From: "Eads, Gage" <gage.eads@intel.com>
To: Jerin Jacob <jerin.jacob@caviumnetworks.com>
Cc: "Richardson, Bruce" <bruce.richardson@intel.com>,
"'dev@dpdk.org'" <dev@dpdk.org>,
"'thomas.monjalon@6wind.com'" <thomas.monjalon@6wind.com>,
"'hemant.agrawal@nxp.com'" <hemant.agrawal@nxp.com>,
"Van Haaren, Harry" <harry.van.haaren@intel.com>,
"McDaniel, Timothy" <timothy.mcdaniel@intel.com>
Subject: Re: [dpdk-dev] [PATCH v4 1/6] eventdev: introduce event driven programming model
Date: Thu, 26 Jan 2017 20:39:57 +0000 [thread overview]
Message-ID: <9184057F7FC11744A2107296B6B8EB1E01E5F76C@FMSMSX108.amr.corp.intel.com> (raw)
In-Reply-To: <20170126093924.GA5276@localhost.localdomain>
> -----Original Message-----
> From: Jerin Jacob [mailto:jerin.jacob@caviumnetworks.com]
> Sent: Thursday, January 26, 2017 3:39 AM
> To: Eads, Gage <gage.eads@intel.com>
> Cc: Richardson, Bruce <bruce.richardson@intel.com>; 'dev@dpdk.org'
> <dev@dpdk.org>; 'thomas.monjalon@6wind.com'
> <thomas.monjalon@6wind.com>; 'hemant.agrawal@nxp.com'
> <hemant.agrawal@nxp.com>; Van Haaren, Harry
> <harry.van.haaren@intel.com>; McDaniel, Timothy
> <timothy.mcdaniel@intel.com>
> Subject: Re: [dpdk-dev] [PATCH v4 1/6] eventdev: introduce event driven
> programming model
>
> On Wed, Jan 25, 2017 at 10:36:21PM +0000, Eads, Gage wrote:
> > > > <jerin.jacob@caviumnetworks.com> > > 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.
After some internal discussion, I don't think the signed return value is necessary for burst dequeue. Burst enqueue is the more interesting case...
>
> Gage,
>
> Just to understand, what is the expected application behavior if the
> implementation returns -ENOSPC
It's application-dependent -- depending on the importance of the event, the application could decide to retry the enqueue some number of times or decide to drop the event.
>
> Apart for the above SW driver behavior, I think, HW implementation has two
> more different behavior
> a) Implementation make sure that it never returns -ENOSPC by allocating more
> space on the fly or any other scheme
> b) Tail drop
>
By "tail drop," do you mean the hardware drops the event (and presumably frees any memory it points to)? Or the enqueue is unsuccessful and the application drops the event?
> Considering different implementation has different behaviors, How about
> enumerating the overflow policy at the port configuration time? and let
> implementation act accordingly to avoid fast-patch change in
> application(effects in all implementation irrespective of the capability)
>
> possible enumerating value at the port configuration time,
> - PANIC or similar scheme to denote it cannot proceed
> - TAIL DROP
> or any expected application behavior you want to add
I wonder if that's necessary? Hardware behavior a) means the function will always return nb_events. If hardware drops the event(s), I assume enqueue_burst would still return nb_events and the app behaves as if all events were sent. If the enqueue fails (ret < nb_events), app software could check rte_errno and take the action it deems necessary. So all fast-path enqueue code could look like:
ret = rte_event_enqueue_burst(..., nb_events);
if (ret < nb_events) {
....
}
next prev parent reply other threads:[~2017-01-26 20:39 UTC|newest]
Thread overview: 109+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-18 5:44 [dpdk-dev] [PATCH 0/4] libeventdev API and northbound implementation Jerin Jacob
2016-11-18 5:44 ` [dpdk-dev] [PATCH 1/4] eventdev: introduce event driven programming model Jerin Jacob
2016-11-23 18:39 ` Thomas Monjalon
2016-11-24 1:59 ` Jerin Jacob
2016-11-24 12:26 ` Bruce Richardson
2016-11-24 15:35 ` Thomas Monjalon
2016-11-25 0:23 ` Jerin Jacob
2016-11-25 11:00 ` Bruce Richardson
2016-11-25 13:09 ` Thomas Monjalon
2016-11-26 0:57 ` Jerin Jacob
2016-11-28 9:10 ` Bruce Richardson
2016-11-26 2:54 ` Jerin Jacob
2016-11-28 9:16 ` Bruce Richardson
2016-11-28 11:30 ` Thomas Monjalon
2016-11-29 4:01 ` Jerin Jacob
2016-11-29 10:00 ` Bruce Richardson
2016-11-25 11:59 ` Van Haaren, Harry
2016-11-25 12:09 ` Richardson, Bruce
2016-11-24 16:24 ` Bruce Richardson
2016-11-24 19:30 ` Jerin Jacob
