Following are change highlights associated with official releases.  Important

bug fixes are all mentioned, but some internal enhancements are omitted here for

brevity.  Much more detail can be found in the git revision history:

    https://github.com/jemalloc/jemalloc

* 5.2.1 (August 5, 2019)

  This release is primarily about Windows.  A critical virtual memory leak is

  resolved on all Windows platforms.  The regression was present in all releases

  since 5.0.0.

  Bug fixes:

  - Fix a severe virtual memory leak on Windows.  This regression was first

    released in 5.0.0.  (@Ignition, @j0t, @frederik-h, @davidtgoldblatt,

    @interwq)

  - Fix size 0 handling in posix_memalign().  This regression was first released

    in 5.2.0.  (@interwq)

  - Fix the prof_log unit test which may observe unexpected backtraces from

    compiler optimizations.  The test was first added in 5.2.0.  (@marxin,

    @gnzlbg, @interwq)

  - Fix the declaration of the extent_avail tree.  This regression was first

    released in 5.1.0.  (@zoulasc)

  - Fix an incorrect reference in jeprof.  This functionality was first released

    in 3.0.0.  (@prehistoric-penguin)

  - Fix an assertion on the deallocation fast-path.  This regression was first

    released in 5.2.0.  (@yinan1048576)

  - Fix the TLS_MODEL attribute in headers.  This regression was first released

    in 5.0.0.  (@zoulasc, @interwq)

  Optimizations and refactors:

  - Implement opt.retain on Windows and enable by default on 64-bit.  (@interwq,

    @davidtgoldblatt)

  - Optimize away a branch on the operator delete[] path.  (@mgrice)

  - Add format annotation to the format generator function.  (@zoulasc)

  - Refactor and improve the size class header generation.  (@yinan1048576)

  - Remove best fit.  (@djwatson)

  - Avoid blocking on background thread locks for stats.  (@oranagra, @interwq)

* 5.2.0 (April 2, 2019)

  This release includes a few notable improvements, which are summarized below:

  1) improved fast-path performance from the optimizations by @djwatson; 2)

  reduced virtual memory fragmentation and metadata usage; and 3) bug fixes on

  setting the number of background threads.  In addition, peak / spike memory

  usage is improved with certain allocation patterns.  As usual, the release and

  prior dev versions have gone through large-scale production testing.

  New features:

  - Implement oversize_threshold, which uses a dedicated arena for allocations

    crossing the specified threshold to reduce fragmentation.  (@interwq)

  - Add extents usage information to stats.  (@tyleretzel)

  - Log time information for sampled allocations.  (@tyleretzel)

  - Support 0 size in sdallocx.  (@djwatson)

  - Output rate for certain counters in malloc_stats.  (@zinoale)

  - Add configure option --enable-readlinkat, which allows the use of readlinkat

    over readlink.  (@davidtgoldblatt)

  - Add configure options --{enable,disable}-{static,shared} to allow not

    building unwanted libraries.  (@Ericson2314)

  - Add configure option --disable-libdl to enable fully static builds.

    (@interwq)

  - Add mallctl interfaces:

	+ opt.oversize_threshold (@interwq)

	+ stats.arenas..extent_avail (@tyleretzel)

	+ stats.arenas..extents.<j>.n{dirty,muzzy,retained} (@tyleretzel)

	+ stats.arenas..extents.<j>.{dirty,muzzy,retained}_bytes

	  (@tyleretzel)

  Portability improvements:

  - Update MSVC builds.  (@maksqwe, @rustyx)

  - Workaround a compiler optimizer bug on s390x.  (@rkmisra)

  - Make use of pthread_set_name_np(3) on FreeBSD.  (@trasz)

  - Implement malloc_getcpu() to enable percpu_arena for windows.  (@santagada)

  - Link against -pthread instead of -lpthread.  (@paravoid)

  - Make background_thread not dependent on libdl.  (@interwq)

  - Add stringify to fix a linker directive issue on MSVC.  (@daverigby)

  - Detect and fall back when 8-bit atomics are unavailable.  (@interwq)

  - Fall back to the default pthread_create if dlsym(3) fails.  (@interwq)

  Optimizations and refactors:

  - Refactor the TSD module.  (@davidtgoldblatt)

  - Avoid taking extents_muzzy mutex when muzzy is disabled.  (@interwq)

  - Avoid taking large_mtx for auto arenas on the tcache flush path.  (@interwq)

  - Optimize ixalloc by avoiding a size lookup.  (@interwq)

  - Implement opt.oversize_threshold which uses a dedicated arena for requests

    crossing the threshold, also eagerly purges the oversize extents.  Default

    the threshold to 8 MiB.  (@interwq)

  - Clean compilation with -Wextra.  (@gnzlbg, @jasone)

  - Refactor the size class module.  (@davidtgoldblatt)

  - Refactor the stats emitter.  (@tyleretzel)

  - Optimize pow2_ceil.  (@rkmisra)

  - Avoid runtime detection of lazy purging on FreeBSD.  (@trasz)

  - Optimize mmap(2) alignment handling on FreeBSD.  (@trasz)

  - Improve error handling for THP state initialization.  (@jsteemann)

  - Rework the malloc() fast path.  (@djwatson)

  - Rework the free() fast path.  (@djwatson)

  - Refactor and optimize the tcache fill / flush paths.  (@djwatson)

  - Optimize sync / lwsync on PowerPC.  (@chmeeedalf)

  - Bypass extent_dalloc() when retain is enabled.  (@interwq)

  - Optimize the locking on large deallocation.  (@interwq)

  - Reduce the number of pages committed from sanity checking in debug build.

