linux-kernel - Re: [PATCH 1/4] vmscan: delegate pageout io to flusher thread if current is kswapd

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Date:	Thu, 15 Apr 2010 20:26:08 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Mel Gorman <mel@....ul.ie>
Cc:	kosaki.motohiro@...fujitsu.com, Dave Chinner <david@...morbit.com>,
	Chris Mason <chris.mason@...cle.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 1/4] vmscan: delegate pageout io to flusher thread if current is kswapd

> On Thu, Apr 15, 2010 at 01:11:37PM +0900, KOSAKI Motohiro wrote:
> > Now, vmscan pageout() is one of IO throuput degression source.
> > Some IO workload makes very much order-0 allocation and reclaim
> > and pageout's 4K IOs are making annoying lots seeks.
> > 
> > At least, kswapd can avoid such pageout() because kswapd don't
> > need to consider OOM-Killer situation. that's no risk.
> > 
> 
> Well, there is some risk here. Direct reclaimers may not be cleaning
> more pages than it had to previously except it splices subsystems
> together increasing stack usage and causing further problems.
> 
> It might not cause OOM-killer issues but it could increase the time
> dirty pages spend on the LRU.
> 
> Am I missing something?

No. you are right. I fully agree your previous mail. so, I need to cool down a bit ;)







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