Go Back    


FreeBSD 11.0 - man page for malloc.conf (freebsd section 5)

Recursive Search Engine for Linux and Unix Man Pages by Neo
Man Page or Keyword Search:   man
Select Man Page Set:       apropos Keyword Search (sections above)


JEMALLOC(3)				   User Manual				      JEMALLOC(3)

NAME
       jemalloc - general purpose memory allocation functions

LIBRARY
       This manual describes jemalloc 3.6.0-0-g46c0af68bd248b04df75e4f92d5fb804c3d75340. More
       information can be found at the jemalloc website[1].

       The following configuration options are enabled in libc's built-in jemalloc: --enable-dss,
       --enable-experimental, --enable-fill, --enable-lazy-lock, --enable-munmap, --enable-stats,
       --enable-tcache, --enable-tls, --enable-utrace, and --enable-xmalloc. Additionally,
       --enable-debug is enabled in development versions of FreeBSD (controlled by the
       MALLOC_PRODUCTION make variable).

SYNOPSIS
       #include <stdlib.h>
       #include <malloc_np.h>

   Standard API
       void *malloc(size_t size);

       void *calloc(size_t number, size_t size);

       int posix_memalign(void **ptr, size_t alignment, size_t size);

       void *aligned_alloc(size_t alignment, size_t size);

       void *realloc(void *ptr, size_t size);

       void free(void *ptr);

   Non-standard API
       void *mallocx(size_t size, int flags);

       void *rallocx(void *ptr, size_t size, int flags);

       size_t xallocx(void *ptr, size_t size, size_t extra, int flags);

       size_t sallocx(void *ptr, int flags);

       void dallocx(void *ptr, int flags);

       size_t nallocx(size_t size, int flags);

       int mallctl(const char *name, void *oldp, size_t *oldlenp, void *newp, size_t newlen);

       int mallctlnametomib(const char *name, size_t *mibp, size_t *miblenp);

       int mallctlbymib(const size_t *mib, size_t miblen, void *oldp, size_t *oldlenp,
			void *newp, size_t newlen);

       void malloc_stats_print(void (*write_cb) (void *, const char *), void *cbopaque,
			       const char *opts);

       size_t malloc_usable_size(const void *ptr);

       void (*malloc_message)(void *cbopaque, const char *s);

       const char *malloc_conf;

   Experimental API
       int allocm(void **ptr, size_t *rsize, size_t size, int flags);

       int rallocm(void **ptr, size_t *rsize, size_t size, size_t extra, int flags);

       int sallocm(const void *ptr, size_t *rsize, int flags);

       int dallocm(void *ptr, int flags);

       int nallocm(size_t *rsize, size_t size, int flags);

DESCRIPTION
   Standard API
       The malloc function allocates size bytes of uninitialized memory. The allocated space is
       suitably aligned (after possible pointer coercion) for storage of any type of object.

       The calloc function allocates space for number objects, each size bytes in length. The
       result is identical to calling malloc with an argument of number * size, with the
       exception that the allocated memory is explicitly initialized to zero bytes.

       The posix_memalign function allocates size bytes of memory such that the allocation's base
       address is an even multiple of alignment, and returns the allocation in the value pointed
       to by ptr. The requested alignment must be a power of 2 at least as large as sizeof(void
       *).

       The aligned_alloc function allocates size bytes of memory such that the allocation's base
       address is an even multiple of alignment. The requested alignment must be a power of 2.
       Behavior is undefined if size is not an integral multiple of alignment.

       The realloc function changes the size of the previously allocated memory referenced by ptr
       to size 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 ptr is freed and a pointer to
       the newly allocated memory is returned. Note that realloc may move the memory allocation,
       resulting in a different return value than ptr. If ptr is NULL, the realloc function
       behaves identically to malloc for the specified size.

       The free function causes the allocated memory referenced by ptr to be made available for
       future allocations. If ptr is NULL, no action occurs.

   Non-standard API
       The mallocx, rallocx, xallocx, sallocx, dallocx, and nallocx functions all have a flags
       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:

       MALLOCX_LG_ALIGN(la)
	   Align the memory allocation to start at an address that is a multiple of (1 << la).
	   This macro does not validate that la is within the valid range.

       MALLOCX_ALIGN(a)
	   Align the memory allocation to start at an address that is a multiple of a, where a is
	   a power of two. This macro does not validate that a is a power of 2.

       MALLOCX_ZERO
	   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.

