Re: [dpdk-dev] [RFC] [PATCH v2] libeventdev: event driven programming model framework for DPDK

[Jerin Jacob <jerin.jacob@caviumnetworks.com>]

On Wed, Nov 02, 2016 at 11:35:51AM +0000, Bruce Richardson wrote:
> On Wed, Nov 02, 2016 at 04:55:22PM +0530, Jerin Jacob wrote:
> > On Fri, Oct 28, 2016 at 02:36:48PM +0530, Jerin Jacob wrote:
> > > On Fri, Oct 28, 2016 at 09:36:46AM +0100, Bruce Richardson wrote:
> > > > On Fri, Oct 28, 2016 at 08:31:41AM +0530, Jerin Jacob wrote:
> > > > > On Wed, Oct 26, 2016 at 01:54:14PM +0100, Bruce Richardson wrote:
> > > > > > On Wed, Oct 26, 2016 at 05:54:17PM +0530, Jerin Jacob wrote:
> > > > > How about making default as "mixed" and let application configures what
> > > > > is not required?. That way application responsibility is clear.
> > > > > something similar to ETH_TXQ_FLAGS_NOMULTSEGS, ETH_TXQ_FLAGS_NOREFCOUNT
> > > > > with default.
> > > > > 
> > > > I suppose it could work, but why bother doing that? If an app knows it's
> > > > only going to use one traffic type, why not let it just state what it
> > > > will do rather than try to specify what it won't do. If mixed is needed,
> > > 
> > > My thought was more inline with ethdev spec, like, ref-count is default,
> > > if application need exception then set ETH_TXQ_FLAGS_NOREFCOUNT. But it is OK, if
> > > you need other way.
> > > 
> > > > then it's easy enough to specify - and we can make it the zero/default
> > > > value too.
> > > 
> > > OK. Then we will make MIX as zero/default and add "allowed_event_types" in
> > > event queue config.
> > >
> > 
> > Bruce,
> > 
> > I have tried to make it as "allowed_event_types" in event queue config.
> > However, rte_event_queue_default_conf_get() can also take NULL for default
> > configuration. So I think, It makes sense to go with negation approach
> > like ethdev to define the default to avoid confusion on the default. So
> > I am thinking like below now,
> > 
> > ➜ [master][libeventdev] $ git diff
> > diff --git a/rte_eventdev.h b/rte_eventdev.h
> > index cf22b0e..cac4642 100644
> > --- a/rte_eventdev.h
> > +++ b/rte_eventdev.h
> > @@ -429,6 +429,12 @@ rte_event_dev_configure(uint8_t dev_id, struct
> > rte_event_dev_config *config);
> >   *
> >   *  \see rte_event_port_setup(), rte_event_port_link()
> >   */
> > +#define RTE_EVENT_QUEUE_CFG_NOATOMIC_TYPE      (1ULL << 1)
> > +/**< Skip configuring atomic schedule type resources */
> > +#define RTE_EVENT_QUEUE_CFG_NOORDERED_TYPE     (1ULL << 2)
> > +/**< Skip configuring ordered schedule type resources */
> > +#define RTE_EVENT_QUEUE_CFG_NOPARALLEL_TYPE    (1ULL << 3)
> > +/**< Skip configuring parallel schedule type resources */
> > 
> >  /** Event queue configuration structure */
> >  struct rte_event_queue_conf {
> > 
> > Thoughts?
> > 
> 
> I'm ok with the default as being all types, in the case where NULL is
> specified for the parameter. It does make the most sense.

Yes. That case I need to explicitly mention in the documentation about what
is default case. With RTE_EVENT_QUEUE_CFG_NOATOMIC_TYPE scheme it quite
understood what is default. Not adding up? :-)

> 
> However, for the cases where the user does specify what they want, I
> think it does make more sense, and is easier on the user for things to
> be specified in a positive, rather than negative sense. For a user who
> wants to just use atomic events, having to specify that as "not-reordered
> and not-unordered" just isn't as clear! :-)
> 
> /Bruce
>