    (@trasz, @interwq)

  - Deprecate OSSpinLock.  (@interwq)

  - Lower the default number of background threads to 4 (when the feature

    is enabled).  (@interwq)

  - Optimize the trylock spin wait.  (@djwatson)

  - Use arena index for arena-matching checks.  (@interwq)

  - Avoid forced decay on thread termination when using background threads.

    (@interwq)

  - Disable muzzy decay by default.  (@djwatson, @interwq)

  - Only initialize libgcc unwinder when profiling is enabled.  (@paravoid,

    @interwq)

  Bug fixes (all only relevant to jemalloc 5.x):

  - Fix background thread index issues with max_background_threads.  (@djwatson,

    @interwq)

  - Fix stats output for opt.lg_extent_max_active_fit.  (@interwq)

  - Fix opt.prof_prefix initialization.  (@davidtgoldblatt)

  - Properly trigger decay on tcache destroy.  (@interwq, @amosbird)

  - Fix tcache.flush.  (@interwq)

  - Detect whether explicit extent zero out is necessary with huge pages or

    custom extent hooks, which may change the purge semantics.  (@interwq)

  - Fix a side effect caused by extent_max_active_fit combined with decay-based

    purging, where freed extents can accumulate and not be reused for an

    extended period of time.  (@interwq, @mpghf)

  - Fix a missing unlock on extent register error handling.  (@zoulasc)

  Testing:

  - Simplify the Travis script output.  (@gnzlbg)

  - Update the test scripts for FreeBSD.  (@devnexen)

  - Add unit tests for the producer-consumer pattern.  (@interwq)

  - Add Cirrus-CI config for FreeBSD builds.  (@jasone)

  - Add size-matching sanity checks on tcache flush.  (@davidtgoldblatt,

    @interwq)

  Incompatible changes:

  - Remove --with-lg-page-sizes.  (@davidtgoldblatt)

  Documentation:

  - Attempt to build docs by default, however skip doc building when xsltproc

    is missing. (@interwq, @cmuellner)

* 5.1.0 (May 4, 2018)

  This release is primarily about fine-tuning, ranging from several new features

  to numerous notable performance and portability enhancements.  The release and

  prior dev versions have been running in multiple large scale applications for

  months, and the cumulative improvements are substantial in many cases.

  Given the long and successful production runs, this release is likely a good

  candidate for applications to upgrade, from both jemalloc 5.0 and before.  For

  performance-critical applications, the newly added TUNING.md provides

  guidelines on jemalloc tuning.

  New features:

  - Implement transparent huge page support for internal metadata.  (@interwq)

  - Add opt.thp to allow enabling / disabling transparent huge pages for all

    mappings.  (@interwq)

  - Add maximum background thread count option.  (@djwatson)

  - Allow prof_active to control opt.lg_prof_interval and prof.gdump.

    (@interwq)

  - Allow arena index lookup based on allocation addresses via mallctl.

    (@lionkov)

  - Allow disabling initial-exec TLS model.  (@davidtgoldblatt, @KenMacD)

  - Add opt.lg_extent_max_active_fit to set the max ratio between the size of

    the active extent selected (to split off from) and the size of the requested

    allocation.  (@interwq, @davidtgoldblatt)

  - Add retain_grow_limit to set the max size when growing virtual address

    space.  (@interwq)

  - Add mallctl interfaces:

    + arena..retain_grow_limit  (@interwq)

    + arenas.lookup  (@lionkov)

    + max_background_threads  (@djwatson)

    + opt.lg_extent_max_active_fit  (@interwq)

    + opt.max_background_threads  (@djwatson)

    + opt.metadata_thp  (@interwq)

    + opt.thp  (@interwq)

    + stats.metadata_thp  (@interwq)

  Portability improvements:

  - Support GNU/kFreeBSD configuration.  (@paravoid)

  - Support m68k, nios2 and SH3 architectures.  (@paravoid)

  - Fall back to FD_CLOEXEC when O_CLOEXEC is unavailable.  (@zonyitoo)

  - Fix symbol listing for cross-compiling.  (@tamird)

  - Fix high bits computation on ARM.  (@davidtgoldblatt, @paravoid)

  - Disable the CPU_SPINWAIT macro for Power.  (@davidtgoldblatt, @marxin)

  - Fix MSVC 2015 & 2017 builds.  (@rustyx)

  - Improve RISC-V support.  (@EdSchouten)

  - Set name mangling script in strict mode.  (@nicolov)

  - Avoid MADV_HUGEPAGE on ARM.  (@marxin)

  - Modify configure to determine return value of strerror_r.

    (@davidtgoldblatt, @cferris1000)

  - Make sure CXXFLAGS is tested with CPP compiler.  (@nehaljwani)

  - Fix 32-bit build on MSVC.  (@rustyx)

  - Fix external symbol on MSVC.  (@maksqwe)

  - Avoid a printf format specifier warning.  (@jasone)

  - Add configure option --disable-initial-exec-tls which can allow jemalloc to

    be dynamically loaded after program startup.  (@davidtgoldblatt, @KenMacD)

  - AArch64: Add ILP32 support.  (@cmuellner)

  - Add --with-lg-vaddr configure option to support cross compiling.

    (@cmuellner, @davidtgoldblatt)

  Optimizations and refactors:

  - Improve active extent fit with extent_max_active_fit.  This considerably

    reduces fragmentation over time and improves virtual memory and metadata

    usage.  (@davidtgoldblatt, @interwq)

  - Eagerly coalesce large extents to reduce fragmentation.  (@interwq)

  - sdallocx: only read size info when page aligned (i.e. possibly sampled),

    which speeds up the sized deallocation path significantly.  (@interwq)

  - Avoid attempting new mappings for in place expansion with retain, since

    it rarely succeeds in practice and causes high overhead.  (@interwq)

  - Refactor OOM handling in newImpl.  (@wqfish)

  - Add internal fine-grained logging functionality for debugging use.

