netdev - [PATCH] NET : tcp_memory_pressure and tcp_socket are__read

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Date:	Tue, 27 Mar 2007 15:25:13 +0200
From:	Eric Dumazet <dada1@...mosbay.com>
To:	David Miller <davem@...emloft.net>
Cc:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: [PATCH] NET : tcp_memory_pressure and tcp_socket are__read_mostly
 candidates


tcp_memory_pressure and tcp_socket currently share a cache line with tcp_memory_allocated, tcp_sockets_allocated.
(Very hot cache line)
It makes sense to declare these variables as __read_mostly, to avoid false sharing on SMP.

ffffffff8081d9c0 B tcp_orphan_count
ffffffff8081d9c4 B tcp_memory_allocated
ffffffff8081d9c8 B tcp_sockets_allocated
ffffffff8081d9cc B tcp_memory_pressure
ffffffff8081d9d0 b tcp_md5sig_users
ffffffff8081d9d8 b tcp_md5sig_pool
ffffffff8081d9e0 b warntime.31570
ffffffff8081d9e8 b tcp_socket

Signed-off-by: Eric Dumazet <dada1@...mosbay.com>

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 18a09a7..bb9d91a 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -297,7 +297,7 @@ EXPORT_SYMBOL(tcp_sockets_allocated);
  * All the sk_stream_mem_schedule() is of this nature: accounting
  * is strict, actions are advisory and have some latency.
  */
-int tcp_memory_pressure;
+int tcp_memory_pressure __read_mostly;
 
 EXPORT_SYMBOL(tcp_memory_pressure);
 
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index a4c46ee..25aec3e 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -88,7 +88,7 @@ int sysctl_tcp_low_latency __read_mostly
 #define ICMP_MIN_LENGTH 8
 
 /* Socket used for sending RSTs */
-static struct socket *tcp_socket;
+static struct socket *tcp_socket __read_mostly;
 
 void tcp_v4_send_check(struct sock *sk, int len, struct sk_buff *skb);
 
-
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