       MALLOCX_ARENA(a)
	   Use the arena specified by the index a (and by necessity bypass the thread cache).
	   This macro has no effect for huge regions, nor for regions that were allocated via an
	   arena other than the one specified. This macro does not validate that a specifies an
	   arena index in the valid range.

       The mallocx function allocates at least size bytes of memory, and returns a pointer to the
       base address of the allocation. Behavior is undefined if size is 0, or if request size
       overflows due to size class and/or alignment constraints.

       The rallocx function resizes the allocation at ptr to be at least size 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 size is 0, or if request size
       overflows due to size class and/or alignment constraints.

       The xallocx function resizes the allocation at ptr in place to be at least size bytes, and
       returns the real size of the allocation. If extra is non-zero, an attempt is made to
       resize the allocation to be at least (size + extra) bytes, though inability to allocate
       the extra byte(s) will not by itself result in failure to resize. Behavior is undefined if
       size is 0, or if (size + extra > SIZE_T_MAX).

       The sallocx function returns the real size of the allocation at ptr.

       The dallocx function causes the memory referenced by ptr to be made available for future
       allocations.

       The nallocx function allocates no memory, but it performs the same size computation as the
       mallocx function, and returns the real size of the allocation that would result from the
       equivalent mallocx function call. Behavior is undefined if size is 0, or if request size
       overflows due to size class and/or alignment constraints.

       The mallctl function provides a general interface for introspecting the memory allocator,
       as well as setting modifiable parameters and triggering actions. The period-separated name
       argument specifies a location in a tree-structured namespace; see the MALLCTL NAMESPACE
       section for documentation on the tree contents. To read a value, pass a pointer via oldp
       to adequate space to contain the value, and a pointer to its length via oldlenp; otherwise
       pass NULL and NULL. Similarly, to write a value, pass a pointer to the value via newp, and
       its length via newlen; otherwise pass NULL and 0.

       The mallctlnametomib 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 "Management Information Base" (MIB) that can be passed repeatedly to
       mallctlbymib. Upon successful return from mallctlnametomib, mibp contains an array of
       *miblenp integers, where *miblenp is the lesser of the number of components in name and
       the input value of *miblenp. Thus it is possible to pass a *miblenp 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 "arenas.bin.2.size"), the corresponding MIB component will always be that
       integer. Therefore, it is legitimate to construct code like the following:

	   unsigned nbins, i;
	   size_t mib[4];
	   size_t len, miblen;

	   len = sizeof(nbins);
	   mallctl("arenas.nbins", &nbins, &len, NULL, 0);

	   miblen = 4;
	   mallctlnametomib("arenas.bin.0.size", mib, &miblen);
	   for (i = 0; i < nbins; i++) {
		size_t bin_size;

		mib[2] = i;
		len = sizeof(bin_size);
		mallctlbymib(mib, miblen, &bin_size, &len, NULL, 0);
		/* Do something with bin_size... */
	   }

       The malloc_stats_print function writes human-readable summary statistics via the write_cb
       callback function pointer and cbopaque data passed to write_cb, or malloc_message if
       write_cb is NULL. This function can be called repeatedly. General information that never
       changes during execution can be omitted by specifying "g" as a character within the opts
       string. Note that malloc_message uses the mallctl* functions internally, so inconsistent
       statistics can be reported if multiple threads use these functions simultaneously. If
       --enable-stats is specified during configuration, "m" and "a" can be specified to omit
       merged arena and per arena statistics, respectively; "b" and "l" 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.

       The malloc_usable_size function returns the usable size of the allocation pointed to by
       ptr. The return value may be larger than the size that was requested during allocation.
       The malloc_usable_size function is not a mechanism for in-place realloc; rather it is
       provided solely as a tool for introspection purposes. Any discrepancy between the
       requested allocation size and the size reported by malloc_usable_size should not be
       depended on, since such behavior is entirely implementation-dependent.

   Experimental API
       The experimental API is subject to change or removal without regard for backward
       compatibility. If --disable-experimental is specified during configuration, the
       experimental API is omitted.

       The allocm, rallocm, sallocm, dallocm, and nallocm functions all have a flags 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:

       ALLOCM_LG_ALIGN(la)
	   Align the memory allocation to start at an address that is a multiple of (1 << la).
	   This macro does not validate that la is within the valid range.

       ALLOCM_ALIGN(a)
	   Align the memory allocation to start at an address that is a multiple of a, where a is
	   a power of two. This macro does not validate that a is a power of 2.

       ALLOCM_ZERO
	   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.

       ALLOCM_NO_MOVE
	   For reallocation, fail rather than moving the object. This constraint can apply to
	   both growth and shrinkage.

