[dpdk-dev] [PATCH v3 1/2] net/failsafe: improve stats accuracy

[Matan Azrad <matan@mellanox.com>]

The stats_get API was changed to signal a potential failure to read
stats. Furthermore, some PMDs are able to provide statistics even
after a removal event occurred.

Considering this, the fail-safe can try to access the latest
statistics of a PMD to improve statistics accuracy.

Attempt an ultimate statistics read on removal time; if that
fails, use the latest recorded snapshot.

Signed-off-by: Matan Azrad <matan@mellanox.com>
---
 drivers/net/failsafe/failsafe_ether.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

V2:
Improve commit message.
Add warning massage when using stats snapshot.
Add time report from last snapshot.

V3:
Separate patch.
Replace "cycles" by "timestamp".

diff --git a/drivers/net/failsafe/failsafe_ether.c b/drivers/net/failsafe/failsafe_ether.c
index f4db423..0282891 100644
--- a/drivers/net/failsafe/failsafe_ether.c
+++ b/drivers/net/failsafe/failsafe_ether.c
@@ -312,8 +312,16 @@
 static void
 fs_dev_stats_save(struct sub_device *sdev)
 {
+	struct rte_eth_stats stats;
+	int err;
+
+	/* Attempt to read current stats. */
+	err = rte_eth_stats_get(PORT_ID(sdev), &stats);
+	if (err)
+		WARN("Could not access latest statistics from sub-device %d,"
+			 " using latest snapshot.\n", SUB_ID(sdev));
 	failsafe_stats_increment(&PRIV(sdev->fs_dev)->stats_accumulator,
-			&sdev->stats_snapshot);
+			err ? &sdev->stats_snapshot : &stats);
 	memset(&sdev->stats_snapshot, 0, sizeof(struct rte_eth_stats));
 }
 
-- 
1.8.3.1