Update ChangeLog for 5.0.0.

Author: jasone

ChangeLog

@@ -4,6 +4,193 @@ brevity.  Much more detail can be found in the git revision history:
 
     https://github.com/jemalloc/jemalloc
 
+* 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
+    + arena.<i>.lg_dirty_mult
+    + arena.<i>.decay_time
+    + arena.<i>.chunk_hooks
+    + arenas.initialized
+    + arenas.lg_dirty_mult
+    + arenas.decay_time
+    + arenas.bin.<i>.run_size
+    + arenas.nlruns
+    + arenas.lrun.<i>.size
+    + arenas.nhchunks
+    + arenas.hchunk.<i>.size
+    + arenas.extend
+    + stats.cactive
+    + stats.arenas.<i>.lg_dirty_mult
+    + stats.arenas.<i>.decay_time
+    + stats.arenas.<i>.metadata.{mapped,allocated}
+    + stats.arenas.<i>.{npurge,nmadvise,purged}
+    + stats.arenas.<i>.huge.{allocated,nmalloc,ndalloc,nrequests}
+    + stats.arenas.<i>.bins.<j>.{nruns,reruns,curruns}
+    + stats.arenas.<i>.lruns.<j>.{nmalloc,ndalloc,nrequests,curruns}
+    + stats.arenas.<i>.hchunks.<j>.{nmalloc,ndalloc,nrequests,curhchunks}
+
+  Bug fixes:
+  - Improve interval-based profile dump triggering to dump only one profile when
+    a single allocation's size exceeds the interval.  (@jasone)
+  - Use prefixed function names (as controlled by --with-jemalloc-prefix) when
+    pruning backtrace frames in jeprof.  (@jasone)
+
 * 4.5.0 (February 28, 2017)
 
   This is the first release to benefit from much broader continuous integration