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Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: [PATCH] Revert "Revert "mm/compaction: fix set skip in fast_find_migrateblock"" To: Mel Gorman , Vlastimil Babka Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <3576e3520c044beb2a81860aecb2d4f597089300.1682521303.git.baolin.wang@linux.alibaba.com> <20230426153331.dfqagb47i4xo3ouv@techsingularity.net> From: Baolin Wang In-Reply-To: <20230426153331.dfqagb47i4xo3ouv@techsingularity.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: AFE30C000E X-Rspamd-Server: rspam01 X-Stat-Signature: utsoy98mts8mjp9dd5qxq7i34h9kf1g7 X-HE-Tag: 1682557084-849290 X-HE-Meta: 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 rQayftcA OkQ1C7KFvUFAg6JSM2YzQSq4DIIUIbjzGu8b13OP6ud6qgQbAz4OoAO2Y7C9IzRPiQTG685vIvrZUmA5WdHOXzVgbJaKgJ+LFPlHT98JCizy7djfZ3uQPkTYT+3x9vUVJPNMqd5zIm9gcbRzLovA5ON9bOdWm966wHo73dquqb1oKEjzCYu5orj5+jg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 4/26/2023 11:33 PM, Mel Gorman wrote: > 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. Ah, I missed that, and will check previous discussion. > 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 Thanks.