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Re: [PATCH 8/8] mm: vmscan: Do not writeback filesystem pages from kswap

To: Johannes Weiner <jweiner@xxxxxxxxxx>
Subject: Re: [PATCH 8/8] mm: vmscan: Do not writeback filesystem pages from kswapd
From: Mel Gorman <mgorman@xxxxxxx>
Date: Wed, 3 Aug 2011 14:58:39 +0100
Cc: Linux-MM <linux-mm@xxxxxxxxx>, LKML <linux-kernel@xxxxxxxxxxxxxxx>, XFS <xfs@xxxxxxxxxxx>, Dave Chinner <david@xxxxxxxxxxxxx>, Christoph Hellwig <hch@xxxxxxxxxxxxx>, Wu Fengguang <fengguang.wu@xxxxxxxxx>, Jan Kara <jack@xxxxxxx>, Rik van Riel <riel@xxxxxxxxxx>, Minchan Kim <minchan.kim@xxxxxxxxx>
In-reply-to: <20110803113706.GF27199@xxxxxxxxxx>
References: <1311265730-5324-1-git-send-email-mgorman@xxxxxxx> <1311265730-5324-9-git-send-email-mgorman@xxxxxxx> <20110803113706.GF27199@xxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Wed, Aug 03, 2011 at 01:37:06PM +0200, Johannes Weiner wrote:
> On Thu, Jul 21, 2011 at 05:28:50PM +0100, Mel Gorman wrote:
> > Assuming that flusher threads will always write back dirty pages promptly
> > then it is always faster for reclaimers to wait for flushers. This patch
> > prevents kswapd writing back any filesystem pages.
> > 
> > Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
> 
> Relying on the flushers may mean that every dirty page in the system
> has to be written back before the pages from the zone of interest are
> clean.
> 

Yes.

> De-facto we have only one mechanism to stay on top of the dirty pages
> from a per-zone perspective, and that is single-page writeout from
> reclaim.
> 

Yes.

> While we all agree that this sucks, we can not remove it unless we
> have a replacement that makes zones reclaimable in a reasonable time
> frame (or keep them reclaimable in the first place, what per-zone
> dirty limits attempt to do).
> 
> As such, please include
> 
> Nacked-by: Johannes Weiner <jweiner@xxxxxxxxxx>

I've already dropped the patch. If I could, I would have signed this at
the time as

Signed-off-but-naking-it-anyway: Mel Gorman <mgorman@xxxxxxx

-- 
Mel Gorman
SUSE Labs

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