microsoft/mimalloc

mimalloc is a memory allocator from Microsoft Research, written in C. A memory allocator is a low-level component that every program uses constantly: whenever your code creates a variable, a list, or any data structure, the allocator decides where in memory to put it and how to get that space back when you are done. Most programs use the allocator built into the operating system or the C standard library. mimalloc is an alternative that is faster and uses memory more efficiently. You can drop it into an existing program without changing any of that program's code. On Linux and similar systems, you prepend a single environment variable to your command and the program automatically uses mimalloc instead of the default. On Windows there is a similar override mechanism. This makes it easy to test whether mimalloc helps a particular workload without any code changes. The design focuses on a few key ideas. Instead of maintaining one global list of available memory blocks, mimalloc keeps many smaller lists, each tied to a specific region of memory. This reduces the chance that two parts of the program compete for the same list at the same time, which improves performance on programs that use many threads. It also returns unused memory to the operating system more aggressively than many other allocators, which matters for long-running server programs that might otherwise grow their memory footprint over time. There is also a secure build mode that adds extra protections against memory-related bugs and attacks, at a modest performance cost. The library is actively maintained across three version branches, and benchmarks in the repository show it consistently outperforming other widely used allocators. The full README is longer than what was shown.