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    1 Following are change highlights associated with official releases.  Important
    2 bug fixes are all mentioned, but some internal enhancements are omitted here for
    3 brevity.  Much more detail can be found in the git revision history:
    4 
    5     https://github.com/jemalloc/jemalloc
    6 
    7 * 5.2.1 (August 5, 2019)
    8 
    9   This release is primarily about Windows.  A critical virtual memory leak is
   10   resolved on all Windows platforms.  The regression was present in all releases
   11   since 5.0.0.
   12 
   13   Bug fixes:
   14   - Fix a severe virtual memory leak on Windows.  This regression was first
   15     released in 5.0.0.  (@Ignition, @j0t, @frederik-h, @davidtgoldblatt,
   16     @interwq)
   17   - Fix size 0 handling in posix_memalign().  This regression was first released
   18     in 5.2.0.  (@interwq)
   19   - Fix the prof_log unit test which may observe unexpected backtraces from
   20     compiler optimizations.  The test was first added in 5.2.0.  (@marxin,
   21     @gnzlbg, @interwq)
   22   - Fix the declaration of the extent_avail tree.  This regression was first
   23     released in 5.1.0.  (@zoulasc)
   24   - Fix an incorrect reference in jeprof.  This functionality was first released
   25     in 3.0.0.  (@prehistoric-penguin)
   26   - Fix an assertion on the deallocation fast-path.  This regression was first
   27     released in 5.2.0.  (@yinan1048576)
   28   - Fix the TLS_MODEL attribute in headers.  This regression was first released
   29     in 5.0.0.  (@zoulasc, @interwq)
   30 
   31   Optimizations and refactors:
   32   - Implement opt.retain on Windows and enable by default on 64-bit.  (@interwq,
   33     @davidtgoldblatt)
   34   - Optimize away a branch on the operator delete[] path.  (@mgrice)
   35   - Add format annotation to the format generator function.  (@zoulasc)
   36   - Refactor and improve the size class header generation.  (@yinan1048576)
   37   - Remove best fit.  (@djwatson)
   38   - Avoid blocking on background thread locks for stats.  (@oranagra, @interwq)
   39 
   40 * 5.2.0 (April 2, 2019)
   41 
   42   This release includes a few notable improvements, which are summarized below:
   43   1) improved fast-path performance from the optimizations by @djwatson; 2)
   44   reduced virtual memory fragmentation and metadata usage; and 3) bug fixes on
   45   setting the number of background threads.  In addition, peak / spike memory
   46   usage is improved with certain allocation patterns.  As usual, the release and
   47   prior dev versions have gone through large-scale production testing.
   48 
   49   New features:
   50   - Implement oversize_threshold, which uses a dedicated arena for allocations
   51     crossing the specified threshold to reduce fragmentation.  (@interwq)
   52   - Add extents usage information to stats.  (@tyleretzel)
   53   - Log time information for sampled allocations.  (@tyleretzel)
   54   - Support 0 size in sdallocx.  (@djwatson)
   55   - Output rate for certain counters in malloc_stats.  (@zinoale)
   56   - Add configure option --enable-readlinkat, which allows the use of readlinkat
   57     over readlink.  (@davidtgoldblatt)
   58   - Add configure options --{enable,disable}-{static,shared} to allow not
   59     building unwanted libraries.  (@Ericson2314)
   60   - Add configure option --disable-libdl to enable fully static builds.
   61     (@interwq)
   62   - Add mallctl interfaces:
   63 	+ opt.oversize_threshold (@interwq)
   64 	+ stats.arenas.<i>.extent_avail (@tyleretzel)
   65 	+ stats.arenas.<i>.extents.<j>.n{dirty,muzzy,retained} (@tyleretzel)
   66 	+ stats.arenas.<i>.extents.<j>.{dirty,muzzy,retained}_bytes
   67 	  (@tyleretzel)
   68 
   69   Portability improvements:
   70   - Update MSVC builds.  (@maksqwe, @rustyx)
   71   - Workaround a compiler optimizer bug on s390x.  (@rkmisra)
   72   - Make use of pthread_set_name_np(3) on FreeBSD.  (@trasz)
   73   - Implement malloc_getcpu() to enable percpu_arena for windows.  (@santagada)
   74   - Link against -pthread instead of -lpthread.  (@paravoid)
   75   - Make background_thread not dependent on libdl.  (@interwq)
   76   - Add stringify to fix a linker directive issue on MSVC.  (@daverigby)
   77   - Detect and fall back when 8-bit atomics are unavailable.  (@interwq)
   78   - Fall back to the default pthread_create if dlsym(3) fails.  (@interwq)
   79 
   80   Optimizations and refactors:
   81   - Refactor the TSD module.  (@davidtgoldblatt)
   82   - Avoid taking extents_muzzy mutex when muzzy is disabled.  (@interwq)
   83   - Avoid taking large_mtx for auto arenas on the tcache flush path.  (@interwq)
   84   - Optimize ixalloc by avoiding a size lookup.  (@interwq)
   85   - Implement opt.oversize_threshold which uses a dedicated arena for requests
   86     crossing the threshold, also eagerly purges the oversize extents.  Default
   87     the threshold to 8 MiB.  (@interwq)
   88   - Clean compilation with -Wextra.  (@gnzlbg, @jasone)
   89   - Refactor the size class module.  (@davidtgoldblatt)
   90   - Refactor the stats emitter.  (@tyleretzel)
   91   - Optimize pow2_ceil.  (@rkmisra)
   92   - Avoid runtime detection of lazy purging on FreeBSD.  (@trasz)
   93   - Optimize mmap(2) alignment handling on FreeBSD.  (@trasz)
   94   - Improve error handling for THP state initialization.  (@jsteemann)
   95   - Rework the malloc() fast path.  (@djwatson)
   96   - Rework the free() fast path.  (@djwatson)
   97   - Refactor and optimize the tcache fill / flush paths.  (@djwatson)
   98   - Optimize sync / lwsync on PowerPC.  (@chmeeedalf)
   99   - Bypass extent_dalloc() when retain is enabled.  (@interwq)
  100   - Optimize the locking on large deallocation.  (@interwq)
  101   - Reduce the number of pages committed from sanity checking in debug build.
  102     (@trasz, @interwq)
  103   - Deprecate OSSpinLock.  (@interwq)
  104   - Lower the default number of background threads to 4 (when the feature
  105     is enabled).  (@interwq)
  106   - Optimize the trylock spin wait.  (@djwatson)
  107   - Use arena index for arena-matching checks.  (@interwq)
  108   - Avoid forced decay on thread termination when using background threads.
  109     (@interwq)
  110   - Disable muzzy decay by default.  (@djwatson, @interwq)
  111   - Only initialize libgcc unwinder when profiling is enabled.  (@paravoid,
  112     @interwq)
  113 
  114   Bug fixes (all only relevant to jemalloc 5.x):
  115   - Fix background thread index issues with max_background_threads.  (@djwatson,
  116     @interwq)
  117   - Fix stats output for opt.lg_extent_max_active_fit.  (@interwq)
  118   - Fix opt.prof_prefix initialization.  (@davidtgoldblatt)
  119   - Properly trigger decay on tcache destroy.  (@interwq, @amosbird)
  120   - Fix tcache.flush.  (@interwq)
  121   - Detect whether explicit extent zero out is necessary with huge pages or
  122     custom extent hooks, which may change the purge semantics.  (@interwq)
  123   - Fix a side effect caused by extent_max_active_fit combined with decay-based
  124     purging, where freed extents can accumulate and not be reused for an
  125     extended period of time.  (@interwq, @mpghf)
  126   - Fix a missing unlock on extent register error handling.  (@zoulasc)
  127 
  128   Testing:
  129   - Simplify the Travis script output.  (@gnzlbg)
  130   - Update the test scripts for FreeBSD.  (@devnexen)
  131   - Add unit tests for the producer-consumer pattern.  (@interwq)
  132   - Add Cirrus-CI config for FreeBSD builds.  (@jasone)
  133   - Add size-matching sanity checks on tcache flush.  (@davidtgoldblatt,
  134     @interwq)
  135 
  136   Incompatible changes:
  137   - Remove --with-lg-page-sizes.  (@davidtgoldblatt)
  138 
  139   Documentation:
  140   - Attempt to build docs by default, however skip doc building when xsltproc
  141     is missing. (@interwq, @cmuellner)
  142 
  143 * 5.1.0 (May 4, 2018)
  144 
  145   This release is primarily about fine-tuning, ranging from several new features
  146   to numerous notable performance and portability enhancements.  The release and
  147   prior dev versions have been running in multiple large scale applications for
  148   months, and the cumulative improvements are substantial in many cases.
  149 
  150   Given the long and successful production runs, this release is likely a good
  151   candidate for applications to upgrade, from both jemalloc 5.0 and before.  For
  152   performance-critical applications, the newly added TUNING.md provides
  153   guidelines on jemalloc tuning.
  154 
  155   New features:
  156   - Implement transparent huge page support for internal metadata.  (@interwq)
  157   - Add opt.thp to allow enabling / disabling transparent huge pages for all
  158     mappings.  (@interwq)
  159   - Add maximum background thread count option.  (@djwatson)
  160   - Allow prof_active to control opt.lg_prof_interval and prof.gdump.
  161     (@interwq)
  162   - Allow arena index lookup based on allocation addresses via mallctl.
  163     (@lionkov)
  164   - Allow disabling initial-exec TLS model.  (@davidtgoldblatt, @KenMacD)
  165   - Add opt.lg_extent_max_active_fit to set the max ratio between the size of
  166     the active extent selected (to split off from) and the size of the requested
  167     allocation.  (@interwq, @davidtgoldblatt)
  168   - Add retain_grow_limit to set the max size when growing virtual address
  169     space.  (@interwq)
  170   - Add mallctl interfaces:
  171     + arena.<i>.retain_grow_limit  (@interwq)
  172     + arenas.lookup  (@lionkov)
  173     + max_background_threads  (@djwatson)
  174     + opt.lg_extent_max_active_fit  (@interwq)
  175     + opt.max_background_threads  (@djwatson)
  176     + opt.metadata_thp  (@interwq)
  177     + opt.thp  (@interwq)
  178     + stats.metadata_thp  (@interwq)
  179 
  180   Portability improvements:
  181   - Support GNU/kFreeBSD configuration.  (@paravoid)
  182   - Support m68k, nios2 and SH3 architectures.  (@paravoid)
  183   - Fall back to FD_CLOEXEC when O_CLOEXEC is unavailable.  (@zonyitoo)
  184   - Fix symbol listing for cross-compiling.  (@tamird)
  185   - Fix high bits computation on ARM.  (@davidtgoldblatt, @paravoid)
  186   - Disable the CPU_SPINWAIT macro for Power.  (@davidtgoldblatt, @marxin)
  187   - Fix MSVC 2015 & 2017 builds.  (@rustyx)
  188   - Improve RISC-V support.  (@EdSchouten)
  189   - Set name mangling script in strict mode.  (@nicolov)
  190   - Avoid MADV_HUGEPAGE on ARM.  (@marxin)
  191   - Modify configure to determine return value of strerror_r.
