> -----Original Message-----
> From: Eads, Gage
> Sent: Wednesday, January 25, 2017 10:54 AM
> To: Richardson, Bruce <[email protected]>; Jerin Jacob
> <[email protected]>; [email protected]
> Cc: [email protected]; [email protected]; Van Haaren,
> Harry <[email protected]>; McDaniel, Timothy
> <[email protected]>
> Subject: RE: [dpdk-dev] [PATCH v4 1/6] eventdev: introduce event driven
> programming model
>
>
>
> > -----Original Message-----
> > From: Richardson, Bruce
> > Sent: Wednesday, January 25, 2017 10:36 AM
> > To: Eads, Gage <[email protected]>; Jerin Jacob
> > <[email protected]>; [email protected]
> > Cc: [email protected]; [email protected]; Van Haaren,
> > Harry <[email protected]>; McDaniel, Timothy
> > <[email protected]>
> > Subject: RE: [dpdk-dev] [PATCH v4 1/6] eventdev: introduce event
> > driven programming model
> >
> >
> >
> > > -----Original Message-----
> > > From: Eads, Gage
> > > Sent: Wednesday, January 25, 2017 4:32 PM > To: Jerin Jacob
> > <[email protected]>; [email protected] > Cc:
> > [email protected]; Richardson, Bruce >
> > <[email protected]>; [email protected]; Van Haaren, >
> > Harry <[email protected]>; McDaniel, Timothy >
> > <[email protected]> > Subject: RE: [dpdk-dev] [PATCH v4 1/6]
> > eventdev: introduce event > driven programming model > > Hi Jerin,
> > > > See the bottom of this email for a proposed tweak to the >
> > rte_event_enqueue_burst() return value.
> > >
> > > > -----Original Message-----
> > > > From: Jerin Jacob [mailto:[email protected]]
> > > > Sent: Wednesday, December 21, 2016 3:25 AM > > To:
> > [email protected] > > Cc: [email protected]; Richardson, Bruce >
> > > <[email protected]>; [email protected]; Eads, Gage >
> > > <[email protected]>; Van Haaren, Harry > >
> > <[email protected]>; Jerin Jacob > >
> > <[email protected]> > > Subject: [dpdk-dev] [PATCH v4
> > 1/6] eventdev: introduce event driven > > programming model > >
> > <message truncated for brevity> > > +/** > > + * Enqueue a burst
> > of events objects or an event object supplied > > in > >
> > *rte_event* > > + * structure on an event device designated by its
> > *dev_id* > > through the event + * port specified by *port_id*. Each
> > event > > object specifies the event queue on + * which it will be
> > enqueued.
> > > > + *
> > > > + * 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,
> > > > + const struct rte_event ev[], uint16_t
> nb_events);
> > >
> > > There are a number of reasons this operation could fail to enqueue
> > all > the events, including:
> > > - Backpressure
> > > - Invalid port ID
> > > - Invalid queue ID
> > > - Invalid sched type when a queue is configured for ATOMIC_ONLY, >
> > ORDERED_ONLY, or PARALLEL_ONLY > - ...
> > >
> > > The current API doesn't provide a straightforward way to determine
> > the > cause of a failure. This is a particular issue on event PMDs
> > that can > backpressure, where the app may want to treat that case
> > differently > than the other failure cases.
> > >
> > > Could we change the return type to int16_t, and define a set of
> > error > cases (e.g. -ENOSPC for backpressure, -EINVAL for an invalid
> argument)?
> > > (With corresponding changes needed in the PMD API) Similarly we
> > could > change rte_event_dequeue_burst() to return an int16_t, with
> > -EINVAL as > a possible error case.
> >
> > Use rte_errno instead, I suggest. That's what it's there for.
> >
> > /Bruce
>
> That makes sense. In that case, the API comment could be tweaked like so:
>
> * If the 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, and
> * rte_errno is set accordingly. Possible errno values include:
> * - EINVAL - The port ID is invalid, an event's queue ID is invalid, or an
> * event's sched type doesn't match the capabilities of the
> * destination queue.
> * - ENOSPC - The event port was backpressured and unable to enqueue one or
> * more events.
However it seems better to use a signed integer for the dequeue burst return
value, if it is to use rte_errno. Application code could be simplified:
(signed return value)
ret = rte_event_dequeue_burst(...);
if (ret < 0)
rte_panic("Dequeued returned errno %d\n", rte_errno);
vs.
(unsigned return value)
ret = rte_event_dequeue_burst(...);
if (ret == 0 && rte_errno != 0)
rte_panic("Dequeued returned errno %d\n", rte_errno);
And with an unsigned return value, all dequeue implementations would have to
clear rte_errno when no events are dequeued.
Thanks,
Gage
