[ovs-dev] [PATCH] ofproto-dpif-xlate: Always generate wildcards.

Ryan Moats rmoats at us.ibm.com
Sat Apr 23 20:40:56 UTC 2016


"dev" <dev-bounces at openvswitch.org> wrote on 04/22/2016 07:45:03 PM:

> From: Ben Pfaff <blp at ovn.org>
> To: dev at openvswitch.org
> Cc: Ben Pfaff <blp at ovn.org>
> Date: 04/22/2016 07:45 PM
> Subject: [ovs-dev] [PATCH] ofproto-dpif-xlate: Always generate wildcards.
> Sent by: "dev" <dev-bounces at openvswitch.org>
>
> Until now, the flow translation code has tried to avoid constructing a
> set of wildcards during translation in the cases where it can, because
> wildcards are large and somewhat expensive.  However, this has problems
> that we hadn't previously realized.  Specifically, the generated actions
> can depend on the constructed wildcards, to decide which bits of a field
> need to be set in a masked set_field action.  This means that in practice
> translation needs to always construct the wildcards.
>
> (It might be possible to avoid masked set_field when we're not
constructing
> wildcards, but this would mean that we'd generate different actions
> depending on whether wildcards were being constructed, which seems rather
> confusing at best.  Also, the cases in which we don't need wildcards
anyway
> are fairly obscure, meaning that the benefits of avoiding them in those
> cases are minimal and that it's going to be hard to get test coverage.
The
> latter is probably why we didn't notice this until now.)
>
> Reported-by: William Tu <u9012063 at gmail.com>
> Reported-at: http://openvswitch.org/pipermail/dev/2016-April/069219.html
> Signed-off-by: Ben Pfaff <blp at ovn.org>
> ---
>  ofproto/ofproto-dpif-xlate.c | 21 ++++++++-------------

As promised:

Acked-by: Ryan Moats <rmoats at us.ibm.com>



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