Re: keeping time

["Yang, Sheng" <sheng.yang-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

On Wednesday 26 December 2007 22:35:29 Yves Dorfsman wrote:
> What is the recommended way to keep the time correct on a UNIX KVM machine
> ?
>
> I am using Linux x86_64 (gentoo) both as a host and as a guest, and can't
> keep the time straight on the guest. Ntpd eventually gives up because the
> clock is too wanky.

What's your guest kernel version? 

When I debug my in kernel PIT(not sent yet, though kept for months), I found 
the kernel version have something to do with the timer accuracy. On my 
limited test, the kernel 2.6.18, 2.6.20, 2.6.22 with default kernel 
parameters works well with my PIT patch. But for kernel 2.6.9, I have to 
use "clock=pit", otherwise the timer is much faster.

And for current KVM, I found 2.6.18 is very slow compared to host. 2.6.20 is 
about 1/3 slow. (host: 30s, guest: 40s, using "sleep"), and 2.6.22 is OK.

>
> I run into this problem both with versions 28 and 57.
>
> Thanks.
>
>
> Yves.
>
> PS: I realize this is for kvm developers, but could not find a KVM user
> list - please point me towards the apropriate list if this is the wrong
> choice.
> ----
> Yves Dorfsman                                             yves-Qq95MN99UUsAvxtiuMwx3w@public.gmane.org
>                                                     http://www.SollerS.ca
>
>
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-- 
Thanks
Yang, Sheng

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