* [Qemu-devel] Greate difference of disk I/O performance for guest on Qemu-2.30 of CentOS.
@ 2015-06-15 13:14 cauchy-love
2015-06-16 13:05 ` Stefan Hajnoczi
0 siblings, 1 reply; 10+ messages in thread
From: cauchy-love @ 2015-06-15 13:14 UTC (permalink / raw)
To: qemu-devel
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Hi all,
I am running a embedded OS on Qemu-2.3.0. However I found that the I/O performance was quite different for different CentOS release (CentOS 6.5 and CentOS 7.0). The CentOS 6.5 uses linux-2.6.32 while the CentOS 7.0 uses linux-3.10.0. The I/O throughput (write) of the former (CentOS 6.5) is about ten times of that on the latter (CentOS 7.0). All configurations are the same except the kernel version. And the command line is as following:
# qemu-kvm -m 2G -smp 4 -enable-kvm -hda guest.img ...
The I/O throughput of the host is almost the same for these two different kernels, as tested by Iozone tool. Actually, I found that the IO throughput degraded significantly since the 3.4 or later kernel version. I also tried different qemu versions such as qemu-1.5.3, qemu-2.1.3 but got no improvements.
Hope someone can provide helps.
Yi
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* Re: [Qemu-devel] Greate difference of disk I/O performance for guest on Qemu-2.30 of CentOS.
2015-06-15 13:14 [Qemu-devel] Greate difference of disk I/O performance for guest on Qemu-2.30 of CentOS cauchy-love
@ 2015-06-16 13:05 ` Stefan Hajnoczi
2015-06-19 0:40 ` cauchy-love
2015-06-19 1:03 ` cauchy-love
0 siblings, 2 replies; 10+ messages in thread
From: Stefan Hajnoczi @ 2015-06-16 13:05 UTC (permalink / raw)
To: cauchy-love; +Cc: qemu-devel
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On Mon, Jun 15, 2015 at 09:14:52PM +0800, cauchy-love wrote:
> I am running a embedded OS on Qemu-2.3.0. However I found that the I/O performance was quite different for different CentOS release (CentOS 6.5 and CentOS 7.0). The CentOS 6.5 uses linux-2.6.32 while the CentOS 7.0 uses linux-3.10.0. The I/O throughput (write) of the former (CentOS 6.5) is about ten times of that on the latter (CentOS 7.0). All configurations are the same except the kernel version. And the command line is as following:
> # qemu-kvm -m 2G -smp 4 -enable-kvm -hda guest.img ...
> The I/O throughput of the host is almost the same for these two different kernels, as tested by Iozone tool. Actually, I found that the IO throughput degraded significantly since the 3.4 or later kernel version. I also tried different qemu versions such as qemu-1.5.3, qemu-2.1.3 but got no improvements.
Please post the iozone command-line you are using and the output.
Your QEMU command-line uses the IDE storage controller, which is not
optimized for performance. Usually virtio-blk is used when good
performance is required:
-drive if=virtio,cache=none,format=raw,aio=native,file=guest.img
The guest OS needs virtio-blk device drivers in order for this to work.
Stefan
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^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [Qemu-devel] Greate difference of disk I/O performance for guest on Qemu-2.30 of CentOS.
2015-06-16 13:05 ` Stefan Hajnoczi
@ 2015-06-19 0:40 ` cauchy-love
2015-06-19 15:24 ` Stefan Hajnoczi
2015-06-19 1:03 ` cauchy-love
1 sibling, 1 reply; 10+ messages in thread
From: cauchy-love @ 2015-06-19 0:40 UTC (permalink / raw)
To: Stefan Hajnoczi; +Cc: qemu-devel
the iozone command line is:
./iozone -i 0 -i 1 -f ./iotmp -Rab ./iotmp.xls -g 8G -n 4G -c
The problem is why the performance difference is so big for different linux kernels. The guest's io performance test is by both FTP tools and raw write, which demonstrate the much lower performance of Centos 7 (1/10 of that on Centos 6.5). And how can I debug this problem?
Thanks again for your help.
Yi
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在 2015-06-16 21:05:39,"Stefan Hajnoczi" <stefanha@gmail.com> 写道:
>On Mon, Jun 15, 2015 at 09:14:52PM +0800, cauchy-love wrote:
>> I am running a embedded OS on Qemu-2.3.0. However I found that the I/O performance was quite different for different CentOS release (CentOS 6.5 and CentOS 7.0). The CentOS 6.5 uses linux-2.6.32 while the CentOS 7.0 uses linux-3.10.0. The I/O throughput (write) of the former (CentOS 6.5) is about ten times of that on the latter (CentOS 7.0). All configurations are the same except the kernel version. And the command line is as following:
>> # qemu-kvm -m 2G -smp 4 -enable-kvm -hda guest.img ...
>> The I/O throughput of the host is almost the same for these two different kernels, as tested by Iozone tool. Actually, I found that the IO throughput degraded significantly since the 3.4 or later kernel version. I also tried different qemu versions such as qemu-1.5.3, qemu-2.1.3 but got no improvements.
>
>Please post the iozone command-line you are using and the output.
>
>Your QEMU command-line uses the IDE storage controller, which is not
>optimized for performance. Usually virtio-blk is used when good
>performance is required:
>
> -drive if=virtio,cache=none,format=raw,aio=native,file=guest.img
>
>The guest OS needs virtio-blk device drivers in order for this to work.
>
>Stefan
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [Qemu-devel] Greate difference of disk I/O performance for guest on Qemu-2.30 of CentOS.
