linux-kernel - Re: [PATCH] vmscan: recalculate lru

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Message-ID: <20100627113422.GA14504@cmpxchg.org>
Date:	Sun, 27 Jun 2010 13:34:23 +0200
From:	Johannes Weiner <hannes@...xchg.org>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	Minchan Kim <minchan.kim@...il.com>
Subject: Re: [PATCH] vmscan: recalculate lru_pages on each priority

On Fri, Jun 25, 2010 at 06:13:20PM +0900, KOSAKI Motohiro wrote:
> shrink_zones() need relatively long time. and lru_pages can be
> changed dramatically while shrink_zones().
> then, lru_pages need recalculate on each priority.

In the direct reclaim path, we bail out of that loop after
SWAP_CLUSTER_MAX reclaimed pages, so in this case, decreasing priority
levels actually mean we do _not_ make any progress and the total
number of lru pages should not change (much).  The possible distortion
in shrink_slab() is small.

However, for the suspend-to-disk case the reclaim target can be a lot
higher and we inevitably end up at higher priorities even though we
make progress, but fail to increase pressure on the shrinkers as well
without your patch.

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