linux-kernel - [PATCH v2 2/2] mm/mm_init.c: do not calculate zone_start_pfn/zone_end_pfn in zone_absent_pages_in

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Message-Id: <20230526085251.1977-2-haifeng.xu@shopee.com>
Date:   Fri, 26 May 2023 08:52:51 +0000
From:   Haifeng Xu <haifeng.xu@...pee.com>
To:     rppt@...nel.org
Cc:     akpm@...ux-foundation.org, mhocko@...e.com, david@...hat.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Haifeng Xu <haifeng.xu@...pee.com>
Subject: [PATCH v2 2/2] mm/mm_init.c: do not calculate zone_start_pfn/zone_end_pfn in zone_absent_pages_in_node()

In calculate_node_totalpages(), zone_start_pfn/zone_end_pfn are already
calculated in zone_spanned_pages_in_node(), so use them as parameters
instead of node_start_pfn/node_end_pfn and the duplicated calculation
process can de dropped.

Signed-off-by: Haifeng Xu <haifeng.xu@...pee.com>
Suggested-by: Mike Rapoport <rppt@...nel.org>
---
v2:
- remove unrelated whitespace changes
- do not replace pgdat->node_id with a local
  variable
- remove redundant variable 'size'
- add check that whether a zone is empty or not
---
 mm/mm_init.c | 30 ++++++++++++------------------
 1 file changed, 12 insertions(+), 18 deletions(-)

diff --git a/mm/mm_init.c b/mm/mm_init.c
index f674e5798f7d..2d91bb52c619 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -1166,20 +1166,15 @@ unsigned long __init absent_pages_in_range(unsigned long start_pfn,
 /* Return the number of page frames in holes in a zone on a node */
 static unsigned long __init zone_absent_pages_in_node(int nid,
 					unsigned long zone_type,
-					unsigned long node_start_pfn,
-					unsigned long node_end_pfn)
+					unsigned long zone_start_pfn,
+					unsigned long zone_end_pfn)
 {
-	unsigned long zone_low = arch_zone_lowest_possible_pfn[zone_type];
-	unsigned long zone_high = arch_zone_highest_possible_pfn[zone_type];
-	unsigned long zone_start_pfn, zone_end_pfn;
 	unsigned long nr_absent;
 
-	zone_start_pfn = clamp(node_start_pfn, zone_low, zone_high);
-	zone_end_pfn = clamp(node_end_pfn, zone_low, zone_high);
+	/* zone is empty, we don't have any absent pages */
+	if (zone_start_pfn == zone_end_pfn)
+		return 0;
 
-	adjust_zone_range_for_zone_movable(nid, zone_type,
-			node_start_pfn, node_end_pfn,
-			&zone_start_pfn, &zone_end_pfn);
 	nr_absent = __absent_pages_in_range(nid, zone_start_pfn, zone_end_pfn);
 
 	/*
@@ -1272,7 +1267,7 @@ static void __init calculate_node_totalpages(struct pglist_data *pgdat,
 		struct zone *zone = pgdat->node_zones + i;
 		unsigned long zone_start_pfn, zone_end_pfn;
 		unsigned long spanned, absent;
-		unsigned long size, real_size;
+		unsigned long real_size;
 
 		spanned = zone_spanned_pages_in_node(pgdat->node_id, i,
 						     node_start_pfn,
@@ -1280,23 +1275,22 @@ static void __init calculate_node_totalpages(struct pglist_data *pgdat,
 						     &zone_start_pfn,
 						     &zone_end_pfn);
 		absent = zone_absent_pages_in_node(pgdat->node_id, i,
-						   node_start_pfn,
-						   node_end_pfn);
+						   zone_start_pfn,
+						   zone_end_pfn);
 
-		size = spanned;
-		real_size = size - absent;
+		real_size = spanned - absent;
 
-		if (size)
+		if (spanned)
 			zone->zone_start_pfn = zone_start_pfn;
 		else
 			zone->zone_start_pfn = 0;
-		zone->spanned_pages = size;
+		zone->spanned_pages = spanned;
 		zone->present_pages = real_size;
 #if defined(CONFIG_MEMORY_HOTPLUG)
 		zone->present_early_pages = real_size;
 #endif
 
-		totalpages += size;
+		totalpages += spanned;
 		realtotalpages += real_size;
 	}
 
-- 
2.25.1