include <jemalloc/jemalloc.h>

int mallctl(const char *name, void *oldp, size_t *oldlenp, void *newp, size_t *newlen);

1. mallctl("arenas.create", &new_arena, &new_len, NULL, 0);

2. mallctl(arena_decay.c_str(), &old_decay, &old_len, &arena_decay_ms, sizeof(arena_decay_ms));

3. mallctl("thread.arena", &old_arena, &old_len, &new_arena, sizeof(new_arena));