[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, 3 insertions, 3 deletions

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 04e850e04e3d..7d3fe6aebcdb 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -473,7 +473,7 @@ static int unix_dgram_connect(struct socket *, struct sockaddr *,
 static int unix_seqpacket_sendmsg(struct kiocb *, struct socket *,
                                   struct msghdr *, size_t);
 
-static struct proto_ops unix_stream_ops = {
+static const struct proto_ops unix_stream_ops = {
         .family =       PF_UNIX,
         .owner =        THIS_MODULE,
         .release =      unix_release,
@@ -494,7 +494,7 @@ static struct proto_ops unix_stream_ops = {
         .sendpage =     sock_no_sendpage,
 };
 
-static struct proto_ops unix_dgram_ops = {
+static const struct proto_ops unix_dgram_ops = {
         .family =       PF_UNIX,
         .owner =        THIS_MODULE,
         .release =      unix_release,
@@ -515,7 +515,7 @@ static struct proto_ops unix_dgram_ops = {
         .sendpage =     sock_no_sendpage,
 };
 
-static struct proto_ops unix_seqpacket_ops = {
+static const struct proto_ops unix_seqpacket_ops = {
         .family =       PF_UNIX,
         .owner =        THIS_MODULE,
         .release =      unix_release,