Re: [patch] memcg: skip scanning active lists based on individualsize

[KAMEZAWA Hiroyuki]

On Wed, 31 Aug 2011 19:13:34 +0900
Minchan Kim <minchan.kim@xxxxxxxxx> wrote:

> On Wed, Aug 31, 2011 at 6:08 PM, Johannes Weiner <jweiner@xxxxxxxxxx> wrote:
> > Reclaim decides to skip scanning an active list when the corresponding
> > inactive list is above a certain size in comparison to leave the
> > assumed working set alone while there are still enough reclaim
> > candidates around.
> >
> > The memcg implementation of comparing those lists instead reports
> > whether the whole memcg is low on the requested type of inactive
> > pages, considering all nodes and zones.
> >
> > This can lead to an oversized active list not being scanned because of
> > the state of the other lists in the memcg, as well as an active list
> > being scanned while its corresponding inactive list has enough pages.
> >
> > Not only is this wrong, it's also a scalability hazard, because the
> > global memory state over all nodes and zones has to be gathered for
> > each memcg and zone scanned.
> >
> > Make these calculations purely based on the size of the two LRU lists
> > that are actually affected by the outcome of the decision.
> >
> > Signed-off-by: Johannes Weiner <jweiner@xxxxxxxxxx>
> > Cc: Rik van Riel <riel@xxxxxxxxxx>
> > Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
> > Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> > Cc: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>
> > Cc: Balbir Singh <bsingharora@xxxxxxxxx>
> 
> Reviewed-by: Minchan Kim <minchan.kim@xxxxxxxxx>
> 
> I can't understand why memcg is designed for considering all nodes and zones.
> Is it a mistake or on purpose?

It's purpose. memcg just takes care of the amount of pages.
Them, any performance numbers ?


But, hmm, this change may be good for softlimit and your work.

I'll ack when you add performance numbers in changelog.

Thanks,
-Kame

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