linux-kernel - Re: [PATCH 4/4] mm: compaction: Abort compaction if too many pages are isolated and caller is asynchronous

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Date:	Tue, 7 Jun 2011 17:26:54 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Minchan Kim <minchan.kim@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Thomas Sattler <tsattler@....de>,
	Ury Stankevich <urykhy@...il.com>,
	Andi Kleen <andi@...stfloor.org>,
	linux-mm <linux-mm@...ck.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/4] mm: compaction: Abort compaction if too many pages
 are isolated and caller is asynchronous

On Wed, Jun 08, 2011 at 12:50:29AM +0900, Minchan Kim wrote:
> > <SNIP>
> > @@ -533,8 +544,14 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
> >  		unsigned long nr_migrate, nr_remaining;
> >  		int err;
> >  
> > -		if (!isolate_migratepages(zone, cc))
> > +		switch (isolate_migratepages(zone, cc)) {
> > +		case ISOLATE_ABORT:
> 
> In this case, you change old behavior slightly.
> In old case, we return COMPACT_PARTIAL to cancel migration.
> But this patch makes to return COMPACT_SUCCESS.
> At present, return value of compact_zone is only used by __alloc_pages_direct_compact
> and it only consider COMPACT_SKIPPED so it would be not a problem.
> But I think it would be better to return COMPACT_PARTIAL instead of COMPACT_CONTINUE
> for consistency with compact_finished and right semantic for the future user of compact_zone.
> 

Agreed. Thanks.

-- 
Mel Gorman
SUSE Labs
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