Re: Commit f50de2d38 seems to be breaking my oom killer

[KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>]

> > Umm..
> > This code looks a bit risky. Please imazine asymmetric numa. If the system has
> > very small node, its nude have unreclaimable state at almost time.
> > 
> > Thus, if all zones in the node are unreclaimable, It should be slept. To retry balance_pgdat()
> > is meaningless. this is original intention, I think.
> > 
> > So why can't we write following?
> > 
> > From c00d7bb29552d3aa4d934b5007f3d52ade5f2dfd Mon Sep 17 00:00:00 2001
> > From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> > Date: Fri, 8 Jan 2010 08:36:05 +0900
> > Subject: [PATCH] vmscan: kswapd don't retry balance_pgdat() if all zones are unreclaimable
> > 
> > Commit f50de2d3 (vmscan: have kswapd sleep for a short interval and
> > double check it should be asleep) can cause kswapd to enter an infinite
> > loop if running on a single-CPU system. If all zones are unreclaimble,
> > sleeping_prematurely return 1 and kswapd will call balance_pgdat()
> > again. but it's totally meaningless, balance_pgdat() doesn't anything
> > against unreclaimable zone!
> > 
> 
> Sure, that would be a safer check in the face of very small NUMA nodes.
> It could do with a comment explaining why unreclaimable zones are being skipped
> but it's no biggie.  Will, can you confirm this patch also fixes your problem.
> 
> Kosaki, if Will reports success, can you then report that patch please
> for upstreaming?  After today, I'm offline for a week so it'd be at
> least 10 days before I'd do it. Thanks

Sure. thanks.


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