Re: [ovirt-users] Ovirt VM Performance abd CPU times

On 29.10.2014 16:44, Xavier Naveira wrote: > On 10/29/2014 04:29 PM, Xavier Naveira wrote: >> On 10/29/2014 04:06 PM, Daniel Helgenberger wrote: >>> >>> >>> On 29.10.2014 15:57, Xavier Naveira wrote: >>>> On 10/29/2014 03:07 PM, Xavier Naveira wrote: >>>>> On 10/29/2014 01:26 PM, Daniel Helgenberger wrote: >>>>>> On 29.10.2014 11:48, Xavier Naveira wrote: >>>>>>> On 10/29/2014 11:47 AM, Xavier Naveira wrote: >>>>>>>> On 10/29/2014 11:40 AM, Daniel Helgenberger wrote: >>>>>>>>> >>>>>>>>> >>>>>>>>> On 29.10.2014 10:21, Xavier Naveira wrote: >>>>>>>>>> Hi, >>>>>>>>>> >>>>>>>>>> We are migrating our ifrastructure from kvm+libvirt hypervisors to >>>>>>>>>> ovirt. >>>>>>>>>> >>>>>>>>>> Everything is working fine but we're noticing that all the >>>>>>>>>> qemu-kvm >>>>>>>>>> processes in the hypervisors take a lot of CPU. >>>>>>>>> Without further details of the workload this is hard tell. One >>>>>>>>> Reason I >>>>>>>>> can think of might be KSM [1]. Is it enabled on your cluster(s)? >>>>>>>>> What is >>>>>>>>> your mem over-commitment setting? >>>>>>>>> >>>>>>>>> Note, IIRC the KSM policy is currently hard coded; it will start at >>>>>>>>> 80% >>>>>>>>> host mem usage. >>>>>>>>> >>>>>>>>> [1] http://www.ovirt.org/Sla/host-mom-policy >>>>>>>>>> >>>>>>>>>> The typical example is an idle machine, running top from the >>>>>>>>>> machine >>>>>>>>>> itself it reports cpu use percentages below 10% and loads (with 2 >>>>>>>>>> processors) of 0.0x. The process running that machine in the >>>>>>>>>> hypervisor >>>>>>>>>> rports cpu uses in the order of the 80-100%. >>>>>>>>>> >>>>>>>>>> Should the values look like this? Why are the idle machines eating >>>>>>>>>> up so >>>>>>>>>> much CPU time? >>>>>>>>>> >>>>>>>>>> Thank you. >>>>>>>>>> Xavier >>>>>>>>>> >>>>>>>>>> _______________________________________________ >>>>>>>>>> Users mailing list >>>>>>>>>> Users(a)ovirt.org >>>>>>>>>> http://lists.ovirt.org/mailman/listinfo/users >>>>>>>>>> >>>>>>>>> >>>>>>>> >>>>>>> Hi, thank you for the answer. >>>>>>> >>>>>>> I've been trying to work out some pattern and realized that the VMs >>>>>>> using that much cpu all are Redhat 5.x, the Readhat 6.x doesn't >>>>>>> exhibit >>>>>>> this kind of high cpu use. (we run only redhat/centos 5.x/6.x on the >>>>>>> cluster) >>>>>> What OS are the hosts running? In case of EL6, make sure you have >>>>>> tuned-0.2.19-13.el6.noarch installed [1]. >>>>> >>>>> That's exactly the version we've in the hypervisors. >>>>> >>>>>> >>>>>> To further investigate please post Engine, VDSM, libvirt and kernel >>>>>> versions from the hosts. >>>>> >>>>> vdsm-xmlrpc-4.14.11.2-0.el6.noarch >>>>> vdsm-cli-4.14.11.2-0.el6.noarch >>>>> vdsm-python-4.14.11.2-0.el6.x86_64 >>>>> vdsm-4.14.11.2-0.el6.x86_64 >>>>> vdsm-python-zombiereaper-4.14.11.2-0.el6.noarch >>>>> >>>>> libvirt-client-0.10.2-29.el6_5.12.x86_64 >>>>> libvirt-0.10.2-29.el6_5.12.x86_64 >>>>> libvirt-lock-sanlock-0.10.2-29.el6_5.12.x86_64 >>>>> libvirt-python-0.10.2-29.el6_5.12.x86_64 >>>>> >>>>> 2.6.32-431.23.3.el6.x86_64 #1 SMP Wed Jul 16 06:12:23 EDT 2014 x86_64 >>>>> x86_64 x86_64 GNU/Linux >>>>> >>>>> >>>>>> >>>>>> [1] https://access.redhat.com/solutions/358033 >>>>>>> >>>>>>> I'll take a look to the KSM config. >>>>>>> >>>>>>> Cheers, >>>>>>> >>>>>>> Xavier >>>>>>> >>>>>> >>>>> >>>> >>>> Actually, this seems to be it. But I'm already at a newer kernel: >>>> https://bugzilla.redhat.com/show_bug.cgi?id=705082 >>> Well, I do not have such hardware so I never run into the issue. You >>> could disable HT as I suspect your physical cores are less then 64? >>> >>> Your workload might differ but my VMs usually do not benefit from >>> 'threaded' cores and I want HT disabled anyway. Also, you can check >>> cluster settings and disable 'count threads as cores' if enabled. But I >>> think this might not make any difference. >>>> >>> >> Yeah, these are machines with 4 sockets, 6 core per socket and HT >> enabled, so total 48 "CPU". Good to know; yet the largest host I have has 32 (2 sockets, 8 cores, HT enabled) CPUs and is not showing this issue (at least I just looked and everything seems fine). >> >> So, are you implying that the problem is the number of "CPUs"? We were >> hoping to add some more hypervisors to the cluster next week that have >> even more cores... >> >> I can probably try to disable HT when we add the next hypervisor next >> week but it feels that it'd be just a workaround? Maybe, but not a bad one as you should not have any disadvantages. > > I opened a bug at redhat just in > case:https://bugzilla.redhat.com/show_bug.cgi?id=1158547 I have to ask as I cannot see the BZ because I have no subscription any more. Against witch component did you open it? >