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JEMALLOC(3)                       User Manual                      JEMALLOC(3)

NAME
       jemalloc - general purpose memory allocation functions

LIBRARY
       This manual describes jemalloc
       3.4.0-0-g0ed518e5dab789ad2171bb38977a8927e2a26775. 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
       size_t malloc_usable_size(const void *ptr);

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

       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_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 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.

       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 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;

           int mib[4];
           size_t len, miblen;

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

           miblen = 4;
           mallnametomib("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... */
           }

   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 option 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. This macro does not
           validate that a specifies an arena 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.

       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, 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.

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                                  |
       |Small           lg   [8]                                   |
       |                16   [16, 32, 48, ..., 128]                |
       |                32   [160, 192, 224, 256]                  |
       |                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.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.dss" (const char *) r-
           dss (sbrk(2)) allocation precedence as related to mmap(2)
           allocation. The following settings are supported: "disabled",
           "primary", and "secondary" (default).

       "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 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) r- [--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".
           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>.npurged" (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 malloc_usable_size function returns the usable size of the
       allocation pointed to by ptr.

       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.

       ENOMEM
           *oldlenp is too short to hold the requested value.

       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.

   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.

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 3.4.0-0-g0ed518e5dab7    06/02/2013                       JEMALLOC(3)

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | TUNING | IMPLEMENTATION NOTES | MALLCTL NAMESPACE | DEBUGGING MALLOC PROBLEMS | DIAGNOSTIC MESSAGES | RETURN VALUES | ENVIRONMENT | EXAMPLES | SEE ALSO | STANDARDS | HISTORY | AUTHOR | NOTES

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