RE: [Xen-devel] [Patch] Fix the slow wall clock time issue in x64 SMPVista

["Cui, Dexuan" <dexuan.cui@xxxxxxxxx>]

I just removed the vcpu_kick() in hpet_timer_fn(), and booted an SMP FC5 guest:
I found a warning message on the console:

Warning: many lost ticks.
Your time source seems to be instable or some driver is hogging interrupts
rip __do_softirq+0x4a/0xd2
Falling back to HPET

So I need do more to see whether we can remove the vcpu_kick().

 -- Dexuan

-----Original Message-----
From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx 
[mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Cui, Dexuan
Sent: 2007年1月10日 19:54
To: Keir Fraser; xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: RE: [Xen-devel] [Patch] Fix the slow wall clock time issue in x64 
SMPVista

1) I made the change mainly for timer1 of HPET. Actually I don't know exactly 
how x64 SMP Vista uses HPET's timer1 to adjust the wall clock time; but without 
the patch, HPET's timer1 can generate and inject interrupts with a frequency of 
20KHz or so! and the wall clock time would become slow.

2) Yes. I think the vcpu_kick() in hpet_timer_fn() is actually unnecessary. 
Thanks for pointing out this!

 -- Dexuan

-----Original Message-----
From: Keir Fraser [mailto:keir@xxxxxxxxxxxxx] 
Sent: 2007年1月10日 19:37
To: Cui, Dexuan; xen-devel@xxxxxxxxxxxxxxxxxxx
Cc: Keir Fraser
Subject: Re: [Xen-devel] [Patch] Fix the slow wall clock time issue in x64 SMP 
Vista

On 10/1/07 11:29, "Cui, Dexuan" <dexuan.cui@xxxxxxxxx> wrote:

> In x64 SMP Vista HVM guest (vcpus=2 in the configuration file), the wall
> clock time is 50% slower than that in the real world. The attached patch
> fixes the issue.

Looks like this code will inject fewer HPET interrupts. How does that make
time go *faster*?

Also, looking at hpet_timer_fn() is vcpu_kick() actually required? The PIC
logic invoked from hpet_route_interrupt() should do any required kicking.

 -- Keir

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