netdev - [PATCH net-next v2 3/5] net: skbuff: move alloc

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Message-Id: <20230417155350.337873-4-kuba@kernel.org>
Date:   Mon, 17 Apr 2023 08:53:48 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     davem@...emloft.net
Cc:     netdev@...r.kernel.org, edumazet@...gle.com, pabeni@...hat.com,
        Jakub Kicinski <kuba@...nel.org>,
        Florian Fainelli <f.fainelli@...il.com>
Subject: [PATCH net-next v2 3/5] net: skbuff: move alloc_cpu into a potential hole

alloc_cpu is currently between 4 byte fields, so it's almost
guaranteed to create a 2B hole. It has a knock on effect of
creating a 4B hole after @end (and @end and @tail being in
different cachelines).

None of this matters hugely, but for kernel configs which
don't enable all the features there may well be a 2B hole
after the bitfield. Move alloc_cpu there.

Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
Reviewed-by: Eric Dumazet <edumazet@...gle.com>
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
---
 include/linux/skbuff.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 98d6b48f4dcf..2595b2cfba0d 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -991,6 +991,8 @@ struct sk_buff {
 	__u16			tc_index;	/* traffic control index */
 #endif
 
+	u16			alloc_cpu;
+
 	union {
 		__wsum		csum;
 		struct {
@@ -1014,7 +1016,6 @@ struct sk_buff {
 		unsigned int	sender_cpu;
 	};
 #endif
-	u16			alloc_cpu;
 #ifdef CONFIG_NETWORK_SECMARK
 	__u32		secmark;
 #endif
-- 
2.39.2