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Re: AW: Re: AW: Re: AW: Re: [Xen-devel] Xen 3.4 strange behaviour as com

To: "keir.fraser" <keir.fraser@xxxxxxxxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: AW: Re: AW: Re: AW: Re: [Xen-devel] Xen 3.4 strange behaviour as compared to Xen 3.3.1
From: Carsten Schiers <carsten@xxxxxxxxxx>
Date: Sun, 31 May 2009 22:39:05 +0200
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By the way: in the forum of my favorite distro (c't Server), I found another guy with exactly
the same problem. 3.3.1 working, 3.4 no stepping up.

BR,
Carsten.

Carsten Schiers schrieb:
No it's the kernel of Xen 3.4.0 with the same config. I will try later with the older kernel, which is the one of 06.04.2009 (I have not realy understood the tagging or versioning of the Xen kernel). The other combination would be Xen 3.3.1 with the latest kernel. That's how we narrow it down to hypervisor vs. kernel.

As I use cpufreq=dom0-kernel and enable cpufreq modules in drivers/cpufreq/Kconfig, I guess it should use the hypercall for idle time. But to double check, I generated load in dom0. No difference. It simply doesn't step upwards. The kernel with cpufreq debugging is enabled. I will also try it, maybe it's loging something usefull.

BR,
Carsten.

-----Ursprüngliche Nachricht-----
Von: Keir Fraser [mailto:keir.fraser@xxxxxxxxxxxxx] Gesendet: Samstag, 30. Mai 2009 11:30
An: Carsten Schiers; xen-devel
Betreff: Re: AW: Re: AW: Re: [Xen-devel] Xen 3.4 strange behaviour as compared to Xen 3.3.1

Are you using the exact same dom0 kernel as before, when it worked? One
theory would be that dom0 is looking at its own idle stats, and it probably is pretty idle. So then it steps down the CPUs and keeps them down. When you
work the CPUs, are you working dom0 hard?

 -- Keir

On 30/05/2009 07:59, "Carsten Schiers" <carsten@xxxxxxxxxx> wrote:

Sorry, it's lowest frequency (1.0 out of 1.0, 1.8, 2.0, and 2.1 GHz).
When booting,
the CPU will be at 2.1 GHz, when switching the governor from
performance
to ondemand,
this one will set it to 1.0 GHz, where it's sort of fixed. I can set
it
manually with
cpufreq-set when switching to userspace governor, though.

So my guess is that the ondemand governor donesn't get te right
information about idle
time though the according hypercall. I recompiled with CPUFREQ DEBUG
set. But as said
earlier, I don't have that much knowledge about how to debug kernels.

BR,
Carsten.

-----Ursprüngliche Nachricht-----
Von: Keir Fraser [mailto:keir.fraser@xxxxxxxxxxxxx]
Gesendet: Freitag, 29. Mai 2009 23:31
An: Carsten Schiers; xen-devel
Betreff: Re: AW: Re: [Xen-devel] Xen 3.4 strange behaviour as compared
to Xen 3.3.1

Is lowest p-state lowest or highest frequency/voltage?

 -- Keir

On 29/05/2009 17:47, "Carsten Schiers" <carsten@xxxxxxxxxx> wrote:

Thanks Keir, I tried it out but there is no difference. And by the
way:
it
is in lowest p-state and doesn't come up, even if under heavy load.
Hmm.
BR,
Carsten.

-----Ursprüngliche Nachricht-----
Von: Keir Fraser [mailto:keir.fraser@xxxxxxxxxxxxx]
Gesendet: Freitag, 29. Mai 2009 17:02
An: Carsten Schiers; xen-devel
Betreff: Re: [Xen-devel] Xen 3.4 strange behaviour as compared to Xen
3.3.1

On 29/05/2009 15:03, "Carsten Schiers" <carsten@xxxxxxxxxx> wrote:

  - as already reported, ondemand manager in dom0-kernel doesn't
step,
manual
    setting works so it seems a bit like the communication between
dom0
and
    hypervisor regarding idle time is not working
Could be an interaction with C-state support, preferring deep sleep
to
running at lower voltage/frequency? You could try no-cpuidle on Xen's
command line at boot time and see if that changes things.

 -- Keir

  - all beside one domu use Xen 3.4.0 kernel, the one who uses it's
customized
    kernel won't start up as first domu. It simply hangs and this
prevents also
    all other domus (I all auto start them, no save/restore) don't
come
up. When
    I start the chain with a different one and this (with the
different
kernel)
    is started as #2 or #3, not problem

  - one domu is for vdr with three dvb pci cards passed trough. This
one, when
    started as the first one, will cause xentop to show 20% load.
When
restarted
    or started as #2, the load is like with 3.3.1 at roughly 3-5%.









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