    (@davidtgoldblatt)

  - Refactor arena / tcache interactions.  (@davidtgoldblatt)

  - Refactor extent management with dumpable flag.  (@davidtgoldblatt)

  - Add runtime detection of lazy purging.  (@interwq)

  - Use pairing heap instead of red-black tree for extents_avail.  (@djwatson)

  - Use sysctl on startup in FreeBSD.  (@trasz)

  - Use thread local prng state instead of atomic.  (@djwatson)

  - Make decay to always purge one more extent than before, because in

    practice large extents are usually the ones that cross the decay threshold.

    Purging the additional extent helps save memory as well as reduce VM

    fragmentation.  (@interwq)

  - Fast division by dynamic values.  (@davidtgoldblatt)

  - Improve the fit for aligned allocation.  (@interwq, @edwinsmith)

  - Refactor extent_t bitpacking.  (@rkmisra)

  - Optimize the generated assembly for ticker operations.  (@davidtgoldblatt)

  - Convert stats printing to use a structured text emitter.  (@davidtgoldblatt)

  - Remove preserve_lru feature for extents management.  (@djwatson)

  - Consolidate two memory loads into one on the fast deallocation path.

    (@davidtgoldblatt, @interwq)

  Bug fixes (most of the issues are only relevant to jemalloc 5.0):

  - Fix deadlock with multithreaded fork in OS X.  (@davidtgoldblatt)

  - Validate returned file descriptor before use.  (@zonyitoo)

  - Fix a few background thread initialization and shutdown issues.  (@interwq)

  - Fix an extent coalesce + decay race by taking both coalescing extents off

    the LRU list.  (@interwq)

  - Fix potentially unbound increase during decay, caused by one thread keep

    stashing memory to purge while other threads generating new pages.  The

    number of pages to purge is checked to prevent this.  (@interwq)

  - Fix a FreeBSD bootstrap assertion.  (@strejda, @interwq)

  - Handle 32 bit mutex counters.  (@rkmisra)

  - Fix a indexing bug when creating background threads.  (@davidtgoldblatt,

    @binliu19)

  - Fix arguments passed to extent_init.  (@yuleniwo, @interwq)

  - Fix addresses used for ordering mutexes.  (@rkmisra)

  - Fix abort_conf processing during bootstrap.  (@interwq)

  - Fix include path order for out-of-tree builds.  (@cmuellner)

  Incompatible changes:

  - Remove --disable-thp.  (@interwq)

  - Remove mallctl interfaces:

    + config.thp  (@interwq)

  Documentation:

  - Add TUNING.md.  (@interwq, @davidtgoldblatt, @djwatson)

* 5.0.1 (July 1, 2017)

  This bugfix release fixes several issues, most of which are obscure enough

  that typical applications are not impacted.

  Bug fixes:

  - Update decay->nunpurged before purging, in order to avoid potential update

    races and subsequent incorrect purging volume.  (@interwq)

  - Only abort on dlsym(3) error if the failure impacts an enabled feature (lazy

    locking and/or background threads).  This mitigates an initialization

    failure bug for which we still do not have a clear reproduction test case.

    (@interwq)

  - Modify tsd management so that it neither crashes nor leaks if a thread's

    only allocation activity is to call free() after TLS destructors have been

    executed.  This behavior was observed when operating with GNU libc, and is

    unlikely to be an issue with other libc implementations.  (@interwq)

  - Mask signals during background thread creation.  This prevents signals from

    being inadvertently delivered to background threads.  (@jasone,

    @davidtgoldblatt, @interwq)

  - Avoid inactivity checks within background threads, in order to prevent

    recursive mutex acquisition.  (@interwq)

  - Fix extent_grow_retained() to use the specified hooks when the

    arena..extent_hooks mallctl is used to override the default hooks.

    (@interwq)

  - Add missing reentrancy support for custom extent hooks which allocate.

    (@interwq)

  - Post-fork(2), re-initialize the list of tcaches associated with each arena

    to contain no tcaches except the forking thread's.  (@interwq)

  - Add missing post-fork(2) mutex reinitialization for extent_grow_mtx.  This

    fixes potential deadlocks after fork(2).  (@interwq)

  - Enforce minimum autoconf version (currently 2.68), since 2.63 is known to

    generate corrupt configure scripts.  (@jasone)

  - Ensure that the configured page size (--with-lg-page) is no larger than the

    configured huge page size (--with-lg-hugepage).  (@jasone)

* 5.0.0 (June 13, 2017)

  Unlike all previous jemalloc releases, this release does not use naturally

  aligned "chunks" for virtual memory management, and instead uses page-aligned

  "extents".  This change has few externally visible effects, but the internal

  impacts are... extensive.  Many other internal changes combine to make this

  the most cohesively designed version of jemalloc so far, with ample

  opportunity for further enhancements.

  Continuous integration is now an integral aspect of development thanks to the

  efforts of @davidtgoldblatt, and the dev branch tends to remain reasonably

  stable on the tested platforms (Linux, FreeBSD, macOS, and Windows).  As a

  side effect the official release frequency may decrease over time.

  New features:

  - Implement optional per-CPU arena support; threads choose which arena to use

    based on current CPU rather than on fixed thread-->arena associations.

    (@interwq)

  - Implement two-phase decay of unused dirty pages.  Pages transition from

    dirty-->muzzy-->clean, where the first phase transition relies on

    madvise(... MADV_FREE) semantics, and the second phase transition discards

    pages such that they are replaced with demand-zeroed pages on next access.

