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CH0PR12MB5347.namprd12.prod.outlook.com (2603:10b6:610:d6::18) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.6455.33; Wed, 7 Jun 2023 11:41:10 +0000 Received: from DS7PR12MB6165.namprd12.prod.outlook.com ([fe80::714c:3289:2d9e:954e]) by DS7PR12MB6165.namprd12.prod.outlook.com ([fe80::714c:3289:2d9e:954e%4]) with mapi id 15.20.6455.030; Wed, 7 Jun 2023 11:41:09 +0000 Message-ID: <53f3872a-4cbf-563a-2658-9222586680da@amd.com> Date: Wed, 7 Jun 2023 17:10:53 +0530 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.6.1 Subject: Re: [RFC PATCH V3 0/1] sched/numa: Fix disjoint set vma scan regression Content-Language: en-US To: Raghavendra K T , linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Ingo Molnar , Peter Zijlstra , Mel Gorman , Andrew Morton , David Hildenbrand , rppt@kernel.org, Juri Lelli , Vincent Guittot , Bharata B Rao , Aithal Srikanth , kernel test robot References: From: 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handled that issue by allowing first two scans at mm level > (mm->numa_scan_seq) unconditionally. But that was not enough. > > One of the test that exercise similar side effect is numa01_THREAD_ALLOC where > allocation happen by main thread and it is divided into memory chunks of 24MB > to be continuously bzeroed (for 128 threads on my machine). > > This was found in internal LKP run and also reported by [4]. > > While RFC V1 [2] tried to address this issue, the logic had more heuristics. > RFC V2 [3] was rewritten based on vma_size. > > Current implementation drops some of additional logic for long running task > and relooked some of the usage of READ_ONCE/WRITE_ONCE(). > > The current patch addresses the same issue in a more accurate way as > follows: > > (1) Any disjoint vma which is not associated with a task, that tries to > scan is now allowed to induce prot_none faults. Total number of such > unconditional scans allowed per vma is derived based on the exact vma size > as follows: > > total scans allowed = 1/2 * vma_size / scan_size. > > (2) Total scans already done is maintained using a per vma scan counter. > > With above patch, numa01_THREAD_ALLOC regression reported is resolved, > but please note that with [1] there was a drastic decrease in system time > for mmtest numa01, this patch adds back some of the system time. > > Summary: numa scan enhancement patch [1] togethor with the current patchset > improves overall system time by filtering unnecessary numa scan > while still retaining necessary scanning in some corner cases which > involves disjoint set vmas. > > Your comments/Ideas are welcome. > > Changes since: > RFC V2: > 1) Drop reset of scan counter that tried to take care of long running workloads > 2) Correct usage of READ_ONCE/WRITE_ONCE (Bharata) > 3) Base is 6.4.0-rc2 > > RFC V1: > 1) Rewrite entire logic based on actual vma size than heuristics > 2) Added Reported-by kernel test robot and internal LKP test > 3) Rebased to 6.4.-rc1 (ba0ad6ed89) > > Result: > SUT: Milan w/ 2 numa nodes 256 cpus > > Run of numa01_THREAD__ALLOC on 6.4.0-rc2 (that has w/ numascan enhancement) > base-numascan base base+fix > real 1m1.507s 1m23.259s 1m2.632s > user 213m51.336s 251m46.363s 220m35.528s > sys 3m3.397s 0m12.492s 2m41.393s > > numa_hit 5615517 4560123 4963875 > numa_local 5615505 4560024 4963700 > numa_other 12 99 175 > numa_pte_updates 1822797 493 1559111 > numa_hint_faults 1307113 523 1469031 > numa_hint_faults_local 612617 488 884829 > numa_pages_migrated 694370 35 584202 > > We can see regression in base real time recovered, but with some additional > system time overhead. > > Below is the mmtest autonuma performance > > autonumabench > =========== > (base 6.4.0-rc2 that has numascan enhancement) > base-numascan base base+fix > Amean syst-NUMA01 300.46 ( 0.00%) 23.97 * 92.02%* 67.18 * 77.64%* > Amean syst-NUMA01_THREADLOCAL 0.20 ( 0.00%) 0.22 * -9.15%* 0.22 * -9.15%* > Amean syst-NUMA02 0.70 ( 0.00%) 0.71 * -0.61%* 0.70 * 0.41%* > Amean syst-NUMA02_SMT 0.58 ( 0.00%) 0.62 * -5.38%* 0.61 * -3.67%* > Amean elsp-NUMA01 320.92 ( 0.00%) 276.13 * 13.96%* 324.11 * -0.99%* > Amean elsp-NUMA01_THREADLOCAL 1.02 ( 0.00%) 1.03 * -1.83%* 1.03 * -1.83%* > Amean elsp-NUMA02 3.16 ( 0.00%) 3.93 * -24.20%* 3.14 * 0.81%* > Amean elsp-NUMA02_SMT 3.82 ( 0.00%) 3.87 * -1.27%* 3.44 * 9.90%* > > Duration User 403532.43 279173.53 359098.23 > Duration System 2114.31 179.20 481.54 > Duration Elapsed 2312.20 2004.48 2335.84 > > Ops NUMA alloc hit 55795455.00 45452739.00 45500387.00 > Ops NUMA alloc local 55794177.00 45435858.00 45500070.00 > Ops NUMA base-page range updates 147858285.00 18601.00 42043107.00 > Ops NUMA PTE updates 147858285.00 18601.00 42043107.00 > Ops NUMA hint faults 150531983.00 18254.00 42450080.00 > Ops NUMA hint local faults % 125691825.00 11964.00 32993313.00 > Ops NUMA hint local percent 83.50 65.54 77.72 > Ops NUMA pages migrated 13535786.00 2207.00 4654628.00 > Ops AutoNUMA cost 753952.10 91.44 212633.14 > > Please note there is a system time overhead added for numa01 but we still have very > good improvement w.r.t base without numascan. > I tested the patch with lkp autonuma benchmark on a dual socket 4th Generation EPYC server (2 X 96C/192T) running in NPS1 mode. Below are the results: commit: 6.4.0-rc2 6.4.0-rc2+patch 6.4.0-rc2 6.4.0-rc2+patch ---------------- --------------------------- %stddev %change %stddev \ | \ 501.84 -12.5% 439.14 numa01.seconds 228.66 -1.8% 224.44 numa01_THREAD_ALLOC.seconds 0.51 +21.6% 0.62 numa02.seconds 107.17 +0.0% 107.17 numa02_SMT.seconds 2936 -9.1% 2669 elapsed_time 794910 +3.7% 824178 system_time 474520 -17.5% 391331 user_time Tested-by: Swapnil Sapkal > [1] Link: https://lore.kernel.org/lkml/cover.1677672277.git.raghavendra.kt@amd.com/T/#t > [2] Link: https://lore.kernel.org/lkml/cover.1683033105.git.raghavendra.kt@amd.com/ > [3] Link: https://lore.kernel.org/lkml/cover.1684228065.git.raghavendra.kt@amd.com/T/ > [4] Link: https://lore.kernel.org/lkml/db995c11-08ba-9abf-812f-01407f70a5d4@amd.com/T/ > > Raghavendra K T (1): > sched/numa: Fix disjoint set vma scan regression > > include/linux/mm_types.h | 1 + > kernel/sched/fair.c | 31 ++++++++++++++++++++++++------- > 2 files changed, 25 insertions(+), 7 deletions(-) > -- Thanks and regards, Swapnil