fib: introduce fib_alias_accessed() helper

Perf tools session at NFWS 2010 pointed out a false sharing on struct
fib_alias that can be avoided pretty easily, if we set FA_S_ACCESSED bit
only if needed (ie : not already set)

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 1 deletions

diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index 31494f33568..cd5e13aee7d 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -1838,7 +1838,8 @@ void fib_table_select_default(struct fib_table *tb,
                 if (!next_fi->fib_nh[0].nh_gw ||
                     next_fi->fib_nh[0].nh_scope != RT_SCOPE_LINK)
                         continue;
-                fa->fa_state |= FA_S_ACCESSED;
+
+                fib_alias_accessed(fa);
 
                 if (fi == NULL) {
                         if (next_fi != res->fi)