  192     (@davidtgoldblatt, @cferris1000)
  193   - Make sure CXXFLAGS is tested with CPP compiler.  (@nehaljwani)
  194   - Fix 32-bit build on MSVC.  (@rustyx)
  195   - Fix external symbol on MSVC.  (@maksqwe)
  196   - Avoid a printf format specifier warning.  (@jasone)
  197   - Add configure option --disable-initial-exec-tls which can allow jemalloc to
  198     be dynamically loaded after program startup.  (@davidtgoldblatt, @KenMacD)
  199   - AArch64: Add ILP32 support.  (@cmuellner)
  200   - Add --with-lg-vaddr configure option to support cross compiling.
  201     (@cmuellner, @davidtgoldblatt)
  202 
  203   Optimizations and refactors:
  204   - Improve active extent fit with extent_max_active_fit.  This considerably
  205     reduces fragmentation over time and improves virtual memory and metadata
  206     usage.  (@davidtgoldblatt, @interwq)
  207   - Eagerly coalesce large extents to reduce fragmentation.  (@interwq)
  208   - sdallocx: only read size info when page aligned (i.e. possibly sampled),
  209     which speeds up the sized deallocation path significantly.  (@interwq)
  210   - Avoid attempting new mappings for in place expansion with retain, since
  211     it rarely succeeds in practice and causes high overhead.  (@interwq)
  212   - Refactor OOM handling in newImpl.  (@wqfish)
  213   - Add internal fine-grained logging functionality for debugging use.
  214     (@davidtgoldblatt)
  215   - Refactor arena / tcache interactions.  (@davidtgoldblatt)
  216   - Refactor extent management with dumpable flag.  (@davidtgoldblatt)
  217   - Add runtime detection of lazy purging.  (@interwq)
  218   - Use pairing heap instead of red-black tree for extents_avail.  (@djwatson)
  219   - Use sysctl on startup in FreeBSD.  (@trasz)
  220   - Use thread local prng state instead of atomic.  (@djwatson)
  221   - Make decay to always purge one more extent than before, because in
  222     practice large extents are usually the ones that cross the decay threshold.
  223     Purging the additional extent helps save memory as well as reduce VM
  224     fragmentation.  (@interwq)
  225   - Fast division by dynamic values.  (@davidtgoldblatt)
  226   - Improve the fit for aligned allocation.  (@interwq, @edwinsmith)
  227   - Refactor extent_t bitpacking.  (@rkmisra)
  228   - Optimize the generated assembly for ticker operations.  (@davidtgoldblatt)
  229   - Convert stats printing to use a structured text emitter.  (@davidtgoldblatt)
  230   - Remove preserve_lru feature for extents management.  (@djwatson)
  231   - Consolidate two memory loads into one on the fast deallocation path.
  232     (@davidtgoldblatt, @interwq)
  233 
  234   Bug fixes (most of the issues are only relevant to jemalloc 5.0):
  235   - Fix deadlock with multithreaded fork in OS X.  (@davidtgoldblatt)
  236   - Validate returned file descriptor before use.  (@zonyitoo)
  237   - Fix a few background thread initialization and shutdown issues.  (@interwq)
  238   - Fix an extent coalesce + decay race by taking both coalescing extents off
  239     the LRU list.  (@interwq)
  240   - Fix potentially unbound increase during decay, caused by one thread keep
  241     stashing memory to purge while other threads generating new pages.  The
  242     number of pages to purge is checked to prevent this.  (@interwq)
  243   - Fix a FreeBSD bootstrap assertion.  (@strejda, @interwq)
  244   - Handle 32 bit mutex counters.  (@rkmisra)
  245   - Fix a indexing bug when creating background threads.  (@davidtgoldblatt,
  246     @binliu19)
  247   - Fix arguments passed to extent_init.  (@yuleniwo, @interwq)
  248   - Fix addresses used for ordering mutexes.  (@rkmisra)
  249   - Fix abort_conf processing during bootstrap.  (@interwq)
  250   - Fix include path order for out-of-tree builds.  (@cmuellner)
  251 
  252   Incompatible changes:
  253   - Remove --disable-thp.  (@interwq)
  254   - Remove mallctl interfaces:
  255     + config.thp  (@interwq)
  256 
  257   Documentation:
  258   - Add TUNING.md.  (@interwq, @davidtgoldblatt, @djwatson)
  259 
  260 * 5.0.1 (July 1, 2017)
  261 
  262   This bugfix release fixes several issues, most of which are obscure enough
  263   that typical applications are not impacted.
  264 
  265   Bug fixes:
  266   - Update decay->nunpurged before purging, in order to avoid potential update
  267     races and subsequent incorrect purging volume.  (@interwq)
  268   - Only abort on dlsym(3) error if the failure impacts an enabled feature (lazy
  269     locking and/or background threads).  This mitigates an initialization
  270     failure bug for which we still do not have a clear reproduction test case.
  271     (@interwq)
  272   - Modify tsd management so that it neither crashes nor leaks if a thread's
  273     only allocation activity is to call free() after TLS destructors have been
  274     executed.  This behavior was observed when operating with GNU libc, and is
  275     unlikely to be an issue with other libc implementations.  (@interwq)
  276   - Mask signals during background thread creation.  This prevents signals from
  277     being inadvertently delivered to background threads.  (@jasone,
  278     @davidtgoldblatt, @interwq)
  279   - Avoid inactivity checks within background threads, in order to prevent
  280     recursive mutex acquisition.  (@interwq)
  281   - Fix extent_grow_retained() to use the specified hooks when the
  282     arena.<i>.extent_hooks mallctl is used to override the default hooks.
  283     (@interwq)
  284   - Add missing reentrancy support for custom extent hooks which allocate.
  285     (@interwq)
  286   - Post-fork(2), re-initialize the list of tcaches associated with each arena
  287     to contain no tcaches except the forking thread's.  (@interwq)
  288   - Add missing post-fork(2) mutex reinitialization for extent_grow_mtx.  This
  289     fixes potential deadlocks after fork(2).  (@interwq)
  290   - Enforce minimum autoconf version (currently 2.68), since 2.63 is known to
  291     generate corrupt configure scripts.  (@jasone)
  292   - Ensure that the configured page size (--with-lg-page) is no larger than the
  293     configured huge page size (--with-lg-hugepage).  (@jasone)
  294 
  295 * 5.0.0 (June 13, 2017)
  296 
  297   Unlike all previous jemalloc releases, this release does not use naturally
  298   aligned "chunks" for virtual memory management, and instead uses page-aligned
  299   "extents".  This change has few externally visible effects, but the internal
  300   impacts are... extensive.  Many other internal changes combine to make this
  301   the most cohesively designed version of jemalloc so far, with ample
  302   opportunity for further enhancements.
  303 
  304   Continuous integration is now an integral aspect of development thanks to the
  305   efforts of @davidtgoldblatt, and the dev branch tends to remain reasonably
  306   stable on the tested platforms (Linux, FreeBSD, macOS, and Windows).  As a
  307   side effect the official release frequency may decrease over time.
  308 
  309   New features:
  310   - Implement optional per-CPU arena support; threads choose which arena to use
  311     based on current CPU rather than on fixed thread-->arena associations.
  312     (@interwq)
  313   - Implement two-phase decay of unused dirty pages.  Pages transition from
  314     dirty-->muzzy-->clean, where the first phase transition relies on
  315     madvise(... MADV_FREE) semantics, and the second phase transition discards
  316     pages such that they are replaced with demand-zeroed pages on next access.
  317     (@jasone)
  318   - Increase decay time resolution from seconds to milliseconds.  (@jasone)
  319   - Implement opt-in per CPU background threads, and use them for asynchronous
  320     decay-driven unused dirty page purging.  (@interwq)
  321   - Add mutex profiling, which collects a variety of statistics useful for
  322     diagnosing overhead/contention issues.  (@interwq)
  323   - Add C++ new/delete operator bindings.  (@djwatson)
  324   - Support manually created arena destruction, such that all data and metadata
  325     are discarded.  Add MALLCTL_ARENAS_DESTROYED for accessing merged stats
  326     associated with destroyed arenas.  (@jasone)
  327   - Add MALLCTL_ARENAS_ALL as a fixed index for use in accessing
  328     merged/destroyed arena statistics via mallctl.  (@jasone)
  329   - Add opt.abort_conf to optionally abort if invalid configuration options are
  330     detected during initialization.  (@interwq)
  331   - Add opt.stats_print_opts, so that e.g. JSON output can be selected for the
  332     stats dumped during exit if opt.stats_print is true.  (@jasone)
  333   - Add --with-version=VERSION for use when embedding jemalloc into another
  334     project's git repository.  (@jasone)
  335   - Add --disable-thp to support cross compiling.  (@jasone)
  336   - Add --with-lg-hugepage to support cross compiling.  (@jasone)
  337   - Add mallctl interfaces (various authors):
  338     + background_thread
  339     + opt.abort_conf
  340     + opt.retain
  341     + opt.percpu_arena
  342     + opt.background_thread
  343     + opt.{dirty,muzzy}_decay_ms
  344     + opt.stats_print_opts
  345     + arena.<i>.initialized
  346     + arena.<i>.destroy
  347     + arena.<i>.{dirty,muzzy}_decay_ms
  348     + arena.<i>.extent_hooks
  349     + arenas.{dirty,muzzy}_decay_ms
  350     + arenas.bin.<i>.slab_size
  351     + arenas.nlextents
  352     + arenas.lextent.<i>.size
  353     + arenas.create
  354     + stats.background_thread.{num_threads,num_runs,run_interval}
  355     + stats.mutexes.{ctl,background_thread,prof,reset}.
