diff mbox

[RFCv7,04/10] sched/fair: add triggers for OPP change requests

Message ID 1456190570-4475-5-git-send-email-smuckle@linaro.org
State New
Headers show

Commit Message

Steve Muckle Feb. 23, 2016, 1:22 a.m. UTC 
From: Juri Lelli <juri.lelli@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.

[smuckle@linaro.org: resolve merge conflicts, define task_new,
 use renamed static key sched_freq]

cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Juri Lelli <juri.lelli@arm.com>

Signed-off-by: Steve Muckle <smuckle@linaro.org>

---
 kernel/sched/fair.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 47 insertions(+), 2 deletions(-)

-- 
2.4.10

Comments

Steve Muckle March 3, 2016, 3:55 a.m. UTC | #1 
Hi Ricky,

On 02/29/2016 10:51 PM, Ricky Liang wrote:
> The change hunks of this patch should probably all depend on

> CONFIG_SMP as capacity_orig_of() and cpu_util() are only available

> when CONFIG_SMP is enabled.


Yeah, I was deferring cleaning that up until there was more buy in on
the overall solution. But it looks like we will be moving forward using
Rafael's schedutil governor. The most recent posting of that is here:

http://thread.gmane.org/gmane.linux.kernel/2166378

thanks,
Steve
diff mbox

Patch

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 3437e01..f1f00a4 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4283,6 +4283,21 @@  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
@@ -4293,6 +4308,7 @@  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)
@@ -4324,9 +4340,23 @@  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);
 }
 
@@ -4384,9 +4414,24 @@  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);
 }