[gentoo-user] Using KVM, what about clocks?

On Thu, Jul 21, 2011 at 12:43 AM, Stefan G. Weichinger wrote:

Maybe a bit OT, but otherwise close to gentoo as well (as we all
configure our kernels individually ) (see ps below):

When I configure my gentoo-server for Linux KVM, how to get the
clock-issues right, in terms of correctness and performance?

I assume that I am not the only one scratching his head ... but maybe
some of us simply hesitate to ask ;-)

HPET, RTC, TSC, blah ...

A new server with a Xeon-CPU tells me:

"kvm: SMP vm created on host with unstable TSC; guest TSC will not be
reliable"

Ah, ok.

Is that bad? Could I do something? Should I?

My question is // questions are:

Are there any recommended kernel-config-settings for a performant and
non-drifting KVM-server?

Is there a "best practise"?

What is your experience, your recommendation?

Maybe it should find its way into the gentoo wiki :-)

Thanks in advance, Stefan

ps: yeah, I know, this should go to the linux-kvm-ml in an ideal world.
We all know that we would end up subscribed to dozens of mailing-lists
just to get our jobs done so pls be tolerant in terms of "what is
off-topic". thx.

This question is totally related to Gentoo!
Try -cpu ? and run with different cpu's to see if this can solve the
problem.

Kfir


<div dir="ltr"><br><br><div class="gmail_quote">On Thu, Jul 21, 2011 at 12:43 AM, Stefan G. Weichinger <span dir="ltr">&lt;<a href="mailto:"></a>&gt;</span> wrote:<br><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">

<br>
Maybe a bit OT, but otherwise close to gentoo as well (as we all<br>
configure our kernels individually ) (see ps below):<br>
<br>
When I configure my gentoo-server for Linux KVM, how to get the<br>
clock-issues right, in terms of correctness and performance?<br>
<br>
I assume that I am not the only one scratching his head ... but maybe<br>
some of us simply hesitate to ask ;-)<br>
<br>
HPET, RTC, TSC, blah ...<br>
<br>
A new server with a Xeon-CPU tells me:<br>
<br>
&quot;kvm: SMP vm created on host with unstable TSC; guest TSC will not be<br>
reliable&quot;<br>
<br>
Ah, ok.<br>
<br>
Is that bad? Could I do something? Should I?<br>
<br>
My question is // questions are:<br>
<br>
Are there any recommended kernel-config-settings for a performant and<br>
non-drifting KVM-server?<br>
<br>
Is there a &quot;best practise&quot;?<br>
<br>
What is your experience, your recommendation?<br>
<br>
Maybe it should find its way into the gentoo wiki :-)<br>
<br>
Thanks in advance, Stefan<br>
<br>
ps: yeah, I know, this should go to the linux-kvm-ml in an ideal world.<br>
We all know that we would end up subscribed to dozens of mailing-lists<br>
just to get our jobs done so pls be tolerant in terms of &quot;what is<br>
off-topic&quot;. thx.<br>
<br>
</blockquote></div><br>This question is totally related to Gentoo!<br>Try -cpu ? and run with different cpu&#39;s to see if this can solve the problem. <br><br>Kfir<br></div>