From 7004bf252c53da18f6b55103e0c92f777f846806 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 18 May 2009 00:34:33 +0000 Subject: [PATCH] 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 +++ net/core/dev.c | 23 ++++++++++++++++++++--- 2 files changed, 23 insertions(+), 3 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index cd547d0..f8574e7 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 14dd725..6d3630d 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); -- 2.7.4