linux-kernel - [PATCH] mm/early_ioremap: Combine two loops to improve performance

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Message-Id: <20220927075239.270583-1-yajun.deng@linux.dev>
Date:   Tue, 27 Sep 2022 15:52:39 +0800
From:   Yajun Deng <yajun.deng@...ux.dev>
To:     akpm@...ux-foundation.org
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Yajun Deng <yajun.deng@...ux.dev>
Subject: [PATCH] mm/early_ioremap: Combine two loops to improve performance

The first loop will waring once if prev_map is init, we can add a
boolean variable to do that. So those two loops can be combined to
improve performance.

Signed-off-by: Yajun Deng <yajun.deng@...ux.dev>
---
 mm/early_ioremap.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/mm/early_ioremap.c b/mm/early_ioremap.c
index 9bc12e526ed0..3076fb47c685 100644
--- a/mm/early_ioremap.c
+++ b/mm/early_ioremap.c
@@ -70,14 +70,15 @@ static unsigned long slot_virt[FIX_BTMAPS_SLOTS] __initdata;
 
 void __init early_ioremap_setup(void)
 {
+	bool init_prev_map = false;
 	int i;
 
-	for (i = 0; i < FIX_BTMAPS_SLOTS; i++)
-		if (WARN_ON(prev_map[i]))
-			break;
+	for (i = 0; i < FIX_BTMAPS_SLOTS; i++) {
+		if (!init_prev_map && WARN_ON(prev_map[i]))
+			init_prev_map = true;
 
-	for (i = 0; i < FIX_BTMAPS_SLOTS; i++)
 		slot_virt[i] = __fix_to_virt(FIX_BTMAP_BEGIN - NR_FIX_BTMAPS*i);
+	}
 }
 
 static int __init check_early_ioremap_leak(void)
-- 
2.25.1