netdev - [PATCH net-next 8/8] net: rps: move received

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Date: Thu, 28 Mar 2024 17:03:09 +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: netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 8/8] net: rps: move received_rps field to a better location

Commit 14d898f3c1b3 ("dev: Move received_rps counter next
to RPS members in softnet data") was unfortunate:

received_rps is dirtied by a cpu and never read by other
cpus in fast path.

Its presence in the hot RPS cache line (shared by many cpus)
is hurting RPS/RFS performance.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/linux/netdevice.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 14f19cc2616452d7e6afbbaa52f8ad3e61a419e9..274d8db48b4858c70b43ea4628544e924ba6a263 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3203,6 +3203,7 @@ struct softnet_data {
 	struct softnet_data	*rps_ipi_list;
 #endif
 
+	unsigned int		received_rps;
 	bool			in_net_rx_action;
 	bool			in_napi_threaded_poll;
 
@@ -3235,7 +3236,6 @@ struct softnet_data {
 	unsigned int		cpu;
 	unsigned int		input_queue_tail;
 #endif
-	unsigned int		received_rps;
 	struct sk_buff_head	input_pkt_queue;
 	struct napi_struct	backlog;
 
-- 
2.44.0.478.gd926399ef9-goog