linux-kernel - [PATCH v2 1/7] mm, page_alloc: clean up pageset high and batch update

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Message-Id: <20201008114201.18824-2-vbabka@suse.cz>
Date:   Thu,  8 Oct 2020 13:41:55 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org, Michal Hocko <mhocko@...nel.org>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        David Hildenbrand <david@...hat.com>,
        Oscar Salvador <osalvador@...e.de>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Michal Hocko <mhocko@...e.com>
Subject: [PATCH v2 1/7] mm, page_alloc: clean up pageset high and batch update

The updates to pcplists' high and batch valued are handled by multiple
functions that make the calculations hard to follow. Consolidate everything
to pageset_set_high_and_batch() and remove pageset_set_batch() and
pageset_set_high() wrappers.

The only special case using one of the removed wrappers was:
build_all_zonelists_init()
  setup_pageset()
    pageset_set_batch()
which was hardcoding batch as 0, so we can just open-code a call to
pageset_update() with constant parameters instead.

No functional change.

Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
Reviewed-by: Oscar Salvador <osalvador@...e.de>
Reviewed-by: David Hildenbrand <david@...hat.com>
Acked-by: Michal Hocko <mhocko@...e.com>
---
 mm/page_alloc.c | 49 ++++++++++++++++++++-----------------------------
 1 file changed, 20 insertions(+), 29 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e74ca22baaa1..81f360c0d9fc 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5899,7 +5899,7 @@ static void build_zonelists(pg_data_t *pgdat)
  * not check if the processor is online before following the pageset pointer.
  * Other parts of the kernel may not check if the zone is available.
  */
-static void setup_pageset(struct per_cpu_pageset *p, unsigned long batch);
+static void setup_pageset(struct per_cpu_pageset *p);
 static DEFINE_PER_CPU(struct per_cpu_pageset, boot_pageset);
 static DEFINE_PER_CPU(struct per_cpu_nodestat, boot_nodestats);
 
@@ -5967,7 +5967,7 @@ build_all_zonelists_init(void)
 	 * (a chicken-egg dilemma).
 	 */
 	for_each_possible_cpu(cpu)
-		setup_pageset(&per_cpu(boot_pageset, cpu), 0);
+		setup_pageset(&per_cpu(boot_pageset, cpu));
 
 	mminit_verify_zonelist();
 	cpuset_init_current_mems_allowed();
@@ -6276,12 +6276,6 @@ static void pageset_update(struct per_cpu_pages *pcp, unsigned long high,
 	pcp->batch = batch;
 }
 
-/* a companion to pageset_set_high() */
-static void pageset_set_batch(struct per_cpu_pageset *p, unsigned long batch)
-{
-	pageset_update(&p->pcp, 6 * batch, max(1UL, 1 * batch));
-}
-
 static void pageset_init(struct per_cpu_pageset *p)
 {
 	struct per_cpu_pages *pcp;
@@ -6294,35 +6288,32 @@ static void pageset_init(struct per_cpu_pageset *p)
 		INIT_LIST_HEAD(&pcp->lists[migratetype]);
 }
 
-static void setup_pageset(struct per_cpu_pageset *p, unsigned long batch)
+static void setup_pageset(struct per_cpu_pageset *p)
 {
 	pageset_init(p);
-	pageset_set_batch(p, batch);
+	pageset_update(&p->pcp, 0, 1);
 }
 
 /*
- * pageset_set_high() sets the high water mark for hot per_cpu_pagelist
- * to the value high for the pageset p.
+ * Calculate and set new high and batch values for given per-cpu pageset of a
+ * zone, based on the zone's size and the percpu_pagelist_fraction sysctl.
  */
-static void pageset_set_high(struct per_cpu_pageset *p,
-				unsigned long high)
-{
-	unsigned long batch = max(1UL, high / 4);
-	if ((high / 4) > (PAGE_SHIFT * 8))
-		batch = PAGE_SHIFT * 8;
-
-	pageset_update(&p->pcp, high, batch);
-}
-
 static void pageset_set_high_and_batch(struct zone *zone,
-				       struct per_cpu_pageset *pcp)
+				       struct per_cpu_pageset *p)
 {
-	if (percpu_pagelist_fraction)
-		pageset_set_high(pcp,
-			(zone_managed_pages(zone) /
-				percpu_pagelist_fraction));
-	else
-		pageset_set_batch(pcp, zone_batchsize(zone));
+	unsigned long new_high, new_batch;
+
+	if (percpu_pagelist_fraction) {
+		new_high = zone_managed_pages(zone) / percpu_pagelist_fraction;
+		new_batch = max(1UL, new_high / 4);
+		if ((new_high / 4) > (PAGE_SHIFT * 8))
+			new_batch = PAGE_SHIFT * 8;
+	} else {
+		new_batch = zone_batchsize(zone);
+		new_high = 6 * new_batch;
+		new_batch = max(1UL, 1 * new_batch);
+	}
+	pageset_update(&p->pcp, new_high, new_batch);
 }
 
 static void __meminit zone_pageset_init(struct zone *zone, int cpu)
-- 
2.28.0