sched/psi: Extract update_triggers side effect

This change moves update_total flag out of update_triggers function,
currently called only in psi_poll_work.
In the next patch, update_triggers will be called also in psi_avgs_work,
but the total update information is specific to psi_poll_work.
Returning update_total value to the caller let us avoid differentiating
the implementation of update_triggers for different aggregators.
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lore.kernel.org/r/20230330105418.77061-4-cerasuolodomenico@gmail.com

kernel/sched/psi.c

@@ -430,11 +430,11 @@ static u64 window_update(struct psi_window *win, u64 now, u64 value)
 	return growth;
 }
 
-static u64 update_triggers(struct psi_group *group, u64 now)
+static u64 update_triggers(struct psi_group *group, u64 now, bool *update_total)
 {
 	struct psi_trigger *t;
-	bool update_total = false;
 	u64 *total = group->total[PSI_POLL];
+	*update_total = false;
 
 	/*
 	 * On subsequent updates, calculate growth deltas and let
@@ -462,7 +462,7 @@ static u64 update_triggers(struct psi_group *group, u64 now)
 			 * been through all of them. Also remember to extend the
 			 * polling time if we see new stall activity.
 			 */
-			update_total = true;
+			*update_total = true;
 
 			/* Calculate growth since last update */
 			growth = window_update(&t->win, now, total[t->state]);
@@ -485,10 +485,6 @@ static u64 update_triggers(struct psi_group *group, u64 now)
 		t->pending_event = false;
 	}
 
-	if (update_total)
-		memcpy(group->rtpoll_total, total,
-				sizeof(group->rtpoll_total));
-
 	return now + group->rtpoll_min_period;
 }
 
@@ -622,6 +618,7 @@ static void psi_rtpoll_work(struct psi_group *group)
 {
 	bool force_reschedule = false;
 	u32 changed_states;
+	bool update_total;
 	u64 now;
 
 	mutex_lock(&group->rtpoll_trigger_lock);
@@ -686,8 +683,12 @@ static void psi_rtpoll_work(struct psi_group *group)
 		goto out;
 	}
 
-	if (now >= group->rtpoll_next_update)
-		group->rtpoll_next_update = update_triggers(group, now);
+	if (now >= group->rtpoll_next_update) {
+		group->rtpoll_next_update = update_triggers(group, now, &update_total);
+		if (update_total)
+			memcpy(group->rtpoll_total, group->total[PSI_POLL],
+				   sizeof(group->rtpoll_total));
+	}
 
 	psi_schedule_rtpoll_work(group,
 		nsecs_to_jiffies(group->rtpoll_next_update - now) + 1,