[Xen-devel] DomU Powernow question

[Christian Roessner <christian@xxxxxxxxxxxxxxxx>]

Hi,

I recently posted the attached mail below to Keir Fraser.

I got an answer:

---- snip ----
The 'stale' frequency info in domU is harmless
---- snap ----


My question is, why the cpu frequency in dom0 ist not jumping to 2GHz,
if the cpu usage inside a domU is very high?

Second question: If in dom0, which value is showing the correct
information: the frequency or the bogomips? Normally the latter would
change, if the frequency changes. Not so in dom0? Why?

Kind regards
Christian


--- snip attached mail ---
Today I have recognized something interestin:

If I boot my Xen-box @ 2GHz, starting 2 DomUs at boottime, I can see
that the cpuinfo is showing:

processor       : 0
vendor_id       : AuthenticAMD
cpu family      : 15
model           : 4
model name      : AMD Athlon(tm) 64 Processor 3200+
stepping        : 8
cpu MHz         : 2019.560
cache size      : 1024 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 1
wp              : yes
flags           : fpu tsc msr pae mce cx8 apic mca cmov pat pse36
clflush mmx fxsr sse sse2 syscall nx mmxext lm 3dnowext 3dnow ts fid vid ttp
bogomips        : 4047.21

inside the DomUs, even the CPU has switched the frequency back to 800MHz.

If I do something like

while true; do ls -l | md5sum; done

in Dom0, the CPU frequency jumps @ 2GHz, while if doing the same inside
a DomU, the CPU still is @ 800MHz.

Now I thought, I would have to compile in cpufreq support into the DomU
kernel, but if I remove the "privileged" host option, the whole ACPI
powermanagement menu is away.

So, what can I change, to get this working correctly?

Maybe noone has tried something like this, but I think this is a little
bug, isnÂt it?

There is something else: Normally, when the CPU frequency is @ 800 MHz,
the Bogomips are much less than 4000. But look at this:

processor       : 0
vendor_id       : AuthenticAMD
cpu family      : 15
model           : 4
model name      : AMD Athlon(tm) 64 Processor 3200+
stepping        : 8
cpu MHz         : 800.000
cache size      : 1024 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 1
wp              : yes
flags           : fpu tsc msr pae mce cx8 apic mtrr mca cmov pat pse36
clflush mmx fxsr sse sse2 syscall nx mmxext lm 3dnowext 3dnow ts fid vid ttp
bogomips        : 4021.05

If you think, I should post this to the xen-devel list, I first would
have to subscribe again.

But thanks in advance. Maybe you have some ideas on that.
---- snap ----

-- 
Tel.: 0641-2097252, Mobil: 0171-3611230
PGP: http://www.roessner-net.com/0x6B929997.asc

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