Re: [PATCH v5 2/3] sched/topology: Rework CPU capacity asymmetry detection

Beata Michalska
2021-05-25T10:30:01Z

On Tue, May 25, 2021 at 10:53:07AM +0100, Valentin Schneider wrote:
> On 24/05/21 23:55, Beata Michalska wrote:
> > On Mon, May 24, 2021 at 07:01:04PM +0100, Valentin Schneider wrote:
> >> On 24/05/21 11:16, Beata Michalska wrote:
> >> > This patch also removes the additional -dflags- parameter used when
> >> ^^^^^^^^^^^^^^^^^^^^^^^
> >> s/^/Also remove/
> > I would kind of ... disagree.
> > All the commit msg is constructed using passive structure, the suggestion
> > would actually break that. And it does 'sound' bit imperative but I guess
> > that is subjective. I'd rather stay with impersonal structure (which is
> > applied through out the whole patchset).
>
> It's mainly about the 'This patch' formulation, some take exception to that :-)
>
Will rephrase
> >>
> >> > building sched domains as the asymmetry flags are now being set
> >> > directly in sd_init.
> >> >
> >>
> >> Few nits below, but beyond that:
> >>
> >> Tested-by: Valentin Schneider <valentin.schneider@arm.com>
> >> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
> >>
> > Thanks a lot for the review and testing!
> >
> >> > +static inline int
> >> > +asym_cpu_capacity_classify(struct sched_domain *sd,
> >> > + const struct cpumask *cpu_map)
> >> > +{
> >> > + int sd_asym_flags = SD_ASYM_CPUCAPACITY | SD_ASYM_CPUCAPACITY_FULL;
> >> > + struct asym_cap_data *entry;
> >> > + int asym_cap_count = 0;
> >> > +
> >> > + if (list_is_singular(&asym_cap_list))
> >> > + goto leave;
> >> > +
> >> > + list_for_each_entry(entry, &asym_cap_list, link) {
> >> > + if (cpumask_intersects(sched_domain_span(sd), entry->cpu_mask)) {
> >> > + ++asym_cap_count;
> >> > + } else {
> >> > + /*
> >> > + * CPUs with given capacity might be offline
> >> > + * so make sure this is not the case
> >> > + */
> >> > + if (cpumask_intersects(entry->cpu_mask, cpu_map)) {
> >> > + sd_asym_flags &= ~SD_ASYM_CPUCAPACITY_FULL;
> >> > + if (asym_cap_count > 1)
> >> > + break;
> >> > + }
> >>
> >> Readability nit: That could be made into an else if ().
> > It could but then this way the -comment- gets more exposed.
> > But that might be my personal perception so I can change that.
>
> As always those are quite subjective! Methink something like this would
> still draw attention to the offline case:
>
> /*
> * Count how many unique capacities this domain covers. If a
> * capacity isn't covered, we need to check if any CPU with
> * that capacity is actually online, otherwise it can be
> * ignored.
> */
> if (cpumask_intersects(sched_domain_span(sd), entry->cpu_mask)) {
> ++asym_cap_count;
> } else if (cpumask_intersects(entry->cpu_mask, cpu_map)) {
> sd_asym_flags &= ~SD_ASYM_CPUCAPACITY_FULL;
> if (asym_cap_count > 1)
> break;
> }
Noted.
Will wait for some more comments before sending out 'polished' version.

---
BR
B.