better stats

[kuszmaul]

We would like the following statistics

• How much rss has been given to the user (assuming the user touches all of what she has requested). This is not the sum of the sizes of the allocations, since, for example, we round up to the next size bin. This is not a multiple of the page size either, since we have unallocated objects not counted here.
• How much rss is currently used for unallocated objects on pages shared with allocated objects.
• How much rss is currently used for supermalloc data structures. If you sum this with the previous two you should get the total rss that supermalloc thinks is in use.
• How much virtual memory is currently allocated by supermalloc. (This only grows)

[kuszmaul]

Mark Callaghan says that he wants to know

1. how much memory my app is using
2. how much memory the allocator is using to provide #1
3. how this changes over time