linux-kernel - Re: [PATCH v3 -mm 1/3] mm: reclaim at order 0 when compaction is enabled

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Message-ID: <20120130102642.GA25268@csn.ul.ie>
Date:	Mon, 30 Jan 2012 10:26:42 +0000
From:	Mel Gorman <mel@....ul.ie>
To:	Rik van Riel <riel@...hat.com>
Cc:	Hillf Danton <dhillf@...il.com>, linux-mm@...ck.org,
	lkml <linux-kernel@...r.kernel.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Minchan Kim <minchan.kim@...il.com>
Subject: Re: [PATCH v3 -mm 1/3] mm: reclaim at order 0 when compaction is
 enabled

On Fri, Jan 27, 2012 at 11:35:02AM -0500, Rik van Riel wrote:
> On 01/27/2012 04:13 AM, Hillf Danton wrote:
> 
> >>@@ -1195,7 +1195,7 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
> >>                        BUG();
> >>                }
> >>
> >>-               if (!order)
> >>+               if (!sc->order || !(sc->reclaim_mode&  RECLAIM_MODE_LUMPYRECLAIM))
> >>                        continue;
> >>
> >Just a tiny advice 8-)
> >
> >mind to move checking lumpy reclaim out of the loop,
> >something like
> 
> Hehe, I made the change the way it is on request
> of Mel Gorman :)
> 

Yes. I recognise that checking inside the loop like this results
in a tiny hit but it is hardly critical. By putting the check here,
it is absolutely clear that this is now a lumpy-reclaim only thing
where it used to be used by both lumpy reclaim and reclaim/compaction.
It'll make deleting lumpy reclaim a little bit easier in the future.

-- 
Mel Gorman
SUSE Labs
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