linux-kernel - [PATCH v2 1/2] mm/zbud: reuse unbuddied[0] as buddied in zbud

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Date:   Tue, 8 Jun 2021 19:45:14 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>, <sjenning@...hat.com>,
        <ddstreet@...e.org>
CC:     <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        <linmiaohe@...wei.com>
Subject: [PATCH v2 1/2] mm/zbud: reuse unbuddied[0] as buddied in zbud_pool

Since commit 9d8c5b5284e4 ("mm: zbud: fix condition check on allocation
size"), zbud_pool.unbuddied[0] is always unused. We can reuse it as buddied
field to save some possible memory.

Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
---
 mm/zbud.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/mm/zbud.c b/mm/zbud.c
index a200121da400..78e80ca58869 100644
--- a/mm/zbud.c
+++ b/mm/zbud.c
@@ -95,8 +95,14 @@
  */
 struct zbud_pool {
 	spinlock_t lock;
-	struct list_head unbuddied[NCHUNKS];
-	struct list_head buddied;
+	union {
+		/*
+		 * Reuse unbuddied[0] as buddied on the ground that
+		 * unbuddied[0] is unused.
+		 */
+		struct list_head buddied;
+		struct list_head unbuddied[NCHUNKS];
+	};
 	struct list_head lru;
 	u64 pages_nr;
 	const struct zbud_ops *ops;
-- 
2.23.0