[dpdk-dev] [PATCH v2 1/6] eventdev: introduce event driven programming model
Jerin Jacob
jerin.jacob at caviumnetworks.com
Thu Dec 8 02:48:01 CET 2016
On Wed, Dec 07, 2016 at 11:12:51AM +0000, Bruce Richardson wrote:
> 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 at caviumnetworks.com>
> > ---
> > +
> > +/**
> > + * Link multiple source event queues supplied in *rte_event_queue_link*
> > + * structure as *queue_id* to the destination event port designated by its
> > + * *port_id* on the event device designated by its *dev_id*.
> > + *
> > + * The link establishment shall enable the event port *port_id* from
> > + * receiving events from the specified event queue *queue_id*
> > + *
> > + * An event queue may link to one or more event ports.
> > + * The number of links can be established from an event queue to event port is
> > + * implementation defined.
> > + *
> > + * Event queue(s) to event port link establishment can be changed at runtime
> > + * without re-configuring the device to support scaling and to reduce the
> > + * latency of critical work by establishing the link with more event ports
> > + * at runtime.
> > + *
> > + * @param dev_id
> > + * The identifier of the device.
> > + *
> > + * @param port_id
> > + * Event port identifier to select the destination port to link.
> > + *
> > + * @param link
> > + * Points to an array of *nb_links* objects of type *rte_event_queue_link*
> > + * structure which contain the event queue to event port link establishment
> > + * attributes.
> > + * NULL value is allowed, in which case this function links all the configured
> > + * event queues *nb_event_queues* which previously supplied to
> > + * rte_event_dev_configure() to the event port *port_id* with normal servicing
> > + * priority(RTE_EVENT_DEV_PRIORITY_NORMAL).
> > + *
> > + * @param nb_links
> > + * The number of links to establish
> > + *
> > + * @return
> > + * The number of links actually established. The return value can be less than
> > + * the value of the *nb_links* parameter when the implementation has the
> > + * limitation on specific queue to port link establishment or if invalid
> > + * parameters are specified in a *rte_event_queue_link*.
> > + * If the return value is less than *nb_links*, the remaining links at the end
> > + * of link[] are not established, and the caller has to take care of them.
> > + * If return value is less than *nb_links* then implementation shall update the
> > + * rte_errno accordingly, Possible rte_errno values are
> > + * (-EDQUOT) Quota exceeded(Application tried to link the queue configured with
> > + * RTE_EVENT_QUEUE_CFG_FLAG_SINGLE_LINK to more than one event ports)
> > + * (-EINVAL) Invalid parameter
> > + *
> > + */
> > +int
> > +rte_event_port_link(uint8_t dev_id, uint8_t port_id,
> > + const struct rte_event_queue_link link[],
> > + uint16_t nb_links);
> > +
>
> Hi again Jerin,
>
> another small suggestion here. I'm not a big fan of using small
> structures to pass parameters into functions, especially when not all
> fields are always going to be used. Rather than use the event queue link
> structure, can we just pass in two array parameters here - the list of
> QIDs, and the list of priorities. In cases where the eventdev
> implementation does not support link prioritization, or where the app
> does not want different priority mappings , then the second
> array can be null [implying NORMAL priority for the don't care case].
>
> int
> rte_event_port_link(uint8_t dev_id, uint8_t port_id,
> const uint8_t queues[], const uint8_t priorities[],
> uint16_t nb_queues);
>
> This just makes mapping an array of queues easier, as we can just pass
> an array of ints directly in, and it especially makes it easier to
> create a single link via:
>
> rte_event_port_link(dev_id, port_id, &queue_id, NULL, 1);
The reason why I thought of creating "struct rte_event_queue_link",
- Its easy to add new parameter in link attributes if required
- Its _easy_ to implement PAUSE and RESUME in application
PAUSE:
nr_links = rte_event_port_links_get(,,link)
rte_event_port_unlink_all
RESUME:
rte_event_port_link(,,link, nr_links);
No strong opinion here. I will go with your proposal then
>
> Regards,
> /Bruce
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