[CentOS] cpuspeed problems with 5.2 and 2.6.18-92.1.18 kernel revision

Kai Schaetzl maillists at conactive.com
Thu Dec 18 12:18:24 UTC 2008


ArcosCom Linux User wrote on Thu, 18 Dec 2008 00:00:29 +0100 (CET):

> The last try:
>    1) Power off the laptop along 2/3 hours.
>    2) Power on and log into gnome.
>    3) The cpuspeed monitor shows that all is working fine.

I don't know what this monitor is. There's a cpuspeed service script. If 
enabled it will load the necessary kernel modules and the configured 
governor. Config is in /etc/sysconfig/cpuspeed. You can also check the 
script yourself to see what it does. It may very well be that it thinks that 
your CPU has a flaw that stops it from correctly working with frequency 
scaling. I know that the script has checks for AMD CPUs in it for instance.

If there is some cpuspeed GUI monitor, this has nothing to do with the 
cpuspeed service script. If cpuspeed is disabled the performance governor 
should be on. As I see you know where to check this. So, as I said earlier, 
shut it off (chkconfig cpuspeed off), reboot, and check the values.
Also, if you think that this has something to do with Gnome then you should 
*not* boot in the GUI and see if you get better results.
If that doesn't help there's more likely a problem with the driver. Have you 
checked that it is loaded?

> # cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
> 800000
> 
> (and I think this last value is the problem because I can't change it with
> echo "1733000" > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq)

I tend to agree. That's why you want to check this value without gnomem 
without cpuspeed and also right after booting up (as you say frequency 
scales down after a few minutes, so theoretically there should be a higher 
value in the beginning and there might indeed be a problem in the driver 
that stops it from scaling up again). It's also possible that the algorithm 
for calculating the speedup is doing something wrong, so it doesn't scale up 
again, because it thinks it's not necessary. You could set the UP_THRESHOLD= 
to something very low like 5

>    4) Some minutes after, the speed goes down to 800 MHz and no more wants
> to grow up. I can't change to force performance or using userspace and
> select the speed.
> 
> Any help more about?
> 
> If I launch any heavy compilation (as kernel compilation), the speed don't
> want to grow up. Really is working fine under these circumstances with the
> performance governor selected?

No, but this wasn't obvious from your earlier posting. As I said: did you 
stop cpuspeed? This is not a xen kernel, isn't it?

About the top posting/qoting etc.: The point is to make your postings as 
readable for others as possible. If you quote what you really answer to and 
then answer that and then quote the next part you answer and answer that 
it's much easier to follow for the reader and also much easier for *you* to 
answer as you cannot easily overlook questions if you go thru one by one. 
And everything that you don't answer (including the signature etc.) simply 
doesn't belong in the quote and is omitted. You can take this posting as an 
example.

Kai

-- 
Kai Schätzl, Berlin, Germany
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