       ALLOCM_ARENA(a)
	   Use the arena specified by the index a (and by necessity bypass the thread cache).
	   This macro has no effect for huge regions, nor for regions that were allocated via an
	   arena other than the one specified. This macro does not validate that a specifies an
	   arena index in the valid range.

       The allocm function allocates at least size bytes of memory, sets *ptr to the base address
       of the allocation, and sets *rsize to the real size of the allocation if rsize is not
       NULL. Behavior is undefined if size is 0, or if request size overflows due to size class
       and/or alignment constraints.

       The rallocm function resizes the allocation at *ptr to be at least size bytes, sets *ptr
       to the base address of the allocation if it moved, and sets *rsize to the real size of the
       allocation if rsize is not NULL. If extra is non-zero, an attempt is made to resize the
       allocation to be at least (size + extra) bytes, though inability to allocate the extra
       byte(s) will not by itself result in failure. Behavior is undefined if size is 0, if
       request size overflows due to size class and/or alignment constraints, or if (size + extra
       > SIZE_T_MAX).

       The sallocm function sets *rsize to the real size of the allocation.

       The dallocm function causes the memory referenced by ptr to be made available for future
       allocations.

       The nallocm function allocates no memory, but it performs the same size computation as the
       allocm function, and if rsize is not NULL it sets *rsize to the real size of the
       allocation that would result from the equivalent allocm function call. Behavior is
       undefined if size is 0, or if request size overflows due to size class and/or alignment
       constraints.

TUNING
       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.

       The string pointed to by the global variable malloc_conf, the "name" of the file
       referenced by the symbolic link named /etc/malloc.conf, and the value of the environment
       variable MALLOC_CONF, will be interpreted, in that order, from left to right as options.
       Note that malloc_conf may be read before main is entered, so the declaration of
       malloc_conf should specify an initializer that contains the final value to be read by
       jemalloc.  malloc_conf is a compile-time setting, whereas /etc/malloc.conf and MALLOC_CONF
       can be safely set any time prior to program invocation.

       An options string is a comma-separated list of option:value pairs. There is one key
       corresponding to each "opt.*"  mallctl (see the MALLCTL NAMESPACE section for options
       documentation). For example, abort:true,narenas:1 sets the "opt.abort" and "opt.narenas"
       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.

IMPLEMENTATION NOTES
       Traditionally, allocators have used sbrk(2) to obtain memory, which is suboptimal for
       several reasons, including race conditions, increased fragmentation, and artificial
       limitations on maximum usable memory. If --enable-dss is specified during configuration,
       this allocator uses both mmap(2) and sbrk(2), in that order of preference; otherwise only
       mmap(2) is used.

       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.

       In addition to multiple arenas, unless --disable-tcache is 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.

       Memory 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.

       User 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.

       Each 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.

       Small 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 sizeof(double). 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 "opt.lg_chunk"
       option), 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.

       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.

       Assuming 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 Table 1.

       Table 1. Size classes
       +---------+---------+--------------------------+
       |Category | Spacing | Size		      |
       +---------+---------+--------------------------+
       |	 |	lg | [8]		      |
       |	 +---------+--------------------------+
       |	 |	16 | [16, 32, 48, ..., 128]   |
       |	 +---------+--------------------------+
       |	 |	32 | [160, 192, 224, 256]     |
       |	 +---------+--------------------------+
       |Small	 |	64 | [320, 384, 448, 512]     |
       |	 +---------+--------------------------+
       |	 |     128 | [640, 768, 896, 1024]    |
       |	 +---------+--------------------------+
       |	 |     256 | [1280, 1536, 1792, 2048] |
       |	 +---------+--------------------------+
       |	 |     512 | [2560, 3072, 3584]       |
       +---------+---------+--------------------------+
       |Large	 |   4 KiB | [4 KiB, 8 KiB, 12 KiB,   |
       |	 |	   | ..., 4072 KiB]	      |
       +---------+---------+--------------------------+
       |Huge	 |   4 MiB | [4 MiB, 8 MiB, 12 MiB,   |
       |	 |	   | ...]		      |
       +---------+---------+--------------------------+

MALLCTL NAMESPACE
       The following names are defined in the namespace accessible via the mallctl* functions.
       Value types are specified in parentheses, their readable/writable statuses are encoded as
       rw, r-, -w, or --, and required build configuration flags follow, if any. A name element
       encoded as <i> or <j> indicates an integer component, where the integer varies from 0 to
       some upper value that must be determined via introspection. In the case of
       "stats.arenas.<i>.*", <i> equal to "arenas.narenas" can be used to access the summation of
       statistics from all arenas. Take special note of the "epoch" mallctl, which controls
       refreshing of cached dynamic statistics.

