RE: [PATCH v2 1/3] eventdev: introduce event pre-scheduling

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

> > From: pbhagavatula@marvell.com <pbhagavatula@marvell.com>
> > Sent: Tuesday, September 17, 2024 3:11 AM
> > To: jerinj@marvell.com; sthotton@marvell.com; Sevincer, Abdullah
> > <abdullah.sevincer@intel.com>; hemant.agrawal@nxp.com;
> > sachin.saxena@oss.nxp.com; Van Haaren, Harry
> <harry.van.haaren@intel.com>;
> > mattias.ronnblom@ericsson.com; liangma@liangbit.com; Mccarthy, Peter
> > <peter.mccarthy@intel.com>
> > Cc: dev@dpdk.org; Pavan Nikhilesh <pbhagavatula@marvell.com>
> > Subject: [PATCH v2 1/3] eventdev: introduce event pre-scheduling
> >
> > From: Pavan Nikhilesh <pbhagavatula@marvell.com>
> >
> > Event pre-scheduling improves scheduling performance by assigning events
> to
> > event ports in advance when dequeues are issued.
> > The dequeue operation initiates the pre-schedule operation, which
> completes in
> > parallel without affecting the dequeued event flow contexts and dequeue
> > latency.
> >
> Is the prescheduling done to get the event more quickly in the next dequeue?
> The first dequeue executes pre-schedule to make events available for the next
> dequeue.
> Is this how it is supposed to work?
> 

Yes, that is correct.

> > 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`.
> >
> > Applications can select the pre-schedule type and configure it through
> > `rte_event_dev_config.preschedule_type` during `rte_event_dev_configure`.
> >
> > The supported pre-schedule types are:
> >  * `RTE_EVENT_DEV_PRESCHEDULE_NONE` - No pre-scheduling.
> >  * `RTE_EVENT_DEV_PRESCHEDULE` - Always issue a pre-schedule on
> dequeue.
> >  * `RTE_EVENT_DEV_PRESCHEDULE_ADAPTIVE` - Delay issuing pre-schedule
> > until
> >    there are no forward progress constraints with the held flow contexts.
> >
> > Signed-off-by: Pavan Nikhilesh <pbhagavatula@marvell.com>
> > ---
> >  app/test/test_eventdev.c                    | 63 +++++++++++++++++++++
> >  doc/guides/prog_guide/eventdev/eventdev.rst | 22 +++++++
> >  lib/eventdev/rte_eventdev.h                 | 48 ++++++++++++++++
> >  3 files changed, 133 insertions(+)
> >
> > diff --git a/app/test/test_eventdev.c b/app/test/test_eventdev.c index
> > e4e234dc98..cf496ee88d 100644
> > --- a/app/test/test_eventdev.c
> > +++ b/app/test/test_eventdev.c
> > @@ -1250,6 +1250,67 @@ test_eventdev_profile_switch(void)
> >  	return TEST_SUCCESS;
> >  }
> >
> > +static int
> > +preschedule_test(rte_event_dev_preschedule_type_t preschedule_type,
> > +const char *preschedule_name) {
> > +#define NB_EVENTS     1024
> > +	uint64_t start, total;
> > +	struct rte_event ev;
> > +	int rc, cnt;
> > +
> > +	ev.event_type = RTE_EVENT_TYPE_CPU;
> > +	ev.queue_id = 0;
> > +	ev.op = RTE_EVENT_OP_NEW;
> > +	ev.u64 = 0xBADF00D0;
> > +
> > +	for (cnt = 0; cnt < NB_EVENTS; cnt++) {
> > +		ev.flow_id = cnt;
> > +		rc = rte_event_enqueue_burst(TEST_DEV_ID, 0, &ev, 1);
> > +		TEST_ASSERT(rc == 1, "Failed to enqueue event");
> > +	}
> > +
> > +	RTE_SET_USED(preschedule_type);
> > +	total = 0;
> > +	while (cnt) {
> > +		start = rte_rdtsc_precise();
> > +		rc = rte_event_dequeue_burst(TEST_DEV_ID, 0, &ev, 1, 0);
> > +		if (rc) {
> > +			total += rte_rdtsc_precise() - start;
> > +			cnt--;
> > +		}
> > +	}
