ChangeLog

Following are change highlights associated with official releases.  Important
bug fixes are all mentioned, but some internal enhancements are omitted here for
brevity.  Much more detail can be found in the git revision history:

    https://github.com/jemalloc/jemalloc

* 5.0.1 (July 1, 2017)

  This bugfix release fixes several issues, most of which are obscure enough
  that typical applications are not impacted.

  Bug fixes:
  - Update decay->nunpurged before purging, in order to avoid potential update
    races and subsequent incorrect purging volume.  (@interwq)
  - Only abort on dlsym(3) error if the failure impacts an enabled feature (lazy
    locking and/or background threads).  This mitigates an initialization
    failure bug for which we still do not have a clear reproduction test case.
    (@interwq)
  - Modify tsd management so that it neither crashes nor leaks if a thread's
    only allocation activity is to call free() after TLS destructors have been
    executed.  This behavior was observed when operating with GNU libc, and is
    unlikely to be an issue with other libc implementations.  (@interwq)
  - Mask signals during background thread creation.  This prevents signals from
    being inadvertently delivered to background threads.  (@jasone,
    @davidgoldblatt, @interwq)
  - Avoid inactivity checks within background threads, in order to prevent
    recursive mutex acquisition.  (@interwq)
  - Fix extent_grow_retained() to use the specified hooks when the
    arena.<i>.extent_hooks mallctl is used to override the default hooks.
    (@interwq)
  - Add missing reentrancy support for custom extent hooks which allocate.
    (@interwq)
  - Post-fork(2), re-initialize the list of tcaches associated with each arena
    to contain no tcaches except the forking thread's.  (@interwq)
  - Add missing post-fork(2) mutex reinitialization for extent_grow_mtx.  This
    fixes potential deadlocks after fork(2).  (@interwq)
  - Enforce minimum autoconf version (currently 2.68), since 2.63 is known to
    generate corrupt configure scripts.  (@jasone)
  - Ensure that the configured page size (--with-lg-page) is no larger than the
    configured huge page size (--with-lg-hugepage).  (@jasone)

* 5.0.0 (June 13, 2017)

  Unlike all previous jemalloc releases, this release does not use naturally
  aligned "chunks" for virtual memory management, and instead uses page-aligned
  "extents".  This change has few externally visible effects, but the internal
  impacts are... extensive.  Many other internal changes combine to make this
  the most cohesively designed version of jemalloc so far, with ample
  opportunity for further enhancements.

  Continuous integration is now an integral aspect of development thanks to the
  efforts of @davidtgoldblatt, and the dev branch tends to remain reasonably
  stable on the tested platforms (Linux, FreeBSD, macOS, and Windows).  As a
  side effect the official release frequency may decrease over time.

  New features:
  - Implement optional per-CPU arena support; threads choose which arena to use
    based on current CPU rather than on fixed thread-->arena associations.
    (@interwq)
  - Implement two-phase decay of unused dirty pages.  Pages transition from
    dirty-->muzzy-->clean, where the first phase transition relies on
    madvise(... MADV_FREE) semantics, and the second phase transition discards
    pages such that they are replaced with demand-zeroed pages on next access.
    (@jasone)
  - Increase decay time resolution from seconds to milliseconds.  (@jasone)
  - Implement opt-in per CPU background threads, and use them for asynchronous
    decay-driven unused dirty page purging.  (@interwq)
  - Add mutex profiling, which collects a variety of statistics useful for
    diagnosing overhead/contention issues.  (@interwq)
  - Add C++ new/delete operator bindings.  (@djwatson)
  - Support manually created arena destruction, such that all data and metadata
    are discarded.  Add MALLCTL_ARENAS_DESTROYED for accessing merged stats
    associated with destroyed arenas.  (@jasone)
  - Add MALLCTL_ARENAS_ALL as a fixed index for use in accessing
    merged/destroyed arena statistics via mallctl.  (@jasone)
  - Add opt.abort_conf to optionally abort if invalid configuration options are
    detected during initialization.  (@interwq)
  - Add opt.stats_print_opts, so that e.g. JSON output can be selected for the
    stats dumped during exit if opt.stats_print is true.  (@jasone)
  - Add --with-version=VERSION for use when embedding jemalloc into another
    project's git repository.  (@jasone)
  - Add --disable-thp to support cross compiling.  (@jasone)
  - Add --with-lg-hugepage to support cross compiling.  (@jasone)
  - Add mallctl interfaces (various authors):
    + background_thread
    + opt.abort_conf
    + opt.retain
    + opt.percpu_arena
    + opt.background_thread
    + opt.{dirty,muzzy}_decay_ms
    + opt.stats_print_opts
    + arena.<i>.initialized
    + arena.<i>.destroy
    + arena.<i>.{dirty,muzzy}_decay_ms
    + arena.<i>.extent_hooks
    + arenas.{dirty,muzzy}_decay_ms
    + arenas.bin.<i>.slab_size
    + arenas.nlextents
    + arenas.lextent.<i>.size
    + arenas.create
    + stats.background_thread.{num_threads,num_runs,run_interval}
    + stats.mutexes.{ctl,background_thread,prof,reset}.
      {num_ops,num_spin_acq,num_wait,max_wait_time,total_wait_time,max_num_thds,
      num_owner_switch}
    + stats.arenas.<i>.{dirty,muzzy}_decay_ms
    + stats.arenas.<i>.uptime
    + stats.arenas.<i>.{pmuzzy,base,internal,resident}
    + stats.arenas.<i>.{dirty,muzzy}_{npurge,nmadvise,purged}
    + stats.arenas.<i>.bins.<j>.{nslabs,reslabs,curslabs}
    + stats.arenas.<i>.bins.<j>.mutex.
      {num_ops,num_spin_acq,num_wait,max_wait_time,total_wait_time,max_num_thds,
      num_owner_switch}
    + stats.arenas.<i>.lextents.<j>.{nmalloc,ndalloc,nrequests,curlextents}
    + stats.arenas.i.mutexes.{large,extent_avail,extents_dirty,extents_muzzy,
      extents_retained,decay_dirty,decay_muzzy,base,tcache_list}.
      {num_ops,num_spin_acq,num_wait,max_wait_time,total_wait_time,max_num_thds,
      num_owner_switch}

