[dpdk-dev] [PATCH] eventdev: add timestamping to received packets

[Nikhil Rao]

Add timestamp to received packets before enqueuing to
event device if the timestamp is not already set. Adding
timestamp in the Rx adapter avoids additional latency due
to the event device.

Signed-off-by: Nikhil Rao <nikhil.rao at intel.com>
---
 lib/librte_eventdev/rte_event_eth_rx_adapter.h      |  6 +++++-
 lib/librte_eventdev/rte_event_eth_rx_adapter.c      | 12 +++++++++++-
 doc/guides/prog_guide/event_ethernet_rx_adapter.rst |  6 +++++-
 3 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/lib/librte_eventdev/rte_event_eth_rx_adapter.h b/lib/librte_eventdev/rte_event_eth_rx_adapter.h
index c20507b..fc9da14 100644
--- a/lib/librte_eventdev/rte_event_eth_rx_adapter.h
+++ b/lib/librte_eventdev/rte_event_eth_rx_adapter.h
@@ -47,7 +47,11 @@
  *
  * The adapter uses a EAL service core function for SW based packet transfer
  * and uses the eventdev PMD functions to configure HW based packet transfer
- * between the ethernet device and the event device.
+ * between the ethernet device and the event device. For SW based packet
+ * transfer, if the mbuf does not have a timestamp set, the adapter adds a
+ * timestamp to the mbuf using rte_get_tsc_cycles(), this provides a more
+ * accurate timestamp as compared to if the application were to set the time
+ * stamp since it avoids event device schedule latency.
  *
  * The ethernet Rx event adapter's functions are:
  *  - rte_event_eth_rx_adapter_create_ext()
diff --git a/lib/librte_eventdev/rte_event_eth_rx_adapter.c b/lib/librte_eventdev/rte_event_eth_rx_adapter.c
index 9aece9f..9cda960 100644
--- a/lib/librte_eventdev/rte_event_eth_rx_adapter.c
+++ b/lib/librte_eventdev/rte_event_eth_rx_adapter.c
@@ -434,11 +434,22 @@ static uint16_t gcd_u16(uint16_t a, uint16_t b)
 	uint32_t rss_mask;
 	uint32_t rss;
 	int do_rss;
+	uint64_t ts;
 
 	/* 0xffff ffff if PKT_RX_RSS_HASH is set, otherwise 0 */
 	rss_mask = ~(((m->ol_flags & PKT_RX_RSS_HASH) != 0) - 1);
 	do_rss = !rss_mask && !eth_rx_queue_info->flow_id_mask;
 
+	if ((m->ol_flags & PKT_RX_TIMESTAMP) == 0) {
+		ts = rte_get_tsc_cycles();
+		for (i = 0; i < num; i++) {
+			m = mbufs[i];
+
+			m->timestamp = ts;
+			m->ol_flags |= PKT_RX_TIMESTAMP;
+		}
+	}
+
 	for (i = 0; i < num; i++) {
 		m = mbufs[i];
 		struct rte_event *ev = &events[i];
@@ -449,7 +460,6 @@ static uint16_t gcd_u16(uint16_t a, uint16_t b)
 		    eth_rx_queue_info->flow_id &
 				eth_rx_queue_info->flow_id_mask;
 		flow_id |= rss & ~eth_rx_queue_info->flow_id_mask;
-
 		ev->flow_id = flow_id;
 		ev->op = RTE_EVENT_OP_NEW;
 		ev->sched_type = sched_type;
diff --git a/doc/guides/prog_guide/event_ethernet_rx_adapter.rst b/doc/guides/prog_guide/event_ethernet_rx_adapter.rst
index 4ab87a3..319e4f0 100644
--- a/doc/guides/prog_guide/event_ethernet_rx_adapter.rst
+++ b/doc/guides/prog_guide/event_ethernet_rx_adapter.rst
@@ -12,7 +12,11 @@ be supported in hardware or require a software thread to receive packets from
 the ethdev port using ethdev poll mode APIs and enqueue these as events to the
 event device using the eventdev API. Both transfer mechanisms may be present on
 the same platform depending on the particular combination of the ethdev and
-the event device.
+the event device. For SW based packet transfer, if the mbuf does not have a
+timestamp set, the adapter adds a timestamp to the mbuf using
+rte_get_tsc_cycles(), this provides a more accurate timestamp as compared to
+if the application were to set the timestamp since it avoids event device
+schedule latency.
 
 The Event Ethernet Rx Adapter library is intended for the application code to
 configure both transfer mechanisms using a common API. A capability API allows
-- 
1.8.3.1