[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/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 617e858beff1..4ed8a814c6cb 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -785,7 +785,7 @@ int inet_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
         return err;
 }
 
-struct proto_ops inet_stream_ops = {
+const struct proto_ops inet_stream_ops = {
         .family =       PF_INET,
         .owner =        THIS_MODULE,
         .release =      inet_release,
@@ -806,7 +806,7 @@ struct proto_ops inet_stream_ops = {
         .sendpage =     tcp_sendpage
 };
 
-struct proto_ops inet_dgram_ops = {
+const struct proto_ops inet_dgram_ops = {
         .family =       PF_INET,
         .owner =        THIS_MODULE,
         .release =      inet_release,
@@ -831,7 +831,7 @@ struct proto_ops inet_dgram_ops = {
  * For SOCK_RAW sockets; should be the same as inet_dgram_ops but without
  * udp_poll
  */
-static struct proto_ops inet_sockraw_ops = {
+static const struct proto_ops inet_sockraw_ops = {
         .family =       PF_INET,
         .owner =        THIS_MODULE,
         .release =      inet_release,