Messages in this thread | | | Date | Fri, 15 Sep 2023 10:15:29 +0100 | Subject | Re: [RFC PATCH 2/7] sched/pelt: Add a new function to approximate runtime to reach given util | From | Hongyan Xia <> |
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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?
> + ___update_load_avg(&sa, 0); > + runtime++; > + } > + > + return runtime; > +} > [...]
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