From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4A9A0C7618E for ; Wed, 26 Apr 2023 15:33:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240897AbjDZPdr (ORCPT ); Wed, 26 Apr 2023 11:33:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48636 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241212AbjDZPdo (ORCPT ); Wed, 26 Apr 2023 11:33:44 -0400 Received: from outbound-smtp05.blacknight.com (outbound-smtp05.blacknight.com [81.17.249.38]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F28CC6EBB for ; Wed, 26 Apr 2023 08:33:34 -0700 (PDT) Received: from mail.blacknight.com (pemlinmail02.blacknight.ie [81.17.254.11]) by outbound-smtp05.blacknight.com (Postfix) with ESMTPS id 739FBCCC7C for ; Wed, 26 Apr 2023 16:33:33 +0100 (IST) Received: (qmail 17964 invoked from network); 26 Apr 2023 15:33:33 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.21.103]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 26 Apr 2023 15:33:33 -0000 Date: Wed, 26 Apr 2023 16:33:31 +0100 From: Mel Gorman To: Vlastimil Babka Cc: Baolin Wang , akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] Revert "Revert "mm/compaction: fix set skip in fast_find_migrateblock"" Message-ID: <20230426153331.dfqagb47i4xo3ouv@techsingularity.net> References: <3576e3520c044beb2a81860aecb2d4f597089300.1682521303.git.baolin.wang@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 26, 2023 at 05:10:14PM +0200, Vlastimil Babka wrote: > On 4/26/23 17:03, Baolin Wang wrote: > > This reverts commit 95e7a450b8190673675836bfef236262ceff084a. > > > > When I tested thpscale with v6.3 kernel, I found the compaction efficiency > > had a great regression compared to v6.2-rc1 kernel. See below numbers: > > v6.2-rc v6.3 > > Percentage huge-3 81.35 ( 0.00%) 32.97 ( -59.47%) > > Percentage huge-5 89.92 ( 0.00%) 41.70 ( -53.63%) > > Percentage huge-7 92.41 ( 0.00%) 34.08 ( -63.12%) > > Percentage huge-12 90.29 ( 0.00%) 41.10 ( -54.49%) > > Percentage huge-18 82.38 ( 0.00%) 41.24 ( -49.95%) > > Percentage huge-24 80.34 ( 0.00%) 35.99 ( -55.20%) > > Percentage huge-30 88.90 ( 0.00%) 44.20 ( -50.28%) > > Percentage huge-32 90.69 ( 0.00%) 79.57 ( -12.25%) > > > > Ops Compaction stalls 113790.00 207099.00 > > Ops Compaction success 33983.00 19488.00 > > Ops Compaction failures 79807.00 187611.00 > > Ops Compaction efficiency 29.86 9.41 > > > > After some investigation, I found the commit 95e7a450b819 > > ("Revert mm/compaction: fix set skip in fast_find_migrateblock") caused > > the regression. This commit revert the commit 7efc3b726103 ("mm/compaction: > > fix set skip in fast_find_migrateblock") to fix a CPU stalling issue, which > > is caused by compaction stucked in repeating fast_find_migrateblock(). > > > > And now the compaction stalling issue is addressed by commit cfccd2e63e7e > > ("mm, compaction: finish pageblocks on complete migration failure"). So > > IIRC at that time I was pointing out some scenarios that could make the > problem appear even after that commit, and we wanted to revisit that > when Mel is back. > Yes, I've prototyped the fix against 6.3-rc7 and the revert is at the end but the revert on its own has the potential for causing problems. The series needs to be rebased, retested and posted. What I last tested should show up shortly at https://git.kernel.org/pub/scm/linux/kernel/git/mel/linux.git/ mm-follupfastmigrate-v1r1 -- Mel Gorman SUSE Labs