[dpdk-dev] [DPDK] lib/librte_ether: add comments RSS flags

[Yang, Qiming]

> -----Original Message-----
> From: Thomas Monjalon [mailto:thomas at monjalon.net]
> Sent: Monday, January 8, 2018 4:33 AM
> To: Yang, Qiming <qiming.yang at intel.com>
> Cc: Shahaf Shuler <shahafs at mellanox.com>; Andrew Rybchenko
> <arybchenko at solarflare.com>; dev at dpdk.org
> Subject: Re: [dpdk-dev] [DPDK] lib/librte_ether: add comments RSS flags
> 
> 07/01/2018 07:32, Shahaf Shuler:
> > Saturday, January 6, 2018 12:22 PM, Andrew Rybchenko:
> >
> > [..]
> >
> > > >   #define ETH_RSS_PORT               (1ULL << RTE_ETH_FLOW_PORT)
> > > > +/** Enable RSS offload on VXLAN packets */
> > > >   #define ETH_RSS_VXLAN              (1ULL << RTE_ETH_FLOW_VXLAN)
> > > > +/** Enable RSS offload on GENEVE packets */
> > > >   #define ETH_RSS_GENEVE             (1ULL << RTE_ETH_FLOW_GENEVE)
> > > > +/** Enable RSS offload on NVGRE packets */
> > > >   #define ETH_RSS_NVGRE              (1ULL << RTE_ETH_FLOW_NVGRE)
> > > >
> > > >   #define ETH_RSS_IP ( \
> > >
> > > These comments just decode the define name and not that useful. What
> > > would be really useful here is specification of which fields of the
> > > packet headers are used to calculate hash especially in the case of tunnels.
> >
> > +1.
> >
> > Also maybe some more clarifications, for example:
> > 1. What is the expected behavior when, for example, setting the
> ETH_RSS_IPV6_EX and regular IPv6 packet arrives? is RSS apply on it?
> > 2. What is the expected behavior from the PMD when not supporting one of
> the RSS types?
> >      For example most of the DPDK examples uses ETH_RSS_IP [1], however
> very few devices actually supports each and every RSS type.
> >      Assuming such configuration returns with no error, what should application
> expect when unsupported packet type arrives.
> >
> > #define ETH_RSS_IP ( \
> >         ETH_RSS_IPV4 | \
> >         ETH_RSS_FRAG_IPV4 | \
> >         ETH_RSS_NONFRAG_IPV4_OTHER | \
> >         ETH_RSS_IPV6 | \
> >         ETH_RSS_FRAG_IPV6 | \
> >         ETH_RSS_NONFRAG_IPV6_OTHER | \
> >         ETH_RSS_IPV6_EX)
> 
> +1
> We really need a detailed documentation of the.
> 

I agree with your comments, but the same RSS configuration may have different behavior(RSS offload and input set) in different driver. Adding driver specific information in rte_ethdev.h  is not suitable.
So I think the best scheme is to update driver's document to detail the exact behavior and add reference doc here.

> It must be at least as detailed as lib/librte_mbuf/rte_mbuf_ptype.h.
> Thanks