       "version" (const char *) r-
	   Return the jemalloc version string.

       "epoch" (uint64_t) rw
	   If a value is passed in, refresh the data from which the mallctl* functions report
	   values, and increment the epoch. Return the current epoch. This is useful for
	   detecting whether another thread caused a refresh.

       "config.debug" (bool) r-
	   --enable-debug was specified during build configuration.

       "config.dss" (bool) r-
	   --enable-dss was specified during build configuration.

       "config.fill" (bool) r-
	   --enable-fill was specified during build configuration.

       "config.lazy_lock" (bool) r-
	   --enable-lazy-lock was specified during build configuration.

       "config.mremap" (bool) r-
	   --enable-mremap was specified during build configuration.

       "config.munmap" (bool) r-
	   --enable-munmap was specified during build configuration.

       "config.prof" (bool) r-
	   --enable-prof was specified during build configuration.

       "config.prof_libgcc" (bool) r-
	   --disable-prof-libgcc was not specified during build configuration.

       "config.prof_libunwind" (bool) r-
	   --enable-prof-libunwind was specified during build configuration.

       "config.stats" (bool) r-
	   --enable-stats was specified during build configuration.

       "config.tcache" (bool) r-
	   --disable-tcache was not specified during build configuration.

       "config.tls" (bool) r-
	   --disable-tls was not specified during build configuration.

       "config.utrace" (bool) r-
	   --enable-utrace was specified during build configuration.

       "config.valgrind" (bool) r-
	   --enable-valgrind was specified during build configuration.

       "config.xmalloc" (bool) r-
	   --enable-xmalloc was specified during build configuration.

       "opt.abort" (bool) r-
	   Abort-on-warning enabled/disabled. If true, most warnings are fatal. The process will
	   call abort(3) in these cases. This option is disabled by default unless --enable-debug
	   is specified during configuration, in which case it is enabled by default.

       "opt.dss" (const char *) r-
	   dss (sbrk(2)) allocation precedence as related to mmap(2) allocation. The following
	   settings are supported: "disabled", "primary", and "secondary". The default is
	   "secondary" if "config.dss" is true, "disabled" otherwise.

       "opt.lg_chunk" (size_t) r-
	   Virtual memory chunk size (log base 2). If a chunk size outside the supported size
	   range is specified, the size is silently clipped to the minimum/maximum supported
	   size. The default chunk size is 4 MiB (2^22).

       "opt.narenas" (size_t) r-
	   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.

       "opt.lg_dirty_mult" (ssize_t) r-
	   Per-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 madvise(2) or 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.

       "opt.stats_print" (bool) r-
	   Enable/disable statistics printing at exit. If enabled, the malloc_stats_print
	   function is called at program exit via an atexit(3) function. If --enable-stats 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. 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.

       "opt.junk" (bool) r- [--enable-fill]
	   Junk filling enabled/disabled. If enabled, each byte of uninitialized allocated memory
	   will be initialized to 0xa5. All deallocated memory will be initialized to 0x5a. This
	   is intended for debugging and will impact performance negatively. This option is
	   disabled by default unless --enable-debug is specified during configuration, in which
	   case it is enabled by default unless running inside Valgrind[2].

       "opt.quarantine" (size_t) r- [--enable-fill]
	   Per 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 "opt.junk" option is enabled. This feature is of particular use in
	   combination with Valgrind[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.

       "opt.redzone" (bool) r- [--enable-fill]
	   Redzones enabled/disabled. If enabled, small allocations have redzones before and
	   after them. Furthermore, if the "opt.junk" option 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 Valgrind[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.

       "opt.zero" (bool) r- [--enable-fill]
	   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 realloc, rallocx and rallocm 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.

       "opt.utrace" (bool) r- [--enable-utrace]
	   Allocation tracing based on utrace(2) enabled/disabled. This option is disabled by
	   default.

       "opt.valgrind" (bool) r- [--enable-valgrind]
	   Valgrind[2] support 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.

       "opt.xmalloc" (bool) r- [--enable-xmalloc]
	   Abort-on-out-of-memory enabled/disabled. If enabled, rather than returning failure for
	   any allocation function, display a diagnostic message on STDERR_FILENO and cause the
	   program to drop core (using abort(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:

	       malloc_conf = "xmalloc:true";

	   This option is disabled by default.

