netlink: move nl_table in read_mostly section
netlink sockets creation and deletion heavily modify nl_table_users
and nl_table_lock.
If nl_table is sharing one cache line with one of them, netlink
performance is really bad on SMP.
ffffffff81ff5f00 B nl_table
ffffffff81ff5f0c b nl_table_users
Putting nl_table in read_mostly section increased performance
of my open/delete netlink sockets test by about 80 %
This came up while diagnosing a getaddrinfo() problem.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index daa0b81..dbe8859 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -89,7 +89,7 @@
return nlk_sk(sk)->flags & NETLINK_KERNEL_SOCKET;
}
-struct netlink_table *nl_table;
+struct netlink_table *nl_table __read_mostly;
EXPORT_SYMBOL_GPL(nl_table);
static DECLARE_WAIT_QUEUE_HEAD(nl_table_wait);