On Tue, May 31, 2011 at 02:56:46PM +0100, Daniel P. Berrange wrote: > On Tue, May 31, 2011 at 09:45:37AM -0400, Vivek Goyal wrote: > > On Mon, May 30, 2011 at 01:09:23PM +0800, Zhi Yong Wu wrote: > > > Hello, all, > > > > > > I have prepared to work on a feature called "Disk I/O limits" for > > > qemu-kvm projeect. > > > This feature will enable the user to cap disk I/O amount performed by > > > a VM.It is important for some storage resources to be shared among > > > multi-VMs. As you've known, if some of VMs are doing excessive disk I/O, > > > they will hurt the performance of other VMs. > > > > > > > Hi Zhiyong, > > > > Why not use kernel blkio controller for this and why reinvent the wheel > > and implement the feature again in qemu? > > The finest level of granularity offered by cgroups apply limits per QEMU > process. So the blkio controller can't be used to apply controls directly > to individual disks used by QEMU, only the VM as a whole.
So are multiple VMs using same disk. Then put multiple VMs in same cgroup and apply the limit on that disk. Or if you want to put a system wide limit on a disk, then put all VMs in root cgroup and put limit on root cgroups. I fail to understand what's the exact requirement here. I thought the biggest use case was isolation one VM from other which might be sharing same device. Hence we were interested in putting per VM limit on disk and not a system wide limit on disk (independent of VM). Thanks Vivek
