From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752402AbdBMKtt (ORCPT ); Mon, 13 Feb 2017 05:49:49 -0500 Received: from outbound-smtp08.blacknight.com ([46.22.139.13]:46240 "EHLO outbound-smtp08.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751747AbdBMKtr (ORCPT ); Mon, 13 Feb 2017 05:49:47 -0500 Date: Mon, 13 Feb 2017 10:49:40 +0000 From: Mel Gorman To: Vlastimil Babka Cc: linux-mm@kvack.org, Johannes Weiner , Joonsoo Kim , David Rientjes , linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH v2 02/10] mm, compaction: remove redundant watermark check in compact_finished() Message-ID: <20170213104940.jifpc5g5m5bty7cx@techsingularity.net> References: <20170210172343.30283-1-vbabka@suse.cz> <20170210172343.30283-3-vbabka@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20170210172343.30283-3-vbabka@suse.cz> User-Agent: Mutt/1.6.2 (2016-07-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 Acked-by: Mel Gorman -- Mel Gorman SUSE Labs