[Bridge] Real time issues when using a bridge

Jean-Michel Hautbois jhautbois at gmail.com
Tue Oct 12 23:40:22 PDT 2010


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
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