Man

Command Section
JEMALLOC(3)                       User Manual                      JEMALLOC(3)

NAME
       jemalloc - general purpose memory allocation functions

LIBRARY
       This manual describes jemalloc
       4.2.1-0-g3de035335255d553bdb344c32ffdb603816195d8. More information can
       be found at the jemalloc website[1].

       The following configuration options are enabled in libc's built-in
       jemalloc: --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);

       void sdallocx(void *ptr, size_t size, 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);)(void *cbopaque, const char *s);

       const char *malloc_conf;

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 a 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 a 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, sdallocx, 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_TCACHE(tc)
           Use the thread-specific cache (tcache) specified by the identifier
           tc, which must have been acquired via the "tcache.create" mallctl.
           This macro does not validate that tc specifies a valid identifier.

       MALLOCX_TCACHE_NONE
           Do not use a thread-specific cache (tcache). Unless
           MALLOCX_TCACHE(tc) or MALLOCX_TCACHE_NONE is specified, an
           automatically managed tcache will be used under many circumstances.
           This macro cannot be used in the same flags argument as
           MALLOCX_TCACHE(tc).

       MALLOCX_ARENA(a)
           Use the arena specified by the index a. This macro has no effect
           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.

       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.

       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 sdallocx function is an extension of dallocx with a size parameter
       to allow the caller to pass in the allocation size as an optimization.
       The minimum valid input size is the original requested size of the
       allocation, and the maximum valid input size is the corresponding value
       returned by nallocx or sallocx.

       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,
       or 0 if the inputs exceed the maximum supported size class and/or
       alignment. Behavior is undefined if size is 0.

       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", "l", and "h" can be specified to omit per size class statistics
       for bins, large objects, and huge 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.

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 specified via --with-malloc-conf, 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.
       --with-malloc-conf and malloc_conf are compile-time mechanisms, 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
       sbrk(2) is supported by the operating system, 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. Multiple small and large objects can reside within a single
       chunk, whereas huge objects each have one or more chunks backing them.
       Each chunk that contains small and/or large objects 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
       bitmap to track which regions are in use. Allocation requests that are
       no more than half the quantum (8 or 16, depending on architecture) are
       rounded up to the nearest power of two that is at least sizeof(double).
       All other object size classes are multiples of the quantum, spaced such
       that there are four size classes for each doubling in size, which
       limits internal fragmentation to approximately 20% for all but the
       smallest size classes. Small size classes are smaller than four times
       the page size, large size classes are smaller than the chunk size (see
       the "opt.lg_chunk" option), and huge size classes extend from the chunk
       size up to the largest size class that does not exceed PTRDIFF_MAX.

       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.

       The realloc, rallocx, and xallocx functions may resize allocations
       without moving them under limited circumstances. Unlike the *allocx
       API, the standard API does not officially round up the usable size of
       an allocation to the nearest size class, so technically it is necessary
       to call realloc to grow e.g. a 9-byte allocation to 16 bytes, or shrink
       a 16-byte allocation to 9 bytes. Growth and shrinkage trivially
       succeeds in place as long as the pre-size and post-size both round up
       to the same size class. No other API guarantees are made regarding
       in-place resizing, but the current implementation also tries to resize
       large and huge allocations in place, as long as the pre-size and
       post-size are both large or both huge. In such cases shrinkage always
       succeeds for large size classes, but for huge size classes the chunk
       allocator must support splitting (see "arena.<i>.chunk_hooks"). Growth
       only succeeds if the trailing memory is currently available, and
       additionally for huge size classes the chunk allocator must support
       merging.