       "opt.tcache" (bool) r- [--enable-tcache]
	   Thread-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 "opt.lg_tcache_max" option for related
	   tuning information. This option is enabled by default unless running inside
	   Valgrind[2].

       "opt.lg_tcache_max" (size_t) r- [--enable-tcache]
	   Maximum 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).

       "opt.prof" (bool) r- [--enable-prof]
	   Memory profiling enabled/disabled. If enabled, profile memory allocation activity. See
	   the "opt.prof_active" option for on-the-fly activation/deactivation. See the
	   "opt.lg_prof_sample" option for probabilistic sampling control. See the
	   "opt.prof_accum" option for control of cumulative sample reporting. See the
	   "opt.lg_prof_interval" option for information on interval-triggered profile dumping,
	   the "opt.prof_gdump" option for information on high-water-triggered profile dumping,
	   and the "opt.prof_final" option for final profile dumping. Profile output is
	   compatible with the included pprof Perl script, which originates from the gperftools
	   package[3].

       "opt.prof_prefix" (const char *) r- [--enable-prof]
	   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
	   jeprof.

       "opt.prof_active" (bool) rw [--enable-prof]
	   Profiling activated/deactivated. This is a secondary control mechanism that makes it
	   possible to start the application with profiling enabled (see the "opt.prof" option)
	   but inactive, then toggle profiling at any time during program execution with the
	   "prof.active" mallctl. This option is enabled by default.

       "opt.lg_prof_sample" (ssize_t) r- [--enable-prof]
	   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).

       "opt.prof_accum" (bool) r- [--enable-prof]
	   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.

       "opt.lg_prof_interval" (ssize_t) r- [--enable-prof]
	   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
	   <prefix>.<pid>.<seq>.i<iseq>.heap, where <prefix> is controlled by the
	   "opt.prof_prefix" option. By default, interval-triggered profile dumping is disabled
	   (encoded as -1).

       "opt.prof_gdump" (bool) r- [--enable-prof]
	   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
	   <prefix>.<pid>.<seq>.u<useq>.heap, where <prefix> is controlled by the
	   "opt.prof_prefix" option. This option is disabled by default.

       "opt.prof_final" (bool) r- [--enable-prof]
	   Use an atexit(3) function to dump final memory usage to a file named according to the
	   pattern <prefix>.<pid>.<seq>.f.heap, where <prefix> is controlled by the
	   "opt.prof_prefix" option. This option is enabled by default.

       "opt.prof_leak" (bool) r- [--enable-prof]
	   Leak reporting enabled/disabled. If enabled, use an atexit(3) function to report
	   memory leaks detected by allocation sampling. See the "opt.prof" option for
	   information on analyzing heap profile output. This option is disabled by default.

       "thread.arena" (unsigned) rw
	   Get or set the arena associated with the calling thread. If the specified arena was
	   not initialized beforehand (see the "arenas.initialized" mallctl), it will be
	   automatically initialized as a side effect of calling this interface.

       "thread.allocated" (uint64_t) r- [--enable-stats]
	   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.

       "thread.allocatedp" (uint64_t *) r- [--enable-stats]
	   Get a pointer to the the value that is returned by the "thread.allocated" mallctl.
	   This is useful for avoiding the overhead of repeated mallctl* calls.

       "thread.deallocated" (uint64_t) r- [--enable-stats]
	   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.

       "thread.deallocatedp" (uint64_t *) r- [--enable-stats]
	   Get a pointer to the the value that is returned by the "thread.deallocated" mallctl.
	   This is useful for avoiding the overhead of repeated mallctl* calls.

       "thread.tcache.enabled" (bool) rw [--enable-tcache]
	   Enable/disable calling thread's tcache. The tcache is implicitly flushed as a side
	   effect of becoming disabled (see "thread.tcache.flush").

       "thread.tcache.flush" (void) -- [--enable-tcache]
	   Flush calling thread's tcache. This interface releases all cached objects and internal
	   data structures associated with the calling thread's 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.

       "arena.<i>.purge" (unsigned) --
	   Purge unused dirty pages for arena <i>, or for all arenas if <i> equals
	   "arenas.narenas".

       "arena.<i>.dss" (const char *) rw
	   Set the precedence of dss allocation as related to mmap allocation for arena <i>, or
	   for all arenas if <i> equals "arenas.narenas". Note that even during huge allocation
	   this setting is read from the arena that would be chosen for small or large allocation
	   so that applications can depend on consistent dss versus mmap allocation regardless of
	   allocation size. See "opt.dss" for supported settings.