    (@jasone)

  - Increase decay time resolution from seconds to milliseconds.  (@jasone)

  - Implement opt-in per CPU background threads, and use them for asynchronous

    decay-driven unused dirty page purging.  (@interwq)

  - Add mutex profiling, which collects a variety of statistics useful for

    diagnosing overhead/contention issues.  (@interwq)

  - Add C++ new/delete operator bindings.  (@djwatson)

  - Support manually created arena destruction, such that all data and metadata

    are discarded.  Add MALLCTL_ARENAS_DESTROYED for accessing merged stats

    associated with destroyed arenas.  (@jasone)

  - Add MALLCTL_ARENAS_ALL as a fixed index for use in accessing

    merged/destroyed arena statistics via mallctl.  (@jasone)

  - Add opt.abort_conf to optionally abort if invalid configuration options are

    detected during initialization.  (@interwq)

  - Add opt.stats_print_opts, so that e.g. JSON output can be selected for the

    stats dumped during exit if opt.stats_print is true.  (@jasone)

  - Add --with-version=VERSION for use when embedding jemalloc into another

    project's git repository.  (@jasone)

  - Add --disable-thp to support cross compiling.  (@jasone)

  - Add --with-lg-hugepage to support cross compiling.  (@jasone)

  - Add mallctl interfaces (various authors):

    + background_thread

    + opt.abort_conf

    + opt.retain

    + opt.percpu_arena

    + opt.background_thread

    + opt.{dirty,muzzy}_decay_ms

    + opt.stats_print_opts

    + arena..initialized

    + arena..destroy

    + arena..{dirty,muzzy}_decay_ms

    + arena..extent_hooks

    + arenas.{dirty,muzzy}_decay_ms

    + arenas.bin..slab_size

    + arenas.nlextents

    + arenas.lextent..size

    + arenas.create

    + stats.background_thread.{num_threads,num_runs,run_interval}

    + stats.mutexes.{ctl,background_thread,prof,reset}.

      {num_ops,num_spin_acq,num_wait,max_wait_time,total_wait_time,max_num_thds,

      num_owner_switch}

    + stats.arenas..{dirty,muzzy}_decay_ms

    + stats.arenas..uptime

    + stats.arenas..{pmuzzy,base,internal,resident}

    + stats.arenas..{dirty,muzzy}_{npurge,nmadvise,purged}

    + stats.arenas..bins.<j>.{nslabs,reslabs,curslabs}

    + stats.arenas..bins.<j>.mutex.

      {num_ops,num_spin_acq,num_wait,max_wait_time,total_wait_time,max_num_thds,

      num_owner_switch}

    + stats.arenas..lextents.<j>.{nmalloc,ndalloc,nrequests,curlextents}

    + stats.arenas.i.mutexes.{large,extent_avail,extents_dirty,extents_muzzy,

      extents_retained,decay_dirty,decay_muzzy,base,tcache_list}.

      {num_ops,num_spin_acq,num_wait,max_wait_time,total_wait_time,max_num_thds,

      num_owner_switch}

  Portability improvements:

  - Improve reentrant allocation support, such that deadlock is less likely if

    e.g. a system library call in turn allocates memory.  (@davidtgoldblatt,

    @interwq)

  - Support static linking of jemalloc with glibc.  (@djwatson)

  Optimizations and refactors:

  - Organize virtual memory as "extents" of virtual memory pages, rather than as

    naturally aligned "chunks", and store all metadata in arbitrarily distant

    locations.  This reduces virtual memory external fragmentation, and will

    interact better with huge pages (not yet explicitly supported).  (@jasone)

  - Fold large and huge size classes together; only small and large size classes

    remain.  (@jasone)

  - Unify the allocation paths, and merge most fast-path branching decisions.

    (@davidtgoldblatt, @interwq)

  - Embed per thread automatic tcache into thread-specific data, which reduces

    conditional branches and dereferences.  Also reorganize tcache to increase

    fast-path data locality.  (@interwq)

  - Rewrite atomics to closely model the C11 API, convert various

    synchronization from mutex-based to atomic, and use the explicit memory

    ordering control to resolve various hypothetical races without increasing

    synchronization overhead.  (@davidtgoldblatt)

  - Extensively optimize rtree via various methods:

    + Add multiple layers of rtree lookup caching, since rtree lookups are now

      part of fast-path deallocation.  (@interwq)

    + Determine rtree layout at compile time.  (@jasone)

    + Make the tree shallower for common configurations.  (@jasone)

    + Embed the root node in the top-level rtree data structure, thus avoiding

      one level of indirection.  (@jasone)

    + Further specialize leaf elements as compared to internal node elements,

      and directly embed extent metadata needed for fast-path deallocation.

      (@jasone)

    + Ignore leading always-zero address bits (architecture-specific).

      (@jasone)

  - Reorganize headers (ongoing work) to make them hermetic, and disentangle

    various module dependencies.  (@davidtgoldblatt)

  - Convert various internal data structures such as size class metadata from

    boot-time-initialized to compile-time-initialized.  Propagate resulting data

    structure simplifications, such as making arena metadata fixed-size.

    (@jasone)

  - Simplify size class lookups when constrained to size classes that are

    multiples of the page size.  This speeds lookups, but the primary benefit is

    complexity reduction in code that was the source of numerous regressions.

