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Jason Evans 2015-02-23 22:28:43 -08:00
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ChangeLog
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@ -5,6 +5,155 @@ found in the git revision history:
https://github.com/jemalloc/jemalloc https://github.com/jemalloc/jemalloc
* 4.0.0 (XXX) See https://github.com/jemalloc/jemalloc/milestones/4.0.0 for
remaining work.
This version contains many speed and space optimizations, both minor and
major. The major themes are generalization, unification, and simplification.
Although many of these optimizations cause no visible behavior change, their
cumulative effect is substantial.
New features:
- Normalize size class spacing to be consistent across the complete size
range. By default there are four size classes per size doubling, but this
is now configurable via the --with-lg-size-class-group option. Also add the
--with-lg-page, --with-lg-page-sizes, --with-lg-quantum, and
--with-lg-tiny-min options, which can be used to tweak page and size class
settings. Impacts:
+ Worst case performance for incrementally growing/shrinking reallocation
is improved because there are far fewer size classes, and therefore
copying happens less often.
+ Internal fragmentation is limited to 20% for all but the smallest size
classes (those less than four times the quantum). (1B + 4 KiB)
and (1B + 4 MiB) previously suffered nearly 50% internal fragmentation.
+ Chunk fragmentation tends to be lower because there are fewer distinct run
sizes to pack.
- Add support for explicit tcaches. The "tcache.create", "tcache.flush", and
"tcache.destroy" mallctls control tcache lifetime and flushing, and the
MALLOCX_TCACHE(tc) and MALLOCX_TCACHE_NONE flags to the *allocx() API
control which tcache is used for each operation.
- Implement per thread heap profiling, as well as the ability to
enable/disable heap profiling on a per thread basis. Add the "prof.reset",
"prof.lg_sample", "thread.prof.name", "thread.prof.active",
"opt.prof_thread_active_init", "prof.thread_active_init", and
"thread.prof.active" mallctls.
- Add support for per arena application-specified chunk allocators, configured
via the "arena<i>.chunk.alloc" and "arena<i>.chunk.dalloc" mallctls.
- Refactor huge allocation to be managed by arenas, so that arenas now
function as general purpose independent allocators. This is important in
the context of user-specified chunk allocators, aside from the scalability
benefits. Related new statistics:
+ The "stats.arenas.<i>.huge.allocated", "stats.arenas.<i>.huge.nmalloc",
"stats.arenas.<i>.huge.ndalloc", and "stats.arenas.<i>.huge.nrequests"
mallctls provide high level per arena huge allocation statistics.
+ The "arenas.nhchunks", "arenas.hchunks.<i>.size",
"stats.arenas.<i>.hchunks.<j>.nmalloc",
"stats.arenas.<i>.hchunks.<j>.ndalloc",
"stats.arenas.<i>.hchunks.<j>.nrequests", and
"stats.arenas.<i>.hchunks.<j>.curhchunks" mallctls provide per size class
statistics.
- Add the 'util' column to malloc_stats_print() output, which reports the
proportion of available regions that are currently in use for each small
size class.
- Add "alloc" and "free" modes for for junk filling (see the "opt.junk"
mallctl), so that it is possible to separately enable junk filling for
allocation versus deallocation.
- Add the jemalloc-config script, which provides information about how
jemalloc was configured, and how to integrate it into application builds.
- Add metadata statistics, which are accessible via the "stats.metadata",
"stats.arenas.<i>.metadata.mapped", and
"stats.arenas.<i>.metadata.allocated" mallctls.
- Add the "prof.gdump" mallctl, which makes it possible to toggle the gdump
feature on/off during program execution.
- Add sdallocx(), which implements sized deallocation. The primary
optimization over dallocx() is the removal of a metadata read, which often
suffers an L1 cache miss.
- Add missing header includes in jemalloc/jemalloc.h, so that applications
only have to #include <jemalloc/jemalloc.h>.
- Add support for additional platforms:
+ Bitrig
+ Cygwin
+ DragonFlyBSD
+ iOS
+ OpenBSD
+ OpenRISC/or1k
Optimizations:
- Switch run and chunk allocation from first-best-fit (among best-fit
candidates, choose the lowest in memory) to first-fit (among all candidates,
choose the lowest in memory). This tends to reduce chunk and virtual memory
fragmentation, respectively.
- Maintain dirty runs in per arena LRUs rather than in per arena trees of
dirty-run-containing chunks. In practice this change significantly reduces
dirty page purging volume.
