Files
linux/include
Eric Dumazet 7004bf252c 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>
2009-05-18 15:15:06 -07:00
..
2009-04-10 21:36:18 +02:00
2009-05-17 21:04:08 -07:00