linux-kernel - [RFC PATCH 15/20] mm: Make kswapd use kthread's preferred affinity

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Message-ID: <20240726215701.19459-16-frederic@kernel.org>
Date: Fri, 26 Jul 2024 23:56:51 +0200
From: Frederic Weisbecker <frederic@...nel.org>
To: LKML <linux-kernel@...r.kernel.org>
Cc: Frederic Weisbecker <frederic@...nel.org>,
	Michal Hocko <mhocko@...nel.org>,
	Vlastimil Babka <vbabka@...e.cz>,
	linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [RFC PATCH 15/20] mm: Make kswapd use kthread's preferred affinity

Now that kthreads have an infrastructure to handle preferred affinity
against CPU hotplug and housekeeping cpumask, convert kswapd to use
it instead of handling halfway all the constraints by itself.

Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
---
 mm/vmscan.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 2e34de9cd0d4..94359a893b4f 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -7116,10 +7116,6 @@ static int kswapd(void *p)
 	unsigned int highest_zoneidx = MAX_NR_ZONES - 1;
 	pg_data_t *pgdat = (pg_data_t *)p;
 	struct task_struct *tsk = current;
-	const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
-
-	if (!cpumask_empty(cpumask))
-		set_cpus_allowed_ptr(tsk, cpumask);
 
 	/*
 	 * Tell the memory management that we're a "memory allocator",
@@ -7288,7 +7284,7 @@ void __meminit kswapd_run(int nid)
 
 	pgdat_kswapd_lock(pgdat);
 	if (!pgdat->kswapd) {
-		pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
+		pgdat->kswapd = kthread_create(kswapd, pgdat, "kswapd%d", nid);
 		if (IS_ERR(pgdat->kswapd)) {
 			/* failure at boot is fatal */
 			pr_err("Failed to start kswapd on node %d，ret=%ld\n",
@@ -7296,6 +7292,8 @@ void __meminit kswapd_run(int nid)
 			BUG_ON(system_state < SYSTEM_RUNNING);
 			pgdat->kswapd = NULL;
 		}
+		kthread_affine_preferred(pgdat->kswapd, cpumask_of_node(pgdat->node_id));
+		wake_up_process(pgdat->kswapd);
 	}
 	pgdat_kswapd_unlock(pgdat);
 }
-- 
2.45.2