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_hash.c b/net/ipv4/fib_hash.c
index 4f1aafd3ba89..43e1c594ce8f 100644
--- a/net/ipv4/fib_hash.c
+++ b/net/ipv4/fib_hash.c
@@ -335,7 +335,8 @@ 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)