[NET]: move struct proto_ops to const

I noticed that some of 'struct proto_ops' used in the kernel may share
a cache line used by locks or other heavily modified data. (default
linker alignement is 32 bytes, and L1_CACHE_LINE is 64 or 128 at
least)

This patch makes sure a 'struct proto_ops' can be declared as const,
so that all cpus can share all parts of it without false sharing.

This is not mandatory : a driver can still use a read/write structure
if it needs to (and eventually a __read_mostly)

I made a global stubstitute to change all existing occurences to make
them const.

This should reduce the possibility of false sharing on SMP, and
speedup some socket system calls.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 2 deletions

diff --git a/net/key/af_key.c b/net/key/af_key.c
index d32f7791f1e4..52efd04cbedb 100644
--- a/net/key/af_key.c
+++ b/net/key/af_key.c
@@ -113,7 +113,7 @@ static __inline__ void pfkey_unlock_table(void)
 }
 
 
-static struct proto_ops pfkey_ops;
+static const struct proto_ops pfkey_ops;
 
 static void pfkey_insert(struct sock *sk)
 {
@@ -3127,7 +3127,7 @@ out:
         return err;
 }
 
-static struct proto_ops pfkey_ops = {
+static const struct proto_ops pfkey_ops = {
         .family         =       PF_KEY,
         .owner          =       THIS_MODULE,
         /* Operations that make no sense on pfkey sockets. */