[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>
diff --git a/include/linux/net.h b/include/linux/net.h
index d6a41e6..28195a2 100644
--- a/include/linux/net.h
+++ b/include/linux/net.h
@@ -107,7 +107,7 @@
struct socket {
socket_state state;
unsigned long flags;
- struct proto_ops *ops;
+ const struct proto_ops *ops;
struct fasync_struct *fasync_list;
struct file *file;
struct sock *sk;
@@ -260,7 +260,7 @@
SOCKCALL_WRAP(name, mmap, (struct file *file, struct socket *sock, struct vm_area_struct *vma), \
(file, sock, vma)) \
\
-static struct proto_ops name##_ops = { \
+static const struct proto_ops name##_ops = { \
.family = fam, \
.owner = THIS_MODULE, \
.release = __lock_##name##_release, \
diff --git a/include/net/inet_common.h b/include/net/inet_common.h
index f943306..227adcb 100644
--- a/include/net/inet_common.h
+++ b/include/net/inet_common.h
@@ -1,8 +1,8 @@
#ifndef _INET_COMMON_H
#define _INET_COMMON_H
-extern struct proto_ops inet_stream_ops;
-extern struct proto_ops inet_dgram_ops;
+extern const struct proto_ops inet_stream_ops;
+extern const struct proto_ops inet_dgram_ops;
/*
* INET4 prototypes used by INET6
diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index e3d5d7b..11a7256 100644
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -538,8 +538,8 @@
extern int sysctl_ip6frag_time;
extern int sysctl_ip6frag_secret_interval;
-extern struct proto_ops inet6_stream_ops;
-extern struct proto_ops inet6_dgram_ops;
+extern const struct proto_ops inet6_stream_ops;
+extern const struct proto_ops inet6_dgram_ops;
extern int ip6_mc_source(int add, int omode, struct sock *sk,
struct group_source_req *pgsr);
diff --git a/include/net/protocol.h b/include/net/protocol.h
index a29cb29..63f7db9 100644
--- a/include/net/protocol.h
+++ b/include/net/protocol.h
@@ -65,7 +65,7 @@
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