       "arenas.narenas" (unsigned) r-
	   Current limit on number of arenas.

       "arenas.initialized" (bool *) r-
	   An array of "arenas.narenas" booleans. Each boolean indicates whether the
	   corresponding arena is initialized.

       "arenas.quantum" (size_t) r-
	   Quantum size.

       "arenas.page" (size_t) r-
	   Page size.

       "arenas.tcache_max" (size_t) r- [--enable-tcache]
	   Maximum thread-cached size class.

       "arenas.nbins" (unsigned) r-
	   Number of bin size classes.

       "arenas.nhbins" (unsigned) r- [--enable-tcache]
	   Total number of thread cache bin size classes.

       "arenas.bin.<i>.size" (size_t) r-
	   Maximum size supported by size class.

       "arenas.bin.<i>.nregs" (uint32_t) r-
	   Number of regions per page run.

       "arenas.bin.<i>.run_size" (size_t) r-
	   Number of bytes per page run.

       "arenas.nlruns" (size_t) r-
	   Total number of large size classes.

       "arenas.lrun.<i>.size" (size_t) r-
	   Maximum size supported by this large size class.

       "arenas.purge" (unsigned) -w
	   Purge unused dirty pages for the specified arena, or for all arenas if none is
	   specified.

       "arenas.extend" (unsigned) r-
	   Extend the array of arenas by appending a new arena, and returning the new arena
	   index.

       "prof.active" (bool) rw [--enable-prof]
	   Control whether sampling is currently active. See the "opt.prof_active" option for
	   additional information.

       "prof.dump" (const char *) -w [--enable-prof]
	   Dump a memory profile to the specified file, or if NULL is specified, to a file
	   according to the pattern <prefix>.<pid>.<seq>.m<mseq>.heap, where <prefix> is
	   controlled by the "opt.prof_prefix" option.

       "prof.interval" (uint64_t) r- [--enable-prof]
	   Average number of bytes allocated between inverval-based profile dumps. See the
	   "opt.lg_prof_interval" option for additional information.

       "stats.cactive" (size_t *) r- [--enable-stats]
	   Pointer 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 "epoch" mallctl 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.

       "stats.allocated" (size_t) r- [--enable-stats]
	   Total number of bytes allocated by the application.

       "stats.active" (size_t) r- [--enable-stats]
	   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 "stats.allocated". This does not
	   include "stats.arenas.<i>.pdirty" and pages entirely devoted to allocator metadata.

       "stats.mapped" (size_t) r- [--enable-stats]
	   Total 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 "stats.active". This does not
	   include inactive chunks.

       "stats.chunks.current" (size_t) r- [--enable-stats]
	   Total number of chunks actively mapped on behalf of the application. This does not
	   include inactive chunks.

       "stats.chunks.total" (uint64_t) r- [--enable-stats]
	   Cumulative number of chunks allocated.

       "stats.chunks.high" (size_t) r- [--enable-stats]
	   Maximum number of active chunks at any time thus far.

       "stats.huge.allocated" (size_t) r- [--enable-stats]
	   Number of bytes currently allocated by huge objects.

       "stats.huge.nmalloc" (uint64_t) r- [--enable-stats]
	   Cumulative number of huge allocation requests.

       "stats.huge.ndalloc" (uint64_t) r- [--enable-stats]
	   Cumulative number of huge deallocation requests.

       "stats.arenas.<i>.dss" (const char *) r-
	   dss (sbrk(2)) allocation precedence as related to mmap(2) allocation. See "opt.dss"
	   for details.

       "stats.arenas.<i>.nthreads" (unsigned) r-
	   Number of threads currently assigned to arena.

       "stats.arenas.<i>.pactive" (size_t) r-
	   Number of pages in active runs.

       "stats.arenas.<i>.pdirty" (size_t) r-
	   Number of pages within unused runs that are potentially dirty, and for which
	   madvise... MADV_DONTNEED or similar has not been called.

       "stats.arenas.<i>.mapped" (size_t) r- [--enable-stats]
	   Number of mapped bytes.

       "stats.arenas.<i>.npurge" (uint64_t) r- [--enable-stats]
	   Number of dirty page purge sweeps performed.

       "stats.arenas.<i>.nmadvise" (uint64_t) r- [--enable-stats]
	   Number of madvise... MADV_DONTNEED or similar calls made to purge dirty pages.

       "stats.arenas.<i>.purged" (uint64_t) r- [--enable-stats]
	   Number of pages purged.

