linux-kernel - Re: [PATCH v3 01/10] compaction: trivial clean up acct

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Message-ID: <20110609144135.GA4878@barrios-laptop>
Date:	Thu, 9 Jun 2011 23:41:36 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Mel Gorman <mgorman@...e.de>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-mm <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH v3 01/10] compaction: trivial clean up acct_isolated

Hi Mel,

On Thu, Jun 09, 2011 at 02:33:27PM +0100, Mel Gorman wrote:
> On Tue, Jun 07, 2011 at 11:38:14PM +0900, Minchan Kim wrote:
> > acct_isolated of compaction uses page_lru_base_type which returns only
> > base type of LRU list so it never returns LRU_ACTIVE_ANON or LRU_ACTIVE_FILE.
> > In addtion, cc->nr_[anon|file] is used in only acct_isolated so it doesn't have
> > fields in conpact_control.
> > This patch removes fields from compact_control and makes clear function of
> > acct_issolated which counts the number of anon|file pages isolated.
> > 
> > Cc: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> > Cc: Mel Gorman <mgorman@...e.de>
> > Cc: Andrea Arcangeli <aarcange@...hat.com>
> > Acked-by: Rik van Riel <riel@...hat.com>
> > Acked-by: Johannes Weiner <hannes@...xchg.org>
> > Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> > Signed-off-by: Minchan Kim <minchan.kim@...il.com>
> > ---
> >  mm/compaction.c |   18 +++++-------------
> >  1 files changed, 5 insertions(+), 13 deletions(-)
> > 
> > diff --git a/mm/compaction.c b/mm/compaction.c
> > index 021a296..61eab88 100644
> > --- a/mm/compaction.c
> > +++ b/mm/compaction.c
> > @@ -35,10 +35,6 @@ struct compact_control {
> >  	unsigned long migrate_pfn;	/* isolate_migratepages search base */
> >  	bool sync;			/* Synchronous migration */
> >  
> > -	/* Account for isolated anon and file pages */
> > -	unsigned long nr_anon;
> > -	unsigned long nr_file;
> > -
> >  	unsigned int order;		/* order a direct compactor needs */
> >  	int migratetype;		/* MOVABLE, RECLAIMABLE etc */
> >  	struct zone *zone;
> > @@ -212,17 +208,13 @@ static void isolate_freepages(struct zone *zone,
> >  static void acct_isolated(struct zone *zone, struct compact_control *cc)
> >  {
> >  	struct page *page;
> > -	unsigned int count[NR_LRU_LISTS] = { 0, };
> > +	unsigned int count[2] = { 0, };
> >  
> > -	list_for_each_entry(page, &cc->migratepages, lru) {
> > -		int lru = page_lru_base_type(page);
> > -		count[lru]++;
> > -	}
> > +	list_for_each_entry(page, &cc->migratepages, lru)
> > +		count[!!page_is_file_cache(page)]++;
> >  
> > -	cc->nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
> > -	cc->nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
> > -	__mod_zone_page_state(zone, NR_ISOLATED_ANON, cc->nr_anon);
> > -	__mod_zone_page_state(zone, NR_ISOLATED_FILE, cc->nr_file);
> > +	__mod_zone_page_state(zone, NR_ISOLATED_ANON, count[0]);
> > +	__mod_zone_page_state(zone, NR_ISOLATED_FILE, count[1]);
> 
> You are hard-coding assumptions about the value of LRU_INACTIVE_ANON
> and LRU_INACTIVE_FILE here. I have no expectation that these will

I used page_is_file_cache and logical not.
If page_is_file_cache returns zero(ie, anon), logicacl not makes it with 0.
If page_is_file_cache doesn't return zero(ie, file), logical not makes it with 1.
So, anon pages would be put in count[0] and file pages would be in count[1].

Do I miss your point?

> change but who knows for sure? To be robust against unexpected
> changes, count should still be NR_LRU_LISTS and you should use the
> LRU_INACTIVE_ANON and LRU_INACTIVE_FILE values.
> 
> I agree that summing LRU_ACTIVE_* is silly.
> 
> -- 
> Mel Gorman
> SUSE Labs

-- 
Kind regards
Minchan Kim
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