Re: [Qemu-devel][RFC]QEMU disk I/O limits

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Tue, May 31, 2011 at 10:10:37AM -0400, Vivek Goyal wrote:
> 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).

No, it isn't about putting limits on a disk independant of a VM. It is
about one VM having multiple disks, and wanting to set different policies
for each of its virtual disks. eg

  qemu-kvm -drive file=/dev/sda1 -drive file=/dev/sdb3

and wanting to say that sda1 is limited to 10 MB/s, while sdb3 is
limited to 50 MB/s.  You can't do that kind of thing with cgroups,
because it can only control the entire process, not individual
resources within the process.

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 :|
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html


[Index of Archives]     [KVM ARM]     [KVM ia64]     [KVM ppc]     [Virtualization Tools]     [Spice Development]     [Libvirt]     [Libvirt Users]     [Linux USB Devel]     [Linux Audio Users]     [Yosemite Questions]     [Linux Kernel]     [Linux SCSI]     [XFree86]
  Powered by Linux