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    SubjectRe: [PATCH v5 01/10] sched/pelt: Move pelt related code in a dedicated file
    Hi Quentin,

    On 29 May 2018 at 16:55, Quentin Perret <quentin.perret@arm.com> wrote:
    >
    > On Friday 25 May 2018 at 19:04:55 (+0100), Patrick Bellasi wrote:
    > > On 25-May 15:26, Quentin Perret wrote:
    > > > And also, I understand these functions are large, but if we _really_
    > > > want to inline them even though they're big, why not putting them in
    > > > sched-pelt.h ?
    > >
    > > Had the same tought at first... but then I recalled that header is
    > > generated from a script. Thus, eventually, it should be a different one.
    >
    > Ah, good point. This patch already introduces a pelt.h so I guess that
    > could work as well.
    >
    > >
    > > > We probably wouldn't accept that for everything, but
    > > > those PELT functions are used all over the place, including latency
    > > > sensitive code paths (e.g. task wake-up).
    > >
    > > We should better measure the overheads, if any, and check what
    > > (a modern) compiler does. Maybe some hackbench run could help on the
    > > first point.
    >
    > FWIW, I ran a few hackbench tests today on my Intel box:
    > - Intel i7-6700 (4 cores / 8 threads) @ 3.40GHz
    > - Base kernel: today's tip/sched/core "2539fc82aa9b sched/fair: Update
    > util_est before updating schedutil"
    > - Compiler: GCC 7.3.0

    Which cpufreq governor are you using ?

    >
    > The tables below summarize the results for:
    > perf stat --repeat 10 perf bench sched messaging --pipe --thread -l 50000 --group G
    >
    > Without patch:
    > +---+-------+----------+---------+
    > | G | Tasks | Duration | Stddev |
    > +---+-------+----------+---------+
    > | 1 | 40 | 3.906 | +-0.84% |
    > | 2 | 80 | 8.569 | +-0.77% |
    > | 4 | 160 | 16.384 | +-0.46% |
    > | 8 | 320 | 33.686 | +-0.42% |
    > +---+-------+----------+---------+
    >
    > With patch:

    Just to make sure. You mean only this patch and not the whole patchset ?

    > +---+-------+----------------+---------+
    > | G | Tasks | Duration | Stddev |
    > +---+-------+----------------+---------+
    > | 1 | 40 | 3.953 (+1.2%) | +-1.43% |
    > | 2 | 80 | 8.646 (+0.9%) | +-0.32% |
    > | 4 | 160 | 16.390 (+0.0%) | +-0.38% |
    > | 8 | 320 | 33.992 (+0.9%) | +-0.27% |
    > +---+-------+----------------+---------+
    >
    > So there is (maybe) a little something on my box, but not so significant
    > IMHO ... :)
    >
    > Thanks,
    > Quentin

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