From 31aa02c53c84658f6694f319f09e232ede27be5a Mon Sep 17 00:00:00 2001 From: Stephen Hemminger Date: Thu, 23 Jun 2005 20:12:48 -0700 Subject: [PATCH] [NET]: Eliminate netif_rx massive packet drops. Eliminate the throttling behaviour when the netif receive queue fills because it behaves badly when using high speed networks under load. The throttling cause multiple packet drops that cause TCP to go into slow start mode. The same effective patch has been part of BIC TCP and H-TCP as well as part of Web100. The existing code drops 100's of packets when the queue fills; this changes it to individual packet drop-tail. Signed-off-by: Stephen Hemmminger Signed-off-by: David S. Miller --- include/linux/netdevice.h | 4 +--- net/core/dev.c | 21 ++------------------- 2 files changed, 3 insertions(+), 22 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 718ad579c65c..3a0ed7f9e801 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -164,7 +164,6 @@ struct netif_rx_stats unsigned total; unsigned dropped; unsigned time_squeeze; - unsigned throttled; unsigned cpu_collision; }; @@ -557,10 +556,9 @@ static inline int unregister_gifconf(unsigned int family) struct softnet_data { - int throttle; + struct net_device *output_queue; struct sk_buff_head input_pkt_queue; struct list_head poll_list; - struct net_device *output_queue; struct sk_buff *completion_queue; struct net_device backlog_dev; /* Sorry. 8) */ diff --git a/net/core/dev.c b/net/core/dev.c index 3156df699f01..1a64508e527f 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -198,7 +198,7 @@ static struct notifier_block *netdev_chain; * Device drivers call our routines to queue packets here. We empty the * queue in the local softnet handler. */ -DEFINE_PER_CPU(struct softnet_data, softnet_data) = { 0, }; +DEFINE_PER_CPU(struct softnet_data, softnet_data) = { NULL }; #ifdef CONFIG_SYSFS extern int netdev_sysfs_init(void); @@ -1372,7 +1372,6 @@ DEFINE_PER_CPU(struct netif_rx_stats, netdev_rx_stat) = { 0, }; int netif_rx(struct sk_buff *skb) { - int this_cpu; struct softnet_data *queue; unsigned long flags; @@ -1388,15 +1387,11 @@ int netif_rx(struct sk_buff *skb) * short when CPU is congested, but is still operating. */ local_irq_save(flags); - this_cpu = smp_processor_id(); queue = &__get_cpu_var(softnet_data); __get_cpu_var(netdev_rx_stat).total++; if (queue->input_pkt_queue.qlen <= netdev_max_backlog) { if (queue->input_pkt_queue.qlen) { - if (queue->throttle) - goto drop; - enqueue: dev_hold(skb->dev); __skb_queue_tail(&queue->input_pkt_queue, skb); @@ -1404,19 +1399,10 @@ int netif_rx(struct sk_buff *skb) return NET_RX_SUCCESS; } - if (queue->throttle) - queue->throttle = 0; - netif_rx_schedule(&queue->backlog_dev); goto enqueue; } - if (!queue->throttle) { - queue->throttle = 1; - __get_cpu_var(netdev_rx_stat).throttled++; - } - -drop: __get_cpu_var(netdev_rx_stat).dropped++; local_irq_restore(flags); @@ -1701,8 +1687,6 @@ static int process_backlog(struct net_device *backlog_dev, int *budget) smp_mb__before_clear_bit(); netif_poll_enable(backlog_dev); - if (queue->throttle) - queue->throttle = 0; local_irq_enable(); return 0; } @@ -1976,7 +1960,7 @@ static int softnet_seq_show(struct seq_file *seq, void *v) struct netif_rx_stats *s = v; seq_printf(seq, "%08x %08x %08x %08x %08x %08x %08x %08x %08x\n", - s->total, s->dropped, s->time_squeeze, s->throttled, + s->total, s->dropped, s->time_squeeze, 0, 0, 0, 0, 0, /* was fastroute */ s->cpu_collision ); return 0; @@ -3220,7 +3204,6 @@ static int __init net_dev_init(void) queue = &per_cpu(softnet_data, i); skb_queue_head_init(&queue->input_pkt_queue); - queue->throttle = 0; queue->completion_queue = NULL; INIT_LIST_HEAD(&queue->poll_list); set_bit(__LINK_STATE_START, &queue->backlog_dev.state);