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authorEric Dumazet <dada1@cosmosbay.com>2009-05-18 00:34:33 +0000
committerDavid S. Miller <davem@davemloft.net>2009-05-18 15:15:06 -0700
commit7004bf252c53da18f6b55103e0c92f777f846806 (patch)
tree29868ce170599fbed3471f53afe3a20f23fb31c3
parentba98898eb3fc07ee54566fcc3626354a44355acb (diff)
net: add tx_packets/tx_bytes/tx_dropped counters in struct netdev_queue
offsetof(struct net_device, features)=0x44 offsetof(struct net_device, stats.tx_packets)=0x54 offsetof(struct net_device, stats.tx_bytes)=0x5c offsetof(struct net_device, stats.tx_dropped)=0x6c Network drivers that touch dev->stats.tx_packets/stats.tx_bytes in their tx path can slow down SMP operations, since they dirty a cache line that should stay shared (dev->features is needed in rx and tx paths) We could move away stats field in net_device but it wont help that much. (Two cache lines dirtied in tx path, we can do one only) Better solution is to add tx_packets/tx_bytes/tx_dropped in struct netdev_queue because this structure is already touched in tx path and counters updates will then be free (no increase in size) Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--include/linux/netdevice.h3
-rw-r--r--net/core/dev.c23
2 files changed, 23 insertions, 3 deletions
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index cd547d04a8c..f8574e76b74 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -474,6 +474,9 @@ struct netdev_queue {
* please use this field instead of dev->trans_start
*/
unsigned long trans_start;
+ unsigned long tx_bytes;
+ unsigned long tx_packets;
+ unsigned long tx_dropped;
} ____cacheline_aligned_in_smp;
diff --git a/net/core/dev.c b/net/core/dev.c
index 14dd725aaab..6d3630d1627 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4943,13 +4943,30 @@ void netdev_run_todo(void)
* the internal statistics structure is used.
*/
const struct net_device_stats *dev_get_stats(struct net_device *dev)
- {
+{
const struct net_device_ops *ops = dev->netdev_ops;
if (ops->ndo_get_stats)
return ops->ndo_get_stats(dev);
- else
- return &dev->stats;
+ else {
+ unsigned long tx_bytes = 0, tx_packets = 0, tx_dropped = 0;
+ struct net_device_stats *stats = &dev->stats;
+ unsigned int i;
+ struct netdev_queue *txq;
+
+ for (i = 0; i < dev->num_tx_queues; i++) {
+ txq = netdev_get_tx_queue(dev, i);
+ tx_bytes += txq->tx_bytes;
+ tx_packets += txq->tx_packets;
+ tx_dropped += txq->tx_dropped;
+ }
+ if (tx_bytes || tx_packets || tx_dropped) {
+ stats->tx_bytes = tx_bytes;
+ stats->tx_packets = tx_packets;
+ stats->tx_dropped = tx_dropped;
+ }
+ return stats;
+ }
}
EXPORT_SYMBOL(dev_get_stats);