Re: [dpdk-dev] [PATCH v2 1/6] eventdev: introduce event driven programming model

[Bruce Richardson <bruce.richardson@intel.com>]

On Tue, Dec 06, 2016 at 09:22:15AM +0530, Jerin Jacob wrote:
> In a polling model, lcores poll ethdev ports and associated
> rx queues directly to look for packet. In an event driven model,
> by contrast, lcores call the scheduler that selects packets for
> them based on programmer-specified criteria. Eventdev library
> adds support for event driven programming model, which offer
> applications automatic multicore scaling, dynamic load balancing,
> pipelining, packet ingress order maintenance and
> synchronization services to simplify application packet processing.
> 
> By introducing event driven programming model, DPDK can support
> both polling and event driven programming models for packet processing,
> and applications are free to choose whatever model
> (or combination of the two) that best suits their needs.
> 
> This patch adds the eventdev specification header file.
> 
> Signed-off-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
> ---
<snip>
> + *
> + * The *nb_events* parameter is the number of event objects to enqueue which are
> + * supplied in the *ev* array of *rte_event* structure.
> + *
> + * The rte_event_enqueue_burst() function returns the number of
> + * events objects it actually enqueued. A return value equal to *nb_events*
> + * means that all event objects have been enqueued.
> + *
> + * @param dev_id
> + *   The identifier of the device.
> + * @param port_id
> + *   The identifier of the event port.
> + * @param ev
> + *   Points to an array of *nb_events* objects of type *rte_event* structure
> + *   which contain the event object enqueue operations to be processed.
> + * @param nb_events
> + *   The number of event objects to enqueue, typically number of
> + *   rte_event_port_enqueue_depth() available for this port.
> + *
> + * @return
> + *   The number of event objects actually enqueued on the event device. The
> + *   return value can be less than the value of the *nb_events* parameter when
> + *   the event devices queue is full or if invalid parameters are specified in a
> + *   *rte_event*. If return value is less than *nb_events*, the remaining events
> + *   at the end of ev[] are not consumed,and the caller has to take care of them
> + *
> + * @see rte_event_port_enqueue_depth()
> + */
> +uint16_t
> +rte_event_enqueue_burst(uint8_t dev_id, uint8_t port_id, struct rte_event ev[],
> +			uint16_t nb_events);
> +
One suggestion - do we want to make the ev[] array const, to disallow
drivers from modifying the events passed in? Since the event structure
is only 16B big, it should be small enough to be copied around in
scheduler instances, allow the original events to remain unmodified.

/Bruce