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Date: Tue, 13 Oct 2009 15:10:02 +0200 From: Laurent CORBES <laurent.corbes@...rtjog.com> To: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org Subject: Re: Ext3 sequential read performance drop 2.6.29 -> 2.6.30,2.6.31,... Some updates and added linux-fsdevel in the loop: > 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. > > 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: I add slabtop infos before and after the runs for 2.6.28.6 and 2.6.31.3. run is just after a system reboot Active / Total Objects (% used) : 83612 / 90199 (92.7%) Active / Total Slabs (% used) : 4643 / 4643 (100.0%) Active / Total Caches (% used) : 93 / 150 (62.0%) Active / Total Size (% used) : 16989.63K / 17858.85K (95.1%) Minimum / Average / Maximum Object : 0.01K / 0.20K / 4096.00K OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME 20820 20688 99% 0.12K 694 30 2776K dentry 12096 12029 99% 0.04K 144 84 576K sysfs_dir_cache 8701 8523 97% 0.03K 77 113 308K size-32 6036 6018 99% 0.32K 503 12 2012K inode_cache 4757 4646 97% 0.05K 71 67 284K buffer_head 4602 4254 92% 0.06K 78 59 312K size-64 4256 4256 100% 0.47K 532 8 2128K ext3_inode_cache 3864 3607 93% 0.08K 84 46 336K vm_area_struct 2509 2509 100% 0.28K 193 13 772K radix_tree_node 2130 1373 64% 0.12K 71 30 284K filp 1962 1938 98% 0.41K 218 9 872K shmem_inode_cache 1580 1580 100% 0.19K 79 20 316K skbuff_head_cache 1524 1219 79% 0.01K 6 254 24K anon_vma 1450 1450 100% 2.00K 725 2 2900K size-2048 1432 1382 96% 0.50K 179 8 716K size-512 1260 1198 95% 0.12K 42 30 168K size-128 > 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 Active / Total Objects (% used) : 78853 / 90405 (87.2%) Active / Total Slabs (% used) : 5079 / 5084 (99.9%) Active / Total Caches (% used) : 93 / 150 (62.0%) Active / Total Size (% used) : 17612.24K / 19391.84K (90.8%) Minimum / Average / Maximum Object : 0.01K / 0.21K / 4096.00K OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME 17589 17488 99% 0.28K 1353 13 5412K radix_tree_node 12096 12029 99% 0.04K 144 84 576K sysfs_dir_cache 9840 5659 57% 0.12K 328 30 1312K dentry 8701 8568 98% 0.03K 77 113 308K size-32 5226 4981 95% 0.05K 78 67 312K buffer_head 4602 4366 94% 0.06K 78 59 312K size-64 4264 4253 99% 0.47K 533 8 2132K ext3_inode_cache 3726 3531 94% 0.08K 81 46 324K vm_area_struct 2130 1364 64% 0.12K 71 30 284K filp 1962 1938 98% 0.41K 218 9 872K shmem_inode_cache 1580 1460 92% 0.19K 79 20 316K skbuff_head_cache 1548 1406 90% 0.32K 129 12 516K inode_cache 1524 1228 80% 0.01K 6 254 24K anon_vma 1450 1424 98% 2.00K 725 2 2900K size-2048 1432 1370 95% 0.50K 179 8 716K size-512 1260 1202 95% 0.12K 42 30 168K size-128 > 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 Active / Total Objects (% used) : 88438 / 97670 (90.5%) Active / Total Slabs (% used) : 5451 / 5451 (100.0%) Active / Total Caches (% used) : 93 / 155 (60.0%) Active / Total Size (% used) : 19564.52K / 20948.54K (93.4%) Minimum / Average / Maximum Object : 0.01K / 0.21K / 4096.00K OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME 21547 21527 99% 0.13K 743 29 2972K dentry 12684 12636 99% 0.04K 151 84 604K sysfs_dir_cache 8927 8639 96% 0.03K 79 113 316K size-32 6721 6720 99% 0.33K 611 11 2444K inode_cache 4425 4007 90% 0.06K 75 59 300K size-64 4240 4237 99% 0.48K 530 8 2120K ext3_inode_cache 4154 4089 98% 0.05K 62 67 248K buffer_head 3910 3574 91% 0.08K 85 46 340K vm_area_struct 2483 2449 98% 0.28K 191 13 764K radix_tree_node 2280 1330 58% 0.12K 76 30 304K filp 2240 2132 95% 0.19K 112 20 448K skbuff_head_cache 2198 2198 100% 2.00K 1099 2 4396K size-2048 1935 1910 98% 0.43K 215 9 860K shmem_inode_cache 1770 1738 98% 0.12K 59 30 236K size-96 1524 1278 83% 0.01K 6 254 24K anon_vma 1056 936 88% 0.50K 132 8 528K size-512 > 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 Active / Total Objects (% used) : 81843 / 97478 (84.0%) Active / Total Slabs (% used) : 5759 / 5763 (99.9%) Active / Total Caches (% used) : 92 / 155 (59.4%) Active / Total Size (% used) : 19486.81K / 22048.45K (88.4%) Minimum / Average / Maximum Object : 0.01K / 0.23K / 4096.00K OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME 17589 17426 99% 0.28K 1353 13 5412K radix_tree_node 12684 12636 99% 0.04K 151 84 604K sysfs_dir_cache 10991 6235 56% 0.13K 379 29 1516K dentry 8927 8624 96% 0.03K 79 113 316K size-32 4824 4819 99% 0.05K 72 67 288K buffer_head 4425 3853 87% 0.06K 75 59 300K size-64 3910 3527 90% 0.08K 85 46 340K vm_area_struct 3560 3268 91% 0.48K 445 8 1780K ext3_inode_cache 2288 1394 60% 0.33K 208 11 832K inode_cache 2280 1236 54% 0.12K 76 30 304K filp 2240 2183 97% 0.19K 112 20 448K skbuff_head_cache 2216 2191 98% 2.00K 1108 2 4432K size-2048 1935 1910 98% 0.43K 215 9 860K shmem_inode_cache 1770 1719 97% 0.12K 59 30 236K size-96 1524 1203 78% 0.01K 6 254 24K anon_vma 1056 921 87% 0.50K 132 8 528K size-512 > ... Things going worst over time ... > > 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 Marquès, 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/
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