linux-kernel - [RFC PATCH V1 1/6] sched/numa: Move up the access pid reset logic

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Date:   Tue, 29 Aug 2023 11:36:09 +0530
From:   Raghavendra K T <raghavendra.kt@....com>
To:     <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>
CC:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Mel Gorman" <mgorman@...e.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "David Hildenbrand" <david@...hat.com>, <rppt@...nel.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Bharata B Rao <bharata@....com>,
        Aithal Srikanth <sraithal@....com>,
        "kernel test robot" <oliver.sang@...el.com>,
        Raghavendra K T <raghavendra.kt@....com>,
        Sapkal Swapnil <Swapnil.Sapkal@....com>,
        K Prateek Nayak <kprateek.nayak@....com>
Subject: [RFC PATCH V1 1/6] sched/numa: Move up the access pid reset logic

otherwise VMA's access pid clearing could get deferred for
a long time when tasks return without scanning.

Suggested-by: Mel Gorman <mgorman@...hsingularity.net>
Signed-off-by: Raghavendra K T <raghavendra.kt@....com>
---
 kernel/sched/fair.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index b3e25be58e2b..2f2e1568c1d4 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3068,14 +3068,7 @@ static void task_numa_work(struct callback_head *work)
 						vma->numab_state->next_scan))
 			continue;
 
-		/* Do not scan the VMA if task has not accessed */
-		if (!vma_is_accessed(vma))
-			continue;
-
-		/*
-		 * RESET access PIDs regularly for old VMAs. Resetting after checking
-		 * vma for recent access to avoid clearing PID info before access..
-		 */
+		/* RESET access PIDs regularly for old VMAs. */
 		if (mm->numa_scan_seq &&
 				time_after(jiffies, vma->numab_state->next_pid_reset)) {
 			vma->numab_state->next_pid_reset = vma->numab_state->next_pid_reset +
@@ -3084,6 +3077,10 @@ static void task_numa_work(struct callback_head *work)
 			vma->numab_state->access_pids[1] = 0;
 		}
 
+		/* Do not scan the VMA if task has not accessed */
+		if (!vma_is_accessed(vma))
+			continue;
+
 		do {
 			start = max(start, vma->vm_start);
 			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
-- 
2.34.1