linux-kernel - [PATCH v1] sched/fair: fix inconsistency in update_task_scan

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Date:   Tue, 25 Apr 2023 06:02:04 -0400
From:   zhaomzhao@....com
To:     mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, vschneid@...hat.com
Cc:     linux-kernel@...r.kernel.org,
        Zhao Mengmeng <zhaomengmeng@...inos.cn>
Subject: [PATCH v1] sched/fair: fix inconsistency in update_task_scan_period

From: Zhao Mengmeng <zhaomengmeng@...inos.cn>

During calculate numa_scan_period diff, the actual code
and the comment are inconsistent. The comment says it is
using shared faults ratio, but code uses private faults
ratio. This patch fixes it.

Signed-off-by: Zhao Mengmeng <zhaomengmeng@...inos.cn>
---
 kernel/sched/fair.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 373ff5f55884..73cc83128072 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2362,7 +2362,7 @@ static void update_task_scan_period(struct task_struct *p,
 			unsigned long shared, unsigned long private)
 {
 	unsigned int period_slot;
-	int lr_ratio, ps_ratio;
+	int lr_ratio, sp_ratio;
 	int diff;
 
 	unsigned long remote = p->numa_faults_locality[0];
@@ -2393,24 +2393,24 @@ static void update_task_scan_period(struct task_struct *p,
 	 */
 	period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
 	lr_ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
-	ps_ratio = (private * NUMA_PERIOD_SLOTS) / (private + shared);
+	sp_ratio = (shared * NUMA_PERIOD_SLOTS) / (private + shared);
 
-	if (ps_ratio >= NUMA_PERIOD_THRESHOLD) {
+	if (lr_ratio >= NUMA_PERIOD_THRESHOLD) {
 		/*
 		 * Most memory accesses are local. There is no need to
 		 * do fast NUMA scanning, since memory is already local.
 		 */
-		int slot = ps_ratio - NUMA_PERIOD_THRESHOLD;
+		int slot = lr_ratio - NUMA_PERIOD_THRESHOLD;
 		if (!slot)
 			slot = 1;
 		diff = slot * period_slot;
-	} else if (lr_ratio >= NUMA_PERIOD_THRESHOLD) {
+	} else if (sp_ratio >= NUMA_PERIOD_THRESHOLD) {
 		/*
 		 * Most memory accesses are shared with other tasks.
 		 * There is no point in continuing fast NUMA scanning,
 		 * since other tasks may just move the memory elsewhere.
 		 */
-		int slot = lr_ratio - NUMA_PERIOD_THRESHOLD;
+		int slot = sp_ratio - NUMA_PERIOD_THRESHOLD;
 		if (!slot)
 			slot = 1;
 		diff = slot * period_slot;
@@ -2420,7 +2420,7 @@ static void update_task_scan_period(struct task_struct *p,
 		 * yet they are not on the local NUMA node. Speed up
 		 * NUMA scanning to get the memory moved over.
 		 */
-		int ratio = max(lr_ratio, ps_ratio);
+		int ratio = max(lr_ratio, sp_ratio);
 		diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
 	}
 
-- 
2.38.1