linux-kernel - [PATCH v1 5/5] cpuidle: menu: Take negative "sleep length" values into account

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Date:   Mon, 29 Mar 2021 20:37:12 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Linux PM <linux-pm@...r.kernel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Zhou Ti (x2019cwm)" <x2019cwm@...x.ca>
Subject: [PATCH v1 5/5] cpuidle: menu: Take negative "sleep length" values into account

From: "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Subject: [PATCH] cpuidle: menu: Take negative "sleep length" values into account

Make the menu governor check the tick_nohz_get_next_hrtimer()
return value so as to avoid dealing with negative "sleep length"
values and make it use that value directly when the tick is stopped.

While at it, rename local variable delta_next in menu_select() to
delta_tick which better reflects its purpose.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/cpuidle/governors/menu.c |   17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

Index: linux-pm/drivers/cpuidle/governors/menu.c
===================================================================
--- linux-pm.orig/drivers/cpuidle/governors/menu.c
+++ linux-pm/drivers/cpuidle/governors/menu.c
@@ -271,7 +271,7 @@ static int menu_select(struct cpuidle_dr
 	u64 predicted_ns;
 	u64 interactivity_req;
 	unsigned long nr_iowaiters;
-	ktime_t delta_next;
+	ktime_t delta, delta_tick;
 	int i, idx;
 
 	if (data->needs_update) {
@@ -280,7 +280,12 @@ static int menu_select(struct cpuidle_dr
 	}
 
 	/* determine the expected residency time, round up */
-	data->next_timer_ns = tick_nohz_get_sleep_length(&delta_next);
+	delta = tick_nohz_get_sleep_length(&delta_tick);
+	if (unlikely(delta < 0)) {
+		delta = 0;
+		delta_tick = 0;
+	}
+	data->next_timer_ns = delta;
 
 	nr_iowaiters = nr_iowait_cpu(dev->cpu);
 	data->bucket = which_bucket(data->next_timer_ns, nr_iowaiters);
@@ -318,7 +323,7 @@ static int menu_select(struct cpuidle_dr
 		 * state selection.
 		 */
 		if (predicted_ns < TICK_NSEC)
-			predicted_ns = delta_next;
+			predicted_ns = data->next_timer_ns;
 	} else {
 		/*
 		 * Use the performance multiplier and the user-configurable
@@ -377,7 +382,7 @@ static int menu_select(struct cpuidle_dr
 			 * stuck in the shallow one for too long.
 			 */
 			if (drv->states[idx].target_residency_ns < TICK_NSEC &&
-			    s->target_residency_ns <= delta_next)
+			    s->target_residency_ns <= delta_tick)
 				idx = i;
 
 			return idx;
@@ -399,7 +404,7 @@ static int menu_select(struct cpuidle_dr
 	     predicted_ns < TICK_NSEC) && !tick_nohz_tick_stopped()) {
 		*stop_tick = false;
 
-		if (idx > 0 && drv->states[idx].target_residency_ns > delta_next) {
+		if (idx > 0 && drv->states[idx].target_residency_ns > delta_tick) {
 			/*
 			 * The tick is not going to be stopped and the target
 			 * residency of the state to be returned is not within
@@ -411,7 +416,7 @@ static int menu_select(struct cpuidle_dr
 					continue;
 
 				idx = i;
-				if (drv->states[i].target_residency_ns <= delta_next)
+				if (drv->states[i].target_residency_ns <= delta_tick)
 					break;
 			}
 		}