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Message-Id: <20221201135045.31663-1-wonder_rock@126.com>
Date: Thu, 1 Dec 2022 21:50:45 +0800
From: wonder_rock@....com
To: akpm@...ux-foundation.org
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
Deyan Wang <wonder_rock@....com>
Subject: [PATCH 1/1] mm/page_alloc: update comments in __free_pages_ok()
From: Deyan Wang <wonder_rock@....com>
Add a comment to explain why we call get_pfnblock_migratetype() twice
in __free_pages_ok().
Signed-off-by: Deyan Wang <wonder_rock@....com>
---
mm/page_alloc.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2d4c81224508..52dd4fff280b 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1702,6 +1702,11 @@ static void __free_pages_ok(struct page *page, unsigned int order,
if (!free_pages_prepare(page, order, true, fpi_flags))
return;
+ /*
+ * Calling get_pfnblock_migratetype() without spin_lock_irqsave() here
+ * is used to avoid calling get_pfnblock_migratetype() under the lock.
+ * This will reduce the lock holding time.
+ */
migratetype = get_pfnblock_migratetype(page, pfn);
spin_lock_irqsave(&zone->lock, flags);
--
2.25.1
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