       Assuming 2 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, 64, 80, 96, 112, 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, 4096]             |
       |             1 KiB   [5 KiB, 6 KiB, 7 KiB, 8 KiB]         |
       |             2 KiB   [10 KiB, 12 KiB, 14 KiB]             |
       |Large        2 KiB   [16 KiB]                             |
       |             4 KiB   [20 KiB, 24 KiB, 28 KiB, 32 KiB]     |
       |             8 KiB   [40 KiB, 48 KiB, 54 KiB, 64 KiB]     |
       |            16 KiB   [80 KiB, 96 KiB, 112 KiB, 128 KiB]   |
       |            32 KiB   [160 KiB, 192 KiB, 224 KiB, 256 KiB] |
       |            64 KiB   [320 KiB, 384 KiB, 448 KiB, 512 KiB] |
       |           128 KiB   [640 KiB, 768 KiB, 896 KiB, 1 MiB]   |
       |           256 KiB   [1280 KiB, 1536 KiB, 1792 KiB]       |
       |Huge       256 KiB   [2 MiB]                              |
       |           512 KiB   [2560 KiB, 3 MiB, 3584 KiB, 4 MiB]   |
       |             1 MiB   [5 MiB, 6 MiB, 7 MiB, 8 MiB]         |
       |             2 MiB   [10 MiB, 12 MiB, 14 MiB, 16 MiB]     |
       |             4 MiB   [20 MiB, 24 MiB, 28 MiB, 32 MiB]     |
       |             8 MiB   [40 MiB, 48 MiB, 56 MiB, 64 MiB]     |
       |               ...   ...                                  |
       |           512 PiB   [2560 PiB, 3 EiB, 3584 PiB, 4 EiB]   |
       |             1 EiB   [5 EiB, 6 EiB, 7 EiB]                |
       +----------------------------------------------------------+

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.cache_oblivious" (bool) r-
           --enable-cache-oblivious was specified during build configuration.

       "config.debug" (bool) r-
           --enable-debug 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.malloc_conf" (const char *) r-
           Embedded configure-time-specified run-time options string, empty
           unless --with-malloc-conf 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 if sbrk(2) is
           supported by the operating system: "disabled", "primary", and
           "secondary"; otherwise only "disabled" is supported. The default is
           "secondary" if sbrk(2) is supported by the operating system;
           "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 2 MiB
           (2^21).

       "opt.narenas" (unsigned) 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.purge" (const char *) r-
           Purge mode is "ratio" (default) or "decay". See "opt.lg_dirty_mult"
           for details of the ratio mode. See "opt.decay_time" for details of
           the decay mode.

       "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. See "arenas.lg_dirty_mult" and "arena.<i>.lg_dirty_mult"
           for related dynamic control options.

       "opt.decay_time" (ssize_t) r-
           Approximate time in seconds from the creation of a set of unused
           dirty pages until an equivalent set of unused dirty pages is purged
           and/or reused. The pages are incrementally purged according to a
           sigmoidal decay curve that starts and ends with zero purge rate. A
           decay time of 0 causes all unused dirty pages to be purged
           immediately upon creation. A decay time of -1 disables purging. The
           default decay time is 10 seconds. See "arenas.decay_time" and
           "arena.<i>.decay_time" for related dynamic control options.

       "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. Furthermore, atexit
           may allocate memory during application initialization and then
           deadlock internally when jemalloc in turn calls atexit, so this
           option is not universally usable (though the application can
           register its own atexit function with equivalent functionality).
           Therefore, this option should only be used with care; it is
           primarily intended as a performance tuning aid during application
           development. This option is disabled by default.

       "opt.junk" (const char *) r- [--enable-fill]
           Junk filling. If set to "alloc", each byte of uninitialized
           allocated memory will be initialized to 0xa5. If set to "free", all
           deallocated memory will be initialized to 0x5a. If set to "true",
           both allocated and deallocated memory will be initialized, and if
           set to "false", junk filling be disabled entirely. This is intended
           for debugging and will impact performance negatively. This option
           is "false" by default unless --enable-debug is specified during
           configuration, in which case it is "true" 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
           rallocx 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.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 (tcache) enabled/disabled. When there are
           multiple threads, each thread uses a tcache for objects up to a
           certain size. Thread-specific caching allows many allocations to be
           satisfied without performing any thread synchronization, at the
           cost of increased memory use. See the "opt.lg_tcache_max" option
           for related tuning information. This option is enabled by default
           unless running inside Valgrind[2], in which case it is forcefully
           disabled.

       "opt.lg_tcache_max" (size_t) r- [--enable-tcache]
           Maximum size class (log base 2) to cache in the thread-specific
           cache (tcache). At a minimum, all small size classes are cached,
           and at a maximum all large size classes are cached. The default
           maximum is 32 KiB (2^15).

       "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 jeprof command, which is based on the pprof that is developed
           as part of the gperftools package[3]. See HEAP PROFILE FORMAT for
           heap profile format documentation.

