* [Qemu-devel] [RFC] block I/O throttling: how to enable in libvirt
@ 2011-09-01 5:05 Zhi Yong Wu
2011-09-01 8:11 ` Stefan Hajnoczi
0 siblings, 1 reply; 7+ messages in thread
From: Zhi Yong Wu @ 2011-09-01 5:05 UTC (permalink / raw)
To: libvir-list; +Cc: stefanha, agl, qemu-devel, zwu.kernel, guijianfeng, hutao
----- Forwarded message from Zhi Yong Wu <wuzhy@linux.vnet.ibm.com> -----
Date: Thu, 1 Sep 2011 11:55:17 +0800
From: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: "Daniel P. Berrange" <berrange@redhat.com>, Stefan Hajnoczi
<stefanha@gmail.com>, Adam Litke <agl@us.ibm.com>, Zhi Yong Wu
<wuzhy@linux.vnet.ibm.com>, QEMU Developers <qemu-devel@nongnu.org>,
guijianfeng@cn.fujitsu.com, hutao@cn.fujitsu.com
Subject: [RFC] block I/O throttling: how to enable in libvirt
Message-ID: <20110901035517.GD16985@f15.cn.ibm.com>
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On Wed, Aug 31, 2011 at 08:18:19AM +0100, Stefan Hajnoczi wrote:
>Subject: Re: The design choice for how to enable block I/O throttling
> function in libvirt
>From: Stefan Hajnoczi <stefanha@gmail.com>
>To: Adam Litke <agl@us.ibm.com>
>Cc: libvir-list@redhat.com, "Daniel P. Berrange" <berrange@redhat.com>, Zhi
> Yong Wu <wuzhy@linux.vnet.ibm.com>, Zhi Yong Wu <zwu.kernel@gmail.com>
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>
>On Tue, Aug 30, 2011 at 2:46 PM, Adam Litke <agl@us.ibm.com> wrote:
>> On Tue, Aug 30, 2011 at 09:53:33AM +0100, Stefan Hajnoczi wrote:
>>> On Tue, Aug 30, 2011 at 3:55 AM, Zhi Yong Wu <zwu.kernel@gmail.com> wrote:
>>> > I am trying to enable block I/O throttling function in libvirt. But
>>> > currently i met some design questions, and don't make sure if we
>>> > should extend blkiotune to support block I/O throttling or introduce
>>> > one new libvirt command "blkiothrottle" to cover it or not. If you
>>> > have some better idea, pls don't hesitate to drop your comments.
>>>
>>> A little bit of context: this discussion is about adding libvirt
>>> support for QEMU disk I/O throttling.
>>
>> Thanks for the additional context Stefan.
>>
>>> Today libvirt supports the cgroups blkio-controller, which handles
>>> proportional shares and throughput/iops limits on host block devices.
>>> blkio-controller does not support network file systems (NFS) or other
>>> QEMU remote block drivers (curl, Ceph/rbd, sheepdog) since they are
>>> not host block devices. QEMU I/O throttling works with all types of
>>> -drive and therefore complements blkio-controller.
>>
>> The first question that pops into my mind is: Should a user need to understand
>> when to use the cgroups blkio-controller vs. the QEMU I/O throttling method? In
>> my opinion, it would be nice if libvirt had a single interface for block I/O
>> throttling and libvirt would decide which mechanism to use based on the type of
>> device and the specific limits that need to be set.
>
>Yes, I agree it would be simplest to pick the right mechanism,
>depending on the type of throttling the user wants. More below.
>
>>> 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-io-throttling-in-qemu.pdf
>>
>> 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.
Daniel and other maintainers,
If you are available, can you make some comments for us?:)
Regards,
Zhi Yong Wu
>
>Stefan
----- End forwarded message -----
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [Qemu-devel] [RFC] block I/O throttling: how to enable in libvirt
2011-09-01 5:05 [Qemu-devel] [RFC] block I/O throttling: how to enable in libvirt Zhi Yong Wu
@ 2011-09-01 8:11 ` Stefan Hajnoczi
2011-09-01 8:49 ` Daniel P. Berrange
2011-09-02 1:16 ` Gui Jianfeng
0 siblings, 2 replies; 7+ messages in thread
From: Stefan Hajnoczi @ 2011-09-01 8:11 UTC (permalink / raw)
To: Zhi Yong Wu; +Cc: libvir-list, guijianfeng, agl, qemu-devel, zwu.kernel, hutao
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@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-io-throttling-in-qemu.pdf
> >>
> >> 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.
