| RHEL6 - IO priority not working ? [message #43579] |
Wed, 28 September 2011 12:57  |
VE4FUN
Messages: 8
Registered: August 2011
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Junior Member |
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Hello,
I did some tests with 2.6.32-042stab037.1 kernel and it looks that IO priority has no impact on disk write operations.
2 identical VE on same disk (block device), one with IO priority 0 and other with IO priority 7. Results are pretty the same for both VE.
root@vps6:/# for i in 1 2 3 4 5; do dd if=/dev/zero of=test bs=64k count=32k conv=fdatasync; done
32768+0 records in
32768+0 records out
2147483648 bytes (2.1 GB) copied, 91.7144 s, 23.4 MB/s
32768+0 records in
32768+0 records out
2147483648 bytes (2.1 GB) copied, 70.1665 s, 30.6 MB/s
32768+0 records in
32768+0 records out
2147483648 bytes (2.1 GB) copied, 123.251 s, 17.4 MB/s
32768+0 records in
32768+0 records out
2147483648 bytes (2.1 GB) copied, 93.4022 s, 23.0 MB/s
32768+0 records in
32768+0 records out
2147483648 bytes (2.1 GB) copied, 126.531 s, 17.0 MB/s
root@vps7:/# for i in 1 2 3 4 5; do dd if=/dev/zero of=test bs=64k count=32k conv=fdatasync; done
32768+0 records in
32768+0 records out
2147483648 bytes (2.1 GB) copied, 98.4753 s, 21.8 MB/s
32768+0 records in
32768+0 records out
2147483648 bytes (2.1 GB) copied, 125.971 s, 17.0 MB/s
32768+0 records in
32768+0 records out
2147483648 bytes (2.1 GB) copied, 115.74 s, 18.6 MB/s
32768+0 records in
32768+0 records out
2147483648 bytes (2.1 GB) copied, 110.097 s, 19.5 MB/s
32768+0 records in
32768+0 records out
2147483648 bytes (2.1 GB) copied, 95.8683 s, 22.4 MB/s
am I doing something wrong ?
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| Re: RHEL6 - IO priority not working ? [message #43593 is a reply to message #43592] |
Thu, 29 September 2011 11:37  |
VE4FUN
Messages: 8
Registered: August 2011
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Junior Member |
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From OpenVZ wiki page about IO priorities.
"This feature is based on CFQ I/O scheduler, so this scheduler should be used for block device in question"
I guess it can not work without CFQ scheduler.
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