  356       {num_ops,num_spin_acq,num_wait,max_wait_time,total_wait_time,max_num_thds,
  357       num_owner_switch}
  358     + stats.arenas.<i>.{dirty,muzzy}_decay_ms
  359     + stats.arenas.<i>.uptime
  360     + stats.arenas.<i>.{pmuzzy,base,internal,resident}
  361     + stats.arenas.<i>.{dirty,muzzy}_{npurge,nmadvise,purged}
  362     + stats.arenas.<i>.bins.<j>.{nslabs,reslabs,curslabs}
  363     + stats.arenas.<i>.bins.<j>.mutex.
  364       {num_ops,num_spin_acq,num_wait,max_wait_time,total_wait_time,max_num_thds,
  365       num_owner_switch}
  366     + stats.arenas.<i>.lextents.<j>.{nmalloc,ndalloc,nrequests,curlextents}
  367     + stats.arenas.i.mutexes.{large,extent_avail,extents_dirty,extents_muzzy,
  368       extents_retained,decay_dirty,decay_muzzy,base,tcache_list}.
  369       {num_ops,num_spin_acq,num_wait,max_wait_time,total_wait_time,max_num_thds,
  370       num_owner_switch}
  371 
  372   Portability improvements:
  373   - Improve reentrant allocation support, such that deadlock is less likely if
  374     e.g. a system library call in turn allocates memory.  (@davidtgoldblatt,
  375     @interwq)
  376   - Support static linking of jemalloc with glibc.  (@djwatson)
  377 
  378   Optimizations and refactors:
  379   - Organize virtual memory as "extents" of virtual memory pages, rather than as
  380     naturally aligned "chunks", and store all metadata in arbitrarily distant
  381     locations.  This reduces virtual memory external fragmentation, and will
  382     interact better with huge pages (not yet explicitly supported).  (@jasone)
  383   - Fold large and huge size classes together; only small and large size classes
  384     remain.  (@jasone)
  385   - Unify the allocation paths, and merge most fast-path branching decisions.
  386     (@davidtgoldblatt, @interwq)
  387   - Embed per thread automatic tcache into thread-specific data, which reduces
  388     conditional branches and dereferences.  Also reorganize tcache to increase
  389     fast-path data locality.  (@interwq)
  390   - Rewrite atomics to closely model the C11 API, convert various
  391     synchronization from mutex-based to atomic, and use the explicit memory
  392     ordering control to resolve various hypothetical races without increasing
  393     synchronization overhead.  (@davidtgoldblatt)
  394   - Extensively optimize rtree via various methods:
  395     + Add multiple layers of rtree lookup caching, since rtree lookups are now
  396       part of fast-path deallocation.  (@interwq)
  397     + Determine rtree layout at compile time.  (@jasone)
  398     + Make the tree shallower for common configurations.  (@jasone)
  399     + Embed the root node in the top-level rtree data structure, thus avoiding
  400       one level of indirection.  (@jasone)
  401     + Further specialize leaf elements as compared to internal node elements,
  402       and directly embed extent metadata needed for fast-path deallocation.
  403       (@jasone)
  404     + Ignore leading always-zero address bits (architecture-specific).
  405       (@jasone)
  406   - Reorganize headers (ongoing work) to make them hermetic, and disentangle
  407     various module dependencies.  (@davidtgoldblatt)
  408   - Convert various internal data structures such as size class metadata from
  409     boot-time-initialized to compile-time-initialized.  Propagate resulting data
  410     structure simplifications, such as making arena metadata fixed-size.
  411     (@jasone)
  412   - Simplify size class lookups when constrained to size classes that are
  413     multiples of the page size.  This speeds lookups, but the primary benefit is
  414     complexity reduction in code that was the source of numerous regressions.
  415     (@jasone)
  416   - Lock individual extents when possible for localized extent operations,
  417     rather than relying on a top-level arena lock.  (@davidtgoldblatt, @jasone)
  418   - Use first fit layout policy instead of best fit, in order to improve
  419     packing.  (@jasone)
  420   - If munmap(2) is not in use, use an exponential series to grow each arena's
  421     virtual memory, so that the number of disjoint virtual memory mappings
  422     remains low.  (@jasone)
  423   - Implement per arena base allocators, so that arenas never share any virtual
  424     memory pages.  (@jasone)
  425   - Automatically generate private symbol name mangling macros.  (@jasone)
  426 
  427   Incompatible changes:
  428   - Replace chunk hooks with an expanded/normalized set of extent hooks.
  429     (@jasone)
  430   - Remove ratio-based purging.  (@jasone)
  431   - Remove --disable-tcache.  (@jasone)
  432   - Remove --disable-tls.  (@jasone)
  433   - Remove --enable-ivsalloc.  (@jasone)
  434   - Remove --with-lg-size-class-group.  (@jasone)
  435   - Remove --with-lg-tiny-min.  (@jasone)
  436   - Remove --disable-cc-silence.  (@jasone)
  437   - Remove --enable-code-coverage.  (@jasone)
  438   - Remove --disable-munmap (replaced by opt.retain).  (@jasone)
  439   - Remove Valgrind support.  (@jasone)
  440   - Remove quarantine support.  (@jasone)
  441   - Remove redzone support.  (@jasone)
  442   - Remove mallctl interfaces (various authors):
  443     + config.munmap
  444     + config.tcache
  445     + config.tls
  446     + config.valgrind
  447     + opt.lg_chunk
  448     + opt.purge
  449     + opt.lg_dirty_mult
  450     + opt.decay_time
  451     + opt.quarantine
  452     + opt.redzone
  453     + opt.thp
  454     + arena.<i>.lg_dirty_mult
  455     + arena.<i>.decay_time
  456     + arena.<i>.chunk_hooks
  457     + arenas.initialized
  458     + arenas.lg_dirty_mult
  459     + arenas.decay_time
  460     + arenas.bin.<i>.run_size
  461     + arenas.nlruns
  462     + arenas.lrun.<i>.size
  463     + arenas.nhchunks
  464     + arenas.hchunk.<i>.size
  465     + arenas.extend
  466     + stats.cactive
  467     + stats.arenas.<i>.lg_dirty_mult
  468     + stats.arenas.<i>.decay_time
  469     + stats.arenas.<i>.metadata.{mapped,allocated}
  470     + stats.arenas.<i>.{npurge,nmadvise,purged}
  471     + stats.arenas.<i>.huge.{allocated,nmalloc,ndalloc,nrequests}
  472     + stats.arenas.<i>.bins.<j>.{nruns,reruns,curruns}
  473     + stats.arenas.<i>.lruns.<j>.{nmalloc,ndalloc,nrequests,curruns}
  474     + stats.arenas.<i>.hchunks.<j>.{nmalloc,ndalloc,nrequests,curhchunks}
  475 
  476   Bug fixes:
  477   - Improve interval-based profile dump triggering to dump only one profile when
  478     a single allocation's size exceeds the interval.  (@jasone)
  479   - Use prefixed function names (as controlled by --with-jemalloc-prefix) when
  480     pruning backtrace frames in jeprof.  (@jasone)
  481 
  482 * 4.5.0 (February 28, 2017)
  483 
  484   This is the first release to benefit from much broader continuous integration
  485   testing, thanks to @davidtgoldblatt.  Had we had this testing infrastructure
  486   in place for prior releases, it would have caught all of the most serious
  487   regressions fixed by this release.
  488 
  489   New features:
  490   - Add --disable-thp and the opt.thp mallctl to provide opt-out mechanisms for
  491     transparent huge page integration.  (@jasone)
  492   - Update zone allocator integration to work with macOS 10.12.  (@glandium)
  493   - Restructure *CFLAGS configuration, so that CFLAGS behaves typically, and
  494     EXTRA_CFLAGS provides a way to specify e.g. -Werror during building, but not
  495     during configuration.  (@jasone, @ronawho)
  496 
  497   Bug fixes:
  498   - Fix DSS (sbrk(2)-based) allocation.  This regression was first released in
  499     4.3.0.  (@jasone)
  500   - Handle race in per size class utilization computation.  This functionality
  501     was first released in 4.0.0.  (@interwq)
  502   - Fix lock order reversal during gdump.  (@jasone)
  503   - Fix/refactor tcache synchronization.  This regression was first released in
  504     4.0.0.  (@jasone)
  505   - Fix various JSON-formatted malloc_stats_print() bugs.  This functionality
  506     was first released in 4.3.0.  (@jasone)
  507   - Fix huge-aligned allocation.  This regression was first released in 4.4.0.
  508     (@jasone)
  509   - When transparent huge page integration is enabled, detect what state pages
  510     start in according to the kernel's current operating mode, and only convert
  511     arena chunks to non-huge during purging if that is not their initial state.
  512     This functionality was first released in 4.4.0.  (@jasone)
  513   - Fix lg_chunk clamping for the --enable-cache-oblivious --disable-fill case.
  514     This regression was first released in 4.0.0.  (@jasone, @428desmo)
  515   - Properly detect sparc64 when building for Linux.  (@glaubitz)
  516 
  517 * 4.4.0 (December 3, 2016)
  518 
  519   New features:
  520   - Add configure support for *-*-linux-android.  (@cferris1000, @jasone)
  521   - Add the --disable-syscall configure option, for use on systems that place
  522     security-motivated limitations on syscall(2).  (@jasone)
  523   - Add support for Debian GNU/kFreeBSD.  (@thesam)
  524 
  525   Optimizations:
  526   - Add extent serial numbers and use them where appropriate as a sort key that
  527     is higher priority than address, so that the allocation policy prefers older
  528     extents.  This tends to improve locality (decrease fragmentation) when
  529     memory grows downward.  (@jasone)
  530   - Refactor madvise(2) configuration so that MADV_FREE is detected and utilized
  531     on Linux 4.5 and newer.  (@jasone)
  532   - Mark partially purged arena chunks as non-huge-page.  This improves
  533     interaction with Linux's transparent huge page functionality.  (@jasone)
  534 
  535   Bug fixes:
  536   - Fix size class computations for edge conditions involving extremely large
  537     allocations.  This regression was first released in 4.0.0.  (@jasone,
  538     @ingvarha)
  539   - Remove overly restrictive assertions related to the cactive statistic.  This
  540     regression was first released in 4.1.0.  (@jasone)
  541   - Implement a more reliable detection scheme for os_unfair_lock on macOS.
