From: Juri Lelli <juri.le...@arm.com>
Each time a task is {en,de}queued we might need to adapt the current
frequency to the new usage. Add triggers on {en,de}queue_task_fair() for
this purpose. Only trigger a freq request if we are effectively waking up
or going to sleep. Filter out load balancing related calls to reduce the
number of triggers.
[smuc...@linaro.org: resolve merge conflicts, define task_new,
use renamed static key sched_freq]
cc: Ingo Molnar <mi...@redhat.com>
cc: Peter Zijlstra <pet...@infradead.org>
Signed-off-by: Juri Lelli <juri.le...@arm.com>
Signed-off-by: Steve Muckle <smuc...@linaro.org>
---
kernel/sched/fair.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 47 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 95b83c4..904188a 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4199,6 +4199,21 @@ static inline void hrtick_update(struct rq *rq)
}
#endif
+static unsigned long capacity_orig_of(int cpu);
+static int cpu_util(int cpu);
+
+static void update_capacity_of(int cpu)
+{
+ unsigned long req_cap;
+
+ if (!sched_freq())
+ return;
+
+ /* Convert scale-invariant capacity to cpu. */
+ req_cap = cpu_util(cpu) * SCHED_CAPACITY_SCALE / capacity_orig_of(cpu);
+ set_cfs_cpu_capacity(cpu, true, req_cap);
+}
+
/*
* The enqueue_task method is called before nr_running is
* increased. Here we update the fair scheduling stats and
@@ -4209,6 +4224,7 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p,
int flags)
{
struct cfs_rq *cfs_rq;
struct sched_entity *se = &p->se;
+ int task_new = !(flags & ENQUEUE_WAKEUP);
for_each_sched_entity(se) {
if (se->on_rq)
@@ -4240,9 +4256,23 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p,
int flags)
update_cfs_shares(cfs_rq);
}
- if (!se)
+ if (!se) {
add_nr_running(rq, 1);
+ /*
+ * We want to potentially trigger a freq switch
+ * request only for tasks that are waking up; this is
+ * because we get here also during load balancing, but
+ * in these cases it seems wise to trigger as single
+ * request after load balancing is done.
+ *
+ * XXX: how about fork()? Do we need a special
+ * flag/something to tell if we are here after a
+ * fork() (wakeup_task_new)?
+ */
+ if (!task_new)
+ update_capacity_of(cpu_of(rq));
+ }
hrtick_update(rq);
}
@@ -4300,9 +4330,24 @@ static void dequeue_task_fair(struct rq *rq, struct
task_struct *p, int flags)
update_cfs_shares(cfs_rq);
}
- if (!se)
+ if (!se) {
sub_nr_running(rq, 1);
+ /*
+ * We want to potentially trigger a freq switch
+ * request only for tasks that are going to sleep;
+ * this is because we get here also during load
+ * balancing, but in these cases it seems wise to
+ * trigger as single request after load balancing is
+ * done.
+ */
+ if (task_sleep) {
+ if (rq->cfs.nr_running)
+ update_capacity_of(cpu_of(rq));
+ else if (sched_freq())
+ set_cfs_cpu_capacity(cpu_of(rq), false, 0);
+ }
+ }
hrtick_update(rq);
}
--
2.4.10
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