linux-kernel - Re: [PATCH 15/17] mm: Do not use unnecessary atomic operations when adding pages to the LRU

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Message-ID: <20140501133340.GE23420@cmpxchg.org>
Date:	Thu, 1 May 2014 09:33:40 -0400
From:	Johannes Weiner <hannes@...xchg.org>
To:	Mel Gorman <mgorman@...e.de>
Cc:	Linux-MM <linux-mm@...ck.org>,
	Linux-FSDevel <linux-fsdevel@...r.kernel.org>,
	Vlastimil Babka <vbabka@...e.cz>, Jan Kara <jack@...e.cz>,
	Michal Hocko <mhocko@...e.cz>, Hugh Dickins <hughd@...gle.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 15/17] mm: Do not use unnecessary atomic operations when
 adding pages to the LRU

On Thu, May 01, 2014 at 09:44:46AM +0100, Mel Gorman wrote:
> When adding pages to the LRU we clear the active bit unconditionally. As the
> page could be reachable from other paths we cannot use unlocked operations
> without risk of corruption such as a parallel mark_page_accessed. This
> patch test if is necessary to clear the atomic flag before using an atomic
> operation. In the unlikely even this races with mark_page_accesssed the

                             event

> consequences are simply that the page may be promoted to the active list
> that might have been left on the inactive list before the patch. This is
> a marginal consequence.
> 
> Signed-off-by: Mel Gorman <mgorman@...e.de>

Acked-by: Johannes Weiner <hannes@...xchg.org>
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