net/failsafe: improve stats accuracy

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>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>

diff --git a/drivers/net/failsafe/failsafe_ether.c b/drivers/net/failsafe/failsafe_ether.c
index f4db423..0282891 100644 (file)
--- a/drivers/net/failsafe/failsafe_ether.c
+++ b/drivers/net/failsafe/failsafe_ether.c
@@ -312,8 +312,16 @@ fs_dev_remove(struct sub_device *sdev)
 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));
 }