On Fri, Sep 2, 2011 at 3:09 AM, Zhi Yong Wu <wuzhy@xxxxxxxxxxxxxxxxxx> 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 <stefanha@xxxxxxxxx> >>To: Zhi Yong Wu <wuzhy@xxxxxxxxxxxxxxxxxx> >>Message-ID: <20110901081149.GB14245@stefanha-thinkpad.localdomain> >>References: <20110901050531.GB17963@xxxxxxxxxxxxxx> >>MIME-Version: 1.0 >>Content-Type: text/plain; charset=iso-8859-1 >>Content-Disposition: inline >>Content-Transfer-Encoding: 8bit >>In-Reply-To: <20110901050531.GB17963@xxxxxxxxxxxxxx> >>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: libvir-list@xxxxxxxxxx, guijianfeng@xxxxxxxxxxxxxx, agl@xxxxxxxxxx, >> qemu-devel@xxxxxxxxxx, zwu.kernel@xxxxxxxxx, hutao@xxxxxxxxxxxxxx >>Subject: Re: [Qemu-devel] [RFC] block I/O throttling: how to enable in >> libvirt >>X-BeenThere: qemu-devel@xxxxxxxxxx >>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@xxxxxxxxxx?subject=unsubscribe> >>List-Archive: </archive/html/qemu-devel> >>List-Post: <mailto:qemu-devel@xxxxxxxxxx> >>List-Help: <mailto:qemu-devel-request@xxxxxxxxxx?subject=help> >>List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>, >> <mailto:qemu-devel-request@xxxxxxxxxx?subject=subscribe> >>X-Mailman-Copy: yes >>Errors-To: qemu-devel-bounces+wuzhy=linux.vnet.ibm.com@xxxxxxxxxx >>Sender: qemu-devel-bounces+wuzhy=linux.vnet.ibm.com@xxxxxxxxxx >>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: stefanha@xxxxxxxxx >>X-Xagent-To: wuzhy@xxxxxxxxxxxxxxxxxx >>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 <agl@xxxxxxxxxx> 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. Stefan -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list