Re: [dpdk-dev] [PATCH v2] eventdev: amend comments for events limit and threshold

[Nipun Gupta <nipun.gupta@nxp.com>]

> -----Original Message-----
> From: Van Haaren, Harry [mailto:harry.van.haaren@intel.com]
> Sent: Friday, February 10, 2017 16:02
> To: Nipun Gupta <nipun.gupta@nxp.com>; dev@dpdk.org
> Cc: Hemant Agrawal <hemant.agrawal@nxp.com>;
> jerin.jacob@caviumnetworks.com; Richardson, Bruce
> <bruce.richardson@intel.com>; Eads, Gage <gage.eads@intel.com>
> Subject: RE: [PATCH v2] eventdev: amend comments for events limit and
> threshold
> 
> > From: Nipun Gupta [mailto:nipun.gupta@nxp.com]
> > Sent: Friday, February 10, 2017 3:50 PM
> > To: dev@dpdk.org
> > Cc: hemant.agrawal@nxp.com; jerin.jacob@caviumnetworks.com;
> Richardson, Bruce
> > <bruce.richardson@intel.com>; Eads, Gage <gage.eads@intel.com>; Van
> Haaren, Harry
> > <harry.van.haaren@intel.com>; Nipun Gupta <nipun.gupta@nxp.com>
> > Subject: [PATCH v2] eventdev: amend comments for events limit and threshold
> >
> > Updated the comments on 'nb_events_limit' of 'struct rte_event_dev_config'
> > and 'new_event_threshold' of 'struct rte_event_port_conf' for open system
> > configuration.
> >
> > Signed-off-by: Nipun Gupta <nipun.gupta@nxp.com>
> > ---
> > Changes for v2:
> >  - Fix errors reported by check-git-log.sh
> >
> >  lib/librte_eventdev/rte_eventdev.h | 12 +++++++-----
> >  1 file changed, 7 insertions(+), 5 deletions(-)
> >
> > diff --git a/lib/librte_eventdev/rte_eventdev.h
> b/lib/librte_eventdev/rte_eventdev.h
> > index c2f9310..171e52e 100644
> > --- a/lib/librte_eventdev/rte_eventdev.h
> > +++ b/lib/librte_eventdev/rte_eventdev.h
> > @@ -404,11 +404,12 @@ struct rte_event_dev_config {
> >  	 * @see RTE_EVENT_DEV_CFG_PER_DEQUEUE_TIMEOUT
> >  	 */
> >  	int32_t nb_events_limit;
> > -	/**< Applies to *closed system* event dev only. This field indicates a
> > -	 * limit to ethdev-like devices to limit the number of events injected
> > -	 * into the system to not overwhelm core-to-core events.
> > +	/**< In a *closed system* this field indicates a limit to ethdev-like
> > +	 * devices to limit the number of events injected into the system to
> > +	 * not overwhelm core-to-core events.
> >  	 * This value cannot exceed the *max_num_events* which previously
> > -	 * provided in rte_event_dev_info_get()
> > +	 * provided in rte_event_dev_info_get().
> > +	 * This should be set to '-1' for *open system*.
> 
> 
> I don't think we should mention ethdev explicitly here - it applies to any
> port that is attempting to enqueue work into a closed-system eventdev.
> 
> What do you think of the following wording? (Suggestion only, feel free to
> re-word if required).
> 
> /**< In a closed system this field is the limit on the maximum number of events
>      that can be inflight in the eventdev at a given time. The limit is required
>      to ensure that the finite space in a closed system is not overwhelmed. The
>      value cannot exceed the *max_num_events* as provided by
> rte_event_dev_info_get().
>      This value should be set to -1 for open systems.
>  */

I agree with you Harry. For *closed systems*, this limit should be valid on all the
enqueues, whether from ethdev type devices or enqueue's from core.

BTW, do you use event limit both on event device and on event ports in your
software implementation? Because I think the limit may be only per event port.

Jerin,

Your views on this for open systems would be very helpful. Thanks.

> 
> >  	 */
> >  	uint8_t nb_event_queues;
> >  	/**< Number of event queues to configure on this device.
> > @@ -633,7 +634,8 @@ struct rte_event_port_conf {
> >  	 * can have a lower threshold so as not to overwhelm the device,
> >  	 * while ports used for worker pools can have a higher threshold.
> >  	 * This value cannot exceed the *nb_events_limit*
> > -	 * which previously supplied to rte_event_dev_configure()
> > +	 * which previously supplied to rte_event_dev_configure().
> > +	 * This should be set to '-1' for *open system*.
> >  	 */
> 
> Minor grammer issue (that was previously there too, but worth fixing anyway),
> there is a _was_ missing from the sentence:

Sure. I'll take care of this in v3.

> 
> +   which was previously supplied to rte_event_dev_configure().
>