[Bridge] Real time issues when using a bridge

Jean-Michel Hautbois jhautbois at gmail.com
Tue Oct 12 23:44:12 PDT 2010

2010/10/13 Jean-Michel Hautbois <jhautbois at gmail.com>

> 2010/10/12 Stephen Hemminger <shemminger at linux-foundation.org>
>> > Thus, my jitter is 47µs.
>> > This may seem low, but this is about two to three times what I expect
>> and I
>> > cannot see why a bridge which is only forwarding a frame would have
>> jitter ?
>> > If you have any idea, everything is interesting for me.
>> > I thought maybe to skb_clone ?
>> You probably have NAPI and/or interrupt coalescing setting
>> enabled on one or both of the devices.
>> --
> Hi Stephen,
> I have NAPI on my ethernet device, at least.
> I will check for interrupt coalescing.
> AFAIK, there is a skb_clone followed by a kfree in netif_receive_skb (the
> frame coming from eth0 to br0).
> There is a jitter in this call of "freeing memory". I am looking at the
> path, in order to see why there is a clone.
> BR,
> JM

I have to tell I am working on a mpc52xx and am currently only interested in
the eth->br path for the moment.
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