  Portability improvements:
  - Improve reentrant allocation support, such that deadlock is less likely if
    e.g. a system library call in turn allocates memory.  (@davidtgoldblatt,
    @interwq)
  - Support static linking of jemalloc with glibc.  (@djwatson)

  Optimizations and refactors:
  - Organize virtual memory as "extents" of virtual memory pages, rather than as
    naturally aligned "chunks", and store all metadata in arbitrarily distant
    locations.  This reduces virtual memory external fragmentation, and will
    interact better with huge pages (not yet explicitly supported).  (@jasone)
  - Fold large and huge size classes together; only small and large size classes
    remain.  (@jasone)
  - Unify the allocation paths, and merge most fast-path branching decisions.
    (@davidtgoldblatt, @interwq)
  - Embed per thread automatic tcache into thread-specific data, which reduces
    conditional branches and dereferences.  Also reorganize tcache to increase
    fast-path data locality.  (@interwq)
  - Rewrite atomics to closely model the C11 API, convert various
    synchronization from mutex-based to atomic, and use the explicit memory
    ordering control to resolve various hypothetical races without increasing
    synchronization overhead.  (@davidtgoldblatt)
  - Extensively optimize rtree via various methods:
    + Add multiple layers of rtree lookup caching, since rtree lookups are now
      part of fast-path deallocation.  (@interwq)
    + Determine rtree layout at compile time.  (@jasone)
    + Make the tree shallower for common configurations.  (@jasone)
    + Embed the root node in the top-level rtree data structure, thus avoiding
      one level of indirection.  (@jasone)
    + Further specialize leaf elements as compared to internal node elements,
      and directly embed extent metadata needed for fast-path deallocation.
      (@jasone)
    + Ignore leading always-zero address bits (architecture-specific).
      (@jasone)
  - Reorganize headers (ongoing work) to make them hermetic, and disentangle
    various module dependencies.  (@davidtgoldblatt)
  - Convert various internal data structures such as size class metadata from
    boot-time-initialized to compile-time-initialized.  Propagate resulting data
    structure simplifications, such as making arena metadata fixed-size.
    (@jasone)
  - Simplify size class lookups when constrained to size classes that are
    multiples of the page size.  This speeds lookups, but the primary benefit is
    complexity reduction in code that was the source of numerous regressions.
    (@jasone)
  - Lock individual extents when possible for localized extent operations,
    rather than relying on a top-level arena lock.  (@davidtgoldblatt, @jasone)
  - Use first fit layout policy instead of best fit, in order to improve
    packing.  (@jasone)
  - If munmap(2) is not in use, use an exponential series to grow each arena's
    virtual memory, so that the number of disjoint virtual memory mappings
    remains low.  (@jasone)
  - Implement per arena base allocators, so that arenas never share any virtual
    memory pages.  (@jasone)
  - Automatically generate private symbol name mangling macros.  (@jasone)

  Incompatible changes:
  - Replace chunk hooks with an expanded/normalized set of extent hooks.
    (@jasone)
  - Remove ratio-based purging.  (@jasone)
  - Remove --disable-tcache.  (@jasone)
  - Remove --disable-tls.  (@jasone)
  - Remove --enable-ivsalloc.  (@jasone)
  - Remove --with-lg-size-class-group.  (@jasone)
  - Remove --with-lg-tiny-min.  (@jasone)
  - Remove --disable-cc-silence.  (@jasone)
  - Remove --enable-code-coverage.  (@jasone)
  - Remove --disable-munmap (replaced by opt.retain).  (@jasone)
  - Remove Valgrind support.  (@jasone)
  - Remove quarantine support.  (@jasone)
  - Remove redzone support.  (@jasone)
  - Remove mallctl interfaces (various authors):
    + config.munmap
    + config.tcache
    + config.tls
    + config.valgrind
    + opt.lg_chunk
    + opt.purge
    + opt.lg_dirty_mult
    + opt.decay_time
    + opt.quarantine
    + opt.redzone
    + opt.thp