linux-kernel - [PATCH 08/22 v2] mm/vmstat: Avoid on each online CPU loops

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Date:   Tue, 29 Nov 2016 15:51:14 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Michal Hocko <mhocko@...nel.org>, linux-kernel@...r.kernel.org,
        rt@...utronix.de, Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org
Subject: [PATCH 08/22 v2] mm/vmstat: Avoid on each online CPU loops

Both iterations over online cpus can be replaced by the proper node
specific functions.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Vlastimil Babka <vbabka@...e.cz>
Cc: Mel Gorman <mgorman@...hsingularity.net>
Cc: Johannes Weiner <hannes@...xchg.org>
Cc: linux-mm@...ck.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
v1…v2: take into account that we may have online nodes with no CPUs.

 mm/vmstat.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 0b63ffb5c407..5152cd1c490f 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1720,19 +1720,21 @@ static void __init start_shepherd_timer(void)
 
 static void __init init_cpu_node_state(void)
 {
-	int cpu;
+	int node;
 
-	for_each_online_cpu(cpu)
-		node_set_state(cpu_to_node(cpu), N_CPU);
+	for_each_online_node(node) {
+		if (cpumask_weight(cpumask_of_node(node)) > 0)
+			node_set_state(node, N_CPU);
+	}
 }
 
 static void vmstat_cpu_dead(int node)
 {
-	int cpu;
+	const struct cpumask *node_cpus;
 
-	for_each_online_cpu(cpu)
-		if (cpu_to_node(cpu) == node)
-			return;
+	node_cpus = cpumask_of_node(node);
+	if (cpumask_weight(node_cpus) > 0)
+		return;
 
 	node_clear_state(node, N_CPU);
 }
-- 
2.10.2