Arch Linux

lman

Member

From: CZ

Registered: 2007-12-18

Posts: 255

ondemand governor acting strange

I'm not sure what the problem is, but it's acting rather strange. When I was hashing in linuxdcpp the cpu frequency remain on minimum (100% cpu use), on other hand, when I was compiling it was working on max frequency.  It's acting much like powersave governor. It won't go to the next level even when I'm starting eclipse, which is kinda strange, becouse until now it did. It's not a big problem, I thought I would just ask, if anybody knew what's causing this.
EDIT: the cpufreq-info output just in case

cpufrequtils 002: cpufreq-info (C) Dominik Brodowski 2004-2006
Report errors and bugs to linux@brodo.de, please.
analyzing CPU 0:
  driver: powernow-k8
  CPUs which need to switch frequency at the same time: 0
  hardware limits: 800 MHz - 1.80 GHz
  available frequency steps: 1.80 GHz, 1.60 GHz, 800 MHz
  available cpufreq governors: conservative, ondemand, powersave, performance
  current policy: frequency should be within 800 MHz and 1.80 GHz.
                  The governor "ondemand" may decide which speed to use
                  within this range.
  current CPU frequency is 800 MHz.

Last edited by lman (2008-03-27 10:46:50)

_nalle

Member

From: Stockholm/Sweden

Registered: 2006-01-11

Posts: 70

Website

Re: ondemand governor acting strange

It shouldn't behave like that. There is one thing I can think off, the ondemand govenor decides when to scale when under strain.. As you said, when you do something like hashing files it doesn't scale up.. Maybe it's because the processor isn't under constant strain but rather under high load during very short sessions?

This would most likely mess up the scaling procedure. It wouldn't be effective it had to jump up and down once or twice every second..

btw, just a theory, no absolute facts except for basic functionality of cpufreq.

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Swedish Archlinux Mirror Administrator - ftp.gigabit.nu

lloeki

Member

From: France

Registered: 2007-02-20

Posts: 456

Website

Re: ondemand governor acting strange

I would have recommended you to look at /sys/devices/system/cpu/cpu*/cpufreq/scaling_i_cant_recall_exactly_but_it_counts_frequency_hops before and after.

in /sys/devices/system/cpu/cpu*/cpufreq/ondemand, there are some interesting options too:

ignore_nice_load  sampling_rate      sampling_rate_min
powersave_bias    sampling_rate_max  up_threshold

also, 100% cpu may not necessarily mean real cpu use, maybe it's partly io wait, where scaling would be useless. look at 'top' %wa output

Last edited by lloeki (2008-03-27 14:55:14)

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To know recursion, you must first know recursion.

lman

Member

From: CZ

Registered: 2007-12-18

Posts: 255

Re: ondemand governor acting strange

Ok, it's getting stranger and stranger. I left my computer for several hours, while I was at school, and all of sudden everything back to normal. But I didn't change a line in config files... It's starting to disturb me, if it changes it's mind this way.... Anyway, maybe it was just a small glitch in the alorithm, but still weird.

Last edited by lman (2008-03-27 15:26:31)