netdev - [PATCH net-next 4/4] bridge: fdb: write to used and updated at most once per jiffy

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Message-Id: <1486227909-18319-5-git-send-email-nikolay@cumulusnetworks.com>
Date:   Sat,  4 Feb 2017 18:05:09 +0100
From:   Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
To:     netdev@...r.kernel.org
Cc:     stephen@...workplumber.org, roopa@...ulusnetworks.com,
        davem@...emloft.net, bridge@...ts.linux-foundation.org,
        Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
Subject: [PATCH net-next 4/4] 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@...emloft.net>
Signed-off-by: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
---
 net/bridge/br_fdb.c   | 3 ++-
 net/bridge/br_input.c | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
index 5cbed5c0db88..5028691fa68a 100644
--- a/net/bridge/br_fdb.c
+++ b/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))
diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
index fba38d8a1a08..220943f920d2 100644
--- a/net/bridge/br_input.c
+++ b/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)
-- 
2.1.4