netdev - [PATCH v2 net-next] Revert "net: init sk

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Message-Id: <1524582465-11055-1-git-send-email-laoar.shao@gmail.com>
Date:   Tue, 24 Apr 2018 23:07:45 +0800
From:   Yafang Shao <laoar.shao@...il.com>
To:     eric.dumazet@...il.com, davem@...emloft.net
Cc:     netdev@...r.kernel.org, Yafang Shao <laoar.shao@...il.com>
Subject: [PATCH v2 net-next] Revert "net: init sk_cookie for inet socket"

This reverts commit <c6849a3ac17e> ("net: init sk_cookie for inet socket")

Per discussion with Eric, when update sock_net(sk)->cookie_gen, the
whole cache cache line will be invalidated, as this cache line is shared
with all cpus, that may cause great performace hit.

Bellow is the data form Eric.
"Performance is reduced from ~5 Mpps to ~3.8 Mpps with 16 RX queues on
my host" when running synflood test.

Have to revert it to prevent from cache line false sharing.

Signed-off-by: Yafang Shao <laoar.shao@...il.com>
---
 include/linux/sock_diag.h | 9 ---------
 net/ipv4/tcp_input.c      | 8 +-------
 2 files changed, 1 insertion(+), 16 deletions(-)

diff --git a/include/linux/sock_diag.h b/include/linux/sock_diag.h
index 5c916e6..15fe980 100644
--- a/include/linux/sock_diag.h
+++ b/include/linux/sock_diag.h
@@ -25,15 +25,6 @@ struct sock_diag_handler {
 void sock_diag_register_inet_compat(int (*fn)(struct sk_buff *skb, struct nlmsghdr *nlh));
 void sock_diag_unregister_inet_compat(int (*fn)(struct sk_buff *skb, struct nlmsghdr *nlh));
 
-static inline
-void sock_init_cookie(struct sock *sk)
-{
-	u64 res;
-
-	res = atomic64_inc_return(&sock_net(sk)->cookie_gen);
-	atomic64_set(&sk->sk_cookie, res);
-}
-
 u64 sock_gen_cookie(struct sock *sk);
 int sock_diag_check_cookie(struct sock *sk, const __u32 *cookie);
 void sock_diag_save_cookie(struct sock *sk, __u32 *cookie);
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 17b7858..5a17cfc 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -78,7 +78,6 @@
 #include <linux/errqueue.h>
 #include <trace/events/tcp.h>
 #include <linux/static_key.h>
-#include <linux/sock_diag.h>
 
 int sysctl_tcp_max_orphans __read_mostly = NR_FILE;
 
@@ -6191,15 +6190,10 @@ struct request_sock *inet_reqsk_alloc(const struct request_sock_ops *ops,
 #if IS_ENABLED(CONFIG_IPV6)
 		ireq->pktopts = NULL;
 #endif
+		atomic64_set(&ireq->ir_cookie, 0);
 		ireq->ireq_state = TCP_NEW_SYN_RECV;
 		write_pnet(&ireq->ireq_net, sock_net(sk_listener));
 		ireq->ireq_family = sk_listener->sk_family;
-
-		BUILD_BUG_ON(offsetof(struct inet_request_sock, ir_cookie) !=
-					offsetof(struct sock, sk_cookie));
-		BUILD_BUG_ON(offsetof(struct inet_request_sock, ireq_net) !=
-					offsetof(struct sock, sk_net));
-		sock_init_cookie((struct sock *)ireq);
 	}
 
 	return req;
-- 
1.8.3.1