[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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

  • To: "Keir Fraser" <keir@xxxxxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • From: "Cui, Dexuan" <dexuan.cui@xxxxxxxxx>
  • Date: Wed, 10 Jan 2007 19:53:46 +0800
  • Delivery-date: Wed, 10 Jan 2007 03:54:14 -0800
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: Acc0qpECUWE/uVerTTS+WkRpZ1GU0QAAQ2zNAABGKxA=
  • Thread-topic: [Xen-devel] [Patch] Fix the slow wall clock time issue in x64 SMP Vista

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 

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

Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.