linux-kernel - Re: [PATCH 05/10] mm, compaction: remember position within pageblock in free pages scanner

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Message-ID: <53983E8C.80207@suse.cz>
Date:	Wed, 11 Jun 2014 13:33:32 +0200
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Minchan Kim <minchan@...nel.org>
CC:	David Rientjes <rientjes@...gle.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Thelen <gthelen@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Michal Nazarewicz <mina86@...a86.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Christoph Lameter <cl@...ux.com>,
	Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH 05/10] mm, compaction: remember position within pageblock
 in free pages scanner

On 06/11/2014 04:12 AM, Minchan Kim wrote:
>> >@@ -314,6 +315,9 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,
>> >  		int isolated, i;
>> >  		struct page *page = cursor;
>> >
>> >+		/* Record how far we have got within the block */
>> >+		*start_pfn = blockpfn;
>> >+
> Couldn't we move this out of the loop for just one store?

You mean using a local variable inside the loop, and assigning once, for 
performance reasons (register vs memory access)?
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