[PATCH 5/6] event/sw: report idle when no work is performed

[Mattias Rönnblom]

Have the SW event device conform to the service core convention, where
-EAGAIN is return in case no work was performed.

Prior to this patch, for an idle SW event device, a service lcore load
estimate based on RTE_SERVICE_ATTR_CYCLES would suggest 48% core
load.

At 7% of its maximum capacity, the SW event device needs about 15% of
the available CPU cycles* to perform its duties, but
RTE_SERVICE_ATTR_CYCLES would suggest the SW service used 48% of the
service core.

After this change, load deduced from RTE_SERVICE_ATTR_CYCLES will only
be a minor overestimation of the actual cycles used.

* The SW scheduler becomes more efficient at higher loads.

Signed-off-by: Mattias Rönnblom <mattias.ronnb...@ericsson.com>
---
 drivers/event/sw/sw_evdev.c           | 3 +--
 drivers/event/sw/sw_evdev.h           | 2 +-
 drivers/event/sw/sw_evdev_scheduler.c | 6 ++++--
 3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/event/sw/sw_evdev.c b/drivers/event/sw/sw_evdev.c
index f93313b31b..f14c6427dd 100644
--- a/drivers/event/sw/sw_evdev.c
+++ b/drivers/event/sw/sw_evdev.c
@@ -933,8 +933,7 @@ set_refill_once(const char *key __rte_unused, const char 
*value, void *opaque)
 static int32_t sw_sched_service_func(void *args)
 {
        struct rte_eventdev *dev = args;
-       sw_event_schedule(dev);
-       return 0;
+       return sw_event_schedule(dev);
 }
 
 static int
diff --git a/drivers/event/sw/sw_evdev.h b/drivers/event/sw/sw_evdev.h
index 4fd1054470..8542b7d34d 100644
--- a/drivers/event/sw/sw_evdev.h
+++ b/drivers/event/sw/sw_evdev.h
@@ -295,7 +295,7 @@ uint16_t sw_event_enqueue_burst(void *port, const struct 
rte_event ev[],
 uint16_t sw_event_dequeue(void *port, struct rte_event *ev, uint64_t wait);
 uint16_t sw_event_dequeue_burst(void *port, struct rte_event *ev, uint16_t num,
                        uint64_t wait);
-void sw_event_schedule(struct rte_eventdev *dev);
+int32_t sw_event_schedule(struct rte_eventdev *dev);
 int sw_xstats_init(struct sw_evdev *dev);
 int sw_xstats_uninit(struct sw_evdev *dev);
 int sw_xstats_get_names(const struct rte_eventdev *dev,
diff --git a/drivers/event/sw/sw_evdev_scheduler.c 
b/drivers/event/sw/sw_evdev_scheduler.c
index 809a54d731..8bc21944f5 100644
--- a/drivers/event/sw/sw_evdev_scheduler.c
+++ b/drivers/event/sw/sw_evdev_scheduler.c
@@ -506,7 +506,7 @@ sw_schedule_pull_port_dir(struct sw_evdev *sw, uint32_t 
port_id)
        return pkts_iter;
 }
 
-void
+int32_t
 sw_event_schedule(struct rte_eventdev *dev)
 {
        struct sw_evdev *sw = sw_pmd_priv(dev);
@@ -517,7 +517,7 @@ sw_event_schedule(struct rte_eventdev *dev)
 
        sw->sched_called++;
        if (unlikely(!sw->started))
-               return;
+               return -EAGAIN;
 
        do {
                uint32_t in_pkts_this_iteration = 0;
@@ -610,4 +610,6 @@ sw_event_schedule(struct rte_eventdev *dev)
        sw->sched_last_iter_bitmask = cqs_scheds_last_iter;
        if (unlikely(sw->port_count >= 64))
                sw->sched_last_iter_bitmask = UINT64_MAX;
+
+       return work_done ? 0 : -EAGAIN;
 }
-- 
2.34.1