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From:   Mel Gorman <mgorman@techsingularity.net>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Raghavendra K T <raghavendra.kt@amd.com>,
        K Prateek Nayak <kprateek.nayak@amd.com>,
        Bharata B Rao <bharata@amd.com>,
        Ingo Molnar <mingo@redhat.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux-MM <linux-mm@kvack.org>,
        Mel Gorman <mgorman@techsingularity.net>
Subject: [PATCH 4/6] sched/numa: Move up the access pid reset logic
Date:   Tue, 10 Oct 2023 09:31:41 +0100
Message-Id: <20231010083143.19593-5-mgorman@techsingularity.net>
In-Reply-To: <20231010083143.19593-1-mgorman@techsingularity.net>
References: <20231010083143.19593-1-mgorman@techsingularity.net>
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From: Raghavendra K T <raghavendra.kt@amd.com>

Recent NUMA hinting faulting activity is reset approximately every
VMA_PID_RESET_PERIOD milliseconds. However, if the current task has not
accessed a VMA then the reset check is missed and the reset is potentially
deferred forever. Check if the PID activity information should be reset
before checking if the current task recently trapped a NUMA hinting fault.

[mgorman@techsingularity.net: Rewrite changelog]
Suggested-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Raghavendra K T <raghavendra.kt@amd.com>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
 kernel/sched/fair.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 0535c57f6a77..05e89a7950d0 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3277,16 +3277,7 @@ static void task_numa_work(struct callback_head *work)
 			continue;
 		}
 
-		/* Do not scan the VMA if task has not accessed */
-		if (!vma_is_accessed(vma)) {
-			trace_sched_skip_vma_numa(mm, vma, NUMAB_SKIP_PID_INACTIVE);
-			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->pids_active_reset)) {
 			vma->numab_state->pids_active_reset = vma->numab_state->pids_active_reset +
@@ -3295,6 +3286,12 @@ static void task_numa_work(struct callback_head *work)
 			vma->numab_state->pids_active[1] = 0;
 		}
 
+		/* Do not scan the VMA if task has not accessed */
+		if (!vma_is_accessed(vma)) {
+			trace_sched_skip_vma_numa(mm, vma, NUMAB_SKIP_PID_INACTIVE);
+			continue;
+		}
+
 		do {
 			start = max(start, vma->vm_start);
 			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
-- 
2.35.3