From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:52547) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QyynE-0001I5-CD for qemu-devel@nongnu.org; Thu, 01 Sep 2011 00:22:21 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1QyynB-0002yl-Gf for qemu-devel@nongnu.org; Thu, 01 Sep 2011 00:22:20 -0400 Received: from mx1.redhat.com ([209.132.183.28]:5720) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QyynB-0002yR-8V for qemu-devel@nongnu.org; Thu, 01 Sep 2011 00:22:17 -0400 Message-ID: <4E5F0840.5010203@redhat.com> Date: Thu, 01 Sep 2011 12:21:20 +0800 From: Osier Yang MIME-Version: 1.0 References: <20110830134636.GB29130@aglitke.rchland.ibm.com> <20110901035517.GD16985@f15.cn.ibm.com> In-Reply-To: <20110901035517.GD16985@f15.cn.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [RFC] block I/O throttling: how to enable in libvirt List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Zhi Yong Wu Cc: Stefan Hajnoczi , Adam Litke , QEMU Developers , guijianfeng@cn.fujitsu.com, hutao@cn.fujitsu.com =E4=BA=8E 2011=E5=B9=B409=E6=9C=8801=E6=97=A5 11:55, Zhi Yong Wu =E5=86=99= =E9=81=93: > 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 >> To: Adam Litke >> Cc: libvir-list@redhat.com, "Daniel P. Berrange",= Zhi >> Yong Wu, Zhi Yong Wu >> Content-Type: text/plain; charset=3DISO-8859-1 >> Content-Transfer-Encoding: quoted-printable >> X-Brightmail-Tracker: AAAAAA=3D=3D >> 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 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 = 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 introduc= e >>>>> 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 othe= r >>>> 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 u= nderstand >>> 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 bl= ock I/O >>> throttling and libvirt would decide which mechanism to use based on t= he 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 o= n >>>> 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 possib= le to apply >>> either method from the same API in a transparent manner. Am I correc= t or are we >>> suggesting that the Qemu throttling approach should always be used fo= r 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