linux-kernel - Re: Why PAGEOUT_IO_SYNC stalls for a long time

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Message-Id: <20100805151630.31CF.A69D9226@jp.fujitsu.com>
Date:	Thu,  5 Aug 2010 15:20:44 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Mel Gorman <mel@....ul.ie>
Cc:	kosaki.motohiro@...fujitsu.com,
	Wu Fengguang <fengguang.wu@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>, stable@...nel.org,
	Rik van Riel <riel@...hat.com>,
	Christoph Hellwig <hch@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Dave Chinner <david@...morbit.com>,
	Chris Mason <chris.mason@...cle.com>,
	Nick Piggin <npiggin@...e.de>,
	Johannes Weiner <hannes@...xchg.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Minchan Kim <minchan.kim@...il.com>,
	Andreas Mohr <andi@...as.de>, Bill Davidsen <davidsen@....com>,
	Ben Gamari <bgamari.foss@...il.com>
Subject: Re: Why PAGEOUT_IO_SYNC stalls for a long time

> On Sun, Aug 01, 2010 at 05:47:08PM +0900, KOSAKI Motohiro wrote:
> > > > side note: page lock contention is very common case.
> > > > 
> > > > For case (8), I don't think sleeping is right way. get_page() is used in really various place of
> > > > our kernel. so we can't assume it's only temporary reference count increasing.
> > > 
> > > In what case is a munlocked pages reference count permanently increased and
> > > why is this not a memory leak?
> > 
> > V4L, audio, GEM and/or other multimedia driver?
> > 
> 
> Ok, that is quite likely. Have you made a start on a series related to
> lumpy reclaim? I was holding off making a start on such a thing while I
> reviewed the other writeback issues and travelling to MM Summit is going
> to delay things for me. If you haven't started when I get back, I'll
> make some sort of stab at it.

Yup, I posted them today. While my lite testing, they works intentionally. it mean
 - reduce low order reclaim latency
 - keep high successfull rate order-9 reclaim under heavy io workload

However, they obviously need more test. comment are welcome :)




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