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 <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.
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 :|