linux-kernel - [PATCH v2 3/5] mm: enlarge NUMA counters threshold size

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Date:   Tue, 19 Dec 2017 14:39:24 +0800
From:   Kemi Wang <kemi.wang@...el.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Johannes Weiner <hannes@...xchg.org>,
        Christopher Lameter <cl@...ux.com>,
        YASUAKI ISHIMATSU <yasu.isimatu@...il.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Nikolay Borisov <nborisov@...e.com>,
        Pavel Tatashin <pasha.tatashin@...cle.com>,
        David Rientjes <rientjes@...gle.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Dave <dave.hansen@...ux.intel.com>,
        Andi Kleen <andi.kleen@...el.com>,
        Tim Chen <tim.c.chen@...el.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Ying Huang <ying.huang@...el.com>,
        Aaron Lu <aaron.lu@...el.com>, Aubrey Li <aubrey.li@...el.com>,
        Kemi Wang <kemi.wang@...el.com>, Linux MM <linux-mm@...ck.org>,
        Linux Kernel <linux-kernel@...r.kernel.org>
Subject: [PATCH v2 3/5] mm: enlarge NUMA counters threshold size

We have seen significant overhead in cache bouncing caused by NUMA counters
update in multi-threaded page allocation. See 'commit 1d90ca897cb0 ("mm:
update NUMA counter threshold size")' for more details.

This patch updates NUMA counters to a fixed size of (MAX_S16 - 2) and deals
with global counter update using different threshold size for node page
stats.

Signed-off-by: Kemi Wang <kemi.wang@...el.com>
---
 mm/vmstat.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 9c681cc..64e08ae 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -30,6 +30,8 @@
 
 #include "internal.h"
 
+#define VM_NUMA_STAT_THRESHOLD (S16_MAX - 2)
+
 #ifdef CONFIG_NUMA
 int sysctl_vm_numa_stat = ENABLE_NUMA_STAT;
 
@@ -394,7 +396,11 @@ void __inc_node_state(struct pglist_data *pgdat, enum node_stat_item item)
 	s16 v, t;
 
 	v = __this_cpu_inc_return(*p);
-	t = __this_cpu_read(pcp->stat_threshold);
+	if (item >= NR_VM_NUMA_STAT_ITEMS)
+		t = __this_cpu_read(pcp->stat_threshold);
+	else
+		t = VM_NUMA_STAT_THRESHOLD;
+
 	if (unlikely(v > t)) {
 		s16 overstep = t >> 1;
 
@@ -549,7 +555,10 @@ static inline void mod_node_state(struct pglist_data *pgdat,
 		 * Most of the time the thresholds are the same anyways
 		 * for all cpus in a node.
 		 */
-		t = this_cpu_read(pcp->stat_threshold);
+		if (item >= NR_VM_NUMA_STAT_ITEMS)
+			t = this_cpu_read(pcp->stat_threshold);
+		else
+			t = VM_NUMA_STAT_THRESHOLD;
 
 		o = this_cpu_read(*p);
 		n = delta + o;
-- 
2.7.4