linux-kernel - [PATCH 07/12] mm/swapfile.c: optimize code in setup

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Message-ID: <20250205092721.9395-8-bhe@redhat.com>
Date: Wed,  5 Feb 2025 17:27:16 +0800
From: Baoquan He <bhe@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org,
	akpm@...ux-foundation.org,
	ryncsn@...il.com,
	chrisl@...nel.org,
	Baoquan He <bhe@...hat.com>
Subject: [PATCH 07/12] mm/swapfile.c: optimize code in setup_clusters()

In the last 'for' loop inside setup_clusters(), using two local variable
'k' and 'j' are obvisouly redundant. Using 'j' is enough and simpler.

And also move macro SWAP_CLUSTER_COLS close to its only user
setup_clusters().

Signed-off-by: Baoquan He <bhe@...hat.com>
---
 mm/swapfile.c | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 9ee2238042a5..78b7329ad2c7 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -3123,13 +3123,6 @@ static unsigned long read_swap_header(struct swap_info_struct *si,
 	return maxpages;
 }
 
-#define SWAP_CLUSTER_INFO_COLS						\
-	DIV_ROUND_UP(L1_CACHE_BYTES, sizeof(struct swap_cluster_info))
-#define SWAP_CLUSTER_SPACE_COLS						\
-	DIV_ROUND_UP(SWAP_ADDRESS_SPACE_PAGES, SWAPFILE_CLUSTER)
-#define SWAP_CLUSTER_COLS						\
-	max_t(unsigned int, SWAP_CLUSTER_INFO_COLS, SWAP_CLUSTER_SPACE_COLS)
-
 static int setup_swap_map_and_extents(struct swap_info_struct *si,
 					union swap_header *swap_header,
 					unsigned char *swap_map,
@@ -3169,13 +3162,20 @@ static int setup_swap_map_and_extents(struct swap_info_struct *si,
 	return nr_extents;
 }
 
+#define SWAP_CLUSTER_INFO_COLS						\
+	DIV_ROUND_UP(L1_CACHE_BYTES, sizeof(struct swap_cluster_info))
+#define SWAP_CLUSTER_SPACE_COLS						\
+	DIV_ROUND_UP(SWAP_ADDRESS_SPACE_PAGES, SWAPFILE_CLUSTER)
+#define SWAP_CLUSTER_COLS						\
+	max_t(unsigned int, SWAP_CLUSTER_INFO_COLS, SWAP_CLUSTER_SPACE_COLS)
+
 static struct swap_cluster_info *setup_clusters(struct swap_info_struct *si,
 						union swap_header *swap_header,
 						unsigned long maxpages)
 {
 	unsigned long nr_clusters = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
 	struct swap_cluster_info *cluster_info;
-	unsigned long i, j, k, idx;
+	unsigned long i, j, idx;
 	int cpu, err = -ENOMEM;
 
 	cluster_info = kvcalloc(nr_clusters, sizeof(*cluster_info), GFP_KERNEL);
@@ -3236,8 +3236,7 @@ static struct swap_cluster_info *setup_clusters(struct swap_info_struct *si,
 	 * Reduce false cache line sharing between cluster_info and
 	 * sharing same address space.
 	 */
-	for (k = 0; k < SWAP_CLUSTER_COLS; k++) {
-		j = k % SWAP_CLUSTER_COLS;
+	for (j = 0; j < SWAP_CLUSTER_COLS; j++) {
 		for (i = 0; i < DIV_ROUND_UP(nr_clusters, SWAP_CLUSTER_COLS); i++) {
 			struct swap_cluster_info *ci;
 			idx = i * SWAP_CLUSTER_COLS + j;
-- 
2.41.0