linux-kernel - [PATCH 7/8] sched/fair: Do not compute overloaded status unnecessarily during lb

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Message-ID: <20241211185552.4553-8-kprateek.nayak@amd.com>
Date: Wed, 11 Dec 2024 18:55:50 +0000
From: K Prateek Nayak <kprateek.nayak@....com>
To: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>, Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>, <x86@...nel.org>,
	<linux-kernel@...r.kernel.org>
CC: "H. Peter Anvin" <hpa@...or.com>, Dietmar Eggemann
	<dietmar.eggemann@....com>, Steven Rostedt <rostedt@...dmis.org>, Ben Segall
	<bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>, Valentin Schneider
	<vschneid@...hat.com>, "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>, Tim Chen
	<tim.c.chen@...ux.intel.com>, Mario Limonciello <mario.limonciello@....com>,
	Meng Li <li.meng@....com>, Huang Rui <ray.huang@....com>, "Gautham R. Shenoy"
	<gautham.shenoy@....com>, K Prateek Nayak <kprateek.nayak@....com>
Subject: [PATCH 7/8] sched/fair: Do not compute overloaded status unnecessarily during lb

Only set sg_overloaded when computing sg_lb_stats() at the highest sched
domain since rd->overloaded status is updated only when load balancing
at the highest domain. While at it, move setting of sg_overloaded below
idle_cpu() check since an idle CPU can never be overloaded.

Signed-off-by: K Prateek Nayak <kprateek.nayak@....com>
---
 kernel/sched/fair.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index ec2a79c8d0e7..3f36805ecdca 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -10358,9 +10358,6 @@ static inline void update_sg_lb_stats(struct lb_env *env,
 		nr_running = rq->nr_running;
 		sgs->sum_nr_running += nr_running;
 
-		if (nr_running > 1)
-			*sg_overloaded = 1;
-
 		if (cpu_overutilized(i))
 			*sg_overutilized = 1;
 
@@ -10373,6 +10370,10 @@ static inline void update_sg_lb_stats(struct lb_env *env,
 			continue;
 		}
 
+		/* Overload indicator is only updated at root domain */
+		if (!env->sd->parent && nr_running > 1)
+			*sg_overloaded = 1;
+
 #ifdef CONFIG_NUMA_BALANCING
 		/* Only fbq_classify_group() uses this to classify NUMA groups */
 		if (sd_flags & SD_NUMA) {
-- 
2.34.1