       "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.prof_thread_active_init" (bool) r- [--enable-prof]
           Initial setting for "thread.prof.active" in newly created threads.
           The initial setting for newly created threads can also be changed
           during execution via the "prof.thread_active_init" mallctl. This
           option is enabled by default.

       "opt.lg_prof_sample" (size_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]
           Set the initial state of "prof.gdump", which when enabled triggers
           a memory profile dump every time the total virtual memory exceeds
           the previous maximum. This option is disabled by default.

       "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. Note that
           atexit may allocate memory during application initialization and
           then deadlock internally when jemalloc in turn calls atexit, so
           this option is not universally usable (though the application can
           register its own atexit function with equivalent functionality).
           This option is disabled 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 thread-specific cache (tcache). This
           interface releases all cached objects and internal data structures
           associated with the calling thread's tcache. Ordinarily, this
           interface need not be called, since automatic periodic incremental
           garbage collection occurs, and the thread cache is automatically
           discarded when a thread exits. However, garbage collection is
           triggered by allocation activity, so it is possible for a thread
           that stops allocating/deallocating to retain its cache
           indefinitely, in which case the developer may find manual flushing
           useful.

       "thread.prof.name" (const char *) r- or -w [--enable-prof]
           Get/set the descriptive name associated with the calling thread in
           memory profile dumps. An internal copy of the name string is
           created, so the input string need not be maintained after this
           interface completes execution. The output string of this interface
           should be copied for non-ephemeral uses, because multiple
           implementation details can cause asynchronous string deallocation.
           Furthermore, each invocation of this interface can only read or
           write; simultaneous read/write is not supported due to string
           lifetime limitations. The name string must be nil-terminated and
           comprised only of characters in the sets recognized by isgraph(3)
           and isblank(3).

       "thread.prof.active" (bool) rw [--enable-prof]
           Control whether sampling is currently active for the calling
           thread. This is an activation mechanism in addition to
           "prof.active"; both must be active for the calling thread to
           sample. This flag is enabled by default.

       "tcache.create" (unsigned) r- [--enable-tcache]
           Create an explicit thread-specific cache (tcache) and return an
           identifier that can be passed to the MALLOCX_TCACHE(tc) macro to
           explicitly use the specified cache rather than the automatically
           managed one that is used by default. Each explicit cache can be
           used by only one thread at a time; the application must assure that
           this constraint holds.

       "tcache.flush" (unsigned) -w [--enable-tcache]
           Flush the specified thread-specific cache (tcache). The same
           considerations apply to this interface as to "thread.tcache.flush",
           except that the tcache will never be automatically discarded.

       "tcache.destroy" (unsigned) -w [--enable-tcache]
           Flush the specified thread-specific cache (tcache) and make the
           identifier available for use during a future tcache creation.

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

       "arena.<i>.decay" (void) --
           Trigger decay-based purging of unused dirty pages for arena <i>, or
           for all arenas if <i> equals "arenas.narenas". The proportion of
           unused dirty pages to be purged depends on the current time; see
           "opt.decay_time" for details.

       "arena.<i>.reset" (void) --
           Discard all of the arena's extant allocations. This interface can
           only be used with arenas created via "arenas.extend". None of the
           arena's discarded/cached allocations may accessed afterward. As
           part of this requirement, all thread caches which were used to
           allocate/deallocate in conjunction with the arena must be flushed
           beforehand. This interface cannot be used if running inside
           Valgrind, nor if the quarantine size is non-zero.

       "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.

       "arena.<i>.lg_dirty_mult" (ssize_t) rw
           Current per-arena minimum ratio (log base 2) of active to dirty
           pages for arena <i>. Each time this interface is set and the ratio
           is increased, pages are synchronously purged as necessary to impose
           the new ratio. See "opt.lg_dirty_mult" for additional information.

       "arena.<i>.decay_time" (ssize_t) rw
           Current per-arena approximate time in seconds from the creation of
           a set of unused dirty pages until an equivalent set of unused dirty
           pages is purged and/or reused. Each time this interface is set, all
           currently unused dirty pages are considered to have fully decayed,
           which causes immediate purging of all unused dirty pages unless the
           decay time is set to -1 (i.e. purging disabled). See
           "opt.decay_time" for additional information.

