Hi, On 18/08/17 17:21, Byungchul Park wrote: > It would be better to try to check other siblings first if > SD_PREFER_SIBLING is flaged when pushing tasks - migration. > > Signed-off-by: Byungchul Park <byungchul.p...@lge.com>
Mmm, this looks like Peter's proposed patch, maybe add (at least) a Suggested-by: him ? https://marc.info/?l=linux-kernel&m=150176183807073 Also, I'm not sure what Peter meant with "But still this isn't quite right, because when we consider this for SMT (as was the intent here) we'll happily occupy a full sibling core over finding an empty one." since we are still using the later_mask, which should not include full cores (unless it is the one with the lates deadline)? > --- > kernel/sched/deadline.c | 55 > ++++++++++++++++++++++++++++++++++++++++++++++--- > 1 file changed, 52 insertions(+), 3 deletions(-) > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > index 0223694..115250b 100644 > --- a/kernel/sched/deadline.c > +++ b/kernel/sched/deadline.c > @@ -1319,12 +1319,35 @@ static struct task_struct > *pick_earliest_pushable_dl_task(struct rq *rq, int cpu > > static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl); > > +/* > + * 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; > + > + for_each_cpu(cpu, mask) { > + if (!cpumask_test_cpu(cpu, sds)) > + continue; > + if (ps && cpumask_test_cpu(cpu, ps)) > + continue; > + break; > + } > + > + return cpu; > +} > + > static int find_later_rq(struct task_struct *task) > { > - struct sched_domain *sd; > + struct sched_domain *sd, *prefer = NULL; > struct cpumask *later_mask = > this_cpu_cpumask_var_ptr(local_cpu_mask_dl); > int this_cpu = smp_processor_id(); > int cpu = task_cpu(task); > + int fallback_cpu = -1; > > /* Make sure the mask is initialized first */ > if (unlikely(!later_mask)) > @@ -1376,8 +1399,7 @@ static int find_later_rq(struct task_struct *task) > return this_cpu; > } > > - best_cpu = cpumask_first_and(later_mask, > - sched_domain_span(sd)); > + best_cpu = find_cpu(later_mask, sd, prefer); > /* > * Last chance: if a cpu being in both later_mask > * and current sd span is valid, that becomes our > @@ -1385,6 +1407,26 @@ static int find_later_rq(struct task_struct *task) > * already under consideration through later_mask. > */ It seems that the comment above should be updated as well. Thanks, - Juri
