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

[Jerin Jacob]

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:
> > > > On Wed, Oct 26, 2016 at 12:11:03PM +0000, Van Haaren, Harry wrote:
> > > > > > -----Original Message-----
> > > > > > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Jerin Jacob
> > > Thanks. One other suggestion is that it might be useful to provide
> > > support for having typed queues explicitly in the API. Right now, when
> > > you create an queue, the queue_conf structure takes as parameters how
> > > many atomic flows that are needed for the queue, or how many reorder
> > > slots need to be reserved for it. This implicitly hints at the type of
> > > traffic which will be sent to the queue, but I'm wondering if it's
> > > better to make it explicit. There are certain optimisations that can be
> > > looked at if we know that a queue only handles packets of a particular
> > > type. [Not having to handle reordering when pulling events from a core
> > > can be a big win for software!].
> > 
> > If it helps in SW implementation, then I think we can add this in queue
> > configuration. 
> > 
> > > 
> > > How about adding: "allowed_event_types" as a field to
> > > rte_event_queue_conf, with possible values:
> > > * atomic
> > > * ordered
> > > * parallel
> > > * mixed - allowing all 3 types. I think allowing 2 of three types might
> > >     make things too complicated.
> > > 
> > > An open question would then be how to behave when the queue type and
> > > requested event type conflict. We can either throw an error, or just
> > > ignore the event type and always treat enqueued events as being of the
> > > queue type. I prefer the latter, because it's faster not having to
> > > error-check, and it pushes the responsibility on the app to know what
> > > it's doing.
> > 
> > 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.

/Jerin

> 
> Our software implementation for now, only supports one type per queue -
> which we suspect should meet a lot of use-cases. We'll have to see about
> adding in mixed types in future.
> 
> /Bruce