       "arena.<i>.chunk_hooks" (chunk_hooks_t) rw
           Get or set the chunk management hook functions for arena <i>. The
           functions must be capable of operating on all extant chunks
           associated with arena <i>, usually by passing unknown chunks to the
           replaced functions. In practice, it is feasible to control
           allocation for arenas created via "arenas.extend" such that all
           chunks originate from an application-supplied chunk allocator (by
           setting custom chunk hook functions just after arena creation), but
           the automatically created arenas may have already created chunks
           prior to the application having an opportunity to take over chunk
           allocation.

               typedef struct {
                    chunk_alloc_t       *alloc;
                    chunk_dalloc_t      *dalloc;
                    chunk_commit_t      *commit;
                    chunk_decommit_t    *decommit;
                    chunk_purge_t       *purge;
                    chunk_split_t       *split;
                    chunk_merge_t       *merge;
               } chunk_hooks_t;

           The chunk_hooks_t structure comprises function pointers which are
           described individually below. jemalloc uses these functions to
           manage chunk lifetime, which starts off with allocation of mapped
           committed memory, in the simplest case followed by deallocation.
           However, there are performance and platform reasons to retain
           chunks for later reuse. Cleanup attempts cascade from deallocation
           to decommit to purging, which gives the chunk management functions
           opportunities to reject the most permanent cleanup operations in
           favor of less permanent (and often less costly) operations. The
           chunk splitting and merging operations can also be opted out of,
           but this is mainly intended to support platforms on which virtual
           memory mappings provided by the operating system kernel do not
           automatically coalesce and split, e.g. Windows.

           typedef void *(chunk_alloc_t)(void *chunk, size_t size,
                                         size_t alignment, bool *zero,
                                         bool *commit, unsigned arena_ind);

           A chunk allocation function conforms to the chunk_alloc_t type and
           upon success returns a pointer to size bytes of mapped memory on
           behalf of arena arena_ind such that the chunk's base address is a
           multiple of alignment, as well as setting *zero to indicate whether
           the chunk is zeroed and *commit to indicate whether the chunk is
           committed. Upon error the function returns NULL and leaves *zero
           and *commit unmodified. The size parameter is always a multiple of
           the chunk size. The alignment parameter is always a power of two at
           least as large as the chunk size. Zeroing is mandatory if *zero is
           true upon function entry. Committing is mandatory if *commit is
           true upon function entry. If chunk is not NULL, the returned
           pointer must be chunk on success or NULL on error. Committed memory
           may be committed in absolute terms as on a system that does not
           overcommit, or in implicit terms as on a system that overcommits
           and satisfies physical memory needs on demand via soft page faults.
           Note that replacing the default chunk allocation function makes the
           arena's "arena.<i>.dss" setting irrelevant.

           typedef bool (chunk_dalloc_t)(void *chunk, size_t size,
                                         bool committed, unsigned arena_ind);

           A chunk deallocation function conforms to the chunk_dalloc_t type
           and deallocates a chunk of given size with committed/decommited
           memory as indicated, on behalf of arena arena_ind, returning false
           upon success. If the function returns true, this indicates opt-out
           from deallocation; the virtual memory mapping associated with the
           chunk remains mapped, in the same commit state, and available for
           future use, in which case it will be automatically retained for
           later reuse.

           typedef bool (chunk_commit_t)(void *chunk, size_t size,
                                         size_t offset, size_t length,
                                         unsigned arena_ind);

           A chunk commit function conforms to the chunk_commit_t type and
           commits zeroed physical memory to back pages within a chunk of
           given size at offset bytes, extending for length on behalf of arena
           arena_ind, returning false upon success. Committed memory may be
           committed in absolute terms as on a system that does not
           overcommit, or in implicit terms as on a system that overcommits
           and satisfies physical memory needs on demand via soft page faults.
           If the function returns true, this indicates insufficient physical
           memory to satisfy the request.

           typedef bool (chunk_decommit_t)(void *chunk, size_t size,
                                           size_t offset, size_t length,
                                           unsigned arena_ind);

           A chunk decommit function conforms to the chunk_decommit_t type and
           decommits any physical memory that is backing pages within a chunk
           of given size at offset bytes, extending for length on behalf of
           arena arena_ind, returning false upon success, in which case the
           pages will be committed via the chunk commit function before being
           reused. If the function returns true, this indicates opt-out from
           decommit; the memory remains committed and available for future
           use, in which case it will be automatically retained for later
           reuse.