2016-12-06 3:52 ` [dpdk-dev] [PATCH v2 0/6] libeventdev API and northbound implementation Jerin Jacob
2016-12-06 3:52 ` [dpdk-dev] [PATCH v2 1/6] eventdev: introduce event driven programming model Jerin Jacob
2016-12-06 16:51 ` Bruce Richardson
2016-12-07 18:53 ` Jerin Jacob
2016-12-08 9:30 ` Bruce Richardson
2016-12-08 20:41 ` Jerin Jacob
2016-12-09 15:11 ` Bruce Richardson
2016-12-14 6:55 ` Jerin Jacob
2016-12-07 10:57 ` Van Haaren, Harry
2016-12-08 1:24 ` Jerin Jacob
2016-12-08 11:02 ` Van Haaren, Harry
2016-12-14 13:13 ` Jerin Jacob
2016-12-14 15:15 ` Bruce Richardson
2016-12-15 16:54 ` Van Haaren, Harry
2016-12-07 11:12 ` Bruce Richardson
2016-12-08 1:48 ` Jerin Jacob
2016-12-08 9:57 ` Bruce Richardson
2016-12-14 6:40 ` Jerin Jacob
2016-12-14 15:19 ` Bruce Richardson
2016-12-15 13:39 ` Jerin Jacob
2016-12-06 3:52 ` [dpdk-dev] [PATCH v2 2/6] eventdev: define southbound driver interface Jerin Jacob
2016-12-06 3:52 ` [dpdk-dev] [PATCH v2 3/6] eventdev: implement the northbound APIs Jerin Jacob
2016-12-06 17:17 ` Bruce Richardson
2016-12-07 17:02 ` Jerin Jacob
2016-12-08 9:59 ` Bruce Richardson
2016-12-14 6:28 ` Jerin Jacob
2016-12-06 3:52 ` [dpdk-dev] [PATCH v2 4/6] eventdev: implement PMD registration functions Jerin Jacob
2016-12-06 3:52 ` [dpdk-dev] [PATCH v2 5/6] event/skeleton: add skeleton eventdev driver Jerin Jacob
2016-12-06 3:52 ` [dpdk-dev] [PATCH v2 6/6] app/test: unit test case for eventdev APIs Jerin Jacob
2016-12-06 16:46 ` [dpdk-dev] [PATCH v2 0/6] libeventdev API and northbound implementation Bruce Richardson
2016-12-21 9:25 ` [dpdk-dev] [PATCH v4 " Jerin Jacob
2016-12-21 9:25 ` [dpdk-dev] [PATCH v4 1/6] eventdev: introduce event driven programming model Jerin Jacob
2017-01-25 16:32 ` Eads, Gage
2017-01-25 16:36 ` Richardson, Bruce
2017-01-25 16:53 ` Eads, Gage
2017-01-25 22:36 ` Eads, Gage
2017-01-26 9:39 ` Jerin Jacob
2017-01-26 20:39 ` Eads, Gage [this message]
2017-01-27 10:03 ` Bruce Richardson
2017-01-30 10:42 ` Jerin Jacob
2017-02-02 11:18 ` Nipun Gupta
2017-02-02 14:09 ` Jerin Jacob
2017-02-03 6:38 ` Nipun Gupta
2017-02-03 10:58 ` Hemant Agrawal
2017-02-07 4:59 ` Jerin Jacob
2016-12-21 9:25 ` [dpdk-dev] [PATCH v4 2/6] eventdev: define southbound driver interface Jerin Jacob
2017-02-02 11:19 ` Nipun Gupta
2017-02-02 11:34 ` Bruce Richardson
2017-02-02 12:53 ` Nipun Gupta
2017-02-02 13:58 ` Bruce Richardson
2017-02-03 5:59 ` Nipun Gupta
2016-12-21 9:25 ` [dpdk-dev] [PATCH v4 3/6] eventdev: implement the northbound APIs Jerin Jacob
2017-02-02 11:19 ` Nipun Gupta
2017-02-02 14:32 ` Jerin Jacob
2017-02-03 6:59 ` Nipun Gupta
2016-12-21 9:25 ` [dpdk-dev] [PATCH v4 4/6] eventdev: implement PMD registration functions Jerin Jacob
2017-02-02 11:20 ` Nipun Gupta
2017-02-05 13:04 ` Jerin Jacob
2016-12-21 9:25 ` [dpdk-dev] [PATCH v4 5/6] event/skeleton: add skeleton eventdev driver Jerin Jacob
2016-12-21 9:25 ` [dpdk-dev] [PATCH v4 6/6] app/test: unit test case for eventdev APIs Jerin Jacob
2016-11-18 5:45 ` [dpdk-dev] [PATCH 2/4] eventdev: implement the northbound APIs Jerin Jacob
2016-11-21 17:45 ` Eads, Gage
2016-11-21 19:13 ` Jerin Jacob
2016-11-21 19:31 ` Jerin Jacob
2016-11-22 15:15 ` Eads, Gage
2016-11-22 18:19 ` Jerin Jacob
2016-11-22 19:43 ` Eads, Gage
2016-11-22 20:00 ` Jerin Jacob
2016-11-22 22:48 ` Eads, Gage
2016-11-22 23:43 ` Jerin Jacob
2016-11-28 15:53 ` Eads, Gage
2016-11-29 2:01 ` Jerin Jacob
2016-11-29 3:43 ` Jerin Jacob
2016-11-29 5:46 ` Eads, Gage
2016-11-23 9:57 ` Bruce Richardson
2016-11-23 19:18 ` Thomas Monjalon
2016-11-25 4:17 ` Jerin Jacob
2016-11-25 9:55 ` Richardson, Bruce
2016-11-25 23:08 ` Jerin Jacob
2016-11-18 5:45 ` [dpdk-dev] [PATCH 3/4] event/skeleton: add skeleton eventdev driver Jerin Jacob
2016-11-18 5:45 ` [dpdk-dev] [PATCH 4/4] app/test: unit test case for eventdev APIs Jerin Jacob
2016-11-18 15:25 ` [dpdk-dev] [PATCH 0/4] libeventdev API and northbound implementation Bruce Richardson
2016-11-18 16:04 ` Bruce Richardson
2016-11-18 19:27 ` Jerin Jacob
2016-11-21 9:40 ` Thomas Monjalon
2016-11-21 9:57 ` Bruce Richardson
2016-11-22 0:11 ` Thomas Monjalon
2016-11-22 2:00 ` Yuanhan Liu
2016-11-22 9:05 ` Shreyansh Jain
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