    (@jasone)

  - Lock individual extents when possible for localized extent operations,

    rather than relying on a top-level arena lock.  (@davidtgoldblatt, @jasone)

  - Use first fit layout policy instead of best fit, in order to improve

    packing.  (@jasone)

  - If munmap(2) is not in use, use an exponential series to grow each arena's

    virtual memory, so that the number of disjoint virtual memory mappings

    remains low.  (@jasone)

  - Implement per arena base allocators, so that arenas never share any virtual

    memory pages.  (@jasone)

  - Automatically generate private symbol name mangling macros.  (@jasone)

  Incompatible changes:

  - Replace chunk hooks with an expanded/normalized set of extent hooks.

    (@jasone)

  - Remove ratio-based purging.  (@jasone)

  - Remove --disable-tcache.  (@jasone)

  - Remove --disable-tls.  (@jasone)

  - Remove --enable-ivsalloc.  (@jasone)

  - Remove --with-lg-size-class-group.  (@jasone)

  - Remove --with-lg-tiny-min.  (@jasone)

  - Remove --disable-cc-silence.  (@jasone)

  - Remove --enable-code-coverage.  (@jasone)

  - Remove --disable-munmap (replaced by opt.retain).  (@jasone)

  - Remove Valgrind support.  (@jasone)

  - Remove quarantine support.  (@jasone)

  - Remove redzone support.  (@jasone)

  - Remove mallctl interfaces (various authors):

    + config.munmap

    + config.tcache

    + config.tls

    + config.valgrind

    + opt.lg_chunk

    + opt.purge

    + opt.lg_dirty_mult

    + opt.decay_time

    + opt.quarantine

    + opt.redzone

    + opt.thp

    + arena..lg_dirty_mult

    + arena..decay_time

    + arena..chunk_hooks

    + arenas.initialized

    + arenas.lg_dirty_mult

    + arenas.decay_time

    + arenas.bin..run_size

    + arenas.nlruns

    + arenas.lrun..size

    + arenas.nhchunks

    + arenas.hchunk..size

    + arenas.extend

    + stats.cactive

    + stats.arenas..lg_dirty_mult

    + stats.arenas..decay_time

    + stats.arenas..metadata.{mapped,allocated}

    + stats.arenas..{npurge,nmadvise,purged}

    + stats.arenas..huge.{allocated,nmalloc,ndalloc,nrequests}

    + stats.arenas..bins.<j>.{nruns,reruns,curruns}

    + stats.arenas..lruns.<j>.{nmalloc,ndalloc,nrequests,curruns}

    + stats.arenas..hchunks.<j>.{nmalloc,ndalloc,nrequests,curhchunks}

  Bug fixes:

  - Improve interval-based profile dump triggering to dump only one profile when

    a single allocation's size exceeds the interval.  (@jasone)

  - Use prefixed function names (as controlled by --with-jemalloc-prefix) when

    pruning backtrace frames in jeprof.  (@jasone)

* 4.5.0 (February 28, 2017)

  This is the first release to benefit from much broader continuous integration

  testing, thanks to @davidtgoldblatt.  Had we had this testing infrastructure

  in place for prior releases, it would have caught all of the most serious

  regressions fixed by this release.

  New features:

  - Add --disable-thp and the opt.thp mallctl to provide opt-out mechanisms for

    transparent huge page integration.  (@jasone)

  - Update zone allocator integration to work with macOS 10.12.  (@glandium)

  - Restructure *CFLAGS configuration, so that CFLAGS behaves typically, and

    EXTRA_CFLAGS provides a way to specify e.g. -Werror during building, but not

    during configuration.  (@jasone, @ronawho)

  Bug fixes:

  - Fix DSS (sbrk(2)-based) allocation.  This regression was first released in

    4.3.0.  (@jasone)

  - Handle race in per size class utilization computation.  This functionality

    was first released in 4.0.0.  (@interwq)

  - Fix lock order reversal during gdump.  (@jasone)

  - Fix/refactor tcache synchronization.  This regression was first released in

    4.0.0.  (@jasone)

  - Fix various JSON-formatted malloc_stats_print() bugs.  This functionality

    was first released in 4.3.0.  (@jasone)

  - Fix huge-aligned allocation.  This regression was first released in 4.4.0.

    (@jasone)

  - When transparent huge page integration is enabled, detect what state pages

    start in according to the kernel's current operating mode, and only convert

    arena chunks to non-huge during purging if that is not their initial state.

    This functionality was first released in 4.4.0.  (@jasone)

  - Fix lg_chunk clamping for the --enable-cache-oblivious --disable-fill case.

    This regression was first released in 4.0.0.  (@jasone, @428desmo)

  - Properly detect sparc64 when building for Linux.  (@glaubitz)

* 4.4.0 (December 3, 2016)

  New features:

  - Add configure support for *-*-linux-android.  (@cferris1000, @jasone)

  - Add the --disable-syscall configure option, for use on systems that place

    security-motivated limitations on syscall(2).  (@jasone)

  - Add support for Debian GNU/kFreeBSD.  (@thesam)

  Optimizations:

  - Add extent serial numbers and use them where appropriate as a sort key that

    is higher priority than address, so that the allocation policy prefers older

    extents.  This tends to improve locality (decrease fragmentation) when

    memory grows downward.  (@jasone)

  - Refactor madvise(2) configuration so that MADV_FREE is detected and utilized

    on Linux 4.5 and newer.  (@jasone)

  - Mark partially purged arena chunks as non-huge-page.  This improves

    interaction with Linux's transparent huge page functionality.  (@jasone)

  Bug fixes:

  - Fix size class computations for edge conditions involving extremely large

    allocations.  This regression was first released in 4.0.0.  (@jasone,

    @ingvarha)

  - Remove overly restrictive assertions related to the cactive statistic.  This

    regression was first released in 4.1.0.  (@jasone)

  - Implement a more reliable detection scheme for os_unfair_lock on macOS.

