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SubjectRe: [PATCH v4 3/5] memcg : stop scanning if enough
On Mon 01-08-11 16:37:45, Michal Hocko wrote:
> On Wed 27-07-11 14:49:00, KAMEZAWA Hiroyuki wrote:
> > memcg :avoid node fallback scan if possible.
> >
> > Now, try_to_free_pages() scans all zonelist because the page allocator
> > should visit all zonelists...but that behavior is harmful for memcg.
> > Memcg just scans memory because it hits limit...no memory shortage
> > in pased zonelist.
> >
> > For example, with following unbalanced nodes
> >
> > Node 0 Node 1
> > File 1G 0
> > Anon 200M 200M
> >
> > memcg will cause swap-out from Node1 at every vmscan.
> >
> > Another example, assume 1024 nodes system.
> > With 1024 node system, memcg will visit 1024 nodes
> > pages per vmscan... This is overkilling.
> >
> > This is why memcg's victim node selection logic doesn't work
> > as expected.
>
> Previous patch adds nodemask filled by
> mem_cgroup_select_victim_node. Shouldn't we rather limit that nodemask
> to a victim node?

Bahh, scratch that. I was jumping from one thing to another and got
totally confused. Victim memcg is not bound to any particular node in
general...
Sorry for noise. I will try to get back to this tomorrow.

--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic


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