  542     (@jszakmeister)
  543 
  544 * 4.3.1 (November 7, 2016)
  545 
  546   Bug fixes:
  547   - Fix a severe virtual memory leak.  This regression was first released in
  548     4.3.0.  (@interwq, @jasone)
  549   - Refactor atomic and prng APIs to restore support for 32-bit platforms that
  550     use pre-C11 toolchains, e.g. FreeBSD's mips.  (@jasone)
  551 
  552 * 4.3.0 (November 4, 2016)
  553 
  554   This is the first release that passes the test suite for multiple Windows
  555   configurations, thanks in large part to @glandium setting up continuous
  556   integration via AppVeyor (and Travis CI for Linux and OS X).
  557 
  558   New features:
  559   - Add "J" (JSON) support to malloc_stats_print().  (@jasone)
  560   - Add Cray compiler support.  (@ronawho)
  561 
  562   Optimizations:
  563   - Add/use adaptive spinning for bootstrapping and radix tree node
  564     initialization.  (@jasone)
  565 
  566   Bug fixes:
  567   - Fix large allocation to search starting in the optimal size class heap,
  568     which can substantially reduce virtual memory churn and fragmentation.  This
  569     regression was first released in 4.0.0.  (@mjp41, @jasone)
  570   - Fix stats.arenas.<i>.nthreads accounting.  (@interwq)
  571   - Fix and simplify decay-based purging.  (@jasone)
  572   - Make DSS (sbrk(2)-related) operations lockless, which resolves potential
  573     deadlocks during thread exit.  (@jasone)
  574   - Fix over-sized allocation of radix tree leaf nodes.  (@mjp41, @ogaun,
  575     @jasone)
  576   - Fix over-sized allocation of arena_t (plus associated stats) data
  577     structures.  (@jasone, @interwq)
  578   - Fix EXTRA_CFLAGS to not affect configuration.  (@jasone)
  579   - Fix a Valgrind integration bug.  (@ronawho)
  580   - Disallow 0x5a junk filling when running in Valgrind.  (@jasone)
  581   - Fix a file descriptor leak on Linux.  This regression was first released in
  582     4.2.0.  (@vsarunas, @jasone)
  583   - Fix static linking of jemalloc with glibc.  (@djwatson)
  584   - Use syscall(2) rather than {open,read,close}(2) during boot on Linux.  This
  585     works around other libraries' system call wrappers performing reentrant
  586     allocation.  (@kspinka, @Whissi, @jasone)
  587   - Fix OS X default zone replacement to work with OS X 10.12.  (@glandium,
  588     @jasone)
  589   - Fix cached memory management to avoid needless commit/decommit operations
  590     during purging, which resolves permanent virtual memory map fragmentation
  591     issues on Windows.  (@mjp41, @jasone)
  592   - Fix TSD fetches to avoid (recursive) allocation.  This is relevant to
  593     non-TLS and Windows configurations.  (@jasone)
  594   - Fix malloc_conf overriding to work on Windows.  (@jasone)
  595   - Forcibly disable lazy-lock on Windows (was forcibly *enabled*).  (@jasone)
  596 
  597 * 4.2.1 (June 8, 2016)
  598 
  599   Bug fixes:
  600   - Fix bootstrapping issues for configurations that require allocation during
  601     tsd initialization (e.g. --disable-tls).  (@cferris1000, @jasone)
  602   - Fix gettimeofday() version of nstime_update().  (@ronawho)
  603   - Fix Valgrind regressions in calloc() and chunk_alloc_wrapper().  (@ronawho)
  604   - Fix potential VM map fragmentation regression.  (@jasone)
  605   - Fix opt_zero-triggered in-place huge reallocation zeroing.  (@jasone)
  606   - Fix heap profiling context leaks in reallocation edge cases.  (@jasone)
  607 
  608 * 4.2.0 (May 12, 2016)
  609 
  610   New features:
  611   - Add the arena.<i>.reset mallctl, which makes it possible to discard all of
  612     an arena's allocations in a single operation.  (@jasone)
  613   - Add the stats.retained and stats.arenas.<i>.retained statistics.  (@jasone)
  614   - Add the --with-version configure option.  (@jasone)
  615   - Support --with-lg-page values larger than actual page size.  (@jasone)
  616 
  617   Optimizations:
  618   - Use pairing heaps rather than red-black trees for various hot data
  619     structures.  (@djwatson, @jasone)
  620   - Streamline fast paths of rtree operations.  (@jasone)
  621   - Optimize the fast paths of calloc() and [m,d,sd]allocx().  (@jasone)
  622   - Decommit unused virtual memory if the OS does not overcommit.  (@jasone)
  623   - Specify MAP_NORESERVE on Linux if [heuristic] overcommit is active, in order
  624     to avoid unfortunate interactions during fork(2).  (@jasone)
  625 
  626   Bug fixes:
  627   - Fix chunk accounting related to triggering gdump profiles.  (@jasone)
  628   - Link against librt for clock_gettime(2) if glibc < 2.17.  (@jasone)
  629   - Scale leak report summary according to sampling probability.  (@jasone)
  630 
  631 * 4.1.1 (May 3, 2016)
  632 
  633   This bugfix release resolves a variety of mostly minor issues, though the
  634   bitmap fix is critical for 64-bit Windows.
  635 
  636   Bug fixes:
  637   - Fix the linear scan version of bitmap_sfu() to shift by the proper amount
  638     even when sizeof(long) is not the same as sizeof(void *), as on 64-bit
  639     Windows.  (@jasone)
  640   - Fix hashing functions to avoid unaligned memory accesses (and resulting
  641     crashes).  This is relevant at least to some ARM-based platforms.
  642     (@rkmisra)
  643   - Fix fork()-related lock rank ordering reversals.  These reversals were
  644     unlikely to cause deadlocks in practice except when heap profiling was
  645     enabled and active.  (@jasone)
  646   - Fix various chunk leaks in OOM code paths.  (@jasone)
  647   - Fix malloc_stats_print() to print opt.narenas correctly.  (@jasone)
  648   - Fix MSVC-specific build/test issues.  (@rustyx, @yuslepukhin)
  649   - Fix a variety of test failures that were due to test fragility rather than
  650     core bugs.  (@jasone)
  651 
  652 * 4.1.0 (February 28, 2016)
  653 
  654   This release is primarily about optimizations, but it also incorporates a lot
  655   of portability-motivated refactoring and enhancements.  Many people worked on
  656   this release, to an extent that even with the omission here of minor changes
  657   (see git revision history), and of the people who reported and diagnosed
  658   issues, so much of the work was contributed that starting with this release,
  659   changes are annotated with author credits to help reflect the collaborative
  660   effort involved.
  661 
  662   New features:
  663   - Implement decay-based unused dirty page purging, a major optimization with
  664     mallctl API impact.  This is an alternative to the existing ratio-based
  665     unused dirty page purging, and is intended to eventually become the sole
  666     purging mechanism.  New mallctls:
  667     + opt.purge
  668     + opt.decay_time
  669     + arena.<i>.decay
  670     + arena.<i>.decay_time
  671     + arenas.decay_time
  672     + stats.arenas.<i>.decay_time
  673     (@jasone, @cevans87)
  674   - Add --with-malloc-conf, which makes it possible to embed a default
  675     options string during configuration.  This was motivated by the desire to
  676     specify --with-malloc-conf=purge:decay , since the default must remain
  677     purge:ratio until the 5.0.0 release.  (@jasone)
  678   - Add MS Visual Studio 2015 support.  (@rustyx, @yuslepukhin)
  679   - Make *allocx() size class overflow behavior defined.  The maximum
  680     size class is now less than PTRDIFF_MAX to protect applications against
  681     numerical overflow, and all allocation functions are guaranteed to indicate
  682     errors rather than potentially crashing if the request size exceeds the
  683     maximum size class.  (@jasone)
  684   - jeprof:
  685     + Add raw heap profile support.  (@jasone)
  686     + Add --retain and --exclude for backtrace symbol filtering.  (@jasone)
  687 
  688   Optimizations:
  689   - Optimize the fast path to combine various bootstrapping and configuration
  690     checks and execute more streamlined code in the common case.  (@interwq)
  691   - Use linear scan for small bitmaps (used for small object tracking).  In
  692     addition to speeding up bitmap operations on 64-bit systems, this reduces
  693     allocator metadata overhead by approximately 0.2%.  (@djwatson)
  694   - Separate arena_avail trees, which substantially speeds up run tree
  695     operations.  (@djwatson)
  696   - Use memoization (boot-time-computed table) for run quantization.  Separate
  697     arena_avail trees reduced the importance of this optimization.  (@jasone)
  698   - Attempt mmap-based in-place huge reallocation.  This can dramatically speed
  699     up incremental huge reallocation.  (@jasone)
  700 
  701   Incompatible changes:
  702   - Make opt.narenas unsigned rather than size_t.  (@jasone)
  703 
  704   Bug fixes:
  705   - Fix stats.cactive accounting regression.  (@rustyx, @jasone)
  706   - Handle unaligned keys in hash().  This caused problems for some ARM systems.
  707     (@jasone, @cferris1000)
  708   - Refactor arenas array.  In addition to fixing a fork-related deadlock, this
  709     makes arena lookups faster and simpler.  (@jasone)
  710   - Move retained memory allocation out of the default chunk allocation
  711     function, to a location that gets executed even if the application installs
  712     a custom chunk allocation function.  This resolves a virtual memory leak.
  713     (@buchgr)
  714   - Fix a potential tsd cleanup leak.  (@cferris1000, @jasone)
  715   - Fix run quantization.  In practice this bug had no impact unless
  716     applications requested memory with alignment exceeding one page.
  717     (@jasone, @djwatson)
  718   - Fix LinuxThreads-specific bootstrapping deadlock.  (Cosmin Paraschiv)
  719   - jeprof:
  720     + Don't discard curl options if timeout is not defined.  (@djwatson)
  721     + Detect failed profile fetches.  (@djwatson)
  722   - Fix stats.arenas.<i>.{dss,lg_dirty_mult,decay_time,pactive,pdirty} for
  723     --disable-stats case.  (@jasone)
  724 
  725 * 4.0.4 (October 24, 2015)
  726 
  727   This bugfix release fixes another xallocx() regression.  No other regressions
  728   have come to light in over a month, so this is likely a good starting point
  729   for people who prefer to wait for "dot one" releases with all the major issues
  730   shaken out.