    (@jszakmeister)

* 4.3.1 (November 7, 2016)

  Bug fixes:

  - Fix a severe virtual memory leak.  This regression was first released in

    4.3.0.  (@interwq, @jasone)

  - Refactor atomic and prng APIs to restore support for 32-bit platforms that

    use pre-C11 toolchains, e.g. FreeBSD's mips.  (@jasone)

* 4.3.0 (November 4, 2016)

  This is the first release that passes the test suite for multiple Windows

  configurations, thanks in large part to @glandium setting up continuous

  integration via AppVeyor (and Travis CI for Linux and OS X).

  New features:

  - Add "J" (JSON) support to malloc_stats_print().  (@jasone)

  - Add Cray compiler support.  (@ronawho)

  Optimizations:

  - Add/use adaptive spinning for bootstrapping and radix tree node

    initialization.  (@jasone)

  Bug fixes:

  - Fix large allocation to search starting in the optimal size class heap,

    which can substantially reduce virtual memory churn and fragmentation.  This

    regression was first released in 4.0.0.  (@mjp41, @jasone)

  - Fix stats.arenas..nthreads accounting.  (@interwq)

  - Fix and simplify decay-based purging.  (@jasone)

  - Make DSS (sbrk(2)-related) operations lockless, which resolves potential

    deadlocks during thread exit.  (@jasone)

  - Fix over-sized allocation of radix tree leaf nodes.  (@mjp41, @ogaun,

    @jasone)

  - Fix over-sized allocation of arena_t (plus associated stats) data

    structures.  (@jasone, @interwq)

  - Fix EXTRA_CFLAGS to not affect configuration.  (@jasone)

  - Fix a Valgrind integration bug.  (@ronawho)

  - Disallow 0x5a junk filling when running in Valgrind.  (@jasone)

  - Fix a file descriptor leak on Linux.  This regression was first released in

    4.2.0.  (@vsarunas, @jasone)

  - Fix static linking of jemalloc with glibc.  (@djwatson)

  - Use syscall(2) rather than {open,read,close}(2) during boot on Linux.  This

    works around other libraries' system call wrappers performing reentrant

    allocation.  (@kspinka, @Whissi, @jasone)

  - Fix OS X default zone replacement to work with OS X 10.12.  (@glandium,

    @jasone)

  - Fix cached memory management to avoid needless commit/decommit operations

    during purging, which resolves permanent virtual memory map fragmentation

    issues on Windows.  (@mjp41, @jasone)

  - Fix TSD fetches to avoid (recursive) allocation.  This is relevant to

    non-TLS and Windows configurations.  (@jasone)

  - Fix malloc_conf overriding to work on Windows.  (@jasone)

  - Forcibly disable lazy-lock on Windows (was forcibly *enabled*).  (@jasone)

* 4.2.1 (June 8, 2016)

  Bug fixes:

  - Fix bootstrapping issues for configurations that require allocation during

    tsd initialization (e.g. --disable-tls).  (@cferris1000, @jasone)

  - Fix gettimeofday() version of nstime_update().  (@ronawho)

  - Fix Valgrind regressions in calloc() and chunk_alloc_wrapper().  (@ronawho)

  - Fix potential VM map fragmentation regression.  (@jasone)

  - Fix opt_zero-triggered in-place huge reallocation zeroing.  (@jasone)

  - Fix heap profiling context leaks in reallocation edge cases.  (@jasone)

* 4.2.0 (May 12, 2016)

  New features:

  - Add the arena..reset mallctl, which makes it possible to discard all of

    an arena's allocations in a single operation.  (@jasone)

  - Add the stats.retained and stats.arenas..retained statistics.  (@jasone)

  - Add the --with-version configure option.  (@jasone)

  - Support --with-lg-page values larger than actual page size.  (@jasone)

  Optimizations:

  - Use pairing heaps rather than red-black trees for various hot data

    structures.  (@djwatson, @jasone)

  - Streamline fast paths of rtree operations.  (@jasone)

  - Optimize the fast paths of calloc() and [m,d,sd]allocx().  (@jasone)

  - Decommit unused virtual memory if the OS does not overcommit.  (@jasone)

  - Specify MAP_NORESERVE on Linux if [heuristic] overcommit is active, in order

    to avoid unfortunate interactions during fork(2).  (@jasone)

  Bug fixes:

  - Fix chunk accounting related to triggering gdump profiles.  (@jasone)

  - Link against librt for clock_gettime(2) if glibc < 2.17.  (@jasone)

  - Scale leak report summary according to sampling probability.  (@jasone)

* 4.1.1 (May 3, 2016)

  This bugfix release resolves a variety of mostly minor issues, though the

  bitmap fix is critical for 64-bit Windows.

  Bug fixes:

  - Fix the linear scan version of bitmap_sfu() to shift by the proper amount

    even when sizeof(long) is not the same as sizeof(void *), as on 64-bit

    Windows.  (@jasone)

  - Fix hashing functions to avoid unaligned memory accesses (and resulting

    crashes).  This is relevant at least to some ARM-based platforms.

    (@rkmisra)

  - Fix fork()-related lock rank ordering reversals.  These reversals were

    unlikely to cause deadlocks in practice except when heap profiling was

    enabled and active.  (@jasone)

  - Fix various chunk leaks in OOM code paths.  (@jasone)

  - Fix malloc_stats_print() to print opt.narenas correctly.  (@jasone)

  - Fix MSVC-specific build/test issues.  (@rustyx, @yuslepukhin)

  - Fix a variety of test failures that were due to test fragility rather than

    core bugs.  (@jasone)

* 4.1.0 (February 28, 2016)

  This release is primarily about optimizations, but it also incorporates a lot

  of portability-motivated refactoring and enhancements.  Many people worked on

  this release, to an extent that even with the omission here of minor changes

  (see git revision history), and of the people who reported and diagnosed

  issues, so much of the work was contributed that starting with this release,

  changes are annotated with author credits to help reflect the collaborative

  effort involved.

