RE: [RFC PATCH] ethdev: advertise flow restore in mbuf

[Ori Kam <orika@nvidia.com>]

> -----Original Message-----
> From: David Marchand <david.marchand@redhat.com>
> Sent: Thursday, June 1, 2023 11:48 AM
> 
> On Wed, May 24, 2023 at 8:44 PM David Marchand
> <david.marchand@redhat.com> wrote:
> > On Wed, May 24, 2023 at 6:00 PM Ori Kam <orika@nvidia.com> wrote:
> > > > As reported by Ilya [1], unconditionally calling
> > > > rte_flow_get_restore_info() impacts an application performance for
> drivers
> > > > that do not provide this ops.
> > > > It could also impact processing of packets that require no call to
> > > > rte_flow_get_restore_info() at all.
> > > >
> > > > Advertise in mbuf (via a dynamic flag) whether the driver has more
> > > > metadata to provide via rte_flow_get_restore_info().
> > > > The application can then call it only when required.
> > > >
> > > > Link: http://inbox.dpdk.org/dev/5248c2ca-f2a6-3fb0-38b8-
> > > > 7f659bfa40de@ovn.org/
> > > > Signed-off-by: David Marchand <david.marchand@redhat.com>
> > > > ---
> > > > Note: I did not test this RFC patch yet but I hope we can resume and
> > > > maybe conclude on the discussion for the tunnel offloading API.
> > > >
> > >
> > > I think your approach has a good base but what happens if
> > > it is not relevant for all flows? In this case your solution will not work.
> >
> > Sorry, I am not following.
> > Could you develop?
> 
> I still don't get your comment, could you give an example/usecase
> where this approach can't work?
> Thanks.
> 
I'm think of a use case that some flows have the restore info, while
other don't for example, we get arp packets or some packets that
are not tunneled, and we also get tunneled packets.

Or for example PMD supports this flag but the application didn't offload such a rule yet.

In those cases application will be slow even if he didn't offload the rules,
I assume we can say that if application wants to use this he should know
that other packets will have some performance issues.

From my point of view if application requested the tunnel offload it should
always check this function.

> 
> --
> David Marchand