On Thu, May 26, 2016 at 4:44 PM, Lennert Buytenhek
[off-list ref] wrote:

Commit 412ca1550cbecb2c ("macvlan: Move broadcasts into a work queue")
moved processing of all macvlan multicasts into a work queue.  This
causes a noticable performance regression when there is heavy multicast
traffic on the underlying interface for multicast groups that the
macvlan subinterfaces are not members of, in which case we end up
cloning all those packets and then freeing them again from a work queue
without really doing any useful work with them in between.

But we only queue up to 1000 packets in our backlog.

How about adding a quick check before cloning it?

diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
index cb01023..1c73d0f 100644
--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c

@@ -315,6 +315,9 @@ static void macvlan_broadcast_enqueue(struct

macvlan_port *port,
        struct sk_buff *nskb;
        int err = -ENOMEM;

+       if (skb_queue_len(&port->bc_queue) >= MACVLAN_BC_QUEUE_LEN)
+               return;
+
        nskb = skb_clone(skb, GFP_ATOMIC);
        if (!nskb)
                goto err;