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[195.135.220.15]) by mx.google.com with ESMTPS id qt9si28103557ejb.283.2019.08.06.04.11.12 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 06 Aug 2019 04:11:12 -0700 (PDT) Received-SPF: softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org 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 DB69CB629; Tue, 6 Aug 2019 11:11:11 +0000 (UTC) Date: Tue, 6 Aug 2019 13:11:09 +0200 From: Michal Hocko To: Minchan Kim Cc: kernel test robot , Andrew Morton , LKML , linux-mm , Miguel de Dios , Wei Wang , Johannes Weiner , Mel Gorman , lkp@01.org Subject: Re: [mm] 755d6edc1a: will-it-scale.per_process_ops -4.1% regression Message-ID: <20190806111109.GV11812@dhcp22.suse.cz> References: <20190729071037.241581-1-minchan@kernel.org> <20190806070547.GA10123@xsang-OptiPlex-9020> <20190806080415.GG11812@dhcp22.suse.cz> <20190806110024.GA32615@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190806110024.GA32615@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) 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 Tue 06-08-19 20:00:24, Minchan Kim wrote: > On Tue, Aug 06, 2019 at 10:04:15AM +0200, Michal Hocko wrote: > > On Tue 06-08-19 15:05:47, kernel test robot wrote: > > > Greeting, > > > > > > FYI, we noticed a -4.1% regression of will-it-scale.per_process_ops due to commit: > > > > I have to confess I cannot make much sense from numbers because they > > seem to be too volatile and the main contributor doesn't stand up for > > me. Anyway, regressions on microbenchmarks like this are not all that > > surprising when a locking is slightly changed and the critical section > > made shorter. I have seen that in the past already. > > I guess if it's multi process workload. The patch will give more chance > to be scheduled out so TLB miss ratio would be bigger than old. > I see it's natural trade-off for latency vs. performance so only thing > I could think is just increase threshold from 32 to 64 or 128? This still feels like a magic number tunning, doesn't it? -- Michal Hocko SUSE Labs