ondemand cpufreq ineffective in 2.6.12 ?

Ken Moffat
2005-07-11T16:30:21Z

Hi,

I've been using the ondemand governor on athlon64 winchesters for a few
weeks. I've just noticed that in 2.6.12 the frequency is not
increasing under load, it remains at the lowest frequency. This seems
to be down to something in 2.6.12-rc6, but I've seen at least one report
since then that ondemand works fine. Anybody else seeing this problem ?

Testcase: boot (my bootscripts set the governor to ondemand), set the
governor to ondemand, performance, powersave and untar a nice big
bzip2'd tarball (gcc-3.4.1) from an nfs mount. All using the config from
2.6.11.9 and defaults for new options.

kernel 2.6.11.9 2.6.12-rc5 2.6.12-rc6 2.6.12

ondemand 20.8 sec 21.3 sec 33.9 sec 34.1 sec
performance 21.3 sec 22.0 sec 22.6 sec 20.1 sec
powersave 32.4 sec 33.1 sec 33.6 sec 33.9 sec

I don't have confidence that the numbers are more repeatable than +/- 2
seconds on this, they just illustrate that ondemand used to give a
similar time to performance, but now doesn't. Other intermediate and
later tests have been omitted for clarity, but 2.6.12.2 does show the
same problem.

Since 2.6.12-rc6, 'ondemand' appears to be still accepted (the echo to
scaling_governor returns 0, and the displayed frequency drops back if
I try going from performance to ondemand).

When ondemand appears to work properly, /proc/cpuinfo shows the speed
jumping to 2 GHz, then falling back to 1.8 after the untar ends, then
back to 1.0 GHz. In the problem cases, the speed remains at 1GHz.

As far as I can see, nothing untoward shows in the logs. Any
suggestions, please ?

Ken
--
das eine Mal als Tragödie, das andere Mal als Farce