Messages in this thread | | | Date | Sat, 16 Sep 2023 20:56:12 +0100 | From | Qais Yousef <> | Subject | Re: [RFC PATCH 2/7] sched/pelt: Add a new function to approximate runtime to reach given util |
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On 09/15/23 10:15, Hongyan Xia wrote: > On 28/08/2023 00:31, Qais Yousef wrote: > > It is basically the ramp-up time from 0 to a given value. Will be used > > later to implement new tunable to control response time for schedutil. > > > > Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io> > > --- > > kernel/sched/pelt.c | 21 +++++++++++++++++++++ > > kernel/sched/sched.h | 1 + > > 2 files changed, 22 insertions(+) > > > > diff --git a/kernel/sched/pelt.c b/kernel/sched/pelt.c > > index 50322005a0ae..f673b9ab92dc 100644 > > --- a/kernel/sched/pelt.c > > +++ b/kernel/sched/pelt.c > > @@ -487,3 +487,24 @@ unsigned long approximate_util_avg(unsigned long util, u64 delta) > > return sa.util_avg; > > } > > + > > +/* > > + * Approximate the required amount of runtime in ms required to reach @util. > > + */ > > +u64 approximate_runtime(unsigned long util) > > +{ > > + struct sched_avg sa = {}; > > + u64 delta = 1024; // period = 1024 = ~1ms > > + u64 runtime = 0; > > + > > + if (unlikely(!util)) > > + return runtime; > > + > > + while (sa.util_avg < util) { > > + accumulate_sum(delta, &sa, 0, 0, 1); > > This looks a bit uncomfortable as the existing comment says that we assume: > > if (!load) > runnable = running = 0; > > I haven't looked at the math in detail, but if this is okay, maybe a comment > saying why this is okay despite the existing comment says otherwise?
Yeah as Dietmar highlighted I should pass 1 for load and it was my bad misreading the code.
So it should be
accumulate_sum(delta, &sa, 1, 0, 1);
If that's what you meant, yes.
Thanks!
-- Qais Yousef
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