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SubjectRe: [PATCH v3 0/6] cpufreq: schedutil: fixes for flags updates
On 22-Dec 11:06, Peter Zijlstra wrote:
> On Wed, Dec 20, 2017 at 06:38:14PM +0100, Juri Lelli wrote:
> > On 20/12/17 16:30, Peter Zijlstra wrote:
> >
> > [...]
> >
> > > @@ -327,12 +331,7 @@ static unsigned int sugov_next_freq_shar
> > > if (delta_ns > TICK_NSEC) {
> > > j_sg_cpu->iowait_boost = 0;
> > > j_sg_cpu->iowait_boost_pending = false;
> > > - j_sg_cpu->util_cfs = 0;
> > > - if (j_sg_cpu->util_dl == 0)
> > > - continue;
> > > }
> >
> > This goes away because with Brendan/Vincent fix we don't need the
> > workaround for stale CFS util contribution for idle CPUs anymore?
>
> An easy fix would be something like the below I suppose (also folded a
> change from Viresh).
>
> This way it completely ignores the demand from idle CPUs. Which I
> suppose is exactly what you want, no?
>
> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> index ab84d2261554..9736b537386a 100644
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -315,8 +315,8 @@ static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time)
> unsigned long j_util, j_max;
> s64 delta_ns;
>
> - if (j_sg_cpu != sg_cpu)
> - sugov_get_util(j_sg_cpu);
> + if (idle_cpu(j))
> + continue;

That should work to skip IDLE CPUs... however I'm missing where now we
get the sugov_get_util(j_sg_cpu) for active CPUs. It has been moved
somewhere else I guess...

Moreover, that way don't we completely disregard CFS blocked load for
IDLE CPUs... as well as DL reserved utilization, which should be
released only at the 0-lag time?

>
> /*
> * If the CFS CPU utilization was last updated before the
> @@ -354,7 +354,6 @@ static void sugov_update_shared(struct update_util_data *hook, u64 time,
>
> raw_spin_lock(&sg_policy->update_lock);
>
> - sugov_get_util(sg_cpu);
> sugov_set_iowait_boost(sg_cpu, time, flags);
> sg_cpu->last_update = time;
>

--
#include <best/regards.h>

Patrick Bellasi

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