linux-kernel - Re: doubled idle count

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Message-ID: <87wsh8nug3.fsf@tac.ki.iif.hu>
Date:	Fri, 19 Sep 2008 15:20:28 +0200
From:	Ferenc Wagner <wferi@...f.hu>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	linux-kernel@...r.kernel.org,
	Xen-devel <xen-devel@...ts.xensource.com>
Subject: Re: doubled idle count

Jeremy Fitzhardinge <jeremy@...p.org> writes:

> Ferenc Wagner wrote:
>
>> After upgrading a Xen virtual machine to Debian's 2.6.26-4 kernel, I
>> noticed that the idle counter doubled its pace on one of the machines:
>> [...]
>> One out of three machines show this effect, with the exact same kernel
>> and Xen versions (3.2.0, dom0 is Debian's stock Etch 2.6.18 kernel).
>> They aren't hosted by the same machine, though: the misbehaving one is
>> on a different installation with very similar hardware (3 vs 2 GHz).
>> All the guest are paravirtual.
>
> So you're saying that they are identical Xen and guest kernel binaries,
> but one of three is showing doubled idle time?

Now I upgraded another domU, and that also shows this doubling effect,
so I've got two domUs (running on xen2-ha) misbehaving, and other two
(running on xen2) behaving correctly.  On the first:

wferi@...2-ha:~$ sudo xm info
host                   : xen2-ha
release                : 2.6.18-6-xen-686
version                : #1 SMP Mon Aug 18 12:56:50 UTC 2008
machine                : i686
nr_cpus                : 4
nr_nodes               : 1
cores_per_socket       : 1
threads_per_core       : 2
cpu_mhz                : 3056
hw_caps                : bfebfbff:00000000:00000000:00000080:00004400
total_memory           : 3071
free_memory            : 991
node_to_cpu            : node0:0-3
xen_major              : 3
xen_minor              : 2
xen_extra              : -1
xen_caps               : xen-3.0-x86_32p 
xen_scheduler          : credit
xen_pagesize           : 4096
platform_params        : virt_start=0xf5800000
xen_changeset          : unavailable
cc_compiler            : gcc version 4.1.2 20061115 (prerelease) (Debian 4.1.1-21)
cc_compile_by          : fs
cc_compile_domain      : debian.org
cc_compile_date        : Mon Mar 10 15:50:27 UTC 2008
xend_config_format     : 4

while on the other the differing lines are:

host                   : xen2
cpu_mhz                : 1993
total_memory           : 4991
free_memory            : 2464

Hope this adds some useful info.
-- 
Regards,
Feri.
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