Re: [ovirt-users] Guest VM Running 160 RCU Processes
On Oct 22, 2014, at 6:43 AM, Michal Skrivanek
<michal.skrivanek(a)redhat.com> wrote:
On Oct 21, 2014, at 18:13 , Darrell Budic <budic(a)onholyground.com> wrote:
> Was poking at this a little to see if there was any tuning that could affect it and
spotted some oddness with the processor counts on my VMs under Ovirt 3.4. They seem to
think they only have the proper number I set in ovirt (as shown in /proc/cpu), but if I
look at dmidecode, there’s 159 bogus processors listed. I’d expect maybe 16 from the -smp
1,maxcpus=16,sockets=16,cores=1,threads=1 argument to qemu-kvm, but there are 0xa0 of
them. Maybe this is a seabios or qemu-kvm issue causing all those extras? Anyway, the # of
rcu* processes matches pretty well, so that’s likely where it’s coming from.
>
> At least they shouldn’t be causing a performance issue, given their purpose as
non-blocking work threads, but it is odd to see.
>
> Punit, did you open a BZ I can add these details to?
>
> BTW, this appears to be corrected with some component of Ovirt 3.5 (probably
qemu-rhev?). On VMs started after I upgraded my Engine (even on 3.4 vdsmds), I’m only
seeing 16 “processors” in the bios, and thus only 16 of the various rcu* processes. Could
have been a general Centos 6.5 update too, since I did those as well, so I can’t get any
finer resolution on that issue (both engine and host nodes, lots of Centos 7 VMs).
>
> If there is a RFE for this, perhaps a configurable max # of CPU sockets for hot add
could be added, or it could be limited to the max physical cpu count of the biggest host
in the cluster?
The max is 16. Roy, what can we change/not change after your latest changes?
I suppose it's related to teh maximum values we send because of hotplug support
Thanks,
michal
Yes, definitely looks like a side effect of hot plug. The 160 rcu issues look like a bug
somewhere else, 16 is more normal for the default. I had missed the engine setting for
MaxNumOfVmCpus, I’ll probably set that for my smaller hosts just to keep it reasonable for
the hardware it’s on.
From: "Punit Dambiwal" <hypunit(a)gmail.com>
To: "Doron Fediuck" <dfediuck(a)redhat.com>
Sent: Wednesday, October 22, 2014 4:19:56 AM
Subject: Re: [ovirt-users] Guest VM Running 160 RCU Processes
Hi Darrell,
I haven't open a BZ for the same...please let me know how i can open BZ ??
Punit, make sure your replies go to the list, this didn’t get to me. But you want to go to
http://www.ovirt.org/Community and look at the “Find and File Bugs” section to raise a bug
or file an RFE.
-Darrell