Some system libraries are using malloc_default_zone() and then using
some of the malloc_zone_* API. Under normal conditions, those functions
check the malloc_zone_t/malloc_introspection_t struct for the values
that are allowed to be NULL, so that a NULL deref doesn't happen.
As of OSX 10.12, malloc_default_zone() doesn't return the actual default
zone anymore, but returns a fake, wrapper zone. The wrapper zone defines
all the possible functions in the malloc_zone_t/malloc_introspection_t
struct (almost), and calls the function from the registered default zone
(jemalloc in our case) on its own. Without checking whether the pointers
are NULL.
This means that a system library that calls e.g.
malloc_zone_batch_malloc(malloc_default_zone(), ...) ends up trying to
call jemalloc_zone.batch_malloc, which is NULL, and crash follows.
So as of OSX 10.12, the default zone is required to have all the
functions available (really, the same as the wrapper zone), even if they
do nothing.
This is arguably a bug in libsystem_malloc in OSX 10.12, but jemalloc
still needs to work in that case.
The SDK jemalloc is built against might be not be the latest for various
reasons, but the resulting binary ought to work on newer versions of
OSX.
In order to ensure this, we need the fullest definitions possible, so
copy what we need from the latest version of malloc/malloc.h available
on opensource.apple.com.
Currently, jemalloc detects sparc64 targets by checking whether
__sparc64__ is defined. However, this definition is used on BSD
targets only. Linux targets define both __sparc__ and __arch64__
for sparc64. Since this also works on BSD, rather use __sparc__
and __arch64__ instead of __sparc64__ to detect sparc64 targets.
The core issue here is the weak linking of the symbol, and in certain
environments--for instance, using the latest Xcode (8.1) with the latest
SDK (10.12)--os_unfair_lock may resolve even though you're compiling on
a host that doesn't support it (10.11).
We can use the availability macros to circumvent this problem, and
detect that we're not compiling for a target that is going to support
them and error out at compile time. The other alternative is to do a
runtime check, but that presents issues for cross-compiling.
Add the pages_[no]huge() functions, which toggle huge page state via
madvise(..., MADV_[NO]HUGEPAGE) calls.
The first time a page run is purged from within an arena chunk, call
pages_nohuge() to tell the kernel to make no further attempts to back
the chunk with huge pages. Upon arena chunk deletion, restore the
associated virtual memory to its original state via pages_huge().
This resolves#243.
Some versions of Android provide a pthreads library without providing
pthread_atfork(), so in practice a separate feature test is necessary
for the latter.
Add feature tests for the MADV_FREE and MADV_DONTNEED flags to
madvise(2), so that MADV_FREE is detected and used for Linux kernel
versions 4.5 and newer. Refactor pages_purge() so that on systems which
support both flags, MADV_FREE is preferred over MADV_DONTNEED.
This resolves#387.
Rather than relying on two's complement negation for alignment mask
generation, use bitwise not and addition. This dodges warnings from
MSVC, and should be strength-reduced by compiler optimization anyway.
Add extent serial numbers and use them where appropriate as a sort key
that is higher priority than address, so that the allocation policy
prefers older extents.
This resolves#147.
2cdf07aba9 (Fix extent_quantize() to
handle greater-than-huge-size extents.) solved a non-problem; the
expression passed in to index2size() was never too large. However the
expression could in principle underflow, so fix the actual (latent) bug
and remove unnecessary complexity.
Remove outer CHUNK_CEILING(s2u(...)) from alloc_size computation, since
s2u() may overflow (and return 0), and CHUNK_CEILING() is only needed
around the alignment portion of the computation.
This fixes a regression caused by
5707d6f952 (Quantize szad trees by size
class.) and first released in 4.0.0.
This resolves#497.
Allocation requests can't directly create extents that exceed
HUGE_MAXCLASS, but extent merging can create them.
This fixes a regression caused by
8a03cf039c (Implement cache index
randomization for large allocations.) and first released in 4.0.0.
This resolves#497.
Fix arena_run_first_best_fit() to search all potentially non-empty
runs_avail heaps, rather than ignoring the heap that contains runs
larger than large_maxclass, but less than chunksize.
This fixes a regression caused by
f193fd80cf (Refactor runs_avail.).
This resolves#493.
Fix paren placement so that QUANTUM_CEILING() applies to the correct
portion of the expression that computes how much memory to base_alloc().
In practice this bug had no impact. This was caused by
5d8db15db9 (Simplify run quantization.),
which in turn fixed an over-allocation regression caused by
3c4d92e82a (Add per size class huge
allocation statistics.).
Fix arena_run_alloc_large_helper() to not convert size to usize when
searching for the first best fit via arena_run_first_best_fit(). This
allows the search to consider the optimal quantized size class, so that
e.g. allocating and deallocating 40 KiB in a tight loop can reuse the
same memory.
This regression was nominally caused by
5707d6f952 (Quantize szad trees by size
class.), but it did not commonly cause problems until
8a03cf039c (Implement cache index
randomization for large allocations.). These regressions were first
released in 4.0.0.
This resolves#487.
Fix chunk_alloc_cache() to support decommitted allocation, and use this
ability in arena_chunk_alloc_internal() and arena_stash_dirty(), so that
chunks don't get permanently stuck in a hybrid state.
This resolves#487.
