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Date: Mon, 13 Feb 2017 10:49:40 +0000 From: Mel Gorman <mgorman@...hsingularity.net> To: Vlastimil Babka <vbabka@...e.cz> Cc: linux-mm@...ck.org, Johannes Weiner <hannes@...xchg.org>, Joonsoo Kim <iamjoonsoo.kim@....com>, David Rientjes <rientjes@...gle.com>, linux-kernel@...r.kernel.org, kernel-team@...com Subject: Re: [PATCH v2 02/10] mm, compaction: remove redundant watermark check in compact_finished() On Fri, Feb 10, 2017 at 06:23:35PM +0100, Vlastimil Babka wrote: > When detecting whether compaction has succeeded in forming a high-order page, > __compact_finished() employs a watermark check, followed by an own search for > a suitable page in the freelists. This is not ideal for two reasons: > > - The watermark check also searches high-order freelists, but has a less strict > criteria wrt fallback. It's therefore redundant and waste of cycles. This was > different in the past when high-order watermark check attempted to apply > reserves to high-order pages. > > - The watermark check might actually fail due to lack of order-0 pages. > Compaction can't help with that, so there's no point in continuing because of > that. It's possible that high-order page still exists and it terminates. > > This patch therefore removes the watermark check. This should save some cycles > and terminate compaction sooner in some cases. > > Signed-off-by: Vlastimil Babka <vbabka@...e.cz> Acked-by: Mel Gorman <mgorman@...hsingularity.net> -- Mel Gorman SUSE Labs
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