bridge: fdb: write to used and updated at most once per jiffy

Writing once per jiffy is enough to limit the bridge's false sharing.
After this change the bridge doesn't show up in the local load HitM stats.
Suggested-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/bridge/br_fdb.c

@@ -597,7 +597,8 @@ void br_fdb_update(struct net_bridge *br, struct net_bridge_port *source,
 				fdb->dst = source;
 				fdb_modified = true;
 			}
-			fdb->updated = jiffies;
+			if (jiffies != fdb->updated)
+				fdb->updated = jiffies;
 			if (unlikely(added_by_user))
 				fdb->added_by_user = 1;
 			if (unlikely(fdb_modified))

net/bridge/br_input.c

@@ -198,7 +198,8 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb
 		if (dst->is_local)
 			return br_pass_frame_up(skb);
 
-		dst->used = jiffies;
+		if (jiffies != dst->used)
+			dst->used = jiffies;
 		br_forward(dst->dst, skb, local_rcv, false);
 	} else {
 		if (!mcast_hit)