Add the --enable-mremap option, and disable the use of mremap(2) by
default, for the same reason that freeing chunks via munmap(2) is
disabled by default on Linux: semi-permanent VM map fragmentation.
Fix a memory corruption bug in chunk_alloc_dss() that was due to
claiming newly allocated memory is zeroed.
Reverse order of preference between mmap() and sbrk() to prefer mmap().
Clean up management of 'zero' parameter in chunk_alloc*().
Change the "opt.lg_prof_sample" default from 0 to 19 (1 B to 512 KiB).
Change the "opt.prof_accum" default from true to false.
Add the "opt.prof_final" mallctl, so that "opt.prof_prefix" need not be
abused to disable final profile dumping.
Add the --disable-munmap option, remove the configure test that
attempted to detect the VM allocation quirk known to exist on Linux
x86[_64], and make --disable-munmap implicit on Linux.
Always disable redzone by default, even when --enable-debug is
specified. The memory overhead for redzones can be substantial, which
makes this feature something that should only be opted into.
Implement Valgrind support, as well as the redzone and quarantine
features, which help Valgrind detect memory errors. Redzones are only
implemented for small objects because the changes necessary to support
redzones around large and huge objects are complicated by in-place
reallocation, to the point that it isn't clear that the maintenance
burden is worth the incremental improvement to Valgrind support.
Merge arena_salloc() and arena_salloc_demote().
Refactor i[v]salloc() to expose the 'demote' option.
s/PAGE_SHIFT/LG_PAGE/g and s/PAGE_SIZE/PAGE/g.
Remove remnants of the dynamic-page-shift code.
Rename the "arenas.pagesize" mallctl to "arenas.page".
Remove the "arenas.chunksize" mallctl, which is redundant with
"opt.lg_chunk".
Implement aligned_alloc(), which was added in the C11 standard. The
function is weakly specified to the point that a minimally compliant
implementation would be painful to use (size must be an integral
multiple of alignment!), which in practice makes posix_memalign() a
safer choice.
Remove the lg_tcache_gc_sweep option, because it is no longer
very useful. Prior to the addition of dynamic adjustment of tcache fill
count, it was possible for fill/flush overhead to be a problem, but this
problem no longer occurs.
Add nallocm(), which computes the real allocation size that would result
from the corresponding allocm() call. nallocm() is a functional
superset of OS X's malloc_good_size(), in that it takes alignment
constraints into account.
Program-generate small size class tables for all valid combinations of
LG_TINY_MIN, LG_QUANTUM, and PAGE_SHIFT. Use the appropriate table to generate
all relevant data structures, and remove the distinction between
tiny/quantum/cacheline/subpage bins.
Remove --enable-dynamic-page-shift. This option didn't prove useful in
practice, and it prevented optimizations.
Add Tilera architecture support.
Remove opt.lg_prof_bt_max, and hard code it to 7. The original
intention of this option was to enable faster backtracing by limiting
backtrace depth. However, this makes graphical pprof output very
difficult to interpret. In practice, decreasing sampling frequency is a
better mechanism for limiting profiling overhead.
Remove the opt.lg_prof_tcmax option and hard-code a cache size of 1024.
This setting is something that users just shouldn't have to worry about.
If lock contention actually ends up being a problem, the simple solution
available to the user is to reduce sampling frequency.
When tiny size class support was first added, it was intended to support
truly tiny size classes (even 2 bytes). However, this wasn't very
useful in practice, so the minimum tiny size class has been limited to
sizeof(void *) for a long time now. This is too small to be standards
compliant, but other commonly used malloc implementations do not even
bother using a 16-byte quantum on systems with vector units (SSE2+,
AltiVEC, etc.). As such, it is safe in practice to support an 8-byte
tiny size class on 64-bit systems that support 16-byte types.
