---
Motivation:
This new experimental memory-allocaction API returns a pointer to
the allocation as well as the usable size of the allocated memory
region.
The `s` in `smallocx` stands for `sized`-`mallocx`, attempting to
convey that this API returns the size of the allocated memory region.
It should allow C++ P0901r0 [0] and Rust Alloc::alloc_excess to make
use of it.
The main purpose of these APIs is to improve telemetry. It is more accurate
to register `smallocx(size, flags)` than `smallocx(nallocx(size), flags)`,
for example. The latter will always line up perfectly with the existing
size classes, causing a loss of telemetry information about the internal
fragmentation induced by potentially poor size-classes choices.
Instrumenting `nallocx` does not help much since user code can cache its
result and use it repeatedly.
---
Implementation:
The implementation adds a new `usize` option to `static_opts_s` and an `usize`
variable to `dynamic_opts_s`. These are then used to cache the result of
`sz_index2size` and similar functions in the code paths in which they are
unconditionally invoked. In the code-paths in which these functions are not
unconditionally invoked, `smallocx` calls, as opposed to `mallocx`, these
functions explicitly.
---
[0]: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0901r0.html
Add JEMALLOC_CXX_THROW to the memalign() function prototype, in order to
match glibc and avoid compilation errors when including both
jemalloc/jemalloc.h and malloc.h in C++ code.
This change was unintentionally omitted from
ae93d6bf36 (Avoid function prototype
incompatibilities.).
- Decorate public function with __declspec(allocator) and __declspec(restrict), just like MSVC 1900
- Support JEMALLOC_HAS_RESTRICT by defining the restrict keyword
- Move __declspec(nothrow) between 'void' and '*' so it compiles once more
As per gcc documentation:
The alloc_size attribute is used to tell the compiler that the function
return value points to memory (...)
This resolves#245.
Add various function attributes to the exported functions to give the
compiler more information to work with during optimization, and also
specify throw() when compiling with C++ on Linux, in order to adequately
match what __THROW does in glibc.
This resolves#237.
This adds a new `sdallocx` function to the external API, allowing the
size to be passed by the caller. It avoids some extra reads in the
thread cache fast path. In the case where stats are enabled, this
avoids the work of calculating the size from the pointer.
An assertion validates the size that's passed in, so enabling debugging
will allow users of the API to debug cases where an incorrect size is
passed in.
The performance win for a contrived microbenchmark doing an allocation
and immediately freeing it is ~10%. It may have a different impact on a
real workload.
Closes#28
Refactor huge allocation to be managed by arenas (though the global
red-black tree of huge allocations remains for lookup during
deallocation). This is the logical conclusion of recent changes that 1)
made per arena dss precedence apply to huge allocation, and 2) made it
possible to replace the per arena chunk allocation/deallocation
functions.
Remove the top level huge stats, and replace them with per arena huge
stats.
Normalize function names and types to *dalloc* (some were *dealloc*).
Remove the --enable-mremap option. As jemalloc currently operates, this
is a performace regression for some applications, but planned work to
logarithmically space huge size classes should provide similar amortized
performance. The motivation for this change was that mremap-based huge
reallocation forced leaky abstractions that prevented refactoring.
Add new mallctl endpoints "arena<i>.chunk.alloc" and
"arena<i>.chunk.dealloc" to allow userspace to configure
jemalloc's chunk allocator and deallocator on a per-arena
basis.
Implement the *allocx() API, which is a successor to the *allocm() API.
The *allocx() functions are slightly simpler to use because they have
fewer parameters, they directly return the results of primary interest,
and mallocx()/rallocx() avoid the strict aliasing pitfall that
allocm()/rallocx() share with posix_memalign(). The following code
violates strict aliasing rules:
foo_t *foo;
allocm((void **)&foo, NULL, 42, 0);
whereas the following is safe:
foo_t *foo;
void *p;
allocm(&p, NULL, 42, 0);
foo = (foo_t *)p;
mallocx() does not have this problem:
foo_t *foo = (foo_t *)mallocx(42, 0);
Refactor the test harness to support three types of tests:
- unit: White box unit tests. These tests have full access to all
internal jemalloc library symbols. Though in actuality all symbols
are prefixed by jet_, macro-based name mangling abstracts this away
from test code.
- integration: Black box integration tests. These tests link with
the installable shared jemalloc library, and with the exception of
some utility code and configure-generated macro definitions, they have
no access to jemalloc internals.
- stress: Black box stress tests. These tests link with the installable
shared jemalloc library, as well as with an internal allocator with
symbols prefixed by jet_ (same as for unit tests) that can be used to
allocate data structures that are internal to the test code.
Move existing tests into test/{unit,integration}/ as appropriate.
Split out internal parts of jemalloc_defs.h.in and put them in
jemalloc_internal_defs.h.in. This reduces internals exposure to
applications that #include <jemalloc/jemalloc.h>.
Refactor jemalloc.h header generation so that a single header file
results, and the prototypes can be used to generate jet_ prototypes for
tests. Split jemalloc.h.in into multiple parts (jemalloc_defs.h.in,
jemalloc_macros.h.in, jemalloc_protos.h.in, jemalloc_mangle.h.in) and
use a shell script to generate a unified jemalloc.h at configure time.
Change the default private namespace prefix from "" to "je_".
Add missing private namespace mangling.
Remove hard-coded private_namespace.h. Instead generate it and
private_unnamespace.h from private_symbols.txt. Use similar logic for
public symbols, which aids in name mangling for jet_ symbols.
Add test_warn() and test_fail(). Replace existing exit(1) calls with
test_fail() calls.
