[Users] RE: slow fsync rate
Martin Maurer
martin at proxmox.com
Tue Aug 24 14:53:51 EDT 2010
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-bounces at openvz.org [mailto:users-bounces at openvz.org] On Behalf Of Dietmar Maurer
Sent: Dienstag, 24. August 2010 10:36
To: users at 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
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