On 24-Jan 17:03, Pavan Kondeti wrote:
> Hi Patrick,
Hi Pavan,
> On Tue, Jan 23, 2018 at 06:08:46PM +0000, Patrick Bellasi wrote:
> > static unsigned long cpu_util_wake(int cpu, struct task_struct *p)
> > {
> > - unsigned long util, capacity;
> > + long util, util_est;
> >
> > /* Task has no contribution or is new */
> > if (cpu != task_cpu(p) || !p->se.avg.last_update_time)
> > - return cpu_util(cpu);
> > + return cpu_util_est(cpu);
> >
> > - capacity = capacity_orig_of(cpu);
> > - util = max_t(long, cpu_rq(cpu)->cfs.avg.util_avg - task_util(p), 0);
> > + /* Discount task's blocked util from CPU's util */
> > + util = cpu_util(cpu) - task_util(p);
> > + util = max(util, 0L);
> >
> > - return (util >= capacity) ? capacity : util;
> > + if (!sched_feat(UTIL_EST))
> > + return util;
>
> At first, It is not clear to me why you are not clamping the capacity to
> CPU original capacity. It looks like it is not needed any more with
> commit f453ae2200b0 ("sched/fair: Consider RT/IRQ pressure in
> capacity_spare_wake()") inclusion.
Mainly because the above code now uses only cpu_util() which is already clamped
by capacity_orig_of().
However, you made me notice that in the few lines which follows, where I do:
> > + /*
> > + * These are the main cases covered:
> > + * - if *p is the only task sleeping on this CPU, then:
> > + * cpu_util (== task_util) > util_est (== 0)
> > + * and thus we return:
> > + * cpu_util_wake = (cpu_util - task_util) = 0
> > + *
> > + * - if other tasks are SLEEPING on the same CPU, which is just
> > waking
> > + * up, then:
> > + * cpu_util >= task_util
> > + * cpu_util > util_est (== 0)
> > + * and thus we discount *p's blocked utilization to return:
> > + * cpu_util_wake = (cpu_util - task_util) >= 0
> > + *
> > + * - if other tasks are RUNNABLE on that CPU and
> > + * util_est > cpu_util
> > + * then we use util_est since it returns a more restrictive
> > + * estimation of the spare capacity on that CPU, by just
> > considering
> > + * the expected utilization of tasks already runnable on that CPU.
> > + */
> > + util_est = cpu_rq(cpu)->cfs.util_est_runnable;
> > + util = max(util, util_est);
> > +
> > + return util;
I should instead clamp util before returning it! ;-)
> May be a separate patch to remove the clamping part?
No, I think we should keep cpu_util_wake clamped to not affect the existing
call sites. I just need to remove it where not needed (done) and add it where
needed (will do on the next iteration).
> Thanks,
> Pavan
Cheers Patrick
--
#include <best/regards.h>
Patrick Bellasi
