From 7004bf252c53da18f6b55103e0c92f777f846806 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 18 May 2009 00:34:33 +0000 Subject: 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 Signed-off-by: David S. Miller --- include/linux/netdevice.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'include/linux') diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index cd547d04a8ce..f8574e76b743 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; -- cgit v1.2.3-59-g8ed1b