> > +	printf("Preschedule type : %s, avg cycles %" PRIu64 "\n",
> > preschedule_name,
> > +	       total / NB_EVENTS);
> > +
> > +	return TEST_SUCCESS;
> > +}
> > +
> > +static int
> > +test_eventdev_preschedule_configure(void)
> > +{
> > +	struct rte_event_dev_config dev_conf;
> > +	struct rte_event_dev_info info;
> > +	int rc;
> > +
> > +	rte_event_dev_info_get(TEST_DEV_ID, &info);
> > +
> > +	if ((info.event_dev_cap &
> RTE_EVENT_DEV_CAP_EVENT_PRESCHEDULE)
> > == 0)
> > +		return TEST_SKIPPED;
> > +
> > +	devconf_set_default_sane_values(&dev_conf, &info);
> > +	dev_conf.preschedule_type = RTE_EVENT_DEV_PRESCHEDULE;
> > +	rc = rte_event_dev_configure(TEST_DEV_ID, &dev_conf);
> > +	TEST_ASSERT_SUCCESS(rc, "Failed to configure eventdev");
> > +
> > +	rc = preschedule_test(RTE_EVENT_DEV_PRESCHEDULE_NONE,
> > "RTE_EVENT_DEV_PRESCHEDULE_NONE");
> > +	rc |= preschedule_test(RTE_EVENT_DEV_PRESCHEDULE,
> > "RTE_EVENT_DEV_PRESCHEDULE");
> > +	if (info.event_dev_cap &
> > RTE_EVENT_DEV_CAP_EVENT_PRESCHEDULE_ADAPTIVE)
> > +		rc |=
> > preschedule_test(RTE_EVENT_DEV_PRESCHEDULE_ADAPTIVE,
> > +
> > "RTE_EVENT_DEV_PRESCHEDULE_ADAPTIVE");
> > +
> > +	return rc;
> > +}
> > +
> >  static int
> >  test_eventdev_close(void)
> >  {
> > @@ -1310,6 +1371,8 @@ static struct unit_test_suite
> > eventdev_common_testsuite  = {
> >  			test_eventdev_start_stop),
> >  		TEST_CASE_ST(eventdev_configure_setup,
> > eventdev_stop_device,
> >  			test_eventdev_profile_switch),
> > +		TEST_CASE_ST(eventdev_configure_setup, NULL,
> > +			test_eventdev_preschedule_configure),
> >  		TEST_CASE_ST(eventdev_setup_device,
> eventdev_stop_device,
> >  			test_eventdev_link),
> >  		TEST_CASE_ST(eventdev_setup_device,
> eventdev_stop_device,
> > diff --git a/doc/guides/prog_guide/eventdev/eventdev.rst
> > b/doc/guides/prog_guide/eventdev/eventdev.rst
> > index fb6dfce102..341b9bb2c6 100644
> > --- a/doc/guides/prog_guide/eventdev/eventdev.rst
> > +++ b/doc/guides/prog_guide/eventdev/eventdev.rst
> > @@ -357,6 +357,28 @@ Worker path:
> >         // Process the event received.
> >     }
> >
> > +Event Pre-scheduling
> > +~~~~~~~~~~~~~~~~~~~~
> > +
> > +Event pre-scheduling improves scheduling performance by assigning
> > +events to event ports in advance when dequeues are issued.
> > +The `rte_event_dequeue_burst` operation initiates the pre-schedule
> > +operation, which completes in parallel without affecting the dequeued
> event
> > flow contexts and dequeue latency.
> > +On the next dequeue operation, the pre-scheduled events are dequeued
> > +and pre-schedule is initiated again.
> > +
> > +An application can use event pre-scheduling if the event device
> > +supports it at either device level or at a individual port level.
> > +The application can check pre-schedule capability by checking if
> > +``rte_event_dev_info.event_dev_cap``
> > +has the bit ``RTE_EVENT_DEV_CAP_PRESCHEDULE`` set, if present
> > +pre-scheduling can be enabled at device configuration time by setting
> > appropriate pre-schedule type in ``rte_event_dev_config.preschedule``.
> > +
> > +Currently, the following pre-schedule types are supported:
> > + * ``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`` - Issue pre-schedule when
> > dequeue is issued and there are
> > +   no forward progress constraints.