Stefan
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [Qemu-devel] [RFC] block I/O throttling: how to enable in libvirt
2011-09-01 8:11 ` Stefan Hajnoczi
@ 2011-09-01 8:49 ` Daniel P. Berrange
2011-09-02 1:16 ` Gui Jianfeng
1 sibling, 0 replies; 7+ messages in thread
From: Daniel P. Berrange @ 2011-09-01 8:49 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: libvir-list, guijianfeng, agl, qemu-devel, zwu.kernel,
Zhi Yong Wu, hutao
On Thu, Sep 01, 2011 at 09:11:49AM +0100, 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@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-io-throttling-in-qemu.pdf
> > >>
> > >> 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, the virDomainGetBlkioParameters/virDomainSetBlkioParameters
APIs, and blkio virsh command are intended to be a generic interface
for setting any block related tuning parameters, regardless of what
the underling implementation is. So any use of QEMU I/O throttling
features should be added to those APIs/commands.
Daniel
--
|: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :|
|: http://libvirt.org -o- http://virt-manager.org :|
|: http://autobuild.org -o- http://search.cpan.org/~danberr/ :|
|: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [Qemu-devel] [RFC] block I/O throttling: how to enable in libvirt
2011-09-01 8:11 ` Stefan Hajnoczi
2011-09-01 8:49 ` Daniel P. Berrange
@ 2011-09-02 1:16 ` Gui Jianfeng
1 sibling, 0 replies; 7+ messages in thread
From: Gui Jianfeng @ 2011-09-02 1:16 UTC (permalink / raw)
To: Stefan Hajnoczi, Zhi Yong Wu
Cc: libvir-list, hutao, qemu-devel, zwu.kernel, agl
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@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-io-throttling-in-qemu.pdf
>>>>
>>>> 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.
Thanks,
Gui
>
> Stefan
>
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [Qemu-devel] [RFC] block I/O throttling: how to enable in libvirt
2011-09-01 4:21 ` Osier Yang
@ 2011-09-01 4:51 ` Zhi Yong Wu
0 siblings, 0 replies; 7+ messages in thread
From: Zhi Yong Wu @ 2011-09-01 4:51 UTC (permalink / raw)
To: Osier Yang
Cc: Stefan Hajnoczi, Adam Litke, QEMU Developers, guijianfeng, hutao
On Thu, Sep 01, 2011 at 12:21:20PM +0800, Osier Yang wrote:
>Message-ID: <4E5F0840.5010203@redhat.com>
>Date: Thu, 01 Sep 2011 12:21:20 +0800
>From: Osier Yang <jyang@redhat.com>
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> Developers <qemu-devel@nongnu.org>, guijianfeng@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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>
>于 2011年09月01日 11:55, Zhi Yong Wu 写道:
>>On Wed, Aug 31, 2011 at 08:18:19AM +0100, Stefan Hajnoczi wrote:
>>>Subject: Re: The design choice for how to enable block I/O throttling
>>>function in libvirt
>>>From: Stefan Hajnoczi<stefanha@gmail.com>
>>>To: Adam Litke<agl@us.ibm.com>
>>>Cc: libvir-list@redhat.com, "Daniel P. Berrange"<berrange@redhat.com>, Zhi
>>>Yong Wu<wuzhy@linux.vnet.ibm.com>, Zhi Yong Wu<zwu.kernel@gmail.com>
>>>Content-Type: text/plain; charset=ISO-8859-1
>>>Content-Transfer-Encoding: quoted-printable
>>>X-Brightmail-Tracker: AAAAAA==
>>>X-Xagent-From: stefanha@gmail.com
>>>X-Xagent-To: wuzhy@linux.vnet.ibm.com
>>>X-Xagent-Gateway: bldgate.vnet.ibm.com (XAGENTU7 at BLDGATE)
>>>
>>>On Tue, Aug 30, 2011 at 2:46 PM, Adam Litke<agl@us.ibm.com> wrote:
>>>>On Tue, Aug 30, 2011 at 09:53:33AM +0100, Stefan Hajnoczi wrote:
>>>>>On Tue, Aug 30, 2011 at 3:55 AM, Zhi Yong Wu<zwu.kernel@gmail.com> wrote:
>>>>>>I am trying to enable block I/O throttling function in libvirt. But
>>>>>>currently i met some design questions, and don't make sure if we
>>>>>>should extend blkiotune to support block I/O throttling or introduce
>>>>>>one new libvirt command "blkiothrottle" to cover it or not. If you
>>>>>>have some better idea, pls don't hesitate to drop your comments.
>>>>>A little bit of context: this discussion is about adding libvirt
>>>>>support for QEMU disk I/O throttling.
>>>>Thanks for the additional context Stefan.
>>>>
>>>>>Today libvirt supports the cgroups blkio-controller, which handles
>>>>>proportional shares and throughput/iops limits on host block devices.
>>>>>blkio-controller does not support network file systems (NFS) or other
>>>>>QEMU remote block drivers (curl, Ceph/rbd, sheepdog) since they are
>>>>>not host block devices. QEMU I/O throttling works with all types of
>>>>>-drive and therefore complements blkio-controller.
