This regression was introduced by
97c04a93 (Use first-fit rather than
first-best-fit run/chunk allocation.).

This tends to more effectively pack active memory toward low addresses.
However, additional tree searches are required in many cases, so whether
this change stands the test of time will depend on real-world
benchmarks.

Treat sizes that round down to the same size class as size-equivalent
in trees that are used to search for first best fit, so that there are
only as many "firsts" as there are size classes.  This comes closer to
the ideal of first fit.

Recent changes have improved huge allocation scalability, which removes
upward pressure to set the chunk size so large that huge allocations are
rare.  Smaller chunks are more likely to completely drain, so set the
default to the smallest size that doesn't leave excessive unusable
trailing space in chunk headers.

TlsGetValue has a semantic difference with pthread_getspecific, in that it
can return a non-error NULL value, so it always sets the LastError.
But allocator callers may not be expecting calling e.g. free() to change
the value of the last error, so preserve it.

9906660e added a --without-export configure option to avoid exporting
jemalloc symbols, but the option didn't actually work.

These regressions were introduced by
ee41ad40 (Integrate whole chunks into
unused dirty page purging machinery.).

Rename "dirty chunks" to "cached chunks", in order to avoid overloading
the term "dirty".

Fix the regression caused by 339c2b23
(Fix chunk_unmap() to propagate dirty state.), and actually address what
that change attempted, which is to only purge chunks once, and propagate
whether zeroed pages resulted into chunk_record().

Fix chunk_unmap() to propagate whether a chunk is dirty, and modify
dirty chunk purging to record this information so it can be passed to
chunk_unmap().  Since the broken version of chunk_unmap() claimed that
all chunks were clean, this resulted in potential memory corruption for
purging implementations that do not zero (e.g. MADV_FREE).

This regression was introduced by
ee41ad40 (Integrate whole chunks into
unused dirty page purging machinery.).

Extend per arena unused dirty page purging to manage unused dirty chunks
in aaddtion to unused dirty runs.  Rather than immediately unmapping
deallocated chunks (or purging them in the --disable-munmap case), store
them in a separate set of trees, chunks_[sz]ad_dirty.  Preferrentially
allocate dirty chunks.  When excessive unused dirty pages accumulate,
purge runs and chunks in ingegrated LRU order (and unmap chunks in the
--enable-munmap case).

Refactor extent_node_t to provide accessor functions.

This regression was introduced by
88fef7ce (Refactor huge_*() calls into
arena internals.), and went undetected because of the --enable-debug
regression.

This regression was introduced by
88fef7ce (Refactor huge_*() calls into
arena internals.), and went undetected because of the --enable-debug
regression.

Fix --enable-debug to actually enable debug mode.  This regression was
introduced by cbf3a6d7 (Move centralized
chunk management into arenas.).

Signed-off-by: Abhishek Kulkarni <adkulkar@umail.iu.edu>

Also allow for the possibility that there exists a VERSION
file in the srcroot, in case of building from a release tarball
out of tree.

Although exceedingly unlikely, it appears that writes to the prof_tctx
field of arena_chunk_map_misc_t could be reordered such that a stale
value could be read during deallocation, with profiler metadata
corruption and invalid pointer dereferences being the most likely
effects.

Make redirects to the huge_*() API the arena code's responsibility,
since arenas now take responsibility for all allocation sizes.

8ddc9329 switched this to over using the
address tree in order to avoid false negatives, so it now needs to check
that the size of the free extent is large enough to satisfy the request.

Migrate all centralized data structures related to huge allocations and
recyclable chunks into arena_t, so that each arena can manage huge
allocations and recyclable virtual memory completely independently of
other arenas.

Add chunk node caching to arenas, in order to avoid contention on the
base allocator.

Use chunks_rtree to look up huge allocations rather than a red-black
tree.  Maintain a per arena unsorted list of huge allocations (which
will be needed to enumerate huge allocations during arena reset).

Remove the --enable-ivsalloc option, make ivsalloc() always available,
and use it for size queries if --enable-debug is enabled.  The only
practical implications to this removal are that 1) ivsalloc() is now
always available during live debugging (and the underlying radix tree is
available during core-based debugging), and 2) size query validation can
no longer be enabled independent of --enable-debug.

Remove the stats.chunks.{current,total,high} mallctls, and replace their
underlying statistics with simpler atomically updated counters used
exclusively for gdump triggering.  These statistics are no longer very
useful because each arena manages chunks independently, and per arena
statistics provide similar information.

Simplify chunk synchronization code, now that base chunk allocation
cannot cause recursive lock acquisition.

Fix a serious regression in tcache_bin_flush_small() that was introduced
by 1cb181ed (Implement explicit tcache
support.).

Add the MALLOCX_TCACHE() and MALLOCX_TCACHE_NONE macros, which can be
used in conjunction with the *allocx() API.

Add the tcache.create, tcache.flush, and tcache.destroy mallctls.

This resolves #145.

Fix arena_get() to refresh the cache as needed in the (!init_if_missing
&& refresh_if_missing) case.

This flaw was introduced by the initial arena_get() implementation,
which was part of 8bb3198f (Refactor/fix
arenas manipulation.).

Recent huge allocation refactoring associates huge allocations with
arenas, but it remains necessary to quickly look up huge allocation
metadata during reallocation/deallocation.  A global radix tree remains
a good solution to this problem, but locking would have become the
primary bottleneck after (upcoming) migration of chunk management from
global to per arena data structures.

This lock-free implementation uses double-checked reads to traverse the
tree, so that in the steady state, each read or write requires only a
single atomic operation.

This implementation also assures that no more than two tree levels
actually exist, through a combination of careful virtual memory
allocation which makes large sparse nodes cheap, and skipping the root
node on x64 (possible because the top 16 bits are all 0 in practice).

lg_floor(0) is undefined, but depending on compiler options may not
cause a crash.  This assertion makes it harder to accidentally abuse
lg_floor().

Refactor base_alloc() to guarantee that allocations are carved from
demand-zeroed virtual memory.  This supports sparse data structures such
as multi-page radix tree nodes.

Enhance base_alloc() to keep track of fragments which were too small to
support previous allocation requests, and try to consume them during
subsequent requests.  This becomes important when request sizes commonly
approach or exceed the chunk size (as could radix tree node
allocations).

- atomic_*_p().
- atomic_cas_*().
- atomic_write_*().

Fix chunk_recycle()'s new_addr functionality to search by address rather
than just size if new_addr is specified.  The functionality added by
a95018ee (Attempt to expand huge
allocations in-place.) only worked if the two search orders happened to
return the same results (e.g. in simple test cases).