[ovs-dev] [PATCH 3/3] xlate: Always recirculate after an MPLS POP to a non-MPLS ethertype.

Simon Horman simon.horman at netronome.com
Thu Mar 3 05:01:05 UTC 2016


On Thu, Feb 25, 2016 at 08:29:53AM -0800, Ben Pfaff wrote:
> On Thu, Feb 25, 2016 at 10:26:28AM +0100, thomas.morin at orange.com wrote:
> > Sorry to chime in a bit late, but this recirculation performance penalty for
> > the basic/key use-case where OVS receives an IP-in-MPLS frame and forwards
> > it to the destination (e.g. a local VM), does not look appealing at all.
> > 
> > To allow having the best of both worlds (avoid perf penalty in all cases,
> > but avoid complex code to automatically determine whether recirculation is
> > needed or not), would it be possible to specify in a flow, after an mpls
> > match, whether or not recirculation is wanted ?
> 
> No.  That would be a layering violation.
> 
> If you can find a better way to do it, that is maintainable, we'd be
> open to that.

I'm curious to know what in particular it was about the code that was
recently changed that was unmaintainable. It seems to me that recirculation
is by its very nature expensive and best to avoid unless it is either
necessary or excessively difficult to avoid (for some value of excess :).
With that in mind the code that was changed seemed to be a reasonable
approach to me.



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