Re: [PATCH v6 08/11] cpufreq/schedutil: take into account interrupt

[Quentin Perret <quentin.perret@arm.com>]

On Tuesday 12 Jun 2018 at 11:16:56 (+0200), Vincent Guittot wrote:
> The time spent under interrupt can be significant but it is not reflected
> in the utilization of CPU when deciding to choose an OPP. Now that we have
> access to this metric, schedutil can take it into account when selecting
> the OPP for a CPU.
> rqs utilization don't see the time spend under interrupt context and report
> their value in the normal context time window. We need to compensate this when
> adding interrupt utilization
> 
> The CPU utilization is :
>   irq util_avg + (1 - irq util_avg / max capacity ) * /Sum rq util_avg
> 
> A test with iperf on hikey (octo arm64) gives:
> iperf -c server_address -r -t 5
> 
> w/o patch		w/ patch
> Tx 276 Mbits/sec        304 Mbits/sec +10%
> Rx 299 Mbits/sec        328 Mbits/sec +09%
> 
> 8 iterations
> stdev is lower than 1%
> Only WFI idle state is enable (shallowest diel state)
                                            ^^^^
nit: s/diel/idle

And, out of curiosity, what happens if you leave the idle states
untouched ? Do you still see an improvement ? Or is it lost in the
noise ?

Thanks,
Quentin