Messages in this thread Patch in this message |  | | From | Byungchul Park <> | Subject | [PATCH v6 2/2] sched/rt: Add support for SD_PREFER_SIBLING on find_lowest_rq() | Date | Mon, 7 Aug 2017 12:50:34 +0900 |
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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.
Signed-off-by: Byungchul Park <byungchul.park@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
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