[libvirt-users] cgroup for VM - does it work properly?
Hi I tried to restrict usage of some running VM by cpu.shares (i.e. set to 10 from original 1024) on loaded system and it seem doesn't work as I expected... all running processes has same CPU usage (by htop) :-/ Does anyone has same experience? Fedora 19, libvirt-1.0.5.9-1.fc19.x86_64 Thanks a lot Martin -- Martin Pavlásek <mpavlase@redhat.com> OpenStack QA Associate/Red Hat Czech/BRQ irc: mpavlase
On 03/05/2014 04:32 PM, Martin Pavlásek wrote:
Hi
I tried to restrict usage of some running VM by cpu.shares (i.e. set to 10 from original 1024) on loaded system and it seem doesn't work as I expected... all running processes has same CPU usage (by htop) :-/
How exactly are you changing the cgroup settings? Are you trying to directly modify cgroup files (unsupported), or using the libvirt API (such as via virsh schedinfo)? -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
On Thu 06 Mar 2014 00:42:27 CET, Eric Blake wrote:
On 03/05/2014 04:32 PM, Martin Pavlásek wrote:
Hi
I tried to restrict usage of some running VM by cpu.shares (i.e. set to 10 from original 1024) on loaded system and it seem doesn't work as I expected... all running processes has same CPU usage (by htop) :-/
How exactly are you changing the cgroup settings? Are you trying to directly modify cgroup files (unsupported), or using the libvirt API (such as via virsh schedinfo)?
Via mounted virtualfs - /sys/fs/cgroup/cpu/machine/<name-of-VM>/{emulator,vcpu0}/cpu.shares -- -- Martin Pavlásek <mpavlase@redhat.com> OpenStack QA Associate/Red Hat Czech/BRQ irc: mpavlase
On 03/05/2014 04:47 PM, Martin Pavlásek wrote:
On Thu 06 Mar 2014 00:42:27 CET, Eric Blake wrote:
On 03/05/2014 04:32 PM, Martin Pavlásek wrote:
Hi
I tried to restrict usage of some running VM by cpu.shares (i.e. set to 10 from original 1024) on loaded system and it seem doesn't work as I expected... all running processes has same CPU usage (by htop) :-/
How exactly are you changing the cgroup settings? Are you trying to directly modify cgroup files (unsupported), or using the libvirt API (such as via virsh schedinfo)?
Via mounted virtualfs - /sys/fs/cgroup/cpu/machine/<name-of-VM>/{emulator,vcpu0}/cpu.shares
Won't work, because it goes behind libvirt's back. Use virsh instead. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
Hi Eric, Sorry to hijack this thread. Have you used vcpu_quota in production? I have come across a CPU stall problem when vcpu_quota is effective not long ago and I'm still looking for an answer. For example, when I set virsh schedinfo <id> --set vcpu_quota=5000 Then no matter the vm is loaded or idle, in about two weeks, sometimes sooner, the vm will have CPU stall in dmesg log. The CPU stall problem makes system not responsible and results in network failure, i.e. ping and ssh will fail. I have tried a few guest distro (ubuntu, CentOS, debian) with different kernel version (3.2, 3.8) and they all have this problem. Do you have any idea what's behind the scenes? The software I am running: hypervisor os: ubuntu 12.04.3 hypervisor kernel: 3.8.0-35-generic vm os: ubuntu 12.04 // I have tried other OSes. vm kernel: 3.2.0-56-virtual libvirt: 1.1.1-0ubuntu8~cloud2 *YY Inc. is hiring openstack and python developers. Interested? Check http://www.nsbeta.info/jobs <http://www.nsbeta.info/jobs>* -- Thanks, Yuanle On Thu, Mar 6, 2014 at 7:42 AM, Eric Blake <eblake@redhat.com> wrote:
On 03/05/2014 04:32 PM, Martin Pavlásek wrote:
Hi
I tried to restrict usage of some running VM by cpu.shares (i.e. set to 10 from original 1024) on loaded system and it seem doesn't work as I expected... all running processes has same CPU usage (by htop) :-/
How exactly are you changing the cgroup settings? Are you trying to directly modify cgroup files (unsupported), or using the libvirt API (such as via virsh schedinfo)?
-- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
_______________________________________________ libvirt-users mailing list libvirt-users@redhat.com https://www.redhat.com/mailman/listinfo/libvirt-users
On Thu, Mar 06, 2014 at 12:32:28AM +0100, Martin Pavlásek wrote:
Hi
I tried to restrict usage of some running VM by cpu.shares (i.e. set to 10 from original 1024) on loaded system and it seem doesn't work as I expected... all running processes has same CPU usage (by htop) :-/ Does anyone has same experience?
The cpu.shares variable doesn't provide absolute restriction on CPU usage, rather it is doing relative prioritization. eg if you have 2 cgroups that are at the same level in the hierarchy and you give one shares=512 and one shared=1024, then the latter VM will get twice the CPU scheduler time of the former. If the latter VM is completely idle though, the former VM will not be capped in any way. If you want absolute caps then you need to use period/quota settings. Also you want todo this via the virsh schedinfo command, not accessing cgroups directly. Regards, 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 :|
participants (4)
-
Daniel P. Berrange -
Eric Blake -
Martin Pavlásek -
sylecn