netdev - [Patch bpf-next v6 3/4] skmsg: optimize struct sk

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Message-Id: <20260115192737.743857-4-xiyou.wangcong@gmail.com>
Date: Thu, 15 Jan 2026 11:27:36 -0800
From: Cong Wang <xiyou.wangcong@...il.com>
To: netdev@...r.kernel.org
Cc: hemanthmalla@...il.com,
	john.fastabend@...il.com,
	jakub@...udflare.com,
	zijianzhang@...edance.com,
	bpf@...r.kernel.org,
	Cong Wang <cong.wang@...edance.com>
Subject: [Patch bpf-next v6 3/4] skmsg: optimize struct sk_psock layout

From: Cong Wang <cong.wang@...edance.com>

Reduce memory waste in struct sk_psock by:

1. Change psock->eval from u32 to u8. The eval field only holds values
   from enum sk_psock_verdict (4 possible values), so 8 bits is
   sufficient.

2. Move refcnt up in the struct to pack with other small fields,
   improving cache locality for psock reference counting operations.
   refcnt is frequently accessed during sk_psock_get/put, and placing
   it near the socket pointers (sk, sk_redir) keeps them in the same
   cache line.

These changes reduce holes in the struct and prepare for subsequent
patches that will add new fields.

Signed-off-by: Cong Wang <cong.wang@...edance.com>
---
 include/linux/skmsg.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h
index 61e2c2e6840b..84657327b0ea 100644
--- a/include/linux/skmsg.h
+++ b/include/linux/skmsg.h
@@ -85,8 +85,9 @@ struct sk_psock {
 	struct sock			*sk_redir;
 	u32				apply_bytes;
 	u32				cork_bytes;
-	u32				eval;
+	u8				eval;
 	bool				redir_ingress; /* undefined if sk_redir is null */
+	refcount_t			refcnt;
 	struct sk_msg			*cork;
 	struct sk_psock_progs		progs;
 #if IS_ENABLED(CONFIG_BPF_STREAM_PARSER)
@@ -100,7 +101,6 @@ struct sk_psock {
 	unsigned long			state;
 	struct list_head		link;
 	spinlock_t			link_lock;
-	refcount_t			refcnt;
 	void (*saved_unhash)(struct sock *sk);
 	void (*saved_destroy)(struct sock *sk);
 	void (*saved_close)(struct sock *sk, long timeout);
-- 
2.34.1