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[91.12.107.41]) by smtp.gmail.com with ESMTPSA id c185sm5341371wma.44.2020.10.23.12.46.19 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 23 Oct 2020 12:46:19 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable From: David Hildenbrand Mime-Version: 1.0 (1.0) Subject: Re: [mm/page_alloc] 7fef431be9: vm-scalability.throughput 87.8% improvement Date: Fri, 23 Oct 2020 21:46:18 +0200 Message-Id: <9F5E9E0C-A367-49EE-8764-58555C742F1E@redhat.com> References: Cc: kernel test robot , Axel Rasmussen , Kevin Ko , David Hildenbrand , Linus Torvalds , Andrew Morton , Vlastimil Babka , Oscar Salvador , Wei Yang , Pankaj Gupta , Michal Hocko , Alexander Duyck , Mel Gorman , Dave Hansen , Mike Rapoport , "K. Y. Srinivasan" , Haiyang Zhang , Stephen Hemminger , Wei Liu , Matthew Wilcox , Michael Ellerman , Michal Hocko , Scott Cheloha , LKML , lkp@lists.01.org, lkp@intel.com, ying.huang@intel.com, feng.tang@intel.com, zhengjun.xing@intel.com In-Reply-To: To: David Rientjes X-Mailer: iPhone Mail (18A393) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > Am 23.10.2020 um 21:29 schrieb David Rientjes : >=20 > =EF=BB=BFOn Wed, 21 Oct 2020, kernel test robot wrote: >=20 >> Greeting, >>=20 >> FYI, we noticed a 87.8% improvement of vm-scalability.throughput due to c= ommit: >>=20 >>=20 >> commit: 7fef431be9c9ac255838a9578331567b9dba4477 ("mm/page_alloc: place p= ages to tail in __free_pages_core()") >> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master >>=20 >>=20 >> in testcase: vm-scalability >> on test machine: 192 threads Intel(R) Xeon(R) Platinum 9242 CPU @ 2.30GHz= with 192G memory >> with following parameters: >>=20 >> runtime: 300s >> size: 512G >> test: anon-wx-rand-mt >> cpufreq_governor: performance >> ucode: 0x5002f01 >>=20 >> test-description: The motivation behind this suite is to exercise functio= ns and regions of the mm/ of the Linux kernel which are of interest to us. >> test-url: https://git.kernel.org/cgit/linux/kernel/git/wfg/vm-scalability= .git/ >>=20 >=20 > I'm curious why we are not able to reproduce this improvement on Skylake=20= > and actually see a slight performance degradation, at least for=20 > 300s_128G_truncate_throughput. >=20 > Axel Rasmussen can provide more details on our=20= > results. >=20 As this patch only affects how we first place pages into the freelists when b= ooting up, I=E2=80=98d be surprised if there would be observable change in a= ctual numbers. Run your system for long enough and it=E2=80=98s all going to= be random in the freelists anyway. Looks more like random measurement anomalies to me. But maybe there are corn= er cases where the initial state of the freelists affects a benchmark when r= un immediately after boot?=