       "stats.arenas.<i>.small.allocated" (size_t) r- [--enable-stats]
	   Number of bytes currently allocated by small objects.

       "stats.arenas.<i>.small.nmalloc" (uint64_t) r- [--enable-stats]
	   Cumulative number of allocation requests served by small bins.

       "stats.arenas.<i>.small.ndalloc" (uint64_t) r- [--enable-stats]
	   Cumulative number of small objects returned to bins.

       "stats.arenas.<i>.small.nrequests" (uint64_t) r- [--enable-stats]
	   Cumulative number of small allocation requests.

       "stats.arenas.<i>.large.allocated" (size_t) r- [--enable-stats]
	   Number of bytes currently allocated by large objects.

       "stats.arenas.<i>.large.nmalloc" (uint64_t) r- [--enable-stats]
	   Cumulative number of large allocation requests served directly by the arena.

       "stats.arenas.<i>.large.ndalloc" (uint64_t) r- [--enable-stats]
	   Cumulative number of large deallocation requests served directly by the arena.

       "stats.arenas.<i>.large.nrequests" (uint64_t) r- [--enable-stats]
	   Cumulative number of large allocation requests.

       "stats.arenas.<i>.bins.<j>.allocated" (size_t) r- [--enable-stats]
	   Current number of bytes allocated by bin.

       "stats.arenas.<i>.bins.<j>.nmalloc" (uint64_t) r- [--enable-stats]
	   Cumulative number of allocations served by bin.

       "stats.arenas.<i>.bins.<j>.ndalloc" (uint64_t) r- [--enable-stats]
	   Cumulative number of allocations returned to bin.

       "stats.arenas.<i>.bins.<j>.nrequests" (uint64_t) r- [--enable-stats]
	   Cumulative number of allocation requests.

       "stats.arenas.<i>.bins.<j>.nfills" (uint64_t) r- [--enable-stats --enable-tcache]
	   Cumulative number of tcache fills.

       "stats.arenas.<i>.bins.<j>.nflushes" (uint64_t) r- [--enable-stats --enable-tcache]
	   Cumulative number of tcache flushes.

       "stats.arenas.<i>.bins.<j>.nruns" (uint64_t) r- [--enable-stats]
	   Cumulative number of runs created.

       "stats.arenas.<i>.bins.<j>.nreruns" (uint64_t) r- [--enable-stats]
	   Cumulative number of times the current run from which to allocate changed.

       "stats.arenas.<i>.bins.<j>.curruns" (size_t) r- [--enable-stats]
	   Current number of runs.

       "stats.arenas.<i>.lruns.<j>.nmalloc" (uint64_t) r- [--enable-stats]
	   Cumulative number of allocation requests for this size class served directly by the
	   arena.

       "stats.arenas.<i>.lruns.<j>.ndalloc" (uint64_t) r- [--enable-stats]
	   Cumulative number of deallocation requests for this size class served directly by the
	   arena.

       "stats.arenas.<i>.lruns.<j>.nrequests" (uint64_t) r- [--enable-stats]
	   Cumulative number of allocation requests for this size class.

       "stats.arenas.<i>.lruns.<j>.curruns" (size_t) r- [--enable-stats]
	   Current number of runs for this size class.

DEBUGGING MALLOC PROBLEMS
       When debugging, it is a good idea to configure/build jemalloc with the --enable-debug and
       --enable-fill 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.

       Programs often accidentally depend on "uninitialized" memory actually being filled with
       zero bytes. Junk filling (see the "opt.junk" option) tends to expose such bugs in the form
       of obviously incorrect results and/or coredumps. Conversely, zero filling (see the
       "opt.zero" option) eliminates the symptoms of such bugs. Between these two options, it is
       usually possible to quickly detect, diagnose, and eliminate such bugs.

       This 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 Valgrind[2] tool if the --enable-valgrind
       configuration option is enabled.

DIAGNOSTIC MESSAGES
       If any of the memory allocation/deallocation functions detect an error or warning
       condition, a message will be printed to file descriptor STDERR_FILENO. Errors will result
       in the process dumping core. If the "opt.abort" option is set, most warnings are treated
       as errors.

       The malloc_message variable allows the programmer to override the function which emits the
       text strings forming the errors and warnings if for some reason the STDERR_FILENO file
       descriptor is not suitable for this.  malloc_message takes the cbopaque pointer argument
       that is NULL unless overridden by the arguments in a call to 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.

       All messages are prefixed by "<jemalloc>:".

