Hi Kir, Yes, we already see the fix and I can confirm that CFQ scheduler is working again. We are already using it in our Proxmox VE, now also with OpenVZ in the 2.6.32 kernel - released today.
(my post was from 25.8, was held back due to size issues). Thanks, Br, martin From: Kirill Korotaev [mailto:d...@parallels.com] Sent: Donnerstag, 02. September 2010 14:27 To: users@openvz.org Cc: Martin Maurer Subject: Re: [Users] RE: slow fsync rate Pavel has already confirmed that this is a problem of mainstream group CFS scheduler, see bug in bugzilla for fix. Will be applied soon. Use deadline scheduler for some time until it is fixed in the tree. Thanks, Kirill On Aug 25, 2010, at 10:33 , Martin Maurer wrote: Hi Kir, Yes, the performance number shows that it does not use the cache so if anyone want to run high load like a database on such a system the performance loss will be significant and the system will be more or less unusable (compared to current stable). I got this behavior ONLY with 2.6.32 OpenVZ kernels. E.g. also the standard Debian Squeeze Kernel give the expected performance, the OpenVZ enabled kernel from Squeeze doesn´t. (see also http://lists.debian.org/debian-kernel/2010/08/msg00217.html). We tested on several hardware and distributions, e.g. with single drives, hardware raid controllers with BBU - e.g. the Intel Modular Server but also on single drives on ICH7/8/9. The logs always shows that the disk has read and write cache enabled, but the values are just bad. Can you reproduce the issue (just run the sysbench)? Br, Martin From: users-boun...@openvz.org<mailto:users-boun...@openvz.org> [mailto:users-boun...@openvz.org] On Behalf Of Kirill Korotaev Sent: Dienstag, 24. August 2010 21:42 To: users@openvz.org<mailto:users@openvz.org> Subject: Re: [Users] RE: slow fsync rate These numbers very much resemble fsync() rate with write cache enabled (~1000/sec) and disabled (50-70/sec). check write cache settings with hdparm + check whether you have barrier mount option on ext3. I believe, 2.6.32 is just more honest on fsync and really forces drive to save data. While earlier kernels did this only with BARRIER mount option (or ignored this problem at all)... Thanks, Kirill On Aug 24, 2010, at 22:53 , Martin Maurer wrote: Hi all, I just tested the latest OpenVZ kernel 2.6.32 (bykovsky) from today with sysbench, I just got 63.12 Requests/sec executed (see below). 2.6.18 and 2.6.24 OpenVZ Kernels performs well, I got 1074.81 Requests/sec executed. What's wrong here, why is the 2.6.32 branch so slow regarding fsyns/sec? (I am using ext3) ____ OpenVZ 2.6.24:~# sysbench --test=fileio --file-num=1 --file-total-size=50G --file-fsync-all=on --file-test-mode=seqrewr --max-time=100 --file-block-size=4096 --max-requests=0 run sysbench 0.4.12: multi-threaded system evaluation benchmark Running the test with following options: Number of threads: 1 Extra file open flags: 0 1 files, 50Gb each 50Gb total file size Block size 4Kb Calling fsync() after each write operation. Using synchronous I/O mode Doing sequential rewrite test Threads started! Time limit exceeded, exiting... Done. Operations performed: 0 Read, 107485 Write, 107485 Other = 214970 Total Read 0b Written 419.86Mb Total transferred 419.86Mb (4.1985Mb/sec) 1074.81 Requests/sec executed Test execution summary: total time: 100.0033s total number of events: 107485 total time taken by event execution: 99.9460 per-request statistics: min: 0.54ms avg: 0.93ms max: 97.34ms approx. 95 percentile: 0.87ms Threads fairness: events (avg/stddev): 107485.0000/0.00 execution time (avg/stddev): 99.9460/0.00 _____ Testing newest Kernel: 2.6.32-bykovsky.1 #1 SMP Mon Aug 23 19:59:54 MSD 2010 x86_64 I just got 63.12 Requests/sec executed. Here are the details, can someone reproduce this? _____ OpenVZ 2.6.32:~# sysbench --test=fileio --file-num=1 --file-total-size=50G --file-fsync-all=on --file-test-mode=seqrewr --max-time=100 --file-block-size=4096 --max-requests=0 run sysbench 0.4.12: multi-threaded system evaluation benchmark Running the test with following options: Number of threads: 1 Extra file open flags: 0 1 files, 50Gb each 50Gb total file size Block size 4Kb Calling fsync() after each write operation. Using synchronous I/O mode Doing sequential rewrite test Threads started! Time limit exceeded, exiting... Done. Operations performed: 0 Read, 6312 Write, 6312 Other = 12624 Total Read 0b Written 24.656Mb Total transferred 24.656Mb (252.46Kb/sec) 63.12 Requests/sec executed Test execution summary: total time: 100.0070s total number of events: 6312 total time taken by event execution: 99.9838 per-request statistics: min: 7.70ms avg: 15.84ms max: 260.40ms approx. 95 percentile: 16.70ms Threads fairness: events (avg/stddev): 6312.0000/0.00 execution time (avg/stddev): 99.9838/0.00 ___ Br, Martin From: users-boun...@openvz.org<mailto:users-boun...@openvz.org> [mailto:users-boun...@openvz.org] On Behalf Of Dietmar Maurer Sent: Dienstag, 24. August 2010 10:36 To: users@openvz.org<mailto:users@openvz.org> Subject: [Users] slow fsync rate Hi all, we observe very slow fsync rates on newer 2.6.32 kernel with OpenVZ: It is possible to reproduce the problem with sysbench: # sysbench --test=fileio --file-num=1 --file-total-size=50G --file-fsync-all=on --file-test-mode=seqrewr --max-time=100 --file-block-size=4096 --max-requests=0 run Requests/sec executed is considerable slower on OpenVZ kernel (factor 20 on Intel Modular Server). Can someone reproduce that problem? - Dietmar <ATT00001..c> <ATT00001..c>
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