On Thu, Sep 01, 2011 at 09:11:49AM +0100, 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 <a...@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-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, the virDomainGetBlkioParameters/virDomainSetBlkioParameters APIs, and blkio virsh command are intended to be a generic interface for setting any block related tuning parameters, regardless of what the underling implementation is. So any use of QEMU I/O throttling features should be added to those APIs/commands. Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :| -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list