Replace the single-character run-time flags with key/value pairs, which
can be set via the malloc_conf global, /etc/malloc.conf, and the
MALLOC_CONF environment variable.
Replace the JEMALLOC_PROF_PREFIX environment variable with the
"opt.prof_prefix" option.
Replace umax2s() with u2s().
Add the R option to control whether cumulative heap profile data
are maintained. Add the T option to control the size of per thread
backtrace caches, primarily because when the R option is specified,
backtraces that no longer have allocations associated with them are
discarded as soon as no thread caches refer to them.
Now that JEMALLOC_OPTIONS=P isn't the only way to cause stats_print() to
be called, opt_stats_print must actually be checked when reporting the
state of the P/p option.
Make it possible to disable interval-triggered profile dumping, even if
profiling is enabled. This is useful if the user only wants a single
dump at exit, or if the application manually triggers profile dumps.
Remove medium size classes, because concurrent dirty page purging is
no longer capable of purging inactive dirty pages inside active runs
(due to recent arena/bin locking changes).
Enhance tcache to support caching large objects, so that the same range
of size classes is still cached, despite the removal of medium size
class support.
For bin-related allocation, protect data structures with bin locks
rather than arena locks. Arena locks remain for run
allocation/deallocation and other miscellaneous operations.
Restructure statistics counters to maintain per bin
allocated/nmalloc/ndalloc, but continue to provide arena-wide statistics
via aggregation in the ctl code.
Use chains of cached objects, rather than using arrays of pointers.
Since tcache_bin_t is no longer dynamically sized, convert tcache_t's
tbin to an array of structures, rather than an array of pointers. This
implicitly removes tcache_bin_{create,destroy}(), which further
simplifies the fast path for malloc/free.
Use cacheline alignment for tcache_t allocations.
Remove runtime configuration option for number of tcache bin slots, and
replace it with a boolean option for enabling/disabling tcache.
Limit the number of tcache objects to the lesser of TCACHE_NSLOTS_MAX
and 2X the number of regions per run for the size class.
For GC-triggered flush, discard 3/4 of the objects below the low water
mark, rather than 1/2.
