On Wed, May 18, 2016 at 8:01 PM, Karli Sjöberg <karli.sjob...@slu.se> wrote:

>
> >> > I tried a vanilla centos-7.1 as well and the same happens. I'm of the
> same opinion that this is more a guest related issue, it's just I'd like to
> find out why this only happens with QXL and not with CIRRUS.
> >> >
> >> > Thanks.
> >>
> >> Very interesting. Are your hosts all of the same architecture(family)?
> >>
> >> /K
> >
> >
> > Actually we have a nice mixture of manufacturers. We run 7 hosts, paired
> 4-2-1 in relation to architecture. All of them have the same resources,
> though (CPUs + RAM). In this case, I can't test the VM on different hosts
> because we've separated one of them (one of the "4") on a standalone oVirt
> datacenter as we're making tests on it, but I remember this has already
> happened to me in the past (I didn't have the time to debug it at that
> time, though).
>
> And it doesn't happen with a similar VM in the other datacenter, on the
> same hardware?
>
> /K
>

Hello,
I would like to come back to the original post to get some clarifications:
you write
"
I've deployed a pretty basic VM (ubuntu 14.04 server, 4GB RAM, 4 CPUs, 15GB
storage).
"
It seems to me not so basic a VM with 4 vcpus for a desktop.... what are
your needs for it?
In general a multi cpu VM could have a worse performance than a mono cpu
one, depending on its actual workload, because from the host side there is
a continuous scheduling of these 4 vcpus among the real cpus/cores/threads.
I worked in the past with a 4 vcpu VM and 24Gb of ram (in vSphere) used as
JDEdwards database server with hundreds of concurrent users ...
Also with JBoss VMs configured with 4-6 vcpus .. But for a basic VM seems
somehow overestimated...
In my case on a nuc6i5 with 2 cores + ht and 32Gb of ram, configured as
hypervisor with self hosted engine VM, I have a CentOS 6 VM configured with
3Gb of ram and 1 cpu and it runs quite smooth from inside a spice session
configured with resolution of 1680x1050 and its cpu usage shows 98.5% idle.
Also from the host point of view

   PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+
COMMAND
16025 qemu      20   0 8988404 3.070g  10524 S   1.7  9.9  90:16.07
qemu-kvm   <--- engine VM
24367 qemu      20   0 3852288 1.929g  12188 S   0.0  6.2  41:12.79
qemu-kvm   <---- CentOS 6 VM

If I add to the mix a CentOS 7.2 VM configured with 1 vcpu and 3Gb of ram
and with a classic gnome desktop session and open it with 1680x1050
resolution too in spice, I can work without problems and with great
fluidity. I see inside vm its cpu jumping from 1% to 6% because of
gnome-shell.

I see this at host side while in CentOS 7 VM the packagekitd daemon is
downloading the updates and so it is comsuming cpu cycles, also due to
virtual network activity

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+
COMMAND

16025 qemu      20   0 9004796 3.077g  10524 S   2.0  9.9  90:27.34
qemu-kvm
24367 qemu      20   0 3852288 1.929g  12188 S   0.7  6.2  41:17.35
qemu-kvm
31277 qemu      20   0 4121224 2.116g  12056 S  16.3  6.8   2:13.80
qemu-kvm

Otherwise very few cpu usage, after packagekitd completes its work;

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+
COMMAND
16025 qemu      20   0 9004796 3.077g  10524 S   2.3  9.9  90:34.42
qemu-kvm
24367 qemu      20   0 3852288 1.929g  12188 S   0.7  6.2  41:20.42
qemu-kvm
31277 qemu      20   0 3834364 2.138g  12056 S   1.0  6.9   2:28.80
qemu-kvm

HIH debugging,
Gianluca
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