linux-kernel - [RFC PATCH V3 09/17] mm: Add initial scan delay

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Message-ID: <20250814153307.1553061-10-raghavendra.kt@amd.com>
Date: Thu, 14 Aug 2025 15:32:59 +0000
From: Raghavendra K T <raghavendra.kt@....com>
To: <raghavendra.kt@....com>
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Subject: [RFC PATCH V3 09/17] mm: Add initial scan delay

 This is  to prevent unnecessary scanning of short lived tasks
to reduce CPU burning.

Signed-off-by: Raghavendra K T <raghavendra.kt@....com>
---
 mm/kscand.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/mm/kscand.c b/mm/kscand.c
index 39a7fcef7de8..880c3693866d 100644
--- a/mm/kscand.c
+++ b/mm/kscand.c
@@ -28,6 +28,7 @@
 
 static struct task_struct *kscand_thread __read_mostly;
 static DEFINE_MUTEX(kscand_mutex);
+extern unsigned int sysctl_numa_balancing_scan_delay;
 
 /*
  * Total VMA size to cover during scan.
@@ -1010,6 +1011,7 @@ void __kscand_enter(struct mm_struct *mm)
 {
 	struct kscand_mm_slot *kscand_slot;
 	struct mm_slot *slot;
+	unsigned long now;
 	int wakeup;
 
 	/* __kscand_exit() must not run from under us */
@@ -1020,10 +1022,12 @@ void __kscand_enter(struct mm_struct *mm)
 	if (!kscand_slot)
 		return;
 
+	now = jiffies;
 	kscand_slot->address = 0;
 	kscand_slot->scan_period = kscand_mm_scan_period_ms;
 	kscand_slot->scan_size = kscand_scan_size;
-	kscand_slot->next_scan = 0;
+	kscand_slot->next_scan = now +
+			2 * msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
 	kscand_slot->scan_delta = 0;
 
 	slot = &kscand_slot->slot;
-- 
2.34.1