           typedef bool (chunk_purge_t)(void *chunk, size_tsize,
                                        size_t offset, size_t length,
                                        unsigned arena_ind);

           A chunk purge function conforms to the chunk_purge_t type and
           optionally discards physical pages within the virtual memory
           mapping associated with chunk of given size at offset bytes,
           extending for length on behalf of arena arena_ind, returning false
           if pages within the purged virtual memory range will be zero-filled
           the next time they are accessed.

           typedef bool (chunk_split_t)(void *chunk, size_t size,
                                        size_t size_a, size_t size_b,
                                        bool committed, unsigned arena_ind);

           A chunk split function conforms to the chunk_split_t type and
           optionally splits chunk of given size into two adjacent chunks, the
           first of size_a bytes, and the second of size_b bytes, operating on
           committed/decommitted memory as indicated, on behalf of arena
           arena_ind, returning false upon success. If the function returns
           true, this indicates that the chunk remains unsplit and therefore
           should continue to be operated on as a whole.

           typedef bool (chunk_merge_t)(void *chunk_a, size_t size_a,
                                        void *chunk_b, size_t size_b,
                                        bool committed, unsigned arena_ind);

           A chunk merge function conforms to the chunk_merge_t type and
           optionally merges adjacent chunks, chunk_a of given size_a and
           chunk_b of given size_b into one contiguous chunk, operating on
           committed/decommitted memory as indicated, on behalf of arena
           arena_ind, returning false upon success. If the function returns
           true, this indicates that the chunks remain distinct mappings and
           therefore should continue to be operated on independently.

       "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.lg_dirty_mult" (ssize_t) rw
           Current default per-arena minimum ratio (log base 2) of active to
           dirty pages, used to initialize "arena.<i>.lg_dirty_mult" during
           arena creation. See "opt.lg_dirty_mult" for additional information.

       "arenas.decay_time" (ssize_t) rw
           Current default per-arena approximate time in seconds from the
           creation of a set of unused dirty pages until an equivalent set of
           unused dirty pages is purged and/or reused, used to initialize
           "arena.<i>.decay_time" during arena creation. See "opt.decay_time"
           for additional information.

       "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" (unsigned) r-
           Total number of large size classes.

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

       "arenas.nhchunks" (unsigned) r-
           Total number of huge size classes.

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

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

       "prof.thread_active_init" (bool) rw [--enable-prof]
           Control the initial setting for "thread.prof.active" in newly
           created threads. See the "opt.prof_thread_active_init" option for
           additional information.

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

       "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.gdump" (bool) rw [--enable-prof]
           When enabled, trigger a memory profile dump every time the total
           virtual memory exceeds the previous maximum. Profiles are dumped to
           files named according to the pattern
           <prefix>.<pid>.<seq>.u<useq>.heap, where <prefix> is controlled by
           the "opt.prof_prefix" option.

       "prof.reset" (size_t) -w [--enable-prof]
           Reset all memory profile statistics, and optionally update the
           sample rate (see "opt.lg_prof_sample" and "prof.lg_sample").

       "prof.lg_sample" (size_t) r- [--enable-prof]
           Get the current sample rate (see "opt.lg_prof_sample").

       "prof.interval" (uint64_t) r- [--enable-prof]
           Average number of bytes allocated between interval-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 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",
           nor pages entirely devoted to allocator metadata.

       "stats.metadata" (size_t) r- [--enable-stats]
           Total number of bytes dedicated to metadata, which comprise base
           allocations used for bootstrap-sensitive internal allocator data
           structures, arena chunk headers (see
           "stats.arenas.<i>.metadata.mapped"), and internal allocations (see
           "stats.arenas.<i>.metadata.allocated").

       "stats.resident" (size_t) r- [--enable-stats]
           Maximum number of bytes in physically resident data pages mapped by
           the allocator, comprising all pages dedicated to allocator
           metadata, pages backing active allocations, and unused dirty pages.
           This is a maximum rather than precise because pages may not
           actually be physically resident if they correspond to demand-zeroed
           virtual memory that has not yet been touched. This is a multiple of
           the page size, and is larger than "stats.active".