- Integrate whole chunks into the unused dirty page purging machinery. This
reduces the cost of repeated huge allocation/deallocation, because it
effectively introduces a cache of chunks.
- Split the arena chunk map into two separate arrays, in order to increase
cache locality for the frequently accessed bits.
- Move small run metadata out of runs, into arena chunk headers. This reduces
run fragmentation, smaller runs reduce external fragmentation for small size
classes, and packed (less uniformly aligned) metadata layout improves CPU
cache set distribution.
- Micro-optimize the fast paths for the public API functions.
- Refactor thread-specific data to reside in a single structure. This assures
that only a single TLS read is necessary per call into the public API.
- Implement in-place huge allocation growing and shrinking.
- Refactor rtree (radix tree for chunk lookups) to be lock-free, and make
additional optimizations that reduce maximum lookup depth to one or two
levels. This resolves what was a concurrency bottleneck for per arena huge
allocation, because a global data structure is critical for determining
which arenas own which huge allocations.
Incompatible changes:
- Replace --enable-cc-silence with --disable-cc-silence to suppress spurious
warnings by default.
- Assure that the constness of malloc_usable_size()'s return type matches that
of the system implementation.
- Change the heap profile dump format to support per thread heap profiling,
and enhance pprof with the --thread=<n> option. As a result, the bundled
pprof must now be used rather than the upstream (gperftools) pprof.
- Disable "opt.prof_final" by default, in order to avoid atexit(3), which can
internally deadlock on some platforms.
- Change the "arenas.nlruns" mallctl type from size_t to unsigned.
- Replace the "stats.arenas.<i>.bins.<j>.allocated" mallctl with
"stats.arenas.<i>.bins.<j>.curregs".
- Ignore MALLOC_CONF in set{uid,gid,cap} binaries.
- Ignore MALLOCX_ARENA(a) in dallocx(), in favor of using the
MALLOCX_TCACHE(tc) and MALLOCX_TCACHE_NONE flags to control tcache usage.
Removed features:
- Remove the *allocm() API, which is superseded by the *allocx() API.
- Remove the --enable-dss options, and make dss non-optional on all platforms
which support sbrk(2).
- Remove the "arenas.purge" mallctl, which was obsoleted by the
"arena.<i>.purge" mallctl in 3.1.0.
- Remove the unnecessary "opt.valgrind" mallctl; jemalloc automatically
detects whether it is running inside Valgrind.
- Remove the "stats.huge.allocated", "stats.huge.nmalloc", and
"stats.huge.ndalloc" mallctls.
- Remove the --enable-mremap option.
- Remove the --enable-ivsalloc option, and merge its functionality into
--enable-debug.
- Remove the "stats.chunks.current", "stats.chunks.total", and
"stats.chunks.high" mallctls.
Bug fixes:
- Fix the cactive statistic to decrease (rather than increase) when active
memory decreases. This regression was first released in 3.5.0.
- Fix OOM handling in memalign() and valloc(). A variant of this bug existed
in all releases since 2.0.0, which introduced these functions.
- Fix the "arena.<i>.dss" mallctl to return an error if "primary" or
"secondary" precedence is specified, but sbrk(2) is not supported.
- Fix fallback lg_floor() implementations to handle extremely large inputs.
- Ensure the default purgeable zone is after the default zone on OS X.
- Fix latent bugs in atomic_*().
- Fix the "arena.<i>.dss" mallctl to handle read-only calls.
- Fix tls_model configuration to enable the initial-exec model when possible.
- Mark malloc_conf as a weak symbol so that the application can override it.
- Correctly detect glibc's adaptive pthread mutexes.
- Fix the --without-export configure option.
* 3.6.0 (March 31, 2014) * 3.6.0 (March 31, 2014)
This version contains a critical bug fix for a regression present in 3.5.0 and This version contains a critical bug fix for a regression present in 3.5.0 and
@ -21,7 +170,7 @@ found in the git revision history:
backtracing to be reliable. backtracing to be reliable.
- Use dss allocation precedence for huge allocations as well as small/large - Use dss allocation precedence for huge allocations as well as small/large
allocations. allocations.
- Fix test assertion failure message formatting. This bug did not manifect on - Fix test assertion failure message formatting. This bug did not manifest on
x86_64 systems because of implementation subtleties in va_list. x86_64 systems because of implementation subtleties in va_list.
- Fix inconsequential test failures for hash and SFMT code. - Fix inconsequential test failures for hash and SFMT code.