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

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Message-ID: <20110802112518.GE10436@suse.de>
Date:	Tue, 2 Aug 2011 12:25:18 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Minchan Kim <minchan.kim@...il.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	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>
Subject: Re: [PATCH 7/8] mm: vmscan: Immediately reclaim end-of-LRU dirty
 pages when writeback completes

On Mon, Aug 01, 2011 at 12:24:01AM +0900, Minchan Kim wrote:
> On Fri, Jul 22, 2011 at 02:23:19PM +0100, Mel Gorman wrote:
> > 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?
> 
> How about "NR_VMSCAN_IMMEDIATE_RECLAIM" like comment rotate_reclaimable_page?
> 

Yeah, I guess. I find it a little misleading because the reclaim does
not happen immediately at the time the counter is incremented but it's
better than "invalidate".

-- 
Mel Gorman
SUSE Labs
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