RETURN VALUES
   Standard API
       The malloc and calloc functions return a pointer to the allocated memory if successful;
       otherwise a NULL pointer is returned and errno is set to ENOMEM.

       The posix_memalign function returns the value 0 if successful; otherwise it returns an
       error value. The posix_memalign function will fail if:

       EINVAL
	   The alignment parameter is not a power of 2 at least as large as sizeof(void *).

       ENOMEM
	   Memory allocation error.

       The aligned_alloc function returns a pointer to the allocated memory if successful;
       otherwise a NULL pointer is returned and errno is set. The aligned_alloc function will
       fail if:

       EINVAL
	   The alignment parameter is not a power of 2.

       ENOMEM
	   Memory allocation error.

       The realloc function returns a pointer, possibly identical to ptr, to the allocated memory
       if successful; otherwise a NULL pointer is returned, and errno is set to ENOMEM if the
       error was the result of an allocation failure. The realloc function always leaves the
       original buffer intact when an error occurs.

       The free function returns no value.

   Non-standard API
       The mallocx and rallocx functions return a pointer to the allocated memory if successful;
       otherwise a NULL pointer is returned to indicate insufficient contiguous memory was
       available to service the allocation request.

       The xallocx function returns the real size of the resulting resized allocation pointed to
       by ptr, which is a value less than size if the allocation could not be adequately grown in
       place.

       The sallocx function returns the real size of the allocation pointed to by ptr.

       The nallocx returns the real size that would result from a successful equivalent mallocx
       function call, or zero if insufficient memory is available to perform the size
       computation.

       The mallctl, mallctlnametomib, and mallctlbymib functions return 0 on success; otherwise
       they return an error value. The functions will fail if:

       EINVAL
	   newp is not NULL, and newlen is too large or too small. Alternatively, *oldlenp is too
	   large or too small; in this case as much data as possible are read despite the error.

       ENOENT
	   name or mib specifies an unknown/invalid value.

       EPERM
	   Attempt to read or write void value, or attempt to write read-only value.

       EAGAIN
	   A memory allocation failure occurred.

       EFAULT
	   An interface with side effects failed in some way not directly related to mallctl*
	   read/write processing.

       The malloc_usable_size function returns the usable size of the allocation pointed to by
       ptr.

   Experimental API
       The allocm, rallocm, sallocm, dallocm, and nallocm functions return ALLOCM_SUCCESS on
       success; otherwise they return an error value. The allocm, rallocm, and nallocm functions
       will fail if:

       ALLOCM_ERR_OOM
	   Out of memory. Insufficient contiguous memory was available to service the allocation
	   request. The allocm function additionally sets *ptr to NULL, whereas the rallocm
	   function leaves *ptr unmodified.
       The rallocm function will also fail if:

       ALLOCM_ERR_NOT_MOVED
	   ALLOCM_NO_MOVE was specified, but the reallocation request could not be serviced
	   without moving the object.

ENVIRONMENT
       The following environment variable affects the execution of the allocation functions:

       MALLOC_CONF
	   If the environment variable MALLOC_CONF is set, the characters it contains will be
	   interpreted as options.

EXAMPLES
       To dump core whenever a problem occurs:

	   ln -s 'abort:true' /etc/malloc.conf

       To specify in the source a chunk size that is 16 MiB:

	   malloc_conf = "lg_chunk:24";

SEE ALSO
       madvise(2), mmap(2), sbrk(2), utrace(2), alloca(3), atexit(3), getpagesize(3)

STANDARDS
       The malloc, calloc, realloc, and free functions conform to ISO/IEC 9899:1990 ("ISO C90").

       The posix_memalign function conforms to IEEE Std 1003.1-2001 ("POSIX.1").

HISTORY
       The malloc_usable_size and posix_memalign functions first appeared in FreeBSD 7.0.

       The aligned_alloc, malloc_stats_print, mallctl*, and *allocm functions first appeared in
       FreeBSD 10.0.

       The *allocx functions first appeared in FreeBSD 11.0.

AUTHOR
       Jason Evans

NOTES
	1. jemalloc website
	   http://www.canonware.com/jemalloc/

	2. Valgrind
	   http://valgrind.org/

	3. gperftools package
	   http://code.google.com/p/gperftools/

jemalloc 3.6.0-0-g46c0af68bd24		    03/31/2014				      JEMALLOC(3)
The UNIX and Linux Forums Man Pages : 2000 - 2015 The UNIX and Linux Forums


All times are GMT -4. The time now is 04:33 PM.