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Re: [Xen-devel] time accounting problem in pvops kernel

To: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Subject: Re: [Xen-devel] time accounting problem in pvops kernel
From: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Date: Wed, 18 Aug 2010 09:49:28 +0200
Cc: Glauber Costa <glommer@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
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On 08/18/2010 12:51 AM, Jeremy Fitzhardinge wrote:
  On 08/17/2010 10:29 AM, Paolo Bonzini wrote:

while experimenting a bit with time.c we found a bug in time
accounting.  Basically, /proc/stat counts idle time twice for PV guests
running a pvops kernel

What version?

I was using the latest RHEL6 snapshot + the 16-patch blkfront series (i.e. without the patch you pointed out).

Upstream and stable kernels contain the changeset "xen:
drop xen_sched_clock in favour of using plain wallclock time" which
should fix a lot of timekeeping/scheduling problems.

I'll try this patch; however, offhand I don't see how it fixes the problem of calling account_idle_ticks twice.


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