Constant MALLOC_ARENAS 

const MALLOC_ARENAS: c_int = 1;

The most malloc arenas of the server. glibc gives every thread an arena of its own, up to eight per CPU, and on AArch64 it backs them with 2 MiB transparent huge pages by default, so each costs up to 2 MiB resident. The runtime, which also runs the RPC LocalSet, runs on one thread, the others only serve short blocking work, so one arena is enough, the per thread caches of the allocator absorb most of the contention.