  New features:

  - Implement decay-based unused dirty page purging, a major optimization with

    mallctl API impact.  This is an alternative to the existing ratio-based

    unused dirty page purging, and is intended to eventually become the sole

    purging mechanism.  New mallctls:

    + opt.purge

    + opt.decay_time

    + arena..decay

    + arena..decay_time

    + arenas.decay_time

    + stats.arenas..decay_time

    (@jasone, @cevans87)

  - Add --with-malloc-conf, which makes it possible to embed a default

    options string during configuration.  This was motivated by the desire to

    specify --with-malloc-conf=purge:decay , since the default must remain

    purge:ratio until the 5.0.0 release.  (@jasone)

  - Add MS Visual Studio 2015 support.  (@rustyx, @yuslepukhin)

  - Make *allocx() size class overflow behavior defined.  The maximum

    size class is now less than PTRDIFF_MAX to protect applications against

    numerical overflow, and all allocation functions are guaranteed to indicate

    errors rather than potentially crashing if the request size exceeds the

    maximum size class.  (@jasone)

  - jeprof:

    + Add raw heap profile support.  (@jasone)

    + Add --retain and --exclude for backtrace symbol filtering.  (@jasone)

  Optimizations:

  - Optimize the fast path to combine various bootstrapping and configuration

    checks and execute more streamlined code in the common case.  (@interwq)

  - Use linear scan for small bitmaps (used for small object tracking).  In

    addition to speeding up bitmap operations on 64-bit systems, this reduces

    allocator metadata overhead by approximately 0.2%.  (@djwatson)

  - Separate arena_avail trees, which substantially speeds up run tree

    operations.  (@djwatson)

  - Use memoization (boot-time-computed table) for run quantization.  Separate

    arena_avail trees reduced the importance of this optimization.  (@jasone)

  - Attempt mmap-based in-place huge reallocation.  This can dramatically speed

    up incremental huge reallocation.  (@jasone)

  Incompatible changes:

  - Make opt.narenas unsigned rather than size_t.  (@jasone)

  Bug fixes:

  - Fix stats.cactive accounting regression.  (@rustyx, @jasone)

  - Handle unaligned keys in hash().  This caused problems for some ARM systems.

    (@jasone, @cferris1000)

  - Refactor arenas array.  In addition to fixing a fork-related deadlock, this

    makes arena lookups faster and simpler.  (@jasone)

  - Move retained memory allocation out of the default chunk allocation

    function, to a location that gets executed even if the application installs

    a custom chunk allocation function.  This resolves a virtual memory leak.

    (@buchgr)

  - Fix a potential tsd cleanup leak.  (@cferris1000, @jasone)

  - Fix run quantization.  In practice this bug had no impact unless

    applications requested memory with alignment exceeding one page.

    (@jasone, @djwatson)

  - Fix LinuxThreads-specific bootstrapping deadlock.  (Cosmin Paraschiv)

  - jeprof:

    + Don't discard curl options if timeout is not defined.  (@djwatson)

    + Detect failed profile fetches.  (@djwatson)

  - Fix stats.arenas..{dss,lg_dirty_mult,decay_time,pactive,pdirty} for

    --disable-stats case.  (@jasone)

* 4.0.4 (October 24, 2015)

  This bugfix release fixes another xallocx() regression.  No other regressions

  have come to light in over a month, so this is likely a good starting point

  for people who prefer to wait for "dot one" releases with all the major issues

  shaken out.

  Bug fixes:

  - Fix xallocx(..., MALLOCX_ZERO to zero the last full trailing page of large

    allocations that have been randomly assigned an offset of 0 when

    --enable-cache-oblivious configure option is enabled.

* 4.0.3 (September 24, 2015)

  This bugfix release continues the trend of xallocx() and heap profiling fixes.

  Bug fixes:

  - Fix xallocx(..., MALLOCX_ZERO) to zero all trailing bytes of large

    allocations when --enable-cache-oblivious configure option is enabled.

  - Fix xallocx(..., MALLOCX_ZERO) to zero trailing bytes of huge allocations

    when resizing from/to a size class that is not a multiple of the chunk size.

  - Fix prof_tctx_dump_iter() to filter out nodes that were created after heap

    profile dumping started.

  - Work around a potentially bad thread-specific data initialization

    interaction with NPTL (glibc's pthreads implementation).

* 4.0.2 (September 21, 2015)

  This bugfix release addresses a few bugs specific to heap profiling.

  Bug fixes:

  - Fix ixallocx_prof_sample() to never modify nor create sampled small

    allocations.  xallocx() is in general incapable of moving small allocations,

    so this fix removes buggy code without loss of generality.

  - Fix irallocx_prof_sample() to always allocate large regions, even when

    alignment is non-zero.

  - Fix prof_alloc_rollback() to read tdata from thread-specific data rather

    than dereferencing a potentially invalid tctx.

* 4.0.1 (September 15, 2015)

  This is a bugfix release that is somewhat high risk due to the amount of

  refactoring required to address deep xallocx() problems.  As a side effect of

  these fixes, xallocx() now tries harder to partially fulfill requests for

  optional extra space.  Note that a couple of minor heap profiling

  optimizations are included, but these are better thought of as performance

  fixes that were integral to discovering most of the other bugs.

