Using PIT to get guest timer faster is a known issue for unmodified Linux of
early version such as 2.6.9.
that is why we introduced some extra complicated logic in Xen to try to fix it
but not perfect.
pv timer should fix this in future, and ntpd is also a good way.
BTW, Yves's case, can u check more on APIC case? Specifically
I want to know how guest TSC is calibrated? How APIC timer IRQ
is delivered after a specific duration. (cat /proc/interrupts before & after
sleep 10s).
thx,eddie
>-----Original Message-----
>From: [EMAIL PROTECTED]
>[mailto:[EMAIL PROTECTED] On Behalf Of
>Yang, Sheng
>Sent: 2007年12月27日 10:29
>To: Yves Dorfsman
>Cc: kvm-devel@lists.sourceforge.net
>Subject: Re: [kvm-devel] keeping time
>
>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
>[EMAIL PROTECTED]
>>
>http://www.SollerS.ca
>>
>>
>>
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>
>
>--
>Thanks
>Yang, Sheng
>
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