linux-kernel - Re: [PATCH] vmscan,tmpfs: treat used once pages on tmpfs as used once

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Date:	Wed, 01 Sep 2010 09:51:14 -0400
From:	Rik van Riel <riel@...hat.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
CC:	Hugh Dickins <hughd@...gle.com>,
	Johannes Weiner <hannes@...xchg.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] vmscan,tmpfs: treat used once pages on tmpfs as used
 once

On 08/31/2010 09:37 PM, KOSAKI Motohiro wrote:
> When a page has PG_referenced, shrink_page_list() discard it only
> if it is no dirty. This rule works completely fine if the backend
> filesystem is regular one. PG_dirty is good signal that it was used
> recently because flusher thread clean pages periodically. In addition,
> page writeback is costly rather than simple page discard.
>
> However, When a page is on tmpfs, this heuristic don't works because
> flusher thread don't writeback tmpfs pages. then, tmpfs pages always
> rotate lru twice at least and it makes unnecessary lru churn. Merely
> tmpfs streaming io shouldn't cause large anonymous page swap-out.
>
> This patch remove this unncessary reclaim bonus of tmpfs pages.
>
> Cc: Hugh Dickins<hughd@...gle.com>
> Cc: Johannes Weiner<hannes@...xchg.org>
> Cc: Rik van Riel<riel@...hat.com>
> Signed-off-by: KOSAKI Motohiro<kosaki.motohiro@...fujitsu.com>

Reviewed-by: Rik van Riel <riel@...hat.com>

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