       "stats.mapped" (size_t) r- [--enable-stats]
           Total number of bytes in active chunks mapped by the allocator.
           This is a multiple of the chunk size, and is larger than
           "stats.active". This does not include inactive chunks, even those
           that contain unused dirty pages, which means that there is no
           strict ordering between this and "stats.resident".

       "stats.retained" (size_t) r- [--enable-stats]
           Total number of bytes in virtual memory mappings that were retained
           rather than being returned to the operating system via e.g.
           munmap(2). Retained virtual memory is typically untouched,
           decommitted, or purged, so it has no strongly associated physical
           memory (see chunk hooks for details). Retained memory is excluded
           from mapped memory statistics, e.g.  "stats.mapped".

       "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>.lg_dirty_mult" (ssize_t) r-
           Minimum ratio (log base 2) of active to dirty pages. See
           "opt.lg_dirty_mult" for details.

       "stats.arenas.<i>.decay_time" (ssize_t) r-
           Approximate time in seconds from the creation of a set of unused
           dirty pages until an equivalent set of unused dirty pages is purged
           and/or reused. See "opt.decay_time" 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>.retained" (size_t) r- [--enable-stats]
           Number of retained bytes. See "stats.retained" for details.

       "stats.arenas.<i>.metadata.mapped" (size_t) r- [--enable-stats]
           Number of mapped bytes in arena chunk headers, which track the
           states of the non-metadata pages.

       "stats.arenas.<i>.metadata.allocated" (size_t) r- [--enable-stats]
           Number of bytes dedicated to internal allocations. Internal
           allocations differ from application-originated allocations in that
           they are for internal use, and that they are omitted from heap
           profiles. This statistic is reported separately from
           "stats.metadata" and "stats.arenas.<i>.metadata.mapped" because it
           overlaps with e.g. the "stats.allocated" and "stats.active"
           statistics, whereas the other metadata statistics do not.

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

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

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

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

       "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>.curregs" (size_t) r- [--enable-stats]
           Current number of regions for this size class.

       "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.

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

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

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

       "stats.arenas.<i>.hchunks.<j>.curhchunks" (size_t) r- [--enable-stats]
           Current number of huge allocations for this size class.

HEAP PROFILE FORMAT
       Although the heap profiling functionality was originally designed to be
       compatible with the pprof command that is developed as part of the
       gperftools package[3], the addition of per thread heap profiling
       functionality required a different heap profile format. The jeprof
       command is derived from pprof, with enhancements to support the heap
       profile format described here.

       In the following hypothetical heap profile, [...] indicates elision for
       the sake of compactness.

           heap_v2/524288
             t*: 28106: 56637512 [0: 0]
             [...]
             t3: 352: 16777344 [0: 0]
             [...]
             t99: 17754: 29341640 [0: 0]
             [...]
           @ 0x5f86da8 0x5f5a1dc [...] 0x29e4d4e 0xa200316 0xabb2988 [...]
             t*: 13: 6688 [0: 0]
             t3: 12: 6496 [0: ]
             t99: 1: 192 [0: 0]
           [...]

           MAPPED_LIBRARIES:
           [...]

       The following matches the above heap profile, but most tokens are
       replaced with <description> to indicate descriptions of the
       corresponding fields.

           <heap_profile_format_version>/<mean_sample_interval>
             <aggregate>: <curobjs>: <curbytes> [<cumobjs>: <cumbytes>]
             [...]
             <thread_3_aggregate>: <curobjs>: <curbytes>[<cumobjs>: <cumbytes>]
             [...]
             <thread_99_aggregate>: <curobjs>: <curbytes>[<cumobjs>: <cumbytes>]
             [...]
           @ <top_frame> <frame> [...] <frame> <frame> <frame> [...]
             <backtrace_aggregate>: <curobjs>: <curbytes> [<cumobjs>: <cumbytes>]
             <backtrace_thread_3>: <curobjs>: <curbytes> [<cumobjs>: <cumbytes>]
             <backtrace_thread_99>: <curobjs>: <curbytes> [<cumobjs>: <cumbytes>]
           [...]

           MAPPED_LIBRARIES:
           </proc/<pid>/maps>

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.

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, and mallctl* 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 4.2.1-0-g3de035335255    06/08/2016                       JEMALLOC(3)
Command Section