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This introduces a backport of C11 atomics. It has four implementations; ranked in order of preference, they are: - GCC/Clang __atomic builtins - GCC/Clang __sync builtins - MSVC _Interlocked builtins - C11 atomics, from <stdatomic.h> The primary advantages are: - Close adherence to the standard API gives us a defined memory model. - Type safety: atomic objects are now separate types from non-atomic ones, so that it's impossible to mix up atomic and non-atomic updates (which is undefined behavior that compilers are starting to take advantage of). - Efficiency: we can specify ordering for operations, avoiding fences and atomic operations on strongly ordered architectures (example: `atomic_write_u32(ptr, val);` involves a CAS loop, whereas `atomic_store(ptr, val, ATOMIC_RELEASE);` is a plain store. This diff leaves in the current atomics API (implementing them in terms of the backport). This lets us transition uses over piecemeal. Testing: This is by nature hard to test. I've manually tested the first three options on Linux on gcc by futzing with the #defines manually, on freebsd with gcc and clang, on MSVC, and on OS X with clang. All of these were x86 machines though, and we don't have any test infrastructure set up for non-x86 platforms.
jemalloc is a general purpose malloc(3) implementation that emphasizes fragmentation avoidance and scalable concurrency support. jemalloc first came into use as the FreeBSD libc allocator in 2005, and since then it has found its way into numerous applications that rely on its predictable behavior. In 2010 jemalloc development efforts broadened to include developer support features such as heap profiling and extensive monitoring/tuning hooks. Modern jemalloc releases continue to be integrated back into FreeBSD, and therefore versatility remains critical. Ongoing development efforts trend toward making jemalloc among the best allocators for a broad range of demanding applications, and eliminating/mitigating weaknesses that have practical repercussions for real world applications. The COPYING file contains copyright and licensing information. The INSTALL file contains information on how to configure, build, and install jemalloc. The ChangeLog file contains a brief summary of changes for each release. URL: http://jemalloc.net/