Re: [libvirt] [Qemu-devel] [RFC] block I/O throttling: how to enable in libvirt

Message-ID: <4E602E8B.6010900(a)cn.fujitsu.com&gt; Date: Fri, 02 Sep 2011 09:16:59 +0800 From: Gui Jianfeng <guijianfeng(a)cn.fujitsu.com&gt; User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:6.0) Gecko/20110812 Thunderbird/6.0 MIME-Version: 1.0 To: Stefan Hajnoczi <stefanha(a)gmail.com&gt;, Zhi Yong Wu <wuzhy(a)linux.vnet.ibm.com&gt; References: <20110901050531.GB17963(a)f15.cn.ibm.com&gt; <20110901081149.GB14245(a)stefanha-thinkpad.localdomain&gt; In-Reply-To: <20110901081149.GB14245(a)stefanha-thinkpad.localdomain&gt; X-MIMETrack: Itemize by SMTP Server on mailserver/fnst(Release 8.5.1FP4|July 25, 2010) at 2011-09-02 09:15:49, Serialize by Router on mailserver/fnst(Release 8.5.1FP4|July 25, 2010) at 2011-09-02 09:15:52, Serialize complete at 2011-09-02 09:15:52 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=ISO-8859-1 X-detected-operating-system: by eggs.gnu.org: FreeBSD 6.x (1) X-Received-From: 222.73.24.84 Cc: libvir-list(a)redhat.com, hutao(a)cn.fujitsu.com, qemu-devel(a)nongnu.org, zwu.kernel(a)gmail.com, agl(a)us.ibm.com Subject: Re: [Qemu-devel] [RFC] block I/O throttling: how to enable in libvirt X-BeenThere: qemu-devel(a)nongnu.org 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:qemu-devel-request@nongnu.org?subject=unsubscribe> List-Archive: </archive/html/qemu-devel> List-Post: <mailto:qemu-devel@nongnu.org> List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help> List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>;, <mailto:qemu-devel-request@nongnu.org?subject=subscribe> X-Mailman-Copy: yes Errors-To: qemu-devel-bounces+wuzhy=linux.vnet.ibm.com(a)nongnu.org Sender: qemu-devel-bounces+wuzhy=linux.vnet.ibm.com(a)nongnu.org X-Brightmail-Tracker: AAAAAA== X-Xagent-From: guijianfeng(a)cn.fujitsu.com X-Xagent-To: wuzhy(a)linux.vnet.ibm.com X-Xagent-Gateway: vmsdvm9.vnet.ibm.com (XAGENTU at VMSDVM9) 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&gt; 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.

Thanks, Gui > > Stefan > >