netdev - [PATCH net-next] tcp/dccp: cache line align inet

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Message-ID: <20230803075334.2321561-1-edumazet@google.com>
Date: Thu,  3 Aug 2023 07:53:34 +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] tcp/dccp: cache line align inet_hashinfo

I have seen tcp_hashinfo starting at a non optimal location,
forcing input handlers to pull two cache lines instead of one,
and sharing a cache line that was dirtied more than necessary:

ffffffff83680600 b tcp_orphan_timer
ffffffff83680628 b tcp_orphan_cache
ffffffff8368062c b tcp_enable_tx_delay.__tcp_tx_delay_enabled
ffffffff83680630 B tcp_hashinfo
ffffffff83680680 b tcp_cong_list_lock

After this patch, ehash, ehash_locks, ehash_mask and ehash_locks_mask
are located in a read-only cache line.

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

diff --git a/include/net/inet_hashtables.h b/include/net/inet_hashtables.h
index 99bd823e97f624e37cf3abb8ac0ec7eef4552b61..74399d20b2184945f2b39bf3dfedb3ae63b500f7 100644
--- a/include/net/inet_hashtables.h
+++ b/include/net/inet_hashtables.h
@@ -177,7 +177,7 @@ struct inet_hashinfo {
 	struct inet_listen_hashbucket	*lhash2;
 
 	bool				pernet;
-};
+} ____cacheline_aligned_in_smp;
 
 static inline struct inet_hashinfo *tcp_or_dccp_get_hashinfo(const struct sock *sk)
 {
-- 
2.41.0.640.ga95def55d0-goog