This document summarizes the organization of overall mongod process memory usage, both outside and inside the tcmalloc allocator. The phrases in bold correspond to statistics that are output by the db.serverStatus() command. Indentation below indicates containment.
- mem: virtual: overall process virtual address space.
- code and initialized data.
- thread stacks, one per connection.
- generic heap_size: virtual memory under control of the
allocator.
- current_allocated_bytes: memory allocated by mongod
- bytes currently in the cache: WiredTiger cache memory
- allocated minus wt cache: memory allocated outside the WiredTiger cache
- freed memory used by mongod and then returned to the allocator
- central_cache_free_bytes: small free regions
- pageheap_free_bytes: large free regions backed by physical memory
- pageheap_unmapped_bytes large free regions not backed by physical memory
- current_allocated_bytes: memory allocated by mongod