FAILED: patch "[PATCH] cpuidle: governors: menu: Select polling state in some more" failed to apply to 6.6-stable tree

FAILED: patch "[PATCH] cpuidle: governors: menu: Select polling state in some more" failed to apply to 6.6-stable tree

[gregkh]

The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x db86f55bf81a3a297be05ee8775ae9a8c6e3a599
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2025110245-mongoose-ravioli-e19d@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From db86f55bf81a3a297be05ee8775ae9a8c6e3a599 Mon Sep 17 00:00:00 2001
From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Date: Thu, 23 Oct 2025 19:12:57 +0200
Subject: [PATCH] cpuidle: governors: menu: Select polling state in some more
 cases

A throughput regression of 11% introduced by commit 779b1a1cb13a ("cpuidle:
governors: menu: Avoid selecting states with too much latency") has been
reported and it is related to the case when the menu governor checks if
selecting a proper idle state instead of a polling one makes sense.

In particular, it is questionable to do so if the exit latency of the
idle state in question exceeds the predicted idle duration, so add a
check for that, which is sufficient to make the reported regression go
away, and update the related code comment accordingly.

Fixes: 779b1a1cb13a ("cpuidle: governors: menu: Avoid selecting states with too much latency")
Closes: https://lore.kernel.org/linux-pm/004501dc43c9$ec8aa930$c59ffb90$@telus.net/
Reported-by: Doug Smythies <dsmythies@telus.net>
Tested-by: Doug Smythies <dsmythies@telus.net>
Cc: All applicable <stable@vger.kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Christian Loehle <christian.loehle@arm.com>
Link: https://patch.msgid.link/12786727.O9o76ZdvQC@rafael.j.wysocki

diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index 7d21fb5a72f4..23239b0c04f9 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -318,10 +318,13 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
 
 		/*
 		 * Use a physical idle state, not busy polling, unless a timer
-		 * is going to trigger soon enough.
+		 * is going to trigger soon enough or the exit latency of the
+		 * idle state in question is greater than the predicted idle
+		 * duration.
 		 */
 		if ((drv->states[idx].flags & CPUIDLE_FLAG_POLLING) &&
-		    s->target_residency_ns <= data->next_timer_ns) {
+		    s->target_residency_ns <= data->next_timer_ns &&
+		    s->exit_latency_ns <= predicted_ns) {
 			predicted_ns = s->target_residency_ns;
 			idx = i;
 			break;

[PATCH 6.6.y 1/2] cpuidle: governors: menu: Rearrange main loop in menu_select()

[Sasha Levin]

From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>

[ Upstream commit 17224c1d2574d29668c4879e1fbf36d6f68cd22b ]

Reduce the indentation level in the main loop of menu_select() by
rearranging some checks and assignments in it.

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Christian Loehle <christian.loehle@arm.com>
Link: https://patch.msgid.link/2389215.ElGaqSPkdT@rafael.j.wysocki
Stable-dep-of: db86f55bf81a ("cpuidle: governors: menu: Select polling state in some more cases")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/cpuidle/governors/menu.c | 70 ++++++++++++++++----------------
 1 file changed, 36 insertions(+), 34 deletions(-)

diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index cafe6eed3349f..8e9d9c448f0f8 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -348,45 +348,47 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
 		if (s->exit_latency_ns > latency_req)
 			break;
 