> > +
> >  Starting the EventDev
> >  ~~~~~~~~~~~~~~~~~~~~~
> >
> > diff --git a/lib/eventdev/rte_eventdev.h b/lib/eventdev/rte_eventdev.h
> index
> > 08e5f9320b..5ea7f5a07b 100644
> > --- a/lib/eventdev/rte_eventdev.h
> > +++ b/lib/eventdev/rte_eventdev.h
> > @@ -446,6 +446,30 @@ struct rte_event;
> >   * @see RTE_SCHED_TYPE_PARALLEL
> >   */
> >
> > +#define RTE_EVENT_DEV_CAP_EVENT_PRESCHEDULE (1ULL << 16) /**<
> Event
> > +device supports event pre-scheduling.
> > + *
> > + * When this capability is available, the application can enable event
> > +pre-scheduling on the event
> > + * device to pre-schedule events to a event port when
> > +`rte_event_dequeue_burst()`
> > + * is issued.
> > + * The pre-schedule process starts with the `rte_event_dequeue_burst()`
> > +call and the
> > + * pre-scheduled events are returned on the next
> `rte_event_dequeue_burst()`
> > call.
> > + *
> > + * @see rte_event_dev_configure()
> > + */
> > +
> > +#define RTE_EVENT_DEV_CAP_EVENT_PRESCHEDULE_ADAPTIVE (1ULL <<
> 17)
> > /**<
> > +Event device supports adaptive event pre-scheduling.
> > + *
> > + * When this capability is available, the application can enable
> > +adaptive pre-scheduling
> > + * on the event device where the events are pre-scheduled when there
> > +are no forward
> > + * progress constraints with the currently held flow contexts.
> > + * The pre-schedule process starts with the `rte_event_dequeue_burst()`
> > +call and the
> > + * pre-scheduled events are returned on the next
> `rte_event_dequeue_burst()`
> > call.
> > + *
> > + * @see rte_event_dev_configure()
> > + */
> > +
> >  /* Event device priority levels */
> >  #define RTE_EVENT_DEV_PRIORITY_HIGHEST   0
> >  /**< Highest priority level for events and queues.
> > @@ -680,6 +704,25 @@ rte_event_dev_attr_get(uint8_t dev_id, uint32_t
> > attr_id,
> >   *  @see rte_event_dequeue_timeout_ticks(), rte_event_dequeue_burst()
> >   */
> >
> > +typedef enum {
> > +	RTE_EVENT_DEV_PRESCHEDULE_NONE = 0,
> > +	/* Disable pre-schedule across the event device or on a given event
> port.
> > +	 * @ref rte_event_dev_config.preschedule_type
> > +	 */
> > +	RTE_EVENT_DEV_PRESCHEDULE,
> > +	/* Enable pre-schedule always across the event device or a given event
> > port.
> > +	 * @ref rte_event_dev_config.preschedule_type
> > +	 * @see RTE_EVENT_DEV_CAP_EVENT_PRESCHEDULE
> > +	 */
> > +	RTE_EVENT_DEV_PRESCHEDULE_ADAPTIVE,
> > +	/* Enable adaptive pre-schedule across the event device or a given
> event
> > port.
> > +	 * Delay issuing pre-schedule until there are no forward progress
> > constraints with
> > +	 * the held flow contexts.
> > +	 * @ref rte_event_dev_config.preschedule_type
> > +	 * @see RTE_EVENT_DEV_CAP_EVENT_PRESCHEDULE_ADAPTIVE
> > +	 */
> > +} rte_event_dev_preschedule_type_t;
> > +
> >  /** Event device configuration structure */  struct rte_event_dev_config {
> >  	uint32_t dequeue_timeout_ns;
> > @@ -752,6 +795,11 @@ struct rte_event_dev_config {
> >  	 * optimized for single-link usage, this field is a hint for how many
> >  	 * to allocate; otherwise, regular event ports and queues will be used.
> >  	 */
> > +	rte_event_dev_preschedule_type_t preschedule_type;
> > +	/**< Event pre-schedule type to use across the event device, if
> > supported.
> > +	 * @see RTE_EVENT_DEV_CAP_EVENT_PRESCHEDULE
> > +	 * @see RTE_EVENT_DEV_CAP_EVENT_PRESCHEDULE_ADAPTIVE
> > +	 */
> >  };
> >
> >  /**
> > --
> > 2.25.1