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

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

On Wed, Nov 02, 2016 at 11:45:07AM +0000, Bruce Richardson wrote:
> On Wed, Nov 02, 2016 at 04:17:04PM +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@dpdk.org] On Behalf Of Jerin Jacob
> > > > 
> > > > So far, I have received constructive feedback from Intel, NXP and Linaro folks.
> > > > Let me know, if anyone else interested in contributing to the definition of eventdev?
> > > > 
> > > > If there are no major issues in proposed spec, then Cavium would like work on
> > > > implementing and up-streaming the common code(lib/librte_eventdev/) and
> > > > an associated HW driver.(Requested minor changes of v2 will be addressed
> > > > in next version).
> > >
> > 
> > Hi All,
> > 
> > Two queries,
> > 
> > 1) In SW implementation, Is their any connection between "struct
> > rte_event_port_conf"'s dequeue_queue_depth and enqueue_queue_depth ?
> > i.e it should be enqueue_queue_depth >= dequeue_queue_depth. Right ?
> > Thought of adding the common checks in common layer.
> 
> I think this is probably best left to the driver layers to enforce. For
> us, such a restriction doesn't really make sense, though in many cases
> that would be the usual setup. For accurate load balancing, the dequeue
> queue depth would be small, and the burst size would probably equal the
> queue depth, meaning the enqueue depth needs to be at least as big.
> However, for better throughput, or in cases where all traffic is being
> coalesced to a single core e.g. for transmit out a network port, there
> is no need to keep the dequeue queue shallow and so it can be many times
> the burst size, while the enqueue queue can be kept to 1-2 times the
> burst size.
> 

OK

> > 
> > 2)Any comments on follow item(section under ----) that needs improvement.
> > -------------------------------------------------------------------------------
> > Abstract the differences in event QoS management with different
> > priority schemes available in different HW or SW implementations with portable
> > application workflow.
> > 
> > Based on the feedback, there three different kinds of QoS support
> > available in
> > three different HW or SW implementations.
> > 1) Priority associated with the event queue
> > 2) Priority associated with each event enqueue
> > (Same flow can have two different priority on two separate enqueue)
> > 3) Priority associated with the flow(each flow has unique priority)
> > 
> > In v2, The differences abstracted based on device capability
> > (RTE_EVENT_DEV_CAP_QUEUE_QOS for the first scheme,
> > RTE_EVENT_DEV_CAP_EVENT_QOS for the second and third scheme).
> > This scheme would call for different application workflow for
> > nontrivial QoS-enabled applications.
> > -------------------------------------------------------------------------------
> > After thinking a while, I think, RTE_EVENT_DEV_CAP_EVENT_QOS is a
> > super-set.if so, the subset RTE_EVENT_DEV_CAP_QUEUE_QOS can be
> > implemented with RTE_EVENT_DEV_CAP_EVENT_QOS. i.e We may not need two
> > flags, Just one flag RTE_EVENT_DEV_CAP_EVENT_QOS is enough to fix
> > portability issue with basic QoS enabled applications.
> > 
> > i.e Introduce RTE_EVENT_DEV_CAP_EVENT_QOS as config option in device
> > configure stage if application needs fine granularity on QoS per event
> > enqueue.For trivial applications, configured
> > rte_event_queue_conf->priority can be used as rte_event_enqueue(struct
> > rte_event.priority)
> > 
> So all implementations should support the concept of priority among
> queues, and then there is optional support for event or flow based
> prioritization. Is that a correct interpretation of what you propose?

Yes. If you _can_ implement it and if possible in the system.

> 
> /Bruce
>