2015-06-16 13:05 ` Stefan Hajnoczi
2015-06-19 0:40 ` cauchy-love
@ 2015-06-19 1:03 ` cauchy-love
2015-06-19 8:37 ` Paolo Bonzini
1 sibling, 1 reply; 10+ messages in thread
From: cauchy-love @ 2015-06-19 1:03 UTC (permalink / raw)
To: Stefan Hajnoczi; +Cc: qemu-devel
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I have tried your qemu cammand line but got no luck (the embedded os have no virtio support but this is not the problem i think). The problem probably lies in the host kernel version as it is the only difference for my tests. I traced the guest kernel and found the ATA drivers always used non-DMA mode (CentOS 7 and CentOS 6.5 are the same at this point).
Yi
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在 2015-06-16 21:05:39,"Stefan Hajnoczi" <stefanha@gmail.com> 写道:
>On Mon, Jun 15, 2015 at 09:14:52PM +0800, cauchy-love wrote:
>> I am running a embedded OS on Qemu-2.3.0. However I found that the I/O performance was quite different for different CentOS release (CentOS 6.5 and CentOS 7.0). The CentOS 6.5 uses linux-2.6.32 while the CentOS 7.0 uses linux-3.10.0. The I/O throughput (write) of the former (CentOS 6.5) is about ten times of that on the latter (CentOS 7.0). All configurations are the same except the kernel version. And the command line is as following:
>> # qemu-kvm -m 2G -smp 4 -enable-kvm -hda guest.img ...
>> The I/O throughput of the host is almost the same for these two different kernels, as tested by Iozone tool. Actually, I found that the IO throughput degraded significantly since the 3.4 or later kernel version. I also tried different qemu versions such as qemu-1.5.3, qemu-2.1.3 but got no improvements.
>
>Please post the iozone command-line you are using and the output.
>
>Your QEMU command-line uses the IDE storage controller, which is not
>optimized for performance. Usually virtio-blk is used when good
>performance is required:
>
> -drive if=virtio,cache=none,format=raw,aio=native,file=guest.img
>
>The guest OS needs virtio-blk device drivers in order for this to work.
>
>Stefan
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^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [Qemu-devel] Greate difference of disk I/O performance for guest on Qemu-2.30 of CentOS.
2015-06-19 1:03 ` cauchy-love
@ 2015-06-19 8:37 ` Paolo Bonzini
2015-06-23 3:22 ` cauchy-love
[not found] ` <5ec70e6c.267de.14e257e00ab.Coremail.cauchy-love@163.com>
0 siblings, 2 replies; 10+ messages in thread
From: Paolo Bonzini @ 2015-06-19 8:37 UTC (permalink / raw)
To: cauchy-love, Stefan Hajnoczi; +Cc: qemu-devel
On 19/06/2015 03:03, cauchy-love wrote:
> I have tried your qemu cammand line but got no luck (the embedded os
> have no virtio support but this is not the problem i think). The
> problem probably lies in the host kernel version as it is the only
> difference for my tests. I traced the guest kernel and found the ATA
> drivers always used non-DMA mode (CentOS 7 and CentOS 6.5 are the
> same at this point).
You can use perf to see what's the difference.
Perhaps CentOS 6.5 used ext4 and 7 uses XFS? Though in general XFS is
the faster one...
Paolo
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [Qemu-devel] Greate difference of disk I/O performance for guest on Qemu-2.30 of CentOS.
2015-06-19 8:37 ` Paolo Bonzini
@ 2015-06-23 3:22 ` cauchy-love
[not found] ` <5ec70e6c.267de.14e257e00ab.Coremail.cauchy-love@163.com>
1 sibling, 0 replies; 10+ messages in thread
From: cauchy-love @ 2015-06-23 3:22 UTC (permalink / raw)
To: Paolo Bonzini; +Cc: Stefan Hajnoczi, qemu-devel
thanks for your help. I don't think it is the filesystem that causes this problem since when I updated the kernel of CentOS6.5 to the CentOS 7.0's version and the disk io performance was nearly the same as CentOS 7.0.
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在 2015-06-19 16:37:23,"Paolo Bonzini" <pbonzini@redhat.com> 写道:
>
>
>On 19/06/2015 03:03, cauchy-love wrote:
>> I have tried your qemu cammand line but got no luck (the embedded os
>> have no virtio support but this is not the problem i think). The
>> problem probably lies in the host kernel version as it is the only
>> difference for my tests. I traced the guest kernel and found the ATA
>> drivers always used non-DMA mode (CentOS 7 and CentOS 6.5 are the
>> same at this point).
>
>You can use perf to see what's the difference.
>
>Perhaps CentOS 6.5 used ext4 and 7 uses XFS? Though in general XFS is
>the faster one...
>
>Paolo
>
^ permalink raw reply [flat|nested] 10+ messages in thread
[parent not found: <5ec70e6c.267de.14e257e00ab.Coremail.cauchy-love@163.com>]
end of thread, other threads:[~2015-06-24 13:06 UTC | newest]
Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed)
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2015-06-15 13:14 [Qemu-devel] Greate difference of disk I/O performance for guest on Qemu-2.30 of CentOS cauchy-love
2015-06-16 13:05 ` Stefan Hajnoczi
2015-06-19 0:40 ` cauchy-love
2015-06-19 15:24 ` Stefan Hajnoczi
2015-06-19 1:03 ` cauchy-love
2015-06-19 8:37 ` Paolo Bonzini
2015-06-23 3:22 ` cauchy-love
[not found] ` <5ec70e6c.267de.14e257e00ab.Coremail.cauchy-love@163.com>
[not found] ` <558AA072.3080507@redhat.com>
2015-06-24 12:31 ` cauchy-love
2015-06-24 12:32 ` Paolo Bonzini
2015-06-24 12:50 ` cauchy-love
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