From: Eric Dumazet <edumazet@google.com>
Date: Mon, 25 Oct 2021 16:48:18 +0000 (-0700)
Subject: net: avoid dirtying sk->sk_napi_id
X-Git-Tag: v5.16-rc1~159^2~88^2~7
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=2b13af8ade38ef3afe48d60c518c64010cfa8b0d;p=thirdparty%2Flinux.git

net: avoid dirtying sk->sk_napi_id

sk_napi_id is located in a cache line that can be kept read mostly.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---

diff --git a/include/net/busy_poll.h b/include/net/busy_poll.h
index 40296ed976a97..4202c609bb0b0 100644
--- a/include/net/busy_poll.h
+++ b/include/net/busy_poll.h
@@ -130,7 +130,8 @@ static inline void skb_mark_napi_id(struct sk_buff *skb,
 static inline void sk_mark_napi_id(struct sock *sk, const struct sk_buff *skb)
 {
 #ifdef CONFIG_NET_RX_BUSY_POLL
-	WRITE_ONCE(sk->sk_napi_id, skb->napi_id);
+	if (unlikely(READ_ONCE(sk->sk_napi_id) != skb->napi_id))
+		WRITE_ONCE(sk->sk_napi_id, skb->napi_id);
 #endif
 	sk_rx_queue_set(sk, skb);
 }