value\&. The functions will fail if:
1342.PP
1343EINVAL
1344.RS 4
1345\fInewp\fR
1346is not
1347\fBNULL\fR, and
1348\fInewlen\fR
1349is too large or too small\&. Alternatively,
1350\fI*oldlenp\fR
1351is too large or too small; in this case as much data as possible are read despite the error\&.
1352.RE
1353.PP
1354ENOMEM
1355.RS 4
1356\fI*oldlenp\fR
1357is too short to hold the requested value\&.
1358.RE
1359.PP
1360ENOENT
1361.RS 4
1362\fIname\fR
1363or
1364\fImib\fR
1365specifies an unknown/invalid value\&.
1366.RE
1367.PP
1368EPERM
1369.RS 4
1370Attempt to read or write void value, or attempt to write read\-only value\&.
1371.RE
1372.PP
1373EAGAIN
1374.RS 4
1375A memory allocation failure occurred\&.
1376.RE
1377.PP
1378EFAULT
1379.RS 4
1380An interface with side effects failed in some way not directly related to
1381\fBmallctl*\fR\fB\fR
1382read/write processing\&.
1383.RE
1384.SS "Experimental API"
1385.PP
1386The
1387\fBallocm\fR\fB\fR,
1388\fBrallocm\fR\fB\fR,
1389\fBsallocm\fR\fB\fR,
1390\fBdallocm\fR\fB\fR, and
1391\fBnallocm\fR\fB\fR
1392functions return
1393\fBALLOCM_SUCCESS\fR
1394on success; otherwise they return an error value\&. The
1395\fBallocm\fR\fB\fR,
1396\fBrallocm\fR\fB\fR, and
1397\fBnallocm\fR\fB\fR
1398functions will fail if:
1399.PP
1400ALLOCM_ERR_OOM
1401.RS 4
1402Out of memory\&. Insufficient contiguous memory was available to service the allocation request\&. The
1403\fBallocm\fR\fB\fR
1404function additionally sets
1405\fI*ptr\fR
1406to
1407\fBNULL\fR, whereas the
1408\fBrallocm\fR\fB\fR
1409function leaves
1410\fB*ptr\fR
1411unmodified\&.
1412.RE
1413The
1414\fBrallocm\fR\fB\fR
1415function will also fail if:
1416.PP
1417ALLOCM_ERR_NOT_MOVED
1418.RS 4
1419\fBALLOCM_NO_MOVE\fR
1420was specified, but the reallocation request could not be serviced without moving the object\&.
1421.RE
1422.SH "ENVIRONMENT"
1423.PP
1424The following environment variable affects the execution of the allocation functions:
1425.PP
1426\fBMALLOC_CONF\fR
1427.RS 4
1428If the environment variable
1429\fBMALLOC_CONF\fR
1430is set, the characters it contains will be interpreted as options\&.
1431.RE
1432.SH "EXAMPLES"
1433.PP
1434To dump core whenever a problem occurs:
1435.sp
1436.if n \{\
1437.RS 4
1438.\}
1439.nf
1440ln \-s \*(Aqabort:true\*(Aq /etc/malloc\&.conf
1441.fi
1442.if n \{\
1443.RE
1444.\}
1445.PP
1446To specify in the source a chunk size that is 16 MiB:
1447.sp
1448.if n \{\
1449.RS 4
1450.\}
1451.nf
1452malloc_conf = "lg_chunk:24";
1453.fi
1454.if n \{\
1455.RE
1456.\}
1457.SH "SEE ALSO"
1458.PP
1459\fBmadvise\fR(2),
1460\fBmmap\fR(2),
1461\fBsbrk\fR(2),
1462\fButrace\fR(2),
1463\fBalloca\fR(3),
1464\fBatexit\fR(3),
1465\fBgetpagesize\fR(3)
1466.SH "STANDARDS"
1467.PP
1468The
1469\fBmalloc\fR\fB\fR,
1470\fBcalloc\fR\fB\fR,
1471\fBrealloc\fR\fB\fR, and
1472\fBfree\fR\fB\fR
1473functions conform to ISO/IEC 9899:1990 (\(lqISO C90\(rq)\&.
1474.PP
1475The
1476\fBposix_memalign\fR\fB\fR
1477function conforms to IEEE Std 1003\&.1\-2001 (\(lqPOSIX\&.1\(rq)\&.
1478.SH "HISTORY"
1479.PP
1480The
1481\fBmalloc_usable_size\fR\fB\fR
1482and
1483\fBposix_memalign\fR\fB\fR
1484functions first appeared in FreeBSD 7\&.0\&.
1485.PP
1486The
1487\fBaligned_alloc\fR\fB\fR,
1488\fBmalloc_stats_print\fR\fB\fR,
1489\fBmallctl*\fR\fB\fR, and
1490\fB*allocm\fR\fB\fR
1491functions first appeared in FreeBSD 10\&.0\&.
1492.SH "AUTHOR"
1493.PP
1494\fBJason Evans\fR
1495.RS 4
1496.RE
1497.SH "NOTES"
1498.IP " 1." 4
1499jemalloc website
1500.RS 4
1501\%http://www.canonware.com/jemalloc/
1502.RE
1503.IP " 2." 4
1504Valgrind
1505.RS 4
1506\%http://valgrind.org/
1507.RE
1508.IP " 3." 4
1509gperftools package
1510.RS 4
1511\%http://code.google.com/p/gperftools/
1512.RE
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