linux-kernel - Re: PERF: performance tests with the split LRU VM in -mm

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Message-ID: <20080729092853.0ddf7013@bree.surriel.com>
Date:	Tue, 29 Jul 2008 09:28:53 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Johannes Weiner <hannes@...urebad.de>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: PERF: performance tests with the split LRU VM in -mm

On Tue, 29 Jul 2008 15:21:47 +0200
Johannes Weiner <hannes@...urebad.de> wrote:

> Here is my original patch that just gets rid of it.  It did not cause
> any problems to me on high pressure.  Rik, you said on IRC that you now
> also think the patch is safe..?

Yes.  Removing the "+ 1" is safe because we do not scan until
zone->lru[l].nr_scan reaches swap_cluster_max, which means that
the scan counter for small lists will also slowly increase and
no list will be left behind.

> From: Johannes Weiner <hannes@...urebad.de>
> Subject: mm: don't accumulate scan pressure on unrelated lists
> 
> During each reclaim scan we accumulate scan pressure on unrelated
> lists which will result in bogus scans and unwanted reclaims
> eventually.

This patch fixes the balancing issues that we have been seeing
with the split LRU VM currently in -mm.

It is my preferred patch because it removes magic from the VM,
instead of adding some.

> Signed-off-by: Johannes Weiner <hannes@...urebad.de>

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

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