netdev - [PATCH net-next] net: add prefetch() in skb_defer_free

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Message-ID: <20251106085500.2438951-1-edumazet@google.com>
Date: Thu,  6 Nov 2025 08:55:00 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <horms@...nel.org>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next] net: add prefetch() in skb_defer_free_flush()

skb_defer_free_flush() is becoming more important these days.

Add a prefetch operation to reduce latency a bit on some
platforms like AMD EPYC 7B12.

On more recent cpus, a stall happens when reading skb_shinfo().
Avoiding it will require a more elaborate strategy.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/core/dev.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/core/dev.c b/net/core/dev.c
index 537aa43edff0e4bfedb42593146cfdf7511d8c37..69515edd17bc6a157046f31b3dd343a59ae192ab 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6782,6 +6782,7 @@ static void skb_defer_free_flush(void)
 		free_list = llist_del_all(&sdn->defer_list);
 
 		llist_for_each_entry_safe(skb, next, free_list, ll_node) {
+			prefetch(next);
 			napi_consume_skb(skb, 1);
 		}
 	}
-- 
2.51.2.1026.g39e6a42477-goog