Re: [PATCH v3 1/3] cpufreq: ondemand: Change the calculation oftarget frequency

From: Viresh Kumar
Date: Thu Jun 06 2013 - 06:10:25 EST

On 6 June 2013 15:31, Borislav Petkov <bp@xxxxxxx> wrote:

> Hold on, you say above "easily saturate minimum frequency and lead the
> CPU to max". I read this as we jump straight to max P-state where we
> even boost.

Probably he meant: "At lowest levels of frequencies, a small load on system
may look like a huge one. like: 20-30% load on max freq can be 95% load
on min freq. And so we jump to max freq even for this load and return back
pretty quickly as this load doesn't sustain for longer. over that we wait for
load to go over up_threshold to increase freq."

> "CPU to max" finishes the work faster than middle frequencies, if you're
> CPU-bound.

He isn't removing this feature at all.

Current code is:

if (load > up_threshold)
goto maxfreq.
don't increase freq, maybe decrease it in steps

What he is doing is:

if (load > up_threshold)
goto maxfreq.
increase/decrease freq based on current load.

So, if up_threshold is 95 and load remains < 95, his patch will
give significant improvement both power & performance wise.

Else, it shouldn't decrease it.
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