Messages in this thread Patch in this message | | | Date | Thu, 19 Feb 2015 17:02:36 +0000 | From | Morten Rasmussen <> | Subject | Re: [PATCH RESEND v9 04/10] sched: Make sched entity usage tracking scale-invariant |
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On Thu, Feb 19, 2015 at 04:34:42PM +0000, Peter Zijlstra wrote: > On Thu, Jan 15, 2015 at 11:09:24AM +0100, Vincent Guittot wrote: > > From: Morten Rasmussen <morten.rasmussen@arm.com> > > > > Apply frequency scale-invariance correction factor to usage tracking. > > Each segment of the running_load_avg geometric series is now scaled by the > > current frequency so the utilization_avg_contrib of each entity will be > > invariant with frequency scaling. > > > As a result, utilization_load_avg which is > > the sum of utilization_avg_contrib, becomes invariant too. So the usage level > > that is returned by get_cpu_usage, stays relative to the max frequency as the > > cpu_capacity which is is compared against. > > > Then, we want the keep the load tracking values in a 32bits type, which implies > > that the max value of {runnable|running}_avg_sum must be lower than > > 2^32/88761=48388 (88761 is the max weigth of a task). > > > As LOAD_AVG_MAX = 47742, > > arch_scale_freq_capacity must return a value less than > > (48388/47742) << SCHED_CAPACITY_SHIFT = 1037 (SCHED_SCALE_CAPACITY = 1024). > > So we define the range to [0..SCHED_SCALE_CAPACITY] in order to avoid overflow. > > > cc: Paul Turner <pjt@google.com> > > cc: Ben Segall <bsegall@google.com> > > > > Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com> > > Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> > > --- > > kernel/sched/fair.c | 21 ++++++++++++++------- > > 1 file changed, 14 insertions(+), 7 deletions(-) > > > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > > index a96affd..a5039da 100644 > > --- a/kernel/sched/fair.c > > +++ b/kernel/sched/fair.c > > @@ -2266,6 +2266,8 @@ static u32 __compute_runnable_contrib(u64 n) > > return contrib + runnable_avg_yN_sum[n]; > > } > > > > +unsigned long __weak arch_scale_freq_capacity(struct sched_domain *sd, int cpu); > > There is no actual function definition in this patch; this would hinder > linking, no?
The function definition already lives further down in fair.c. I can move it up here if you prefer?
> > > > if (running) > > + sa->running_avg_sum += delta_w * scale_freq > > + >> SCHED_CAPACITY_SHIFT; > > > > if (running) > > + sa->running_avg_sum += runnable_contrib * scale_freq > > + >> SCHED_CAPACITY_SHIFT; > > > if (running) > > + sa->running_avg_sum += delta * scale_freq > > + >> SCHED_CAPACITY_SHIFT; > > If you're going to respin; please but {} around that.
Sure.
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