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ixgbe: Fix TX stats accounting

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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>
This commit is contained in:
Eric Dumazet
2009-12-08 07:22:03 +00:00
committed by David S. Miller
parent 3421eecdee
commit 60d5113428
2 changed files with 5 additions and 16 deletions
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1
drivers/net/ixgbe/ixgbe_ethtool.c
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@@ -990,6 +990,7 @@ static void ixgbe_get_ethtool_stats(struct net_device *netdev,
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: