08260a6b94
--- 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
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/