[PATCH v2 0/3] Introduce event pre-scheduling

[<pbhagavatula@marvell.com>]

From: Pavan Nikhilesh <pbhagavatula@marvell.com>

Event pre-scheduling improves scheduling performance by assigning events
to event ports in advance when dequeues are issued.
This series introduces various types and levels of pre-scheduling to the
eventdev library.

pre-scheduling Types:
 * RTE_EVENT_DEV_PRESCHEDULE_NONE: No pre-scheduling.
 * RTE_EVENT_DEV_PRESCHEDULE: Always issue a pre-schedule when dequeue is issued.
 * RTE_EVENT_DEV_PRESCHEDULE_ADAPTIVE: Delay issuing pre-schedule until there
   are no forward progress constraints with the held flow contexts.

pre-scheduling Levels:
 * Event Device Level Pre-scheduling: Pre-scheduling can be enabled or disabled at the
   event device during configuration. Event devices can indicate pre-scheduling
   capabilities using `RTE_EVENT_DEV_CAP_EVENT_PRESCHEDULE` and
  `RTE_EVENT_DEV_CAP_EVENT_PRESCHEDULE_ADAPTIVE` via the event device info
  function `info.event_dev_cap`.
 * Event Port Level Prefetch: Pre-scheduling can be selectively enabled or disabled
   at the event port during runtime. Event devices can indicate this capability
   using `RTE_EVENT_PORT_CAP_EVENT_PER_PORT_PRESCHEDULE` via the event device info
   function `info.event_port_cap`.
 * Application Controlled Prefetch Hint: Applications can provide hints to the
   event device to start pre-scheduling events using the new API
   `rte_event_port_pre-schedule`. Event devices can indicate this capabilities using
   `RTE_EVENT_DEV_CAP_SW_PRESCHEDULE` via the event device info function
   `info.event_dev_cap`.

The rte_event_dequeue_burst operation initiates the pre-schedule operation, which
completes in parallel without affecting the flow context of the dequeued events and
dequeue latency. On the next dequeue operation, the pre-scheduleed events are
dequeued, and pre-schedule operation is initiated again.

In the case of application-controlled pre-schedule hints, the currently held flow
contexts, if any, are not affected by the pre-schedule operation. On the next
dequeue operation, the pre-scheduleed events are returned, but pre-schedule is not
initiated again until the application provides the hint again. If pre-scheduling
is already enabled at the event device level or event port level, the hint is ignored.

v2 Changes:
- s/prefetch/pre-schedule (Mattias)

Pavan Nikhilesh (3):
  eventdev: introduce event pre-scheduling
  eventdev: add event port pre-schedule modify
  eventdev: add SW event preschedule hint

 app/test/test_eventdev.c                    | 114 +++++++++++++++
 doc/guides/prog_guide/eventdev/eventdev.rst |  42 ++++++
 lib/eventdev/eventdev_pmd.h                 |   4 +
 lib/eventdev/eventdev_private.c             |  22 ++-
 lib/eventdev/eventdev_trace_points.c        |   6 +
 lib/eventdev/rte_eventdev.h                 | 152 ++++++++++++++++++++
 lib/eventdev/rte_eventdev_core.h            |  11 ++
 lib/eventdev/rte_eventdev_trace_fp.h        |  19 ++-
 lib/eventdev/version.map                    |   6 +
 9 files changed, 373 insertions(+), 3 deletions(-)

--
2.25.1