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dkim=none (message not signed) header.d=none;toxicpanda.com; dmarc=none action=none header.from=oracle.com; Received: from BN6PR10MB1683.namprd10.prod.outlook.com (2603:10b6:405:b::15) by BN8PR10MB3137.namprd10.prod.outlook.com (2603:10b6:408:c3::33) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3846.25; Wed, 10 Feb 2021 06:14:45 +0000 Received: from BN6PR10MB1683.namprd10.prod.outlook.com ([fe80::9d63:7b79:33d4:a802]) by BN6PR10MB1683.namprd10.prod.outlook.com ([fe80::9d63:7b79:33d4:a802%3]) with mapi id 15.20.3825.030; Wed, 10 Feb 2021 06:14:45 +0000 Subject: Re: [PATCH v4 1/3] btrfs: add read_policy latency To: Michal Rostecki Cc: dsterba@suse.cz, linux-btrfs@vger.kernel.org, dsterba@suse.com, josef@toxicpanda.com References: <63f6f00e2ecc741efd2200c3c87b5db52c6be2fd.1611114341.git.anand.jain@oracle.com> <20210120121416.GX6430@twin.jikos.cz> <20210121175243.GF6430@twin.jikos.cz> <28b7ef3d-b5b9-f4a6-8d6f-1e6fc1103815@oracle.com> <9f406301-c16a-72a5-4ff3-d3bda127895e@oracle.com> <34cecc3d-235e-2f47-0992-675dc576b5be@oracle.com> <20210209211200.GA1662@wotan.suse.de> From: Anand Jain Message-ID: Date: Wed, 10 Feb 2021 14:14:34 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; 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Sorry for late response. > > For the singlethreaded test: > > [global] > name=btrfs-raid1-seqread > filename=btrfs-raid1-seqread > rw=read > bs=64k > direct=0 > numjobs=1 > time_based=0 > > [file1] > size=10G > ioengine=libaio > > results are: > > - raid1c3 with 3 HDDs: > 3 x Segate Barracuda ST2000DM008 (2TB) > * pid policy > READ: bw=215MiB/s (226MB/s), 215MiB/s-215MiB/s (226MB/s-226MB/s), > io=10.0GiB (10.7GB), run=47537-47537msec > * latency policy > READ: bw=219MiB/s (229MB/s), 219MiB/s-219MiB/s (229MB/s-229MB/s), > io=10.0GiB (10.7GB), run=46852-46852msec > * device policy - didn't test it here, I guess it doesn't make sense > to check it on non-mixed arrays ;) Hum. device policy provided best performance in non-mixed arrays with fio sequential workload. raid1c3 Read 500m (time = 60sec) ----------------------------------------------------- | nvme+ssd nvme+ssd all-nvme all-nvme | random seq random seq ------------+----------------------------------------- pid | 973MiB/s 955MiB/s 2144MiB/s 1962MiB/s latency | 2005MiB/s 1924MiB/s 2083MiB/s 1980MiB/s device(nvme)| 2021MiB/s 2034MiB/s 1920MiB/s 2132MiB/s roundrobin | 707MiB/s 701MiB/s 1760MiB/s 1990MiB/s > - raid1c3 with 2 HDDs and 1 SSD: > 2 x Segate Barracuda ST2000DM008 (2TB) > 1 x Crucial CT256M550SSD1 (256GB) > * pid policy > READ: bw=219MiB/s (230MB/s), 219MiB/s-219MiB/s (230MB/s-230MB/s), > io=10.0GiB (10.7GB), run=46749-46749msec > * latency policy > READ: bw=517MiB/s (542MB/s), 517MiB/s-517MiB/s (542MB/s-542MB/s), > io=10.0GiB (10.7GB), run=19823-19823msec > * device policy > READ: bw=517MiB/s (542MB/s), 517MiB/s-517MiB/s (542MB/s-542MB/s), > io=10.0GiB (10.7GB), run=19810-19810msec > > For the multithreaded test: > > [global] > name=btrfs-raid1-seqread > filename=btrfs-raid1-seqread > rw=read > bs=64k > direct=0 > numjobs=1 > time_based=0 > > [file1] > size=10G > ioengine=libaio > > results are: > > - raid1c3 with 3 HDDs: > 3 x Segate Barracuda ST2000DM008 (2TB) > * pid policy > READ: bw=1608MiB/s (1686MB/s), 201MiB/s-201MiB/s (211MB/s-211MB/s), > io=80.0GiB (85.9GB), run=50948-50949msec > * latency policy > READ: bw=1515MiB/s (1588MB/s), 189MiB/s-189MiB/s (199MB/s-199MB/s), > io=80.0GiB (85.9GB), run=54081-54084msec > - raid1c3 with 2 HDDs and 1 SSD: > 2 x Segate Barracuda ST2000DM008 (2TB) > 1 x Crucial CT256M550SSD1 (256GB) > * pid policy > READ: bw=1843MiB/s (1932MB/s), 230MiB/s-230MiB/s (242MB/s-242MB/s), > io=80.0GiB (85.9GB), run=44449-44450msec > * latency policy > READ: bw=4213MiB/s (4417MB/s), 527MiB/s-527MiB/s (552MB/s-552MB/s), > io=80.0GiB (85.9GB), run=19444-19446msec > * device policy > READ: bw=4196MiB/s (4400MB/s), 525MiB/s-525MiB/s (550MB/s-550MB/s), > io=80.0GiB (85.9GB), run=19522-19522msec > > To sum it up - I think that your policies are indeed a very good match > for mixed (nonrot and rot) arrays. > > They perform either slightly better or worse (depending on the test) > than pid policy on all-HDD arrays. Theoretically, latency would perform better, as the latency parameter works as a feedback loop. Dynamically adjusting itself to the delivered performance. But there is overhead to calculate the latency. Thanks, Anand > I've just sent out my proposal of roundrobin policy, which seems to give > better performance for all-HDD than your policies (and better than pid > policy in all cases): > > https://patchwork.kernel.org/project/linux-btrfs/patch/20210209203041.21493-7-mrostecki@suse.de/ > > Cheers, > Michal >