Added Ingo + Peter.
Sam
On Sat, Jan 26, 2008 at 10:38:15PM +0100, Toralf Förster wrote:
> It seems to be rather a scheduler issue than a governor issue b/c
> the issue went away after unsetting CONFIG_FAIR_GROUP_SCHED.
>
> If I unselect CONFIG_FAIR_GROUP_SCHED then the %CPU value raises 80%
> - which forces the ondemand governor do speed up the CPU frequency:
>
>
> PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
> 7137 tfoerste 20 0 1796 488 428 R 95.5 0.0 0:01.40 factor
> 7083 dnetc 39 19 664 348 264 R 2.1 0.0 3:08.33 dnetc
> 4033 root 20 0 97252 9420 4008 R 0.7 0.9 0:09.43 X
>
>
> Am Samstag, 26. Januar 2008 schrieben Sie:
> > Toralf Förster wrote:
> >
> > > I use a 1-liner for a simple performance check : "time factor
> > > 819734028463158891"
> > > Here is the result for the new (Gentoo) kernel 2.6.24:
> > >
> > > With the ondemand governor of the I get:
> > >
> > > [EMAIL PROTECTED] ~/tmp $ time factor 819734028463158891
> > > 819734028463158891: 3 273244676154386297
> > >
> > > real 0m32.997s
> > > user 0m15.732s
> > > sys 0m0.014s
> > >
> > > With the ondemand governor the CPU runs at 600 MHz,
> > > whereas with the performance governor I get :
> > >
> > > [EMAIL PROTECTED] ~/tmp $ time factor 819734028463158891
> > > 819734028463158891: 3 273244676154386297
> > >
> > > real 0m10.893s
> > > user 0m5.444s
> > > sys 0m0.000s
> > >
> > > (~5.5 sec as I expected) b/c the CPU is set to 1.7 GHz.
> > >
> > > The ondeman governor of previous kernel versions however automatically
> > > increased
> > > the CPU speed from 600 MHz to 1.7 GHz.
> > >
> > > My system is a ThinkPad T41, I'll attach the .config
> >
> > During the test, run top, and watch your CPU usage. Does it go above 80%
> > (the default for
> > /sys/devices/system/cpu/cpu0/cpufreq/ondemand/up_threshold).
> >
> > ondemand CPUfreq governor has a few tunables, described in
> > Documentation/cpu-freq. One of them is up_threshold:
> >
> > up_threshold: defines what the average CPU usaged between the samplings
> > of 'sampling_rate' needs to be for the kernel to make a decision on
> > whether it should increase the frequency. For example when it is set
> > to its default value of '80' it means that between the checking
> > intervals the CPU needs to be on average more than 80% in use to then
> > decide that the CPU frequency needs to be increased.
> >
> > What CPUFreq processor driver are you using?
> >
> >
> > I had a similar problem with CPUfreq and dm-crypt (slow reads), see
> > (more setup problem than something kernel-related):
> >
> > http://blog.wpkg.org/2008/01/22/cpufreq-and-dm-crypt-performance-problems/
> >
> >
>
> --
> MfG/Sincerely
>
> Toralf Förster
> pgp finger print: 7B1A 07F4 EC82 0F90 D4C2 8936 872A E508 7DB6 9DA3
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