>>>>The first question that pops into my mind is: Should a user need to understand
>>>>when to use the cgroups blkio-controller vs. the QEMU I/O throttling method? In
>>>>my opinion, it would be nice if libvirt had a single interface for block I/O
>>>>throttling and libvirt would decide which mechanism to use based on the type of
>>>>device and the specific limits that need to be set.
>>>Yes, I agree it would be simplest to pick the right mechanism,
>>>depending on the type of throttling the user wants. More below.
>>>
>>>>>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-io-throttling-in-qemu.pdf
>>>> 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.
>>
>>Danial and other maintainers,
>>
>>If you are available, can you make some comments for us?:)
>
>Seems you posted to wrong list? This should be discussed in libvir-list
>instead.
No, libvirt-list is where i want to post.
>
>And if you meant to post to libvir-list, then s/Danial/Daniel/ :-)
Sorry, thanks for your correcting, Jintao. We have not met for several years.
>
>>
>>Regards,
>>
>>Zhi Yong Wu
>>>Stefan
>
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [Qemu-devel] [RFC] block I/O throttling: how to enable in libvirt
2011-09-01 3:55 ` [Qemu-devel] [RFC] block I/O throttling: how to enable " Zhi Yong Wu
@ 2011-09-01 4:21 ` Osier Yang
2011-09-01 4:51 ` Zhi Yong Wu
0 siblings, 1 reply; 7+ messages in thread
From: Osier Yang @ 2011-09-01 4:21 UTC (permalink / raw)
To: Zhi Yong Wu
Cc: Stefan Hajnoczi, Adam Litke, QEMU Developers, guijianfeng, hutao
于 2011年09月01日 11:55, Zhi Yong Wu 写道:
> On Wed, Aug 31, 2011 at 08:18:19AM +0100, Stefan Hajnoczi wrote:
>> Subject: Re: The design choice for how to enable block I/O throttling
>> function in libvirt
>> From: Stefan Hajnoczi<stefanha@gmail.com>
>> To: Adam Litke<agl@us.ibm.com>
>> Cc: libvir-list@redhat.com, "Daniel P. Berrange"<berrange@redhat.com>, Zhi
>> Yong Wu<wuzhy@linux.vnet.ibm.com>, Zhi Yong Wu<zwu.kernel@gmail.com>
>> Content-Type: text/plain; charset=ISO-8859-1
>> Content-Transfer-Encoding: quoted-printable
>> X-Brightmail-Tracker: AAAAAA==
>> X-Xagent-From: stefanha@gmail.com
>> X-Xagent-To: wuzhy@linux.vnet.ibm.com
>> X-Xagent-Gateway: bldgate.vnet.ibm.com (XAGENTU7 at BLDGATE)
>>
>> On Tue, Aug 30, 2011 at 2:46 PM, Adam Litke<agl@us.ibm.com> wrote:
>>> On Tue, Aug 30, 2011 at 09:53:33AM +0100, Stefan Hajnoczi wrote:
>>>> On Tue, Aug 30, 2011 at 3:55 AM, Zhi Yong Wu<zwu.kernel@gmail.com> wrote:
>>>>> I am trying to enable block I/O throttling function in libvirt. But
>>>>> currently i met some design questions, and don't make sure if we
>>>>> should extend blkiotune to support block I/O throttling or introduce
>>>>> one new libvirt command "blkiothrottle" to cover it or not. If you
>>>>> have some better idea, pls don't hesitate to drop your comments.
>>>> A little bit of context: this discussion is about adding libvirt
>>>> support for QEMU disk I/O throttling.
>>> Thanks for the additional context Stefan.
>>>
>>>> Today libvirt supports the cgroups blkio-controller, which handles
>>>> proportional shares and throughput/iops limits on host block devices.
>>>> blkio-controller does not support network file systems (NFS) or other
>>>> QEMU remote block drivers (curl, Ceph/rbd, sheepdog) since they are
>>>> not host block devices. QEMU I/O throttling works with all types of
>>>> -drive and therefore complements blkio-controller.
>>> The first question that pops into my mind is: Should a user need to understand
>>> when to use the cgroups blkio-controller vs. the QEMU I/O throttling method? In
>>> my opinion, it would be nice if libvirt had a single interface for block I/O
>>> throttling and libvirt would decide which mechanism to use based on the type of
>>> device and the specific limits that need to be set.
>> Yes, I agree it would be simplest to pick the right mechanism,
>> depending on the type of throttling the user wants. More below.
>>
>>>> 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-io-throttling-in-qemu.pdf
>>> 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.
>
> Danial and other maintainers,
>
> If you are available, can you make some comments for us?:)
Seems you posted to wrong list? This should be discussed in libvir-list
instead.
