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@gmail.com> To: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com> Message-ID: <20110901081149.GB14245@stefanha-thinkpad.localdomain> References: <20110901050531.GB17963@f15.cn.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20110901050531.GB17963@f15.cn.ibm.com> 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@redhat.com, guijianfeng@cn.fujitsu.com, agl@us.ibm.com, qemu-devel@nongnu.org, zwu.kernel@gmail.com, hutao@cn.fujitsu.com Subject: Re: [Qemu-devel] [RFC] block I/O throttling: how to enable in libvirt X-BeenThere: qemu-devel@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@nongnu.org Sender: qemu-devel-bounces+wuzhy=linux.vnet.ibm.com@nongnu.org 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@gmail.com X-Xagent-To: wuzhy@linux.vnet.ibm.com 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@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-t...
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.
Regards, Zhi Yong Wu
Stefan