On Fri, Sep 02, 2011 at 09:50:42AM +0100, Stefan Hajnoczi wrote: >Date: Fri, 2 Sep 2011 09:50:42 +0100 >Message-ID: ><CAJSP0QWc9OcOKxG3jGgYD3r5f=2fqv3snvcrarc2tm0ymp+...@mail.gmail.com> >Subject: Re: [Qemu-devel] [RFC] block I/O throttling: how to enable in > libvirt >From: Stefan Hajnoczi <[email protected]> >To: Zhi Yong Wu <[email protected]> >Cc: [email protected] >Content-Type: text/plain; charset=ISO-8859-1 >Content-Transfer-Encoding: quoted-printable >X-Brightmail-Tracker: AAAAAA== >X-Xagent-From: [email protected] >X-Xagent-To: [email protected] >X-Xagent-Gateway: vmsdvm4.vnet.ibm.com (XAGENTU5 at VMSDVM4) > >On Fri, Sep 2, 2011 at 3:09 AM, Zhi Yong Wu <[email protected]> wrote: >> On Thu, Sep 01, 2011 at 09:11:49AM +0100, Stefan Hajnoczi wrote: >>>Date: Thu, 1 Sep 2011 09:11:49 +0100 >>>From: Stefan Hajnoczi <[email protected]> >>>To: Zhi Yong Wu <[email protected]> >>>Message-ID: <[email protected]> >>>References: <[email protected]> >>>MIME-Version: 1.0 >>>Content-Type: text/plain; charset=iso-8859-1 >>>Content-Disposition: inline >>>Content-Transfer-Encoding: 8bit >>>In-Reply-To: <[email protected]> >>>User-Agent: Mutt/1.5.21 (2010-09-15) >>>X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.6 (newer, 2) >>>X-Received-From: 74.125.82.173 >>>Cc: [email protected], [email protected], [email protected], >>> [email protected], [email protected], [email protected] >>>Subject: Re: [Qemu-devel] [RFC] block I/O throttling: how to enable in >>> libvirt >>>X-BeenThere: [email protected] >>>X-Mailman-Version: 2.1.14 >>>Precedence: list >>>List-Id: <qemu-devel.nongnu.org> >>>List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>, >>> <mailto:[email protected]?subject=unsubscribe> >>>List-Archive: </archive/html/qemu-devel> >>>List-Post: <mailto:[email protected]> >>>List-Help: <mailto:[email protected]?subject=help> >>>List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>, >>> <mailto:[email protected]?subject=subscribe> >>>X-Mailman-Copy: yes >>>Errors-To: [email protected] >>>Sender: [email protected] >>>x-cbid: 11090108-7282-0000-0000-0000010970B0 >>>X-IBM-ISS-SpamDetectors: Score=0; BY=0; FL=0; FP=0; FZ=0; HX=0; KW=0; PH=0; >>> SC=0; ST=0; TS=0; UL=0; ISC= >>>X-IBM-ISS-DetailInfo: BY=3.00000211; HX=3.00000168; KW=3.00000007; >>> PH=3.00000001; SC=3.00000001; SDB=6.00067104; UDB=6.00020326; >>> UTC=2011-09-01 08:12:15 >>>X-Xagent-From: [email protected] >>>X-Xagent-To: [email protected] >>>X-Xagent-Gateway: vmsdvm6.vnet.ibm.com (XAGENTU5 at VMSDVM6) >>> >>>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 <[email protected]> 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. >> QEMU I/O throttling currently don't support those options of blkiotune, such >> as --live, --config and --current.If those bps/iops settings are modified, >> it will immediately take effect. > >The --live, --config, and --current options are implemented inside >libvirt and do not require hypervisor support. Take a look at >src/qemu/qemu_driver.c:qemuDomainSetBlkioParameters() to see how these >options are implemented for blkiotune today. I have understood this, thanks.
BTW: i have seen your comments against block I/O throttling patchset, and will respond next week. Regards, Zhi Yong Wu > >Stefan -- libvir-list mailing list [email protected] https://www.redhat.com/mailman/listinfo/libvir-list
