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