9:27 p.m.
On 2011-9-2 9:58, Zhi Yong Wu wrote:
On Fri, Sep 02, 2011 at 09:16:59AM +0800, Gui Jianfeng wrote:
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> Date: Fri, 02 Sep 2011 09:16:59 +0800
> From: Gui Jianfeng <guijianfeng(a)cn.fujitsu.com>
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> Subject: Re: [Qemu-devel] [RFC] block I/O throttling: how to enable in
> libvirt
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> On 2011-9-1 16:11, Stefan Hajnoczi wrote:
>> On Thu, Sep 01, 2011 at 01:05:31PM +0800, Zhi Yong Wu wrote:
>>> On Wed, Aug 31, 2011 at 08:18:19AM +0100, Stefan Hajnoczi wrote:
>>>> On Tue, Aug 30, 2011 at 2:46 PM, Adam Litke <agl(a)us.ibm.com>
wrote:
>>>>> On Tue, Aug 30, 2011 at 09:53:33AM +0100, Stefan Hajnoczi wrote:
>>>>>> I/O throttling can be applied independently to each -drive
attached to
>>>>>> a guest and supports throughput/iops limits. For more
information on
>>>>>> this QEMU feature and a comparison with blkio-controller, see
Ryan
>>>>>> Harper's KVM Forum 2011 presentation:
>>>>>
>>>>>>
http://www.linux-kvm.org/wiki/images/7/72/2011-forum-keep-a-limit-on-it-i...
>>>>>
>>>>> From the presentation, it seems that both the cgroups method the the
qemu method
>>>>> offer comparable control (assuming a block device) so it might
possible to apply
>>>>> either method from the same API in a transparent manner. Am I
correct or are we
>>>>> suggesting that the Qemu throttling approach should always be used
for Qemu
>>>>> domains?
>>>>
>>>> QEMU I/O throttling does not provide a proportional share mechanism.
>>>> So you cannot assign weights to VMs and let them receive a fraction of
>>>> the available disk time. That is only supported by cgroups
>>>> blkio-controller because it requires a global view which QEMU does not
>>>> have.
>>>>
>>>> So I think the two are complementary:
>>>>
>>>> If proportional share should be used on a host block device, use
>>>> cgroups blkio-controller.
>>>> Otherwise use QEMU I/O throttling.
>>> Stefan,
>>>
>>> Do you agree with introducing one new libvirt command blkiothrottle now?
>>> If so, i will work on the code draft to make it work.
>>
>> No, I think that the blkiotune command should be extended to support
>> QEMU I/O throttling. This is not new functionality, we already have
>> cgroups blkio-controller support today. Therefore I think it makes
>> sense to keep a unified interface instead of adding a new command.
>
> Agreed.
> Proportional controlling interfaces and throttling interfaces are all
> the same cgroup subsystem. So Just extend blkiotune to add new options
> to support throttling tuning.
Hi, Gui,
QEMU block I/O throttling is not relative to cgroup subsystem, i think.
anyway, thanks for your sugguests.
Ahh, I misunderstand you before. I thought you mentioned the blkio cgroup throttling
interfaces.
Ok, I think QEmu I/O throttling has similar semantic with blkio cgroup. So extending
blkiotune command is preferred, IMHO.
Thanks,
Gui
Regards,
Zhi Yong Wu
>
> Thanks,
> Gui
>
>>
>> Stefan
>>
>>
>
>
>