On 17-07-20, 11:46, Vincent Guittot wrote:
On Thu, 16 Jul 2020 at 16:24, Lukasz Luba <lukasz.luba@xxxxxxx> wrote:
On 7/16/20 12:56 PM, Peter Zijlstra wrote:
Currently cpufreq_cooling appears to estimate the CPU energy usage by
calculating the percentage of idle time using the per-cpu cpustat stuff,
which is pretty horrific.
Even worse, it then *samples* the *current* CPU frequency at that
particular point in time and assumes that when the CPU wasn't idle
during that period - it had *this* frequency...
So there is 2 problems in the power calculation of cpufreq cooling device :
- How to get an accurate utilization level of the cpu which is what
this patch is trying to fix because using idle time is just wrong
whereas scheduler utilization is frequency invariant
Since this patch is targeted only towards fixing this particular
problem, should I change something in the patch to make it acceptable
?
- How to get power estimate from this utilization level. And as you
pointed out, using the current freq which is not accurate.
This should be tackled separately I believe.