Memory usage regression

[Mike Hommey]

On Wed, Oct 24, 2012 at 09:36:54PM +0200, Mike Hommey wrote:
> With that replayed workload, I can see two main things:
> - The amount of resident memory used by jemalloc 3 is greater than that
>   of mozjemalloc after freeing big parts of what was allocated (in
>   Firefox, after closing all tabs, waiting for a settle, and forcing GC).
>   This is most likely due to different allocation patterns leading to
>   some kind of fragmentation after freeing part of the allocated memory.
>   See http://i.imgur.com/fQKi4.png for a graphical representation of
>   what happens to the RSS value at the different checkpoints during the
>   Firefox workload.
> - The amount of mmap()ed memory is dangerously increasing during the
>   workload. It almost (but not quite) looks like jemalloc don't reuse
>   pages it purged. See http://i.imgur.com/klfJv.png ; VmData is
>   essentially the sum of all anonymous ranges of memory in the process.
>   Such an increase in VmData means we'd eventually exhaust the 32-bits
>   address space on 32-bits OSes, even though the resident memory usage
>   is pretty low.

FWIW, both jemalloc 2.0.0 and 1.0.3 have the same behaviour as jemalloc
3, both for VmRSS and VmData.

Mike