On Mon 01-08-11 16:37:45, Michal Hocko wrote:

On Wed 27-07-11 14:49:00, KAMEZAWA Hiroyuki wrote:

quoted

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

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>