linux-kernel - Re: (ondemand) CPU governor regression between 2.6.23 and 2.6.24

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Date:	Mon, 28 Jan 2008 09:38:27 +0100
From:	Helge Hafting <helge.hafting@...el.hist.no>
To:	Toralf Förster <toralf.foerster@....de>
CC:	vatsa@...ux.vnet.ibm.com, Tomasz Chmielewski <mangoo@...g.org>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	a.p.zijlstra@...llo.nl, dhaval@...ux.vnet.ibm.com
Subject: Re: (ondemand) CPU governor  regression between 2.6.23 and 2.6.24

Toralf Förster wrote:
> At Sunday 27 January 2008 Srivatsa Vaddagiri wrote :
>   
>> You can set that to 0 to ask ondemand gov to include nice load into
>> account while calculating cpu freq changes:
>>
>> # echo 0 > /sys/devices/system/cpu/cpu0/cpufreq/ondemand/ignore_nice_load
>>
>> This should restore the behavior of ondemand governor as seen in 2.6.23
>> in your case (even with CONFIG_FAIR_GROUP_SCHED enabled). Can you pls confirm 
>> if that happens?
>>     
>
> Yes, of course, unfortunately this speeds up the CPU up to max power consumption
> which isn't wanted at least at a notebook b/c temperature and fan speed are at
> maximum in that case :-(
>
> It would be nice to run a grid application at lowest priority without impact to
> power / fan / temperature but OTOH have full performance for desktop
> applications, isn't it ?
>   
In theory, the fix is simple:
If _non-niced_ tasks use more than 80% of the cputime _made available to 
them_,
then  increase the processor speed.

The cputime allocated to niced tasks (that may be cpu intensive but 
shouldn't
cause max speed on their own) won't matter then.

Helge Hafting
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