[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, 1 insertions, 1 deletions

diff --git a/include/net/protocol.h b/include/net/protocol.h
index a29cb29647d0..63f7db99c2a6 100644
--- a/include/net/protocol.h
+++ b/include/net/protocol.h
@@ -65,7 +65,7 @@ struct inet_protosw {
 	int		 protocol; /* This is the L4 protocol number.  */
 
 	struct proto	 *prot;
-	struct proto_ops *ops;
+	const struct proto_ops *ops;
   
 	int              capability; /* Which (if any) capability do
 				      * we need to use this socket