[PATCH v2 1/3] eventdev: 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.
The dequeue operation initiates the pre-schedule operation, which completes
in parallel without affecting the dequeued event flow contexts and
dequeue latency.

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