RE: [EXT] Re: [PATCH 1/2] doc: add enqueue depth for new event type

[Pavan Nikhilesh Bhagavatula <pbhagavatula@marvell.com>]

> -----Original Message-----
> From: Mattias Rönnblom <mattias.ronnblom@ericsson.com>
> Sent: Wednesday, July 13, 2022 2:39 PM
> To: Pavan Nikhilesh Bhagavatula <pbhagavatula@marvell.com>; Thomas
> Monjalon <thomas@monjalon.net>
> Cc: Jerin Jacob Kollanukkaran <jerinj@marvell.com>; Ray Kinsella
> <mdr@ashroe.eu>; dev@dpdk.org; timothy.mcdaniel@intel.com; Hemant
> Agrawal <hemant.agrawal@nxp.com>; sachin.saxena@oss.nxp.com;
> liangma@liangbit.com; peter.mccarthy@intel.com;
> harry.van.haaren@intel.com; erik.g.carrillo@intel.com;
> abhinandan.gujjar@intel.com; jay.jayatheerthan@intel.com;
> anatoly.burakov@intel.com
> Subject: Re: [EXT] Re: [PATCH 1/2] doc: add enqueue depth for new event
> type
> 
> On 2022-07-12 20:11, Pavan Nikhilesh Bhagavatula wrote:
> > +Cc
> > timothy.mcdaniel@intel.com;
> > hemant.agrawal@nxp.com;
> > sachin.saxena@oss.nxp.com;
> > mattias.ronnblom@ericsson.com;
> > jerinj@marvell.com;
> > liangma@liangbit.com;
> > peter.mccarthy@intel.com;
> > harry.van.haaren@intel.com;
> > erik.g.carrillo@intel.com;
> > abhinandan.gujjar@intel.com;
> > jay.jayatheerthan@intel.com;
> > mdr@ashroe.eu;
> > anatoly.burakov@intel.com;
> >
> >
> >> -----Original Message-----
> >> From: Thomas Monjalon <thomas@monjalon.net>
> >> Sent: Tuesday, July 12, 2022 8:31 PM
> >> To: Pavan Nikhilesh Bhagavatula <pbhagavatula@marvell.com>
> >> Cc: Jerin Jacob Kollanukkaran <jerinj@marvell.com>; Ray Kinsella
> >> <mdr@ashroe.eu>; dev@dpdk.org; Pavan Nikhilesh Bhagavatula
> >> <pbhagavatula@marvell.com>
> >> Subject: [EXT] Re: [PATCH 1/2] doc: add enqueue depth for new event
> type
> >>
> >> External Email
> >>
> >> ----------------------------------------------------------------------
> >> I'm not your teacher, but please consider Cc'ing people outside of your
> >> company.
> >>
> >
> > I generally add --to-cmd=./devtools/get-maintainer.sh but looks like it's
> useless for
> > sending deprecation notices.
> >
> > Maybe we should update it to include lib/driver maintainers when diff sees
> deprecation.rst
> >
> >>
> >> 27/06/2022 11:57, pbhagavatula@marvell.com:
> >>> From: Pavan Nikhilesh <pbhagavatula@marvell.com>
> >>>
> >>> A new field ``max_event_port_enqueue_new_burst`` will be added to
> the
> >>> structure ``rte_event_dev_info``. The field defines the max enqueue
> >>> burst size of new events (OP_NEW) supported by the underlying event
> >>> device.
> >>>
> >>> Signed-off-by: Pavan Nikhilesh <pbhagavatula@marvell.com>
> >>> ---
> >>>   doc/guides/rel_notes/deprecation.rst | 5 +++++
> >>>   1 file changed, 5 insertions(+)
> >>>
> >>> diff --git a/doc/guides/rel_notes/deprecation.rst
> >> b/doc/guides/rel_notes/deprecation.rst
> >>> index 4e5b23c53d..071317e8e3 100644
> >>> --- a/doc/guides/rel_notes/deprecation.rst
> >>> +++ b/doc/guides/rel_notes/deprecation.rst
> >>> @@ -125,3 +125,8 @@ Deprecation Notices
> >>>     applications should be updated to use the ``dmadev`` library instead,
> >>>     with the underlying HW-functionality being provided by the ``ioat`` or
> >>>     ``idxd`` dma drivers
> >>> +
> >>> +* eventdev: The structure ``rte_event_dev_info`` will be extended to
> >> include the
> >>> +  max enqueue burst size of new events supported by the underlying
> >> event device.
> >>> +  A new field ``max_event_port_enqueue_new_burst`` will be added
> to
> >> the structure
> >>> +  ``rte_event_dev_info`` in DPDK 22.11.
> >>>
> >>
> >>
> >>
> >>
> 
> Why is this needed, or useful? Why isn't called something with
> "enqueue_depth" in it, like the already-present field?
> 

This is for a case where enqueues with OP_FORWARD/OP_RELEASE only supports
enqueue depth of 1.
Where as OP_NEW supports higher burst size.

This is already tied into capability description :
 
#define RTE_EVENT_DEV_CAP_BURST_MODE          (1ULL << 4)
/**< Event device is capable of operating in burst mode for enqueue(forward,
 * release) and dequeue operation. If this capability is not set, application
 * still uses the rte_event_dequeue_burst() and rte_event_enqueue_burst() but
 * PMD accepts only one event at a time.
 *
 * @see rte_event_dequeue_burst() rte_event_enqueue_burst()
 */

> I think I would rather remove all fields related to the max
> enqueue/dequeue burst sizes. They serve no purpose, as far as I see. If
> you have some HW limit on the maximum number of new events it can
> accept, have the driver retry until backpressure occurs.