[ovs-dev] [slow path 11/11] ofproto-dpif: Segregate CFM, LACP, and STP traffic into separate queues.

Ben Pfaff blp at nicira.com
Mon May 7 21:49:04 UTC 2012


On Sat, May 05, 2012 at 11:10:48AM -0700, Ben Pfaff wrote:
> Until now, packets for these special protocols have been mixed with general
> traffic in the kernel-to-userspace queues.  This means that a big-enough
> storm of new flows in these queues can cause packets for these special
> protocols to be dropped at this interface, fooling userspace into believing
> that, say, no CFM packets have been received even though they are arriving
> at the expected rate.
> 
> This commit moves special protocols to a dedicated kernel-to-userspace
> queue to avoid the problem.
> 
> Bug #7550.
> Signed-off-by: Ben Pfaff <blp at nicira.com>

I hadn't had a chance to properly test this before I sent it out, but
I've now tested it in an environment that makes me confident that it
helps a lot.  I used a pair of OVS instances connected by a cable,
with the default settings for CFM between them.  Running "hping3
--flood" at the same time, with this series it took a long time
(minutes, at least) for CFM faults to start appearing, whereas without
this series they appeared within seconds.

I'm not sure how to figure out whether the CFM faults that did appear
are because the CFM packets didn't actually make it out on the wire on
the sending machine.  It seems entirely possible that they didn't.



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