the glibc allocator is based off of Doug Lea's malloc that was developed before multithreading was common. Optimizations for multiple threads + arenas were ret

the glibc allocator is based off of Doug Lea's malloc that was developed before multithreading was common. Optimizations for multiple threads + arenas were retrofitted on top of the existing code, whereas jemalloc was designed more recently from scratch for multi-threaded workloads, and was able to take advantage of recent research.