linux-kernel - Re: [PATCH 3/4] mm: memory-failure: Fix isolated page count during memory failure

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Message-ID: <20110608100720.GF6742@tiehlicka.suse.cz>
Date:	Wed, 8 Jun 2011 12:07:20 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Mel Gorman <mgorman@...e.de>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Minchan Kim <minchan.kim@...il.com>,
	Thomas Sattler <tsattler@....de>,
	Ury Stankevich <urykhy@...il.com>,
	Andi Kleen <andi@...stfloor.org>,
	linux-mm <linux-mm@...ck.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/4] mm: memory-failure: Fix isolated page count during
 memory failure

On Tue 07-06-11 16:07:04, Mel Gorman wrote:
> From: Minchan Kim <minchan.kim@...il.com>
> 
> From: Minchan Kim <minchan.kim@...il.com>
> 
> Pages isolated for migration are accounted with the vmstat counters
> NR_ISOLATE_[ANON|FILE]. Callers of migrate_pages() are expected to
> increment these counters when pages are isolated from the LRU. Once
> the pages have been migrated, they are put back on the LRU or freed
> and the isolated count is decremented.

Aren't we missing this in compact_zone as well? AFAICS there is no
accounting done after we isolate pages from LRU? Or am I missing
something?

> 
> Memory failure is not properly accounting for pages it isolates
> causing the NR_ISOLATED counters to be negative. On SMP builds,
> this goes unnoticed as negative counters are treated as 0 due to
> expected per-cpu drift. On UP builds, the counter is treated by
> too_many_isolated() as a large value causing processes to enter D
> state during page reclaim or compaction. This patch accounts for
> pages isolated by memory failure correctly.
> 
> [mgorman@...e.de: Updated changelog]
> Signed-off-by: Minchan Kim <minchan.kim@...il.com>
> Signed-off-by: Mel Gorman <mgorman@...e.de>
> Reviewed-by: Andrea Arcangeli <aarcange@...hat.com>

Reviewed-by: Michal Hocko <mhocko@...e.cz>

-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic
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