I haven't tested the performance differences with or without HT. We were running pure kvm-libvirt hosts on these machines and we're migrating them to oVirt and that's what triggered the problem with the Redhat 5 vms.
I'll probably give it a try and disable HT on the next hypervisor that we'll be adding to the cluster next week and see if that solves the problem or it just mitigates it. X On Thu, Oct 30, 2014 at 10:09 AM, Arman Khalatyan <[email protected]> wrote: > On our clusters with pure computation we use always HT off, HT was slowing > down scientific calculations. > Just I'm interested if any benefit of enabling HT on the Ovirt host? > At least on my system host-Centos6.5, guest-Centos7VM-LAMPstack with > separate CentOS7-MariaDBVM did not show any performance boost if I switch > on/off HT on 2650v2. > a. > > > > On Wed, Oct 29, 2014 at 5:24 PM, Xavier Naveira <[email protected]> > wrote: > >> On 10/29/2014 05:15 PM, Daniel Helgenberger wrote: >> >>> >>> >>> 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 >>>>>>>>>>>>> [email protected] >>>>>>>>>>>>> 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? >>> >>>> >>>> >>> I did as in the original bug: kernel, and then I took KVM as subsystem. >> >> _______________________________________________ >> Users mailing list >> [email protected] >> http://lists.ovirt.org/mailman/listinfo/users >> > >
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