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@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. 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 > > -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list