  731 
  732   Bug fixes:
  733   - Fix xallocx(..., MALLOCX_ZERO to zero the last full trailing page of large
  734     allocations that have been randomly assigned an offset of 0 when
  735     --enable-cache-oblivious configure option is enabled.
  736 
  737 * 4.0.3 (September 24, 2015)
  738 
  739   This bugfix release continues the trend of xallocx() and heap profiling fixes.
  740 
  741   Bug fixes:
  742   - Fix xallocx(..., MALLOCX_ZERO) to zero all trailing bytes of large
  743     allocations when --enable-cache-oblivious configure option is enabled.
  744   - Fix xallocx(..., MALLOCX_ZERO) to zero trailing bytes of huge allocations
  745     when resizing from/to a size class that is not a multiple of the chunk size.
  746   - Fix prof_tctx_dump_iter() to filter out nodes that were created after heap
  747     profile dumping started.
  748   - Work around a potentially bad thread-specific data initialization
  749     interaction with NPTL (glibc's pthreads implementation).
  750 
  751 * 4.0.2 (September 21, 2015)
  752 
  753   This bugfix release addresses a few bugs specific to heap profiling.
  754 
  755   Bug fixes:
  756   - Fix ixallocx_prof_sample() to never modify nor create sampled small
  757     allocations.  xallocx() is in general incapable of moving small allocations,
  758     so this fix removes buggy code without loss of generality.
  759   - Fix irallocx_prof_sample() to always allocate large regions, even when
  760     alignment is non-zero.
  761   - Fix prof_alloc_rollback() to read tdata from thread-specific data rather
  762     than dereferencing a potentially invalid tctx.
  763 
  764 * 4.0.1 (September 15, 2015)
  765 
  766   This is a bugfix release that is somewhat high risk due to the amount of
  767   refactoring required to address deep xallocx() problems.  As a side effect of
  768   these fixes, xallocx() now tries harder to partially fulfill requests for
  769   optional extra space.  Note that a couple of minor heap profiling
  770   optimizations are included, but these are better thought of as performance
  771   fixes that were integral to discovering most of the other bugs.
  772 
  773   Optimizations:
  774   - Avoid a chunk metadata read in arena_prof_tctx_set(), since it is in the
  775     fast path when heap profiling is enabled.  Additionally, split a special
  776     case out into arena_prof_tctx_reset(), which also avoids chunk metadata
  777     reads.
  778   - Optimize irallocx_prof() to optimistically update the sampler state.  The
  779     prior implementation appears to have been a holdover from when
  780     rallocx()/xallocx() functionality was combined as rallocm().
  781 
  782   Bug fixes:
  783   - Fix TLS configuration such that it is enabled by default for platforms on
  784     which it works correctly.
  785   - Fix arenas_cache_cleanup() and arena_get_hard() to handle
  786     allocation/deallocation within the application's thread-specific data
  787     cleanup functions even after arenas_cache is torn down.
  788   - Fix xallocx() bugs related to size+extra exceeding HUGE_MAXCLASS.
  789   - Fix chunk purge hook calls for in-place huge shrinking reallocation to
  790     specify the old chunk size rather than the new chunk size.  This bug caused
  791     no correctness issues for the default chunk purge function, but was
  792     visible to custom functions set via the "arena.<i>.chunk_hooks" mallctl.
  793   - Fix heap profiling bugs:
  794     + Fix heap profiling to distinguish among otherwise identical sample sites
  795       with interposed resets (triggered via the "prof.reset" mallctl).  This bug
  796       could cause data structure corruption that would most likely result in a
  797       segfault.
  798     + Fix irealloc_prof() to prof_alloc_rollback() on OOM.
  799     + Make one call to prof_active_get_unlocked() per allocation event, and use
  800       the result throughout the relevant functions that handle an allocation
  801       event.  Also add a missing check in prof_realloc().  These fixes protect
  802       allocation events against concurrent prof_active changes.
  803     + Fix ixallocx_prof() to pass usize_max and zero to ixallocx_prof_sample()
  804       in the correct order.
  805     + Fix prof_realloc() to call prof_free_sampled_object() after calling
  806       prof_malloc_sample_object().  Prior to this fix, if tctx and old_tctx were
  807       the same, the tctx could have been prematurely destroyed.
  808   - Fix portability bugs:
  809     + Don't bitshift by negative amounts when encoding/decoding run sizes in
  810       chunk header maps.  This affected systems with page sizes greater than 8
  811       KiB.
  812     + Rename index_t to szind_t to avoid an existing type on Solaris.
  813     + Add JEMALLOC_CXX_THROW to the memalign() function prototype, in order to
  814       match glibc and avoid compilation errors when including both
  815       jemalloc/jemalloc.h and malloc.h in C++ code.
  816     + Don't assume that /bin/sh is appropriate when running size_classes.sh
  817       during configuration.
  818     + Consider __sparcv9 a synonym for __sparc64__ when defining LG_QUANTUM.
  819     + Link tests to librt if it contains clock_gettime(2).
  820 
  821 * 4.0.0 (August 17, 2015)
  822 
  823   This version contains many speed and space optimizations, both minor and
  824   major.  The major themes are generalization, unification, and simplification.
  825   Although many of these optimizations cause no visible behavior change, their
  826   cumulative effect is substantial.
  827 
  828   New features:
  829   - Normalize size class spacing to be consistent across the complete size
  830     range.  By default there are four size classes per size doubling, but this
  831     is now configurable via the --with-lg-size-class-group option.  Also add the
  832     --with-lg-page, --with-lg-page-sizes, --with-lg-quantum, and
  833     --with-lg-tiny-min options, which can be used to tweak page and size class
  834     settings.  Impacts:
  835     + Worst case performance for incrementally growing/shrinking reallocation
  836       is improved because there are far fewer size classes, and therefore
  837       copying happens less often.
  838     + Internal fragmentation is limited to 20% for all but the smallest size
  839       classes (those less than four times the quantum).  (1B + 4 KiB)
  840       and (1B + 4 MiB) previously suffered nearly 50% internal fragmentation.
  841     + Chunk fragmentation tends to be lower because there are fewer distinct run
  842       sizes to pack.
  843   - Add support for explicit tcaches.  The "tcache.create", "tcache.flush", and
  844     "tcache.destroy" mallctls control tcache lifetime and flushing, and the
  845     MALLOCX_TCACHE(tc) and MALLOCX_TCACHE_NONE flags to the *allocx() API
  846     control which tcache is used for each operation.
  847   - Implement per thread heap profiling, as well as the ability to
  848     enable/disable heap profiling on a per thread basis.  Add the "prof.reset",
  849     "prof.lg_sample", "thread.prof.name", "thread.prof.active",
  850     "opt.prof_thread_active_init", "prof.thread_active_init", and
  851     "thread.prof.active" mallctls.
  852   - Add support for per arena application-specified chunk allocators, configured
  853     via the "arena.<i>.chunk_hooks" mallctl.
  854   - Refactor huge allocation to be managed by arenas, so that arenas now
  855     function as general purpose independent allocators.  This is important in
  856     the context of user-specified chunk allocators, aside from the scalability
  857     benefits.  Related new statistics:
  858     + The "stats.arenas.<i>.huge.allocated", "stats.arenas.<i>.huge.nmalloc",
  859       "stats.arenas.<i>.huge.ndalloc", and "stats.arenas.<i>.huge.nrequests"
  860       mallctls provide high level per arena huge allocation statistics.
  861     + The "arenas.nhchunks", "arenas.hchunk.<i>.size",
  862       "stats.arenas.<i>.hchunks.<j>.nmalloc",
  863       "stats.arenas.<i>.hchunks.<j>.ndalloc",
  864       "stats.arenas.<i>.hchunks.<j>.nrequests", and
  865       "stats.arenas.<i>.hchunks.<j>.curhchunks" mallctls provide per size class
  866       statistics.
  867   - Add the 'util' column to malloc_stats_print() output, which reports the
  868     proportion of available regions that are currently in use for each small
  869     size class.
  870   - Add "alloc" and "free" modes for for junk filling (see the "opt.junk"
  871     mallctl), so that it is possible to separately enable junk filling for
  872     allocation versus deallocation.
  873   - Add the jemalloc-config script, which provides information about how
  874     jemalloc was configured, and how to integrate it into application builds.
  875   - Add metadata statistics, which are accessible via the "stats.metadata",
  876     "stats.arenas.<i>.metadata.mapped", and
  877     "stats.arenas.<i>.metadata.allocated" mallctls.
  878   - Add the "stats.resident" mallctl, which reports the upper limit of
  879     physically resident memory mapped by the allocator.
  880   - Add per arena control over unused dirty page purging, via the
  881     "arenas.lg_dirty_mult", "arena.<i>.lg_dirty_mult", and
  882     "stats.arenas.<i>.lg_dirty_mult" mallctls.
  883   - Add the "prof.gdump" mallctl, which makes it possible to toggle the gdump
  884     feature on/off during program execution.
  885   - Add sdallocx(), which implements sized deallocation.  The primary
  886     optimization over dallocx() is the removal of a metadata read, which often
  887     suffers an L1 cache miss.
  888   - Add missing header includes in jemalloc/jemalloc.h, so that applications
  889     only have to #include <jemalloc/jemalloc.h>.
  890   - Add support for additional platforms:
  891     + Bitrig
  892     + Cygwin
  893     + DragonFlyBSD
  894     + iOS
  895     + OpenBSD
  896     + OpenRISC/or1k
  897 
  898   Optimizations:
  899   - Maintain dirty runs in per arena LRUs rather than in per arena trees of
  900     dirty-run-containing chunks.  In practice this change significantly reduces
  901     dirty page purging volume.
  902   - Integrate whole chunks into the unused dirty page purging machinery.  This
  903     reduces the cost of repeated huge allocation/deallocation, because it
  904     effectively introduces a cache of chunks.
  905   - Split the arena chunk map into two separate arrays, in order to increase
  906     cache locality for the frequently accessed bits.
  907   - Move small run metadata out of runs, into arena chunk headers.  This reduces
  908     run fragmentation, smaller runs reduce external fragmentation for small size
  909     classes, and packed (less uniformly aligned) metadata layout improves CPU
  910     cache set distribution.
  911   - Randomly distribute large allocation base pointer alignment relative to page
  912     boundaries in order to more uniformly utilize CPU cache sets.  This can be
  913     disabled via the --disable-cache-oblivious configure option, and queried via
  914     the "config.cache_oblivious" mallctl.
