netdev - [PATCH net-next 22/48] can: raw: reorder struct uniqframe's members to optimise packing

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Message-ID: <20250924082104.595459-23-mkl@pengutronix.de>
Date: Wed, 24 Sep 2025 10:06:39 +0200
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: netdev@...r.kernel.org
Cc: davem@...emloft.net,
	kuba@...nel.org,
	linux-can@...r.kernel.org,
	kernel@...gutronix.de,
	Vincent Mailhol <mailhol@...nel.org>,
	Oliver Hartkopp <socketcan@...tkopp.net>,
	Marc Kleine-Budde <mkl@...gutronix.de>
Subject: [PATCH net-next 22/48] can: raw: reorder struct uniqframe's members to optimise packing

From: Vincent Mailhol <mailhol@...nel.org>

struct uniqframe has one hole. Reorder the fields to save 8 bytes.

Statistics before:

  $ pahole --class_name=uniqframe net/can/raw.o
  struct uniqframe {
  	int                        skbcnt;               /*     0     4 */

  	/* XXX 4 bytes hole, try to pack */

  	const struct sk_buff  *    skb;                  /*     8     8 */
  	unsigned int               join_rx_count;        /*    16     4 */

  	/* size: 24, cachelines: 1, members: 3 */
  	/* sum members: 16, holes: 1, sum holes: 4 */
  	/* padding: 4 */
  	/* last cacheline: 24 bytes */
  };

...and after:

  $ pahole --class_name=uniqframe net/can/raw.o
  struct uniqframe {
  	const struct sk_buff  *    skb;                  /*     0     8 */
  	int                        skbcnt;               /*     8     4 */
  	unsigned int               join_rx_count;        /*    12     4 */

  	/* size: 16, cachelines: 1, members: 3 */
  	/* last cacheline: 16 bytes */
  };

Acked-by: Oliver Hartkopp <socketcan@...tkopp.net>
Signed-off-by: Vincent Mailhol <mailhol@...nel.org>
Link: https://patch.msgid.link/20250917-can-raw-repack-v2-1-395e8b3a4437@kernel.org
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
---
 net/can/raw.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/can/raw.c b/net/can/raw.c
index 76b867d21def..db21d8a8c54d 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -75,8 +75,8 @@ MODULE_ALIAS("can-proto-1");
  */
 
 struct uniqframe {
-	int skbcnt;
 	const struct sk_buff *skb;
+	int skbcnt;
 	unsigned int join_rx_count;
 };
 
-- 
2.51.0