Re: [dpdk-dev] [PATCH v3] doc: update RSS action with best effort

[Ori Kam <orika@nvidia.com>]

Hi Andrew,


> -----Original Message-----
> From: Andrew Rybchenko <arybchenko@solarflare.com>
> 
> On 8/7/20 8:02 AM, Ori Kam wrote:
> > Using the rte_flow action RSS types field,
> > may result in undefined outcome.
> >
> > For example selecting both UDP and TCP,
> > selecting TCP RSS type but the pattern is targeting UDP traffic.
> > another option is that the PMD doesn't support all requested types.
> >
> > Until now, it wasn't clear what will happen in such cases.
> > This commit clarify this issue by stating that the PMD
> > will work in the best-effort mode, and will fail
> > in case the requested type is not supported.
> >
> > Signed-off-by: Ori Kam <orika@mellanox.com>
> > ---
> > v3:
> >  * Address ML comments.
> >
> > v2:
> >  * Address ML comments.
> > ---
> >  doc/guides/prog_guide/rte_flow.rst | 12 ++++++++++++
> >  1 file changed, 12 insertions(+)
> >
> > diff --git a/doc/guides/prog_guide/rte_flow.rst
> b/doc/guides/prog_guide/rte_flow.rst
> > index 3e5cd1e..eada283 100644
> > --- a/doc/guides/prog_guide/rte_flow.rst
> > +++ b/doc/guides/prog_guide/rte_flow.rst
> > @@ -1735,6 +1735,18 @@ unspecified "best-effort" settings from the
> underlying PMD, which depending
> >  on the flow rule, may result in anything ranging from empty (single queue)
> >  to all-inclusive RSS.
> >
> > +In case there are Non-applicable RSS types in the rule,
> > +Best effort will be used.
> > +This may be the result of:
> > +
> > +- Setting both UDP and TCP on the same rule.
> > +
> > +- Setting RSS types that don't match the requested pattern,
> > +  for example, matching on UDP and hashing RSS on TCP.
> > +
> > +If requested RSS hash type is not supported in ``dev_info``.
> > +The flow creation will fail.
> > +
> 
> Consider:
> If non-applicable for matching packets RSS types are requested,
> these RSS types are simply ignored. For example, it happens if:
> 
>   - Hashing of both TCP and UDP ports is requested
>     (only one can present in a packet).
> 
>   - Requested RSS types contradict to flow rule pattern
>     (e.g. pattern has UDP item, but RSS types contain TCP).
> 
> If requested RSS types are not supported by the Ethernet device
> at all (not reported in ``dev_info.flow_type_rss_offloads``),
> the flow creation will fail.
> 
Sure sounds good, but since this is just copying your words, 
I will add your Signed-off-by to this patch, is that O.K?

> >  Note: RSS hash result is stored in the ``hash.rss`` mbuf field which
> >  overlaps ``hash.fdir.lo``. Since `Action: MARK`_ sets the ``hash.fdir.hi``
> >  field only, both can be requested simultaneously.
> >