  915   - Micro-optimize the fast paths for the public API functions.
  916   - Refactor thread-specific data to reside in a single structure.  This assures
  917     that only a single TLS read is necessary per call into the public API.
  918   - Implement in-place huge allocation growing and shrinking.
  919   - Refactor rtree (radix tree for chunk lookups) to be lock-free, and make
  920     additional optimizations that reduce maximum lookup depth to one or two
  921     levels.  This resolves what was a concurrency bottleneck for per arena huge
  922     allocation, because a global data structure is critical for determining
  923     which arenas own which huge allocations.
  924 
  925   Incompatible changes:
  926   - Replace --enable-cc-silence with --disable-cc-silence to suppress spurious
  927     warnings by default.
  928   - Assure that the constness of malloc_usable_size()'s return type matches that
  929     of the system implementation.
  930   - Change the heap profile dump format to support per thread heap profiling,
  931     rename pprof to jeprof, and enhance it with the --thread=<n> option.  As a
  932     result, the bundled jeprof must now be used rather than the upstream
  933     (gperftools) pprof.
  934   - Disable "opt.prof_final" by default, in order to avoid atexit(3), which can
  935     internally deadlock on some platforms.
  936   - Change the "arenas.nlruns" mallctl type from size_t to unsigned.
  937   - Replace the "stats.arenas.<i>.bins.<j>.allocated" mallctl with
  938     "stats.arenas.<i>.bins.<j>.curregs".
  939   - Ignore MALLOC_CONF in set{uid,gid,cap} binaries.
  940   - Ignore MALLOCX_ARENA(a) in dallocx(), in favor of using the
  941     MALLOCX_TCACHE(tc) and MALLOCX_TCACHE_NONE flags to control tcache usage.
  942 
  943   Removed features:
  944   - Remove the *allocm() API, which is superseded by the *allocx() API.
  945   - Remove the --enable-dss options, and make dss non-optional on all platforms
  946     which support sbrk(2).
  947   - Remove the "arenas.purge" mallctl, which was obsoleted by the
  948     "arena.<i>.purge" mallctl in 3.1.0.
  949   - Remove the unnecessary "opt.valgrind" mallctl; jemalloc automatically
  950     detects whether it is running inside Valgrind.
  951   - Remove the "stats.huge.allocated", "stats.huge.nmalloc", and
  952     "stats.huge.ndalloc" mallctls.
  953   - Remove the --enable-mremap option.
  954   - Remove the "stats.chunks.current", "stats.chunks.total", and
  955     "stats.chunks.high" mallctls.
  956 
  957   Bug fixes:
  958   - Fix the cactive statistic to decrease (rather than increase) when active
  959     memory decreases.  This regression was first released in 3.5.0.
  960   - Fix OOM handling in memalign() and valloc().  A variant of this bug existed
  961     in all releases since 2.0.0, which introduced these functions.
  962   - Fix an OOM-related regression in arena_tcache_fill_small(), which could
  963     cause cache corruption on OOM.  This regression was present in all releases
  964     from 2.2.0 through 3.6.0.
  965   - Fix size class overflow handling for malloc(), posix_memalign(), memalign(),
  966     calloc(), and realloc() when profiling is enabled.
  967   - Fix the "arena.<i>.dss" mallctl to return an error if "primary" or
  968     "secondary" precedence is specified, but sbrk(2) is not supported.
  969   - Fix fallback lg_floor() implementations to handle extremely large inputs.
  970   - Ensure the default purgeable zone is after the default zone on OS X.
  971   - Fix latent bugs in atomic_*().
  972   - Fix the "arena.<i>.dss" mallctl to handle read-only calls.
  973   - Fix tls_model configuration to enable the initial-exec model when possible.
  974   - Mark malloc_conf as a weak symbol so that the application can override it.
  975   - Correctly detect glibc's adaptive pthread mutexes.
  976   - Fix the --without-export configure option.
  977 
  978 * 3.6.0 (March 31, 2014)
  979 
  980   This version contains a critical bug fix for a regression present in 3.5.0 and
  981   3.5.1.
  982 
  983   Bug fixes:
  984   - Fix a regression in arena_chunk_alloc() that caused crashes during
  985     small/large allocation if chunk allocation failed.  In the absence of this
  986     bug, chunk allocation failure would result in allocation failure, e.g.  NULL
  987     return from malloc().  This regression was introduced in 3.5.0.
  988   - Fix backtracing for gcc intrinsics-based backtracing by specifying
  989     -fno-omit-frame-pointer to gcc.  Note that the application (and all the
  990     libraries it links to) must also be compiled with this option for
  991     backtracing to be reliable.
  992   - Use dss allocation precedence for huge allocations as well as small/large
  993     allocations.
  994   - Fix test assertion failure message formatting.  This bug did not manifest on
  995     x86_64 systems because of implementation subtleties in va_list.
  996   - Fix inconsequential test failures for hash and SFMT code.
  997 
  998   New features:
  999   - Support heap profiling on FreeBSD.  This feature depends on the proc
 1000     filesystem being mounted during heap profile dumping.
 1001 
 1002 * 3.5.1 (February 25, 2014)
 1003 
 1004   This version primarily addresses minor bugs in test code.
 1005 
 1006   Bug fixes:
 1007   - Configure Solaris/Illumos to use MADV_FREE.
 1008   - Fix junk filling for mremap(2)-based huge reallocation.  This is only
 1009     relevant if configuring with the --enable-mremap option specified.
 1010   - Avoid compilation failure if 'restrict' C99 keyword is not supported by the
 1011     compiler.
 1012   - Add a configure test for SSE2 rather than assuming it is usable on i686
 1013     systems.  This fixes test compilation errors, especially on 32-bit Linux
 1014     systems.
 1015   - Fix mallctl argument size mismatches (size_t vs. uint64_t) in the stats unit
 1016     test.
 1017   - Fix/remove flawed alignment-related overflow tests.
 1018   - Prevent compiler optimizations that could change backtraces in the
 1019     prof_accum unit test.
 1020 
 1021 * 3.5.0 (January 22, 2014)
 1022 
 1023   This version focuses on refactoring and automated testing, though it also
 1024   includes some non-trivial heap profiling optimizations not mentioned below.
 1025 
 1026   New features:
 1027   - Add the *allocx() API, which is a successor to the experimental *allocm()
 1028     API.  The *allocx() functions are slightly simpler to use because they have
 1029     fewer parameters, they directly return the results of primary interest, and
 1030     mallocx()/rallocx() avoid the strict aliasing pitfall that
 1031     allocm()/rallocm() share with posix_memalign().  Note that *allocm() is
 1032     slated for removal in the next non-bugfix release.
 1033   - Add support for LinuxThreads.
 1034 
 1035   Bug fixes:
 1036   - Unless heap profiling is enabled, disable floating point code and don't link
 1037     with libm.  This, in combination with e.g. EXTRA_CFLAGS=-mno-sse on x64
 1038     systems, makes it possible to completely disable floating point register
 1039     use.  Some versions of glibc neglect to save/restore caller-saved floating
 1040     point registers during dynamic lazy symbol loading, and the symbol loading
 1041     code uses whatever malloc the application happens to have linked/loaded
 1042     with, the result being potential floating point register corruption.
 1043   - Report ENOMEM rather than EINVAL if an OOM occurs during heap profiling
 1044     backtrace creation in imemalign().  This bug impacted posix_memalign() and
 1045     aligned_alloc().
 1046   - Fix a file descriptor leak in a prof_dump_maps() error path.
 1047   - Fix prof_dump() to close the dump file descriptor for all relevant error
 1048     paths.
 1049   - Fix rallocm() to use the arena specified by the ALLOCM_ARENA(s) flag for
 1050     allocation, not just deallocation.
 1051   - Fix a data race for large allocation stats counters.
 1052   - Fix a potential infinite loop during thread exit.  This bug occurred on
 1053     Solaris, and could affect other platforms with similar pthreads TSD
 1054     implementations.
 1055   - Don't junk-fill reallocations unless usable size changes.  This fixes a
 1056     violation of the *allocx()/*allocm() semantics.
 1057   - Fix growing large reallocation to junk fill new space.
 1058   - Fix huge deallocation to junk fill when munmap is disabled.
 1059   - Change the default private namespace prefix from empty to je_, and change
 1060     --with-private-namespace-prefix so that it prepends an additional prefix
 1061     rather than replacing je_.  This reduces the likelihood of applications
 1062     which statically link jemalloc experiencing symbol name collisions.
 1063   - Add missing private namespace mangling (relevant when
 1064     --with-private-namespace is specified).
 1065   - Add and use JEMALLOC_INLINE_C so that static inline functions are marked as
 1066     static even for debug builds.
 1067   - Add a missing mutex unlock in a malloc_init_hard() error path.  In practice
 1068     this error path is never executed.
 1069   - Fix numerous bugs in malloc_strotumax() error handling/reporting.  These
 1070     bugs had no impact except for malformed inputs.
 1071   - Fix numerous bugs in malloc_snprintf().  These bugs were not exercised by
 1072     existing calls, so they had no impact.
 1073 
 1074 * 3.4.1 (October 20, 2013)
 1075 
 1076   Bug fixes:
 1077   - Fix a race in the "arenas.extend" mallctl that could cause memory corruption
 1078     of internal data structures and subsequent crashes.
 1079   - Fix Valgrind integration flaws that caused Valgrind warnings about reads of
 1080     uninitialized memory in:
 1081     + arena chunk headers
 1082     + internal zero-initialized data structures (relevant to tcache and prof
 1083       code)
 1084   - Preserve errno during the first allocation.  A readlink(2) call during
 1085     initialization fails unless /etc/malloc.conf exists, so errno was typically
 1086     set during the first allocation prior to this fix.
 1087   - Fix compilation warnings reported by gcc 4.8.1.
 1088 
 1089 * 3.4.0 (June 2, 2013)
 1090 
 1091   This version is essentially a small bugfix release, but the addition of
 1092   aarch64 support requires that the minor version be incremented.
 1093 
 1094   Bug fixes:
 1095   - Fix race-triggered deadlocks in chunk_record().  These deadlocks were
 1096     typically triggered by multiple threads concurrently deallocating huge
 1097     objects.
 1098 
 1099   New features:
 1100   - Add support for the aarch64 architecture.
 1101 
 1102 * 3.3.1 (March 6, 2013)
 1103 
 1104   This version fixes bugs that are typically encountered only when utilizing
 1105   custom run-time options.
