linux-kernel - Re: [PATCH 7/8] mm: vmscan: Immediately reclaim end-of-LRU dirty pages when writeback completes

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Date:	Fri, 22 Jul 2011 14:23:19 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Linux-MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
	XFS <xfs@....sgi.com>, Dave Chinner <david@...morbit.com>,
	Christoph Hellwig <hch@...radead.org>,
	Johannes Weiner <jweiner@...hat.com>,
	Wu Fengguang <fengguang.wu@...el.com>, Jan Kara <jack@...e.cz>,
	Rik van Riel <riel@...hat.com>,
	Minchan Kim <minchan.kim@...il.com>
Subject: Re: [PATCH 7/8] mm: vmscan: Immediately reclaim end-of-LRU dirty
 pages when writeback completes

On Fri, Jul 22, 2011 at 02:53:48PM +0200, Peter Zijlstra wrote:
> On Thu, 2011-07-21 at 17:28 +0100, Mel Gorman wrote:
> > When direct reclaim encounters a dirty page, it gets recycled around
> > the LRU for another cycle. This patch marks the page PageReclaim
> > similar to deactivate_page() so that the page gets reclaimed almost
> > immediately after the page gets cleaned. This is to avoid reclaiming
> > clean pages that are younger than a dirty page encountered at the
> > end of the LRU that might have been something like a use-once page.
> > 
> 
> > @@ -834,7 +834,15 @@ static unsigned long shrink_page_list(struct list_head *page_list,
> >  			 */
> >  			if (page_is_file_cache(page) &&
> >  					(!current_is_kswapd() || priority >= DEF_PRIORITY - 2)) {
> > -				inc_zone_page_state(page, NR_VMSCAN_WRITE_SKIP);
> > +				/*
> > +				 * Immediately reclaim when written back.
> > +				 * Similar in principal to deactivate_page()
> > +				 * except we already have the page isolated
> > +				 * and know it's dirty
> > +				 */
> > +				inc_zone_page_state(page, NR_VMSCAN_INVALIDATE);
> > +				SetPageReclaim(page);
> > +
> 
> I find the invalidate name somewhat confusing. It makes me think we'll
> drop the page without writeback, like invalidatepage().

I wasn't that happy with it either to be honest but didn't think of a
better one at the time. nr_reclaim_deferred?

-- 
Mel Gorman
SUSE Labs
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