-		if (s->target_residency_ns > predicted_ns) {
-			/*
-			 * Use a physical idle state, not busy polling, unless
-			 * a timer is going to trigger soon enough.
-			 */
-			if ((drv->states[idx].flags & CPUIDLE_FLAG_POLLING) &&
-			    s->target_residency_ns <= data->next_timer_ns) {
-				predicted_ns = s->target_residency_ns;
-				idx = i;
-				break;
-			}
-			if (predicted_ns < TICK_NSEC)
-				break;
-
-			if (!tick_nohz_tick_stopped()) {
-				/*
-				 * If the state selected so far is shallow,
-				 * waking up early won't hurt, so retain the
-				 * tick in that case and let the governor run
-				 * again in the next iteration of the loop.
-				 */
-				predicted_ns = drv->states[idx].target_residency_ns;
-				break;
-			}
+		if (s->target_residency_ns <= predicted_ns) {
+			idx = i;
+			continue;
+		}
+
+		/*
+		 * Use a physical idle state, not busy polling, unless a timer
+		 * is going to trigger soon enough.
+		 */
+		if ((drv->states[idx].flags & CPUIDLE_FLAG_POLLING) &&
+		    s->target_residency_ns <= data->next_timer_ns) {
+			predicted_ns = s->target_residency_ns;
+			idx = i;
+			break;
+		}
 
+		if (predicted_ns < TICK_NSEC)
+			break;
+
+		if (!tick_nohz_tick_stopped()) {
 			/*
-			 * If the state selected so far is shallow and this
-			 * state's target residency matches the time till the
-			 * closest timer event, select this one to avoid getting
-			 * stuck in the shallow one for too long.
+			 * If the state selected so far is shallow, waking up
+			 * early won't hurt, so retain the tick in that case and
+			 * let the governor run again in the next iteration of
+			 * the idle loop.
 			 */
-			if (drv->states[idx].target_residency_ns < TICK_NSEC &&
-			    s->target_residency_ns <= delta_tick)
-				idx = i;
-
-			return idx;
+			predicted_ns = drv->states[idx].target_residency_ns;
+			break;
 		}
 
-		idx = i;
+		/*
+		 * If the state selected so far is shallow and this state's
+		 * target residency matches the time till the closest timer
+		 * event, select this one to avoid getting stuck in the shallow
+		 * one for too long.
+		 */
+		if (drv->states[idx].target_residency_ns < TICK_NSEC &&
+		    s->target_residency_ns <= delta_tick)
+			idx = i;
+
+		return idx;
 	}
 
 	if (idx == -1)
-- 
2.51.0

[PATCH 6.6.y 2/2] cpuidle: governors: menu: Select polling state in some more cases

[Sasha Levin]

From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>

[ Upstream commit db86f55bf81a3a297be05ee8775ae9a8c6e3a599 ]

A throughput regression of 11% introduced by commit 779b1a1cb13a ("cpuidle:
governors: menu: Avoid selecting states with too much latency") has been
reported and it is related to the case when the menu governor checks if
selecting a proper idle state instead of a polling one makes sense.

In particular, it is questionable to do so if the exit latency of the
idle state in question exceeds the predicted idle duration, so add a
check for that, which is sufficient to make the reported regression go
away, and update the related code comment accordingly.

Fixes: 779b1a1cb13a ("cpuidle: governors: menu: Avoid selecting states with too much latency")
Closes: https://lore.kernel.org/linux-pm/004501dc43c9$ec8aa930$c59ffb90$@telus.net/
Reported-by: Doug Smythies <dsmythies@telus.net>
Tested-by: Doug Smythies <dsmythies@telus.net>
Cc: All applicable <stable@vger.kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Christian Loehle <christian.loehle@arm.com>
Link: https://patch.msgid.link/12786727.O9o76ZdvQC@rafael.j.wysocki
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/cpuidle/governors/menu.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index 8e9d9c448f0f8..8c591dde61023 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -355,10 +355,13 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
 
 		/*
 		 * Use a physical idle state, not busy polling, unless a timer
-		 * is going to trigger soon enough.
+		 * is going to trigger soon enough or the exit latency of the
+		 * idle state in question is greater than the predicted idle
+		 * duration.
 		 */
 		if ((drv->states[idx].flags & CPUIDLE_FLAG_POLLING) &&
-		    s->target_residency_ns <= data->next_timer_ns) {
+		    s->target_residency_ns <= data->next_timer_ns &&
+		    s->exit_latency_ns <= predicted_ns) {
 			predicted_ns = s->target_residency_ns;
 			idx = i;
 			break;
-- 
2.51.0