 1106 
 1107   Bug fixes:
 1108   - Fix a locking order bug that could cause deadlock during fork if heap
 1109     profiling were enabled.
 1110   - Fix a chunk recycling bug that could cause the allocator to lose track of
 1111     whether a chunk was zeroed.  On FreeBSD, NetBSD, and OS X, it could cause
 1112     corruption if allocating via sbrk(2) (unlikely unless running with the
 1113     "dss:primary" option specified).  This was completely harmless on Linux
 1114     unless using mlockall(2) (and unlikely even then, unless the
 1115     --disable-munmap configure option or the "dss:primary" option was
 1116     specified).  This regression was introduced in 3.1.0 by the
 1117     mlockall(2)/madvise(2) interaction fix.
 1118   - Fix TLS-related memory corruption that could occur during thread exit if the
 1119     thread never allocated memory.  Only the quarantine and prof facilities were
 1120     susceptible.
 1121   - Fix two quarantine bugs:
 1122     + Internal reallocation of the quarantined object array leaked the old
 1123       array.
 1124     + Reallocation failure for internal reallocation of the quarantined object
 1125       array (very unlikely) resulted in memory corruption.
 1126   - Fix Valgrind integration to annotate all internally allocated memory in a
 1127     way that keeps Valgrind happy about internal data structure access.
 1128   - Fix building for s390 systems.
 1129 
 1130 * 3.3.0 (January 23, 2013)
 1131 
 1132   This version includes a few minor performance improvements in addition to the
 1133   listed new features and bug fixes.
 1134 
 1135   New features:
 1136   - Add clipping support to lg_chunk option processing.
 1137   - Add the --enable-ivsalloc option.
 1138   - Add the --without-export option.
 1139   - Add the --disable-zone-allocator option.
 1140 
 1141   Bug fixes:
 1142   - Fix "arenas.extend" mallctl to output the number of arenas.
 1143   - Fix chunk_recycle() to unconditionally inform Valgrind that returned memory
 1144     is undefined.
 1145   - Fix build break on FreeBSD related to alloca.h.
 1146 
 1147 * 3.2.0 (November 9, 2012)
 1148 
 1149   In addition to a couple of bug fixes, this version modifies page run
 1150   allocation and dirty page purging algorithms in order to better control
 1151   page-level virtual memory fragmentation.
 1152 
 1153   Incompatible changes:
 1154   - Change the "opt.lg_dirty_mult" default from 5 to 3 (32:1 to 8:1).
 1155 
 1156   Bug fixes:
 1157   - Fix dss/mmap allocation precedence code to use recyclable mmap memory only
 1158     after primary dss allocation fails.
 1159   - Fix deadlock in the "arenas.purge" mallctl.  This regression was introduced
 1160     in 3.1.0 by the addition of the "arena.<i>.purge" mallctl.
 1161 
 1162 * 3.1.0 (October 16, 2012)
 1163 
 1164   New features:
 1165   - Auto-detect whether running inside Valgrind, thus removing the need to
 1166     manually specify MALLOC_CONF=valgrind:true.
 1167   - Add the "arenas.extend" mallctl, which allows applications to create
 1168     manually managed arenas.
 1169   - Add the ALLOCM_ARENA() flag for {,r,d}allocm().
 1170   - Add the "opt.dss", "arena.<i>.dss", and "stats.arenas.<i>.dss" mallctls,
 1171     which provide control over dss/mmap precedence.
 1172   - Add the "arena.<i>.purge" mallctl, which obsoletes "arenas.purge".
 1173   - Define LG_QUANTUM for hppa.
 1174 
 1175   Incompatible changes:
 1176   - Disable tcache by default if running inside Valgrind, in order to avoid
 1177     making unallocated objects appear reachable to Valgrind.
 1178   - Drop const from malloc_usable_size() argument on Linux.
 1179 
 1180   Bug fixes:
 1181   - Fix heap profiling crash if sampled object is freed via realloc(p, 0).
 1182   - Remove const from __*_hook variable declarations, so that glibc can modify
 1183     them during process forking.
 1184   - Fix mlockall(2)/madvise(2) interaction.
 1185   - Fix fork(2)-related deadlocks.
 1186   - Fix error return value for "thread.tcache.enabled" mallctl.
 1187 
 1188 * 3.0.0 (May 11, 2012)
 1189 
 1190   Although this version adds some major new features, the primary focus is on
 1191   internal code cleanup that facilitates maintainability and portability, most
 1192   of which is not reflected in the ChangeLog.  This is the first release to
 1193   incorporate substantial contributions from numerous other developers, and the
 1194   result is a more broadly useful allocator (see the git revision history for
 1195   contribution details).  Note that the license has been unified, thanks to
 1196   Facebook granting a license under the same terms as the other copyright
 1197   holders (see COPYING).
 1198 
 1199   New features:
 1200   - Implement Valgrind support, redzones, and quarantine.
 1201   - Add support for additional platforms:
 1202     + FreeBSD
 1203     + Mac OS X Lion
 1204     + MinGW
 1205     + Windows (no support yet for replacing the system malloc)
 1206   - Add support for additional architectures:
 1207     + MIPS
 1208     + SH4
 1209     + Tilera
 1210   - Add support for cross compiling.
 1211   - Add nallocm(), which rounds a request size up to the nearest size class
 1212     without actually allocating.
 1213   - Implement aligned_alloc() (blame C11).
 1214   - Add the "thread.tcache.enabled" mallctl.
 1215   - Add the "opt.prof_final" mallctl.
 1216   - Update pprof (from gperftools 2.0).
 1217   - Add the --with-mangling option.
 1218   - Add the --disable-experimental option.
 1219   - Add the --disable-munmap option, and make it the default on Linux.
 1220   - Add the --enable-mremap option, which disables use of mremap(2) by default.
 1221 
 1222   Incompatible changes:
 1223   - Enable stats by default.
 1224   - Enable fill by default.
 1225   - Disable lazy locking by default.
 1226   - Rename the "tcache.flush" mallctl to "thread.tcache.flush".
 1227   - Rename the "arenas.pagesize" mallctl to "arenas.page".
 1228   - Change the "opt.lg_prof_sample" default from 0 to 19 (1 B to 512 KiB).
 1229   - Change the "opt.prof_accum" default from true to false.
 1230 
 1231   Removed features:
 1232   - Remove the swap feature, including the "config.swap", "swap.avail",
 1233     "swap.prezeroed", "swap.nfds", and "swap.fds" mallctls.
 1234   - Remove highruns statistics, including the
 1235     "stats.arenas.<i>.bins.<j>.highruns" and
 1236     "stats.arenas.<i>.lruns.<j>.highruns" mallctls.
 1237   - As part of small size class refactoring, remove the "opt.lg_[qc]space_max",
 1238     "arenas.cacheline", "arenas.subpage", "arenas.[tqcs]space_{min,max}", and
 1239     "arenas.[tqcs]bins" mallctls.
 1240   - Remove the "arenas.chunksize" mallctl.
 1241   - Remove the "opt.lg_prof_tcmax" option.
 1242   - Remove the "opt.lg_prof_bt_max" option.
 1243   - Remove the "opt.lg_tcache_gc_sweep" option.
 1244   - Remove the --disable-tiny option, including the "config.tiny" mallctl.
 1245   - Remove the --enable-dynamic-page-shift configure option.
 1246   - Remove the --enable-sysv configure option.
 1247 
 1248   Bug fixes:
 1249   - Fix a statistics-related bug in the "thread.arena" mallctl that could cause
 1250     invalid statistics and crashes.
 1251   - Work around TLS deallocation via free() on Linux.  This bug could cause
 1252     write-after-free memory corruption.
 1253   - Fix a potential deadlock that could occur during interval- and
 1254     growth-triggered heap profile dumps.
 1255   - Fix large calloc() zeroing bugs due to dropping chunk map unzeroed flags.
 1256   - Fix chunk_alloc_dss() to stop claiming memory is zeroed.  This bug could
 1257     cause memory corruption and crashes with --enable-dss specified.
 1258   - Fix fork-related bugs that could cause deadlock in children between fork
 1259     and exec.
 1260   - Fix malloc_stats_print() to honor 'b' and 'l' in the opts parameter.
 1261   - Fix realloc(p, 0) to act like free(p).
 1262   - Do not enforce minimum alignment in memalign().
 1263   - Check for NULL pointer in malloc_usable_size().
 1264   - Fix an off-by-one heap profile statistics bug that could be observed in
 1265     interval- and growth-triggered heap profiles.
 1266   - Fix the "epoch" mallctl to update cached stats even if the passed in epoch
 1267     is 0.
 1268   - Fix bin->runcur management to fix a layout policy bug.  This bug did not
 1269     affect correctness.
 1270   - Fix a bug in choose_arena_hard() that potentially caused more arenas to be
 1271     initialized than necessary.
 1272   - Add missing "opt.lg_tcache_max" mallctl implementation.
 1273   - Use glibc allocator hooks to make mixed allocator usage less likely.
 1274   - Fix build issues for --disable-tcache.
 1275   - Don't mangle pthread_create() when --with-private-namespace is specified.
 1276 
 1277 * 2.2.5 (November 14, 2011)
 1278 
 1279   Bug fixes:
 1280   - Fix huge_ralloc() race when using mremap(2).  This is a serious bug that
 1281     could cause memory corruption and/or crashes.
 1282   - Fix huge_ralloc() to maintain chunk statistics.
 1283   - Fix malloc_stats_print(..., "a") output.
 1284 
 1285 * 2.2.4 (November 5, 2011)
 1286 
 1287   Bug fixes:
 1288   - Initialize arenas_tsd before using it.  This bug existed for 2.2.[0-3], as
 1289     well as for --disable-tls builds in earlier releases.
 1290   - Do not assume a 4 KiB page size in test/rallocm.c.
 1291 
 1292 * 2.2.3 (August 31, 2011)
 1293 
 1294   This version fixes numerous bugs related to heap profiling.
 1295 
 1296   Bug fixes:
 1297   - Fix a prof-related race condition.  This bug could cause memory corruption,
 1298     but only occurred in non-default configurations (prof_accum:false).
 1299   - Fix off-by-one backtracing issues (make sure that prof_alloc_prep() is
 1300     excluded from backtraces).
 1301   - Fix a prof-related bug in realloc() (only triggered by OOM errors).
