Currently there are 4 Chunk instances used for native memory allocation. They are each used for different sized allocations, and the chunk size for each varies.

    tiny_size = 256 - slack, // Size of first chunk (tiny)
    init_size = 1*K - slack, // Size of first chunk (normal aka small)
    medium_size= 10*K - slack, // Size of medium-sized chunk
    size = 32*K - slack, // Default size of an Arena chunk (following the first)

By default each of these Chunk instances will keep up to 5 free/empty chunks of memory allocated. It will only release those free/empty chunks in excess of 5. This is done during the periodic timer. About 215k of memory can be freed by not keeping any free/empty chunks allocated.