Message-ID: <53983E8C.80207@suse.cz>
Date: Wed, 11 Jun 2014 13:33:32 +0200
From: Vlastimil Babka <vbabka@suse.cz>
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To: Minchan Kim <minchan@kernel.org>
CC: David Rientjes <rientjes@google.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Greg Thelen <gthelen@google.com>, Mel Gorman <mgorman@suse.de>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Michal Nazarewicz <mina86@mina86.com>,
        Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
        Christoph Lameter <cl@linux.com>, Rik van Riel <riel@redhat.com>
Subject: Re: [PATCH 05/10] mm, compaction: remember position within pageblock
 in free pages scanner
References: <1402305982-6928-1-git-send-email-vbabka@suse.cz> <1402305982-6928-5-git-send-email-vbabka@suse.cz> <20140611021213.GF15630@bbox>
In-Reply-To: <20140611021213.GF15630@bbox>
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Sender: linux-kernel-owner@vger.kernel.org

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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