 1302   - Fix prof-related bugs in allocm() and rallocm().
 1303   - Fix prof_tdata_cleanup() for --disable-tls builds.
 1304   - Fix a relative include path, to fix objdir builds.
 1305 
 1306 * 2.2.2 (July 30, 2011)
 1307 
 1308   Bug fixes:
 1309   - Fix a build error for --disable-tcache.
 1310   - Fix assertions in arena_purge() (for real this time).
 1311   - Add the --with-private-namespace option.  This is a workaround for symbol
 1312     conflicts that can inadvertently arise when using static libraries.
 1313 
 1314 * 2.2.1 (March 30, 2011)
 1315 
 1316   Bug fixes:
 1317   - Implement atomic operations for x86/x64.  This fixes compilation failures
 1318     for versions of gcc that are still in wide use.
 1319   - Fix an assertion in arena_purge().
 1320 
 1321 * 2.2.0 (March 22, 2011)
 1322 
 1323   This version incorporates several improvements to algorithms and data
 1324   structures that tend to reduce fragmentation and increase speed.
 1325 
 1326   New features:
 1327   - Add the "stats.cactive" mallctl.
 1328   - Update pprof (from google-perftools 1.7).
 1329   - Improve backtracing-related configuration logic, and add the
 1330     --disable-prof-libgcc option.
 1331 
 1332   Bug fixes:
 1333   - Change default symbol visibility from "internal", to "hidden", which
 1334     decreases the overhead of library-internal function calls.
 1335   - Fix symbol visibility so that it is also set on OS X.
 1336   - Fix a build dependency regression caused by the introduction of the .pic.o
 1337     suffix for PIC object files.
 1338   - Add missing checks for mutex initialization failures.
 1339   - Don't use libgcc-based backtracing except on x64, where it is known to work.
 1340   - Fix deadlocks on OS X that were due to memory allocation in
 1341     pthread_mutex_lock().
 1342   - Heap profiling-specific fixes:
 1343     + Fix memory corruption due to integer overflow in small region index
 1344       computation, when using a small enough sample interval that profiling
 1345       context pointers are stored in small run headers.
 1346     + Fix a bootstrap ordering bug that only occurred with TLS disabled.
 1347     + Fix a rallocm() rsize bug.
 1348     + Fix error detection bugs for aligned memory allocation.
 1349 
 1350 * 2.1.3 (March 14, 2011)
 1351 
 1352   Bug fixes:
 1353   - Fix a cpp logic regression (due to the "thread.{de,}allocatedp" mallctl fix
 1354     for OS X in 2.1.2).
 1355   - Fix a "thread.arena" mallctl bug.
 1356   - Fix a thread cache stats merging bug.
 1357 
 1358 * 2.1.2 (March 2, 2011)
 1359 
 1360   Bug fixes:
 1361   - Fix "thread.{de,}allocatedp" mallctl for OS X.
 1362   - Add missing jemalloc.a to build system.
 1363 
 1364 * 2.1.1 (January 31, 2011)
 1365 
 1366   Bug fixes:
 1367   - Fix aligned huge reallocation (affected allocm()).
 1368   - Fix the ALLOCM_LG_ALIGN macro definition.
 1369   - Fix a heap dumping deadlock.
 1370   - Fix a "thread.arena" mallctl bug.
 1371 
 1372 * 2.1.0 (December 3, 2010)
 1373 
 1374   This version incorporates some optimizations that can't quite be considered
 1375   bug fixes.
 1376 
 1377   New features:
 1378   - Use Linux's mremap(2) for huge object reallocation when possible.
 1379   - Avoid locking in mallctl*() when possible.
 1380   - Add the "thread.[de]allocatedp" mallctl's.
 1381   - Convert the manual page source from roff to DocBook, and generate both roff
 1382     and HTML manuals.
 1383 
 1384   Bug fixes:
 1385   - Fix a crash due to incorrect bootstrap ordering.  This only impacted
 1386     --enable-debug --enable-dss configurations.
 1387   - Fix a minor statistics bug for mallctl("swap.avail", ...).
 1388 
 1389 * 2.0.1 (October 29, 2010)
 1390 
 1391   Bug fixes:
 1392   - Fix a race condition in heap profiling that could cause undefined behavior
 1393     if "opt.prof_accum" were disabled.
 1394   - Add missing mutex unlocks for some OOM error paths in the heap profiling
 1395     code.
 1396   - Fix a compilation error for non-C99 builds.
 1397 
 1398 * 2.0.0 (October 24, 2010)
 1399 
 1400   This version focuses on the experimental *allocm() API, and on improved
 1401   run-time configuration/introspection.  Nonetheless, numerous performance
 1402   improvements are also included.
 1403 
 1404   New features:
 1405   - Implement the experimental {,r,s,d}allocm() API, which provides a superset
 1406     of the functionality available via malloc(), calloc(), posix_memalign(),
 1407     realloc(), malloc_usable_size(), and free().  These functions can be used to
 1408     allocate/reallocate aligned zeroed memory, ask for optional extra memory
 1409     during reallocation, prevent object movement during reallocation, etc.
 1410   - Replace JEMALLOC_OPTIONS/JEMALLOC_PROF_PREFIX with MALLOC_CONF, which is
 1411     more human-readable, and more flexible.  For example:
 1412       JEMALLOC_OPTIONS=AJP
 1413     is now:
 1414       MALLOC_CONF=abort:true,fill:true,stats_print:true
 1415   - Port to Apple OS X.  Sponsored by Mozilla.
 1416   - Make it possible for the application to control thread-->arena mappings via
 1417     the "thread.arena" mallctl.
 1418   - Add compile-time support for all TLS-related functionality via pthreads TSD.
 1419     This is mainly of interest for OS X, which does not support TLS, but has a
 1420     TSD implementation with similar performance.
 1421   - Override memalign() and valloc() if they are provided by the system.
 1422   - Add the "arenas.purge" mallctl, which can be used to synchronously purge all
 1423     dirty unused pages.
 1424   - Make cumulative heap profiling data optional, so that it is possible to
 1425     limit the amount of memory consumed by heap profiling data structures.
 1426   - Add per thread allocation counters that can be accessed via the
 1427     "thread.allocated" and "thread.deallocated" mallctls.
 1428 
 1429   Incompatible changes:
 1430   - Remove JEMALLOC_OPTIONS and malloc_options (see MALLOC_CONF above).
 1431   - Increase default backtrace depth from 4 to 128 for heap profiling.
 1432   - Disable interval-based profile dumps by default.
 1433 
 1434   Bug fixes:
 1435   - Remove bad assertions in fork handler functions.  These assertions could
 1436     cause aborts for some combinations of configure settings.
 1437   - Fix strerror_r() usage to deal with non-standard semantics in GNU libc.
 1438   - Fix leak context reporting.  This bug tended to cause the number of contexts
 1439     to be underreported (though the reported number of objects and bytes were
 1440     correct).
 1441   - Fix a realloc() bug for large in-place growing reallocation.  This bug could
 1442     cause memory corruption, but it was hard to trigger.
 1443   - Fix an allocation bug for small allocations that could be triggered if
 1444     multiple threads raced to create a new run of backing pages.
 1445   - Enhance the heap profiler to trigger samples based on usable size, rather
 1446     than request size.
 1447   - Fix a heap profiling bug due to sometimes losing track of requested object
 1448     size for sampled objects.
 1449 
 1450 * 1.0.3 (August 12, 2010)
 1451 
 1452   Bug fixes:
 1453   - Fix the libunwind-based implementation of stack backtracing (used for heap
 1454     profiling).  This bug could cause zero-length backtraces to be reported.
 1455   - Add a missing mutex unlock in library initialization code.  If multiple
 1456     threads raced to initialize malloc, some of them could end up permanently
 1457     blocked.
 1458 
 1459 * 1.0.2 (May 11, 2010)
 1460 
 1461   Bug fixes:
 1462   - Fix junk filling of large objects, which could cause memory corruption.
 1463   - Add MAP_NORESERVE support for chunk mapping, because otherwise virtual
 1464     memory limits could cause swap file configuration to fail.  Contributed by
 1465     Jordan DeLong.
 1466 
 1467 * 1.0.1 (April 14, 2010)
 1468 
 1469   Bug fixes:
 1470   - Fix compilation when --enable-fill is specified.
 1471   - Fix threads-related profiling bugs that affected accuracy and caused memory
 1472     to be leaked during thread exit.
 1473   - Fix dirty page purging race conditions that could cause crashes.
 1474   - Fix crash in tcache flushing code during thread destruction.
 1475 
 1476 * 1.0.0 (April 11, 2010)
 1477 
 1478   This release focuses on speed and run-time introspection.  Numerous
 1479   algorithmic improvements make this release substantially faster than its
 1480   predecessors.
 1481 
 1482   New features:
 1483   - Implement autoconf-based configuration system.
 1484   - Add mallctl*(), for the purposes of introspection and run-time
 1485     configuration.
 1486   - Make it possible for the application to manually flush a thread's cache, via
 1487     the "tcache.flush" mallctl.
 1488   - Base maximum dirty page count on proportion of active memory.
 1489   - Compute various additional run-time statistics, including per size class
 1490     statistics for large objects.
 1491   - Expose malloc_stats_print(), which can be called repeatedly by the
 1492     application.
 1493   - Simplify the malloc_message() signature to only take one string argument,
 1494     and incorporate an opaque data pointer argument for use by the application
 1495     in combination with malloc_stats_print().
 1496   - Add support for allocation backed by one or more swap files, and allow the
 1497     application to disable over-commit if swap files are in use.
 1498   - Implement allocation profiling and leak checking.
 1499 
 1500   Removed features:
 1501   - Remove the dynamic arena rebalancing code, since thread-specific caching
 1502     reduces its utility.
 1503 
 1504   Bug fixes:
 1505   - Modify chunk allocation to work when address space layout randomization
 1506     (ASLR) is in use.
 1507   - Fix thread cleanup bugs related to TLS destruction.
 1508   - Handle 0-size allocation requests in posix_memalign().
 1509   - Fix a chunk leak.  The leaked chunks were never touched, so this impacted
 1510     virtual memory usage, but not physical memory usage.
 1511 
 1512 * linux_2008082[78]a (August 27/28, 2008)
 1513 
 1514   These snapshot releases are the simple result of incorporating Linux-specific
 1515   support into the FreeBSD malloc sources.
 1516 
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