[BUG] System runs very slow with high cooling_device state

[BUG] System runs very slow with high cooling_device state

[David Herrmann]

Hi

I tried running:
echo 10 >/sys/class/thermal/cooling_device0/cur_state
echo 10 >/sys/class/thermal/cooling_device1/cur_state
Both "max_state" is 10 and cur_state was 0 before.

After that the whole system runs horribly slow. Running "htop" didn't
show any CPU consuming process, though. Even the kernel threads were
idle. Setting *either of them* to 0 made the system response timer
much better again. Setting one to 10 and the other one to 5 makes the
system slow again, but not as slow as with both at 10 so I think this
is incremental.

Since htop doesn't show anything I guess this attribute either changes
the wrong option or the kernel is running in lots of interrupt
handlers. Also I didn't notice any speed change of my fans. They run
at the same "noise-level" with state 0 and 10.
"cooling_device2" (LCD) doesn't show this behaviour.

I run an Intel Atom N450 @ 1.66ghz (dual core or HT, I am not sure).
Both cooling_devices correspond to one of the CPUs.


Is there an easy way to debug this? Does running oprofile help? Or am
I just misunderstanding what "cooling_deviceX" does?

Regards
David

Re: [BUG] System runs very slow with high cooling_device state

[Matthew Garrett]

On Thu, Jul 28, 2011 at 10:39:06AM +0200, David Herrmann wrote:

> Is there an easy way to debug this? Does running oprofile help? Or am
> I just misunderstanding what "cooling_deviceX" does?

When the colling device type is "Processor", that means that it's 
reducing heat output by slowing down the processor.

-- 
Matthew Garrett | mjg59@srcf.ucam.org