linux-kernel - [PATCH] sched/psi: Skip CPUs with zero non-idle jiffies in per-cpu aggregation

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Message-ID: <20260203100007.22044-1-zhanxusheng@xiaomi.com>
Date: Tue,  3 Feb 2026 18:00:07 +0800
From: Zhan Xusheng <zhanxusheng1024@...il.com>
To: Johannes Weiner <hannes@...xchg.org>
Cc: linux-kernel@...r.kernel.org,
	linux-sched@...r.kernel.org,
	Zhan Xusheng <zhanxusheng@...omi.com>
Subject: [PATCH] sched/psi: Skip CPUs with zero non-idle jiffies in per-cpu aggregation

PSI per-cpu aggregation weights each CPU's contribution by its
non-idle time converted to jiffies. CPUs with zero non-idle jiffies
do not contribute to the weighted result, but are still processed in
the current implementation.

Skip CPUs with zero non-idle jiffies early to avoid unnecessary
per-cpu arithmetic during aggregation.

No functional change intended.

Signed-off-by: Zhan Xusheng <zhanxusheng@...omi.com>
---
 kernel/sched/psi.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index 59fdb7ebbf22..ce2321793a67 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -387,6 +387,13 @@ static void collect_percpu_times(struct psi_group *group,
 		changed_states |= cpu_changed_states;
 
 		nonidle = nsecs_to_jiffies(times[PSI_NONIDLE]);
+		/*
+		 * A CPU with zero non-idle jiffies does not contribute to the
+		 * weighted per-CPU aggregation. There is no need to include it
+		 * in deltas or total accumulation.
+		 */
+		if (!nonidle)
+			continue;
 		nonidle_total += nonidle;
 
 		for (s = 0; s < PSI_NONIDLE; s++)
-- 
2.43.0