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[195.135.220.15]) by mx.google.com with ESMTPS id j17si2395393ejb.33.2019.01.31.07.39.21 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 31 Jan 2019 07:39:21 -0800 (PST) Received-SPF: pass (google.com: domain of vbabka@suse.cz designates 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=pass (google.com: domain of vbabka@suse.cz designates 195.135.220.15 as permitted sender) smtp.mailfrom=vbabka@suse.cz X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 7C4BEAD5D; Thu, 31 Jan 2019 15:39:20 +0000 (UTC) Subject: Re: [PATCH 20/22] mm, compaction: Sample pageblocks for free pages To: Mel Gorman , Andrew Morton Cc: David Rientjes , Andrea Arcangeli , Linux List Kernel Mailing , Linux-MM References: <20190118175136.31341-1-mgorman@techsingularity.net> <20190118175136.31341-21-mgorman@techsingularity.net> From: Vlastimil Babka Openpgp: preference=signencrypt Message-ID: <919af440-28d2-465b-3414-bb4719b844ae@suse.cz> Date: Thu, 31 Jan 2019 16:39:19 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190118175136.31341-21-mgorman@techsingularity.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit 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 1/18/19 6:51 PM, Mel Gorman wrote: > Once fast searching finishes, there is a possibility that the linear > scanner is scanning full blocks found by the fast scanner earlier. This > patch uses an adaptive stride to sample pageblocks for free pages. The > more consecutive full pageblocks encountered, the larger the stride until > a pageblock with free pages is found. The scanners might meet slightly > sooner but it is an acceptable risk given that the search of the free > lists may still encounter the pages and adjust the cached PFN of the free > scanner accordingly. > > 5.0.0-rc1 5.0.0-rc1 > roundrobin-v3r17 samplefree-v3r17 > Amean fault-both-1 0.00 ( 0.00%) 0.00 * 0.00%* > Amean fault-both-3 2752.37 ( 0.00%) 2729.95 ( 0.81%) > Amean fault-both-5 4341.69 ( 0.00%) 4397.80 ( -1.29%) > Amean fault-both-7 6308.75 ( 0.00%) 6097.61 ( 3.35%) > Amean fault-both-12 10241.81 ( 0.00%) 9407.15 ( 8.15%) > Amean fault-both-18 13736.09 ( 0.00%) 10857.63 * 20.96%* > Amean fault-both-24 16853.95 ( 0.00%) 13323.24 * 20.95%* > Amean fault-both-30 15862.61 ( 0.00%) 17345.44 ( -9.35%) > Amean fault-both-32 18450.85 ( 0.00%) 16892.00 ( 8.45%) > > The latency is mildly improved offseting some overhead from earlier > patches that are prerequisites for the rest of the series. However, > a major impact is on the free scan rate with an 82% reduction. > > 5.0.0-rc1 5.0.0-rc1 > roundrobin-v3r17 samplefree-v3r17 > Compaction migrate scanned 21607271 20116887 > Compaction free scanned 95336406 16668703 > > It's also the first time in the series where the number of pages scanned > by the migration scanner is greater than the free scanner due to the > increased search efficiency. > > Signed-off-by: Mel Gorman Acked-by: Vlastimil Babka