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Date: Mon, 2 Nov 2009 13:55:54 -0800 From: Andrew Morton <akpm@...ux-foundation.org> To: Laurent CORBES <laurent.corbes@...rtjog.com> Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org, dm-devel@...hat.com Subject: Re: Ext3 sequential read performance drop 2.6.29 -> 2.6.30,2.6.31,... On Tue, 13 Oct 2009 12:09:55 +0200 Laurent CORBES <laurent.corbes@...rtjog.com> wrote: > Hi all, > > While benchmarking some systems I discover a big sequential read performance > drop using ext3 on ~ big files. The drop seems to be introduced in 2.6.30. I'm > testing with 2.6.28.6 -> 2.6.29.6 -> 2.6.30.4 -> 2.6.31.3. Seems that large performance regressions aren't of interest to this list :( > I'm running a software raid6 (chunk 256k) on 6 750Go 7200rpm disks. here are > the raw datas of disks and raid device: > > $ dd if=/dev/sda of=/dev/null bs=1M count=10240 > 10240+0 records in > 10240+0 records out > 10737418240 bytes (11 GB) copied, 98.7483 seconds, 109 MB/s > > $ dd if=/dev/md7 of=/dev/null bs=1M count=10240 > 10240+0 records in > 10240+0 records out > 10737418240 bytes (11 GB) copied, 34.8744 seconds, 308 MB/s > > Over the different kernels changes here are not important (~1MB on the raw disk > and ~5MB on the raid device). The write of a 10GB file over the fs here is also > almost constant at ~100MB/s. > > $ dd if=/dev/zero of=/mnt/space/benchtmp//dd.out bs=1M count=10240 > 10240+0 records in > 10240+0 records out > 10737418240 bytes (11 GB) copied, 102.547 seconds, 105 MB/s > > However while reading this file there is a huge perf drop between 2.6.29.6 and > 2.6.30.4 and 2.6.31.3: > > 2.6.28.6: > sj-dev-7:/mnt/space/Benchmark# dd if=dd.out of=/dev/null bs=1M > 10240+0 records in > 10240+0 records out > 10737418240 bytes (11 GB) copied, 43.8288 seconds, 245 MB/s > > 2.6.29.6: > sj-dev-7:/mnt/space/Benchmark# dd if=dd.out of=/dev/null bs=1M > 10240+0 records in > 10240+0 records out > 10737418240 bytes (11 GB) copied, 42.745 seconds, 251 MB/s > > 2.6.30.4: > $ dd if=/mnt/space/benchtmp//dd.out of=/dev/null bs=1M > 10240+0 records in > 10240+0 records out > 10737418240 bytes (11 GB) copied, 48.621 seconds, 221 MB/s > > 2.6.31.3: > sj-dev-7:/mnt/space/Benchmark# dd if=dd.out of=/dev/null bs=1M > 10240+0 records in > 10240+0 records out > 10737418240 bytes (11 GB) copied, 51.4148 seconds, 209 MB/s > > ... Things going worst over time ... Did you do any further investigation? Do you think the regression is due to MD changes, or to something else? Thanks. > Numbers are average over ~10 runs each. > > I first check for stripe/stride aligment of the ext3 fs that is quite important > in raid6. I recheck it and everything seems fine from my understandings and > formula: > raid6 chunk 256k -> stride = 64. 4 data disks -> stripe-width = 256 ? > > In both case I'm using cfq IO scheduler and no special tuning is done with it. > > > For informations the test server is a Dell PowerEdge R710 with SAS 6iR, 4GB > ram and 6*750GB sata disks. I got the same behavior on PE2950 Perc6i, 2GB > ram and 6*750GB sata disks. > > Here are misc informations about the setup: > sj-dev-7:/mnt/space/Benchmark# cat /proc/mdstat > md7 : active raid6 sdf7[5] sde7[4] sdd7[3] sdc7[2] sdb7[1] sda7[0] > 2923443200 blocks level 6, 256k chunk, algorithm 2 [6/6] [UUUUUU] > bitmap: 0/175 pages [0KB], 2048KB chunk > > sj-dev-7:/mnt/space/Benchmark# dumpe2fs -h /dev/md7 > dumpe2fs 1.40-WIP (14-Nov-2006) > Filesystem volume name: <none> > Last mounted on: <not available> > Filesystem UUID: 9c29f236-e4f2-4db4-bf48-ea613cd0ebad > Filesystem magic number: 0xEF53 > Filesystem revision #: 1 (dynamic) > Filesystem features: has_journal resize_inode dir_index filetype > needs_recovery sparse_super large_file Filesystem flags: signed > directory hash Default mount options: (none) > Filesystem state: clean > Errors behavior: Continue > Filesystem OS type: Linux > Inode count: 713760 > Block count: 730860800 > Reserved block count: 0 > Free blocks: 705211695 > Free inodes: 713655 > First block: 0 > Block size: 4096 > Fragment size: 4096 > Reserved GDT blocks: 849 > Blocks per group: 32768 > Fragments per group: 32768 > Inodes per group: 32 > Inode blocks per group: 1 > Filesystem created: Thu Oct 1 15:45:01 2009 > Last mount time: Mon Oct 12 13:17:45 2009 > Last write time: Mon Oct 12 13:17:45 2009 > Mount count: 10 > Maximum mount count: 30 > Last checked: Thu Oct 1 15:45:01 2009 > Check interval: 15552000 (6 months) > Next check after: Tue Mar 30 15:45:01 2010 > Reserved blocks uid: 0 (user root) > Reserved blocks gid: 0 (group root) > First inode: 11 > Inode size: 128 > Journal inode: 8 > Default directory hash: tea > Directory Hash Seed: 378d4fd2-23c9-487c-b635-5601585f0da7 > Journal backup: inode blocks > Journal size: 128M > > > Thanks all. > > -- > Laurent Corbes - laurent.corbes@...rtjog.com > SmartJog SAS | Phone: +33 1 5868 6225 | Fax: +33 1 5868 6255 | www.smartjog.com > 27 Blvd Hippolyte Marqu__s, 94200 Ivry-sur-Seine, France > A TDF Group company > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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