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| author | Byungchul Park <byungchul.park@lge.com> | 2017-05-23 11:00:56 +0900 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-08-10 12:18:17 +0200 |
| commit | b18c3ca11c20caa4a397baa9b893ebc4aaa4fe9f (patch) | |
| tree | b997103c208c16e04c5032a8118de0037df32b36 /kernel/sched | |
| parent | b5dd77c8bdada7b6262d0cba02a6ed525bf4e6e1 (diff) | |
| download | linux-b18c3ca11c20caa4a397baa9b893ebc4aaa4fe9f.tar.bz2 | |
sched/deadline: Make find_later_rq() choose a closer CPU in topology
When cpudl_find() returns any among free_cpus, the CPU might not be
closer than others, considering sched domain. For example:
this_cpu: 15
free_cpus: 0, 1,..., 14 (== later_mask)
best_cpu: 0
topology:
0 --+
+--+
1 --+ |
+-- ... --+
2 --+ | |
+--+ |
3 --+ |
... ...
12 --+ |
+--+ |
13 --+ | |
+-- ... -+
14 --+ |
+--+
15 --+
In this case, it would be best to select 14 since it's a free CPU and
closest to 15 (this_cpu). However, currently the code selects 0 (best_cpu)
even though that's just any among free_cpus. Fix it.
This (re)aligns the deadline behaviour with the rt behaviour.
Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <bristot@redhat.com>
Cc: <juri.lelli@gmail.com>
Cc: <kernel-team@lge.com>
Cc: <rostedt@goodmis.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1495504859-10960-2-git-send-email-byungchul.park@lge.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched')
| -rw-r--r-- | kernel/sched/deadline.c | 27 |
1 files changed, 14 insertions, 13 deletions
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index a205ac7cf435..ac07d7c3a978 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1798,7 +1798,7 @@ static int find_later_rq(struct task_struct *task) struct sched_domain *sd; struct cpumask *later_mask = this_cpu_cpumask_var_ptr(local_cpu_mask_dl); int this_cpu = smp_processor_id(); - int best_cpu, cpu = task_cpu(task); + int cpu = task_cpu(task); /* Make sure the mask is initialized first */ if (unlikely(!later_mask)) @@ -1811,17 +1811,14 @@ static int find_later_rq(struct task_struct *task) * We have to consider system topology and task affinity * first, then we can look for a suitable cpu. */ - best_cpu = cpudl_find(&task_rq(task)->rd->cpudl, - task, later_mask); - if (best_cpu == -1) + if (cpudl_find(&task_rq(task)->rd->cpudl, task, later_mask) == -1) return -1; /* - * If we are here, some target has been found, - * the most suitable of which is cached in best_cpu. - * This is, among the runqueues where the current tasks - * have later deadlines than the task's one, the rq - * with the latest possible one. + * If we are here, some targets have been found, including + * the most suitable which is, among the runqueues where the + * current tasks have later deadlines than the task's one, the + * rq with the latest possible one. * * Now we check how well this matches with task's * affinity and system topology. @@ -1841,6 +1838,7 @@ static int find_later_rq(struct task_struct *task) rcu_read_lock(); for_each_domain(cpu, sd) { if (sd->flags & SD_WAKE_AFFINE) { + int best_cpu; /* * If possible, preempting this_cpu is @@ -1852,12 +1850,15 @@ static int find_later_rq(struct task_struct *task) return this_cpu; } + best_cpu = cpumask_first_and(later_mask, + sched_domain_span(sd)); /* - * Last chance: if best_cpu is valid and is - * in the mask, that becomes our choice. + * Last chance: if a cpu being in both later_mask + * and current sd span is valid, that becomes our + * choice. Of course, the latest possible cpu is + * already under consideration through later_mask. */ - if (best_cpu < nr_cpu_ids && - cpumask_test_cpu(best_cpu, sched_domain_span(sd))) { + if (best_cpu < nr_cpu_ids) { rcu_read_unlock(); return best_cpu; } |