On Mon, Aug 07, 2017 at 12:50:34PM +0900, Byungchul Park wrote: > It would be better to avoid pushing tasks to other cpu within > a SD_PREFER_SIBLING domain, instead, get more chances to check other > siblings.
I applied your suggestion. Could you let me know your opinions about this? > > Signed-off-by: Byungchul Park <byungchul.p...@lge.com> > --- > kernel/sched/rt.c | 47 ++++++++++++++++++++++++++++++++++++++++++++--- > 1 file changed, 44 insertions(+), 3 deletions(-) > > diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c > index 979b734..50639e5 100644 > --- a/kernel/sched/rt.c > +++ b/kernel/sched/rt.c > @@ -1618,12 +1618,35 @@ static struct task_struct > *pick_highest_pushable_task(struct rq *rq, int cpu) > > static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask); > > +/* > + * Find the first cpu in: mask & sd & ~prefer > + */ > +static int find_cpu(const struct cpumask *mask, > + const struct sched_domain *sd, > + const struct sched_domain *prefer) > +{ > + const struct cpumask *sds = sched_domain_span(sd); > + const struct cpumask *ps = prefer ? sched_domain_span(prefer) : NULL; > + int cpu = -1; > + > + while ((cpu = cpumask_next(cpu, mask)) < nr_cpu_ids) { > + if (!cpumask_test_cpu(cpu, sds)) > + continue; > + if (ps && cpumask_test_cpu(cpu, ps)) > + continue; > + break; > + } > + > + return cpu; > +} > + > static int find_lowest_rq(struct task_struct *task) > { > - struct sched_domain *sd; > + struct sched_domain *sd, *prefer = NULL; > struct cpumask *lowest_mask = this_cpu_cpumask_var_ptr(local_cpu_mask); > int this_cpu = smp_processor_id(); > int cpu = task_cpu(task); > + int fallback_cpu = -1; > > /* Make sure the mask is initialized first */ > if (unlikely(!lowest_mask)) > @@ -1668,9 +1691,20 @@ static int find_lowest_rq(struct task_struct *task) > return this_cpu; > } > > - best_cpu = cpumask_first_and(lowest_mask, > - sched_domain_span(sd)); > + best_cpu = find_cpu(lowest_mask, sd, prefer); > + > if (best_cpu < nr_cpu_ids) { > + /* > + * If current domain is SD_PREFER_SIBLING > + * flaged, we have to get more chances to > + * check other siblings. > + */ > + if (sd->flags & SD_PREFER_SIBLING) { > + prefer = sd; > + if (fallback_cpu == -1) > + fallback_cpu = best_cpu; > + continue; > + } > rcu_read_unlock(); > return best_cpu; > } > @@ -1679,6 +1713,13 @@ static int find_lowest_rq(struct task_struct *task) > rcu_read_unlock(); > > /* > + * If fallback_cpu is valid, all our quesses failed *except* for > + * SD_PREFER_SIBLING domain. Now, we can return the fallback cpu. > + */ > + if (fallback_cpu != -1) > + return fallback_cpu; > + > + /* > * And finally, if there were no matches within the domains > * just give the caller *something* to work with from the compatible > * locations. > -- > 1.9.1