[libc] Search empty bits after failed allocation (#149910) Summary: The scheme we use to find a free bit is to just do a random walk. This works very well up until you start to completely saturate the bitfield. Because the result of the fetch_or yields the previous value, we can search this to go to any known empty bits as our next guess. This effectively increases our liklihood of finding a match after two tries by 32x since the distribution is random. This *massively* improves performance when a lot of memory is allocated without freeing, as it now doesn't takea one in a million shot to fill that last bit. A further change could improve this further by only *mostly* filling the slab, allowing 1% to be free at all times.
Welcome to the LLVM project!
This repository contains the source code for LLVM, a toolkit for the construction of highly optimized compilers, optimizers, and run-time environments.
The LLVM project has multiple components. The core of the project is itself called “LLVM”. This contains all of the tools, libraries, and header files needed to process intermediate representations and convert them into object files. Tools include an assembler, disassembler, bitcode analyzer, and bitcode optimizer.
C-like languages use the Clang frontend. This component compiles C, C++, Objective-C, and Objective-C++ code into LLVM bitcode -- and from there into object files, using LLVM.
Other components include: the libc++ C++ standard library, the LLD linker, and more.
Consult the Getting Started with LLVM page for information on building and running LLVM.
For information on how to contribute to the LLVM project, please take a look at the Contributing to LLVM guide.
Join the LLVM Discourse forums, Discord chat, LLVM Office Hours or Regular sync-ups.
The LLVM project has adopted a code of conduct for participants to all modes of communication within the project.