linux-kernel - Re: [BISECTED] "conservative" cpufreq governor broken

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Date:	Wed, 07 Oct 2009 10:49:38 +0300
From:	Eero Nurkkala <ext-eero.nurkkala@...ia.com>
To:	ext Steven Noonan <steven@...inklabs.net>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Rik van Riel <riel@...hat.com>,
	Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>
Subject: Re: [BISECTED] "conservative" cpufreq governor broken

On Wed, 2009-10-07 at 09:30 +0200, ext Steven Noonan wrote:
> 
> Okay, wow, I'm a moron. I misread what cpu_idle() was intended to be
> for. I thought that cpu_idle() was a function that was periodically
> called whenever the CPU had nothing to do, but now I see that it's
> actually the main loop. I should really read the code next time.
> 
> I've moved the statistics printout code to the _inside_ of that
> infinite loop and retested. I had it print every several hundred
> iterations. Here's the results (note the machine was idle the whole
> time, except for about the first 10-20 seconds while the machine
> booted):
> 
> [    3.627716] timings[0]: 2250511125 / 3627716116
> [    6.946216] timings[0]: 4780901366 / 6946213531
> [   13.355182] timings[0]: 9385417604 / 13355183525
> [   18.551304] timings[1]: 16300853077 / 18551301189
> [   21.589039] timings[0]: 15984495433 / 21589037480
> [   47.152733] timings[1]: 44386121538 / 47152731476
> [   51.682630] timings[0]: 45713834076 / 51682628295
> [   79.587359] timings[0]: 73524821916 / 79587356820
> [   88.630110] timings[1]: 85324277596 / 88630109605
> [   96.082386] timings[0]: 89691306072 / 96082384539
> 

Those look good.

Well, might as well then go for:
/drivers/cpufreq/cpufreq_conservative.c
dbs_check_cpu() ->
load = 100 * (wall_time - idle_time) / wall_time; <- What is your load?

Let assume load is sane, look for (in dbs_check_cpu())
	if (load < (dbs_tuners_ins.down_threshold - 10)) {

whether it is taken ever...if not, what is your
(dbs_tuners_ins.down_threshold - 10) ?

- Eero

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