Date: Tue, 16 Jun 2015 14:45:06 +0900
From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, Minchan Kim <minchan@kernel.org>,
        Mel Gorman <mgorman@suse.de>, Michal Nazarewicz <mina86@mina86.com>,
        Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
        Christoph Lameter <cl@linux.com>, Rik van Riel <riel@redhat.com>,
        David Rientjes <rientjes@google.com>
Subject: Re: [PATCH 5/6] mm, compaction: skip compound pages by order in free
 scanner
Message-ID: <20150616054505.GE12641@js1304-P5Q-DELUXE>
References: <1433928754-966-1-git-send-email-vbabka@suse.cz>
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On Wed, Jun 10, 2015 at 11:32:33AM +0200, Vlastimil Babka wrote:
> The compaction free scanner is looking for PageBuddy() pages and skipping all
> others.  For large compound pages such as THP or hugetlbfs, we can save a lot
> of iterations if we skip them at once using their compound_order(). This is
> generally unsafe and we can read a bogus value of order due to a race, but if
> we are careful, the only danger is skipping too much.
> 
> When tested with stress-highalloc from mmtests on 4GB system with 1GB hugetlbfs
> pages, the vmstat compact_free_scanned count decreased by at least 15%.
> 
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>


Acked-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

Thanks.
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