linux-kernel - Re: [PATCH 06/10] mm: vmscan: Have kswapd writeback pages based on dirty pages encountered, not priority

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Message-ID: <20130317151155.GC2026@suse.de>
Date:	Sun, 17 Mar 2013 15:11:55 +0000
From:	Mel Gorman <mgorman@...e.de>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Linux-MM <linux-mm@...ck.org>, Jiri Slaby <jslaby@...e.cz>,
	Valdis Kletnieks <Valdis.Kletnieks@...edu>,
	Rik van Riel <riel@...hat.com>,
	Zlatko Calusic <zcalusic@...sync.net>,
	Johannes Weiner <hannes@...xchg.org>,
	dormando <dormando@...ia.net>,
	Satoru Moriya <satoru.moriya@....com>,
	Michal Hocko <mhocko@...e.cz>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 06/10] mm: vmscan: Have kswapd writeback pages based on
 dirty pages encountered, not priority

On Sun, Mar 17, 2013 at 07:42:39AM -0700, Andi Kleen wrote:
> Mel Gorman <mgorman@...e.de> writes:
> 
> > @@ -495,6 +495,9 @@ typedef enum {
> >  	ZONE_CONGESTED,			/* zone has many dirty pages backed by
> >  					 * a congested BDI
> >  					 */
> > +	ZONE_DIRTY,			/* reclaim scanning has recently found
> > +					 * many dirty file pages
> > +					 */
> 
> Needs a better name. ZONE_DIRTY_CONGESTED ? 
> 

That might be confusing. The underlying BDI is not necessarily
congested. I accept your point though and will try thinking of a better
name.

> > +	 * currently being written then flag that kswapd should start
> > +	 * writing back pages.
> > +	 */
> > +	if (global_reclaim(sc) && nr_dirty &&
> > +			nr_dirty >= (nr_taken >> (DEF_PRIORITY - sc->priority)))
> > +		zone_set_flag(zone, ZONE_DIRTY);
> > +
> >  	trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
> 
> I suppose you want to trace the dirty case here too.
> 

I guess it wouldn't hurt to have a new tracepoint for when the flag gets
set. A vmstat might be helpful as well.

-- 
Mel Gorman
SUSE Labs
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