  Optimizations:

  - Avoid a chunk metadata read in arena_prof_tctx_set(), since it is in the

    fast path when heap profiling is enabled.  Additionally, split a special

    case out into arena_prof_tctx_reset(), which also avoids chunk metadata

    reads.

  - Optimize irallocx_prof() to optimistically update the sampler state.  The

    prior implementation appears to have been a holdover from when

    rallocx()/xallocx() functionality was combined as rallocm().

  Bug fixes:

  - Fix TLS configuration such that it is enabled by default for platforms on

    which it works correctly.

  - Fix arenas_cache_cleanup() and arena_get_hard() to handle

    allocation/deallocation within the application's thread-specific data

    cleanup functions even after arenas_cache is torn down.

  - Fix xallocx() bugs related to size+extra exceeding HUGE_MAXCLASS.

  - Fix chunk purge hook calls for in-place huge shrinking reallocation to

    specify the old chunk size rather than the new chunk size.  This bug caused

    no correctness issues for the default chunk purge function, but was

    visible to custom functions set via the "arena..chunk_hooks" mallctl.

  - Fix heap profiling bugs:

    + Fix heap profiling to distinguish among otherwise identical sample sites

      with interposed resets (triggered via the "prof.reset" mallctl).  This bug

      could cause data structure corruption that would most likely result in a

      segfault.

    + Fix irealloc_prof() to prof_alloc_rollback() on OOM.

    + Make one call to prof_active_get_unlocked() per allocation event, and use

      the result throughout the relevant functions that handle an allocation

      event.  Also add a missing check in prof_realloc().  These fixes protect

      allocation events against concurrent prof_active changes.

    + Fix ixallocx_prof() to pass usize_max and zero to ixallocx_prof_sample()

      in the correct order.

    + Fix prof_realloc() to call prof_free_sampled_object() after calling

      prof_malloc_sample_object().  Prior to this fix, if tctx and old_tctx were

      the same, the tctx could have been prematurely destroyed.

  - Fix portability bugs:

    + Don't bitshift by negative amounts when encoding/decoding run sizes in

      chunk header maps.  This affected systems with page sizes greater than 8

      KiB.

    + Rename index_t to szind_t to avoid an existing type on Solaris.

    + Add JEMALLOC_CXX_THROW to the memalign() function prototype, in order to

      match glibc and avoid compilation errors when including both

      jemalloc/jemalloc.h and malloc.h in C++ code.

    + Don't assume that /bin/sh is appropriate when running size_classes.sh

      during configuration.

    + Consider __sparcv9 a synonym for __sparc64__ when defining LG_QUANTUM.

    + Link tests to librt if it contains clock_gettime(2).

* 4.0.0 (August 17, 2015)

  This version contains many speed and space optimizations, both minor and

  major.  The major themes are generalization, unification, and simplification.

  Although many of these optimizations cause no visible behavior change, their

  cumulative effect is substantial.

  New features:

  - Normalize size class spacing to be consistent across the complete size

    range.  By default there are four size classes per size doubling, but this

    is now configurable via the --with-lg-size-class-group option.  Also add the

    --with-lg-page, --with-lg-page-sizes, --with-lg-quantum, and

    --with-lg-tiny-min options, which can be used to tweak page and size class

    settings.  Impacts:

    + Worst case performance for incrementally growing/shrinking reallocation

      is improved because there are far fewer size classes, and therefore

      copying happens less often.

    + Internal fragmentation is limited to 20% for all but the smallest size

      classes (those less than four times the quantum).  (1B + 4 KiB)

      and (1B + 4 MiB) previously suffered nearly 50% internal fragmentation.

    + Chunk fragmentation tends to be lower because there are fewer distinct run

      sizes to pack.

  - Add support for explicit tcaches.  The "tcache.create", "tcache.flush", and

    "tcache.destroy" mallctls control tcache lifetime and flushing, and the

    MALLOCX_TCACHE(tc) and MALLOCX_TCACHE_NONE flags to the *allocx() API

    control which tcache is used for each operation.

  - Implement per thread heap profiling, as well as the ability to

    enable/disable heap profiling on a per thread basis.  Add the "prof.reset",

    "prof.lg_sample", "thread.prof.name", "thread.prof.active",

    "opt.prof_thread_active_init", "prof.thread_active_init", and

    "thread.prof.active" mallctls.

  - Add support for per arena application-specified chunk allocators, configured

    via the "arena..chunk_hooks" mallctl.

  - Refactor huge allocation to be managed by arenas, so that arenas now

    function as general purpose independent allocators.  This is important in

    the context of user-specified chunk allocators, aside from the scalability

    benefits.  Related new statistics:

    + The "stats.arenas..huge.allocated", "stats.arenas..huge.nmalloc",

      "stats.arenas..huge.ndalloc", and "stats.arenas..huge.nrequests"

      mallctls provide high level per arena huge allocation statistics.

    + The "arenas.nhchunks", "arenas.hchunk..size",

      "stats.arenas..hchunks.<j>.nmalloc",

      "stats.arenas..hchunks.<j>.ndalloc",

      "stats.arenas..hchunks.<j>.nrequests", and

      "stats.arenas..hchunks.<j>.curhchunks" mallctls provide per size class

      statistics.

  - Add the 'util' column to malloc_stats_print() output, which reports the

    proportion of available regions that are currently in use for each small

    size class.

  - Add "alloc" and "free" modes for for junk filling (see the "opt.junk"

    mallctl), so that it is possible to separately enable junk filling for

    allocation versus deallocation.

  - Add the jemalloc-config script, which provides information about how

    jemalloc was configured, and how to integrate it into application builds.