Re: [dpdk-dev] [RFC] ethdev: support hairpin queue

[Ori Kam <orika@mellanox.com>]

> -----Original Message-----
> From: Ori Kam
> Sent: Wednesday, August 14, 2019 8:36 AM
> To: Stephen Hemminger <stephen@networkplumber.org>
> Cc: Thomas Monjalon <thomas@monjalon.net>; ferruh.yigit@intel.com;
> arybchenko@solarflare.com; Shahaf Shuler <shahafs@mellanox.com>; Slava
> Ovsiienko <viacheslavo@mellanox.com>; Alex Rosenbaum
> <Alexr@mellanox.com>; dev@dpdk.org
> Subject: RE: [dpdk-dev] [RFC] ethdev: support hairpin queue
> 
> Hi Stephen,
> 
> > -----Original Message-----
> > From: Stephen Hemminger <stephen@networkplumber.org>
> > Sent: Tuesday, August 13, 2019 6:46 PM
> > To: Ori Kam <orika@mellanox.com>
> > Cc: Thomas Monjalon <thomas@monjalon.net>; ferruh.yigit@intel.com;
> > arybchenko@solarflare.com; Shahaf Shuler <shahafs@mellanox.com>; Slava
> > Ovsiienko <viacheslavo@mellanox.com>; Alex Rosenbaum
> > <alexr@mellanox.com>; dev@dpdk.org
> > Subject: Re: [dpdk-dev] [RFC] ethdev: support hairpin queue
> >
> > On Tue, 13 Aug 2019 13:37:48 +0000
> > Ori Kam <orika@mellanox.com> wrote:
> >
> > > This RFC replaces RFC[1].
> > >
> > > The hairpin feature (different name can be forward) acts as "bump on the
> > wire",
> > > meaning that a packet that is received from the wire can be modified using
> > > offloaded action and then sent back to the wire without application
> > intervention
> > > which save CPU cycles.
> > >
> > > The hairpin is the inverse function of loopback in which application
> > > sends a packet then it is received again by the
> > > application without being sent to the wire.
> > >
> > > The hairpin can be used by a number of different NVF, for example load
> > > balancer, gateway and so on.
> > >
> > > As can be seen from the hairpin description, hairpin is basically RX queue
> > > connected to TX queue.
> > >
> > > During the design phase I was thinking of two ways to implement this
> > > feature the first one is adding a new rte flow action. and the second
> > > one is create a special kind of queue.
> >
> >
> > Life would be easier for users if the hairpin was an attribute
> > of queue configuration, not a separate API call.
> 
> I was thinking about it. the reason that I split the functions is that they use
> different
> parameters sets. For example the hairpin queue doesn't need memory region
> while it does need
> the hairpin configuration. So in each case hairpin queue / normal queue there
> will be
> parameters that are not in use. I think this is less preferred. What do you think?
> 

Forgot in my last mail two more reasons I had for this for this:
1. changing to existing function will break API, and will force all applications to update date.
2.  2 API are easier to document and explain.
3. the reason stated above that there will be unused parameters in each call.

What do you think?


> Thanks,
> Ori