linux-kernel - Re: [PATCH 1/5] vmscan: remove all_unreclaimable check from direct reclaim path completely

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Date:	Wed, 23 Mar 2011 16:55:12 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	kosaki.motohiro@...fujitsu.com, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	Oleg Nesterov <oleg@...hat.com>, linux-mm <linux-mm@...ck.org>,
	Andrey Vagin <avagin@...nvz.org>,
	Hugh Dickins <hughd@...gle.com>,
	Nick Piggin <npiggin@...nel.dk>,
	Minchan Kim <minchan.kim@...il.com>,
	Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH 1/5] vmscan: remove all_unreclaimable check from direct reclaim path completely

> > Reported-by: Andrey Vagin <avagin@...nvz.org>
> > Cc: Nick Piggin <npiggin@...nel.dk>
> > Cc: Minchan Kim <minchan.kim@...il.com>
> > Cc: Johannes Weiner <hannes@...xchg.org>
> > Cc: Rik van Riel <riel@...hat.com>
> > Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> 
> IIUC, I saw the pehnomenon which you pointed out, as
>  - all zone->all_unreclaimable = yes
>  - zone_reclaimable() returns true
>  - no pgscan proceeds.
> 
> on a swapless system. So, I'd like to vote for this patch.
> 
> But hmm...what happens all of pages are isolated or locked and now under freeing ?
> I think we should have alternative safe-guard logic for avoiding to call
> oom-killer. Hmm.

Yes, this patch has small risk. but 1) this logic didn't work about two
years (see changelog) 2) memcg haven't use this logic and I haven't get
any bug report from memcg developers. therefore I decided to take most
simple way.

Of cource, I'll make another protection if I'll get any regression report.



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