ixgbe: Fix TX stats accounting
Here is an updated version, because ixgbe_get_ethtool_stats()
needs to call dev_get_stats() or "ethtool -S" wont give
correct tx_bytes/tx_packets values.
Several cpus can update netdev->stats.tx_bytes & netdev->stats.tx_packets
in parallel. In this case, TX stats are under estimated and false sharing
takes place.
After a pktgen session sending exactly 200000000 packets :
# ifconfig fiber0 | grep TX
TX packets:198501982 errors:0 dropped:0 overruns:0 carrier:0
Multi queue devices should instead use txq->tx_bytes & txq->tx_packets
in their xmit() method (appropriate txq lock already held by caller, no
cache line miss), or use appropriate locking.
After patch, same pktgen session gives :
# ifconfig fiber0 | grep TX
TX packets:200000000 errors:0 dropped:0 overruns:0 carrier:0
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ixgbe/ixgbe_ethtool.c b/drivers/net/ixgbe/ixgbe_ethtool.c
index 06a9d18..0bd49d3 100644
--- a/drivers/net/ixgbe/ixgbe_ethtool.c
+++ b/drivers/net/ixgbe/ixgbe_ethtool.c
@@ -990,6 +990,7 @@
char *p = NULL;
ixgbe_update_stats(adapter);
+ dev_get_stats(netdev);
for (i = 0; i < IXGBE_GLOBAL_STATS_LEN; i++) {
switch (ixgbe_gstrings_stats[i].type) {
case NETDEV_STATS: