linux-kernel - [RFC PATCH V1 5/6] sched/numa: Allow recently accessed VMAs to be scanned

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Date:   Tue, 29 Aug 2023 11:36:13 +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 5/6] sched/numa: Allow recently accessed VMAs to be scanned

This ensures hot VMAs get scanned on priority irresepctive of their
access by current task.

Suggested-by: Bharata B Rao <bharata@....com>
Signed-off-by: Raghavendra K T <raghavendra.kt@....com>
---
 kernel/sched/fair.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 3ae2a1a3ef5c..6529da7f370a 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2971,8 +2971,22 @@ static inline bool vma_test_access_pid_history(struct vm_area_struct *vma)
 	return test_bit(pid_bit, &pids);
 }
 
+static inline bool vma_accessed_recent(struct vm_area_struct *vma)
+{
+	unsigned long *pids, pid_idx;
+
+	pid_idx = vma->numab_state->access_pid_idx;
+	pids = vma->numab_state->access_pids + pid_idx;
+
+	return (bitmap_weight(pids, BITS_PER_LONG) >= 1);
+}
+
 static bool vma_is_accessed(struct vm_area_struct *vma)
 {
+	/* Check at least one task had accessed VMA recently. */
+	if (vma_accessed_recent(vma))
+		return true;
+
 	/* Check if the current task had historically accessed VMA. */
 	if (vma_test_access_pid_history(vma))
 		return true;
-- 
2.34.1