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    SubjectRe: [PATCH v6 08/11] cpufreq/schedutil: take into account interrupt
    On 12 June 2018 at 11:20, Quentin Perret <quentin.perret@arm.com> wrote:
    > 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 ?

    the result are less stable because c-state wake up time impact
    performance and cpuidle is not good to select the right idle state in
    such case. Normally, an app should use qos dma latency or a driver per
    device resume latency

    >
    > Thanks,
    > Quentin

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