And if you meant to post to libvir-list, then s/Danial/Daniel/ :-)
>
> Regards,
>
> Zhi Yong Wu
>> Stefan
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Qemu-devel] [RFC] block I/O throttling: how to enable in libvirt
[not found] ` <CAJSP0QUHm=y8XJC_KXRg7ufFZt3K_XDDfQb--sxjC+c0GjO8qg@mail.gmail.com>
@ 2011-09-01 3:55 ` Zhi Yong Wu
2011-09-01 4:21 ` Osier Yang
0 siblings, 1 reply; 7+ messages in thread
From: Zhi Yong Wu @ 2011-09-01 3:55 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: hutao, Adam Litke, QEMU Developers, Zhi Yong Wu, guijianfeng
On Wed, Aug 31, 2011 at 08:18:19AM +0100, Stefan Hajnoczi wrote:
>Subject: Re: The design choice for how to enable block I/O throttling
> function in libvirt
>From: Stefan Hajnoczi <stefanha@gmail.com>
>To: Adam Litke <agl@us.ibm.com>
>Cc: libvir-list@redhat.com, "Daniel P. Berrange" <berrange@redhat.com>, Zhi
> Yong Wu <wuzhy@linux.vnet.ibm.com>, Zhi Yong Wu <zwu.kernel@gmail.com>
>Content-Type: text/plain; charset=ISO-8859-1
>Content-Transfer-Encoding: quoted-printable
>X-Brightmail-Tracker: AAAAAA==
>X-Xagent-From: stefanha@gmail.com
>X-Xagent-To: wuzhy@linux.vnet.ibm.com
>X-Xagent-Gateway: bldgate.vnet.ibm.com (XAGENTU7 at BLDGATE)
>
>On Tue, Aug 30, 2011 at 2:46 PM, Adam Litke <agl@us.ibm.com> wrote:
>> On Tue, Aug 30, 2011 at 09:53:33AM +0100, Stefan Hajnoczi wrote:
>>> On Tue, Aug 30, 2011 at 3:55 AM, Zhi Yong Wu <zwu.kernel@gmail.com> wrote:
>>> > I am trying to enable block I/O throttling function in libvirt. But
>>> > currently i met some design questions, and don't make sure if we
>>> > should extend blkiotune to support block I/O throttling or introduce
>>> > one new libvirt command "blkiothrottle" to cover it or not. If you
>>> > have some better idea, pls don't hesitate to drop your comments.
>>>
>>> A little bit of context: this discussion is about adding libvirt
>>> support for QEMU disk I/O throttling.
>>
>> Thanks for the additional context Stefan.
>>
>>> Today libvirt supports the cgroups blkio-controller, which handles
>>> proportional shares and throughput/iops limits on host block devices.
>>> blkio-controller does not support network file systems (NFS) or other
>>> QEMU remote block drivers (curl, Ceph/rbd, sheepdog) since they are
>>> not host block devices. QEMU I/O throttling works with all types of
>>> -drive and therefore complements blkio-controller.
>>
>> The first question that pops into my mind is: Should a user need to understand
>> when to use the cgroups blkio-controller vs. the QEMU I/O throttling method? In
>> my opinion, it would be nice if libvirt had a single interface for block I/O
>> throttling and libvirt would decide which mechanism to use based on the type of
>> device and the specific limits that need to be set.
>
>Yes, I agree it would be simplest to pick the right mechanism,
>depending on the type of throttling the user wants. More below.
>
>>> 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-io-throttling-in-qemu.pdf
>>
>> 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.
Danial and other maintainers,
If you are available, can you make some comments for us?:)
Regards,
Zhi Yong Wu
>
>Stefan
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2011-09-02 1:16 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2011-09-01 5:05 [Qemu-devel] [RFC] block I/O throttling: how to enable in libvirt Zhi Yong Wu
2011-09-01 8:11 ` Stefan Hajnoczi
2011-09-01 8:49 ` Daniel P. Berrange
2011-09-02 1:16 ` Gui Jianfeng
-- strict thread matches above, loose matches on Subject: below --
2011-08-30 2:55 [Qemu-devel] The design choice for how to enable block I/O throttling function " Zhi Yong Wu
[not found] ` <CAJSP0QW1CPCokX=F5z7y==vn1S4wH0VtOaQ7oj4kC7f7uQM4MQ@mail.gmail.com>
[not found] ` <20110830134636.GB29130@aglitke.rchland.ibm.com>
[not found] ` <CAJSP0QUHm=y8XJC_KXRg7ufFZt3K_XDDfQb--sxjC+c0GjO8qg@mail.gmail.com>
2011-09-01 3:55 ` [Qemu-devel] [RFC] block I/O throttling: how to enable " Zhi Yong Wu
2011-09-01 4:21 ` Osier Yang
2011-09-01 4:51 ` Zhi Yong Wu
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