Commit 41852497 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net: batch calls to flush_all_backlogs() 



After commit 145dd5f9 ("net: flush the softnet backlog in process
context"), we can easily batch calls to flush_all_backlogs() for all
devices processed in rollback_registered_many()

Tested:

Before patch, on an idle host.

modprobe dummy numdummies=10000
perf stat -e context-switches -a rmmod dummy

 Performance counter stats for 'system wide':

         1,211,798      context-switches

       1.302137465 seconds time elapsed

After patch:

perf stat -e context-switches -a rmmod dummy

 Performance counter stats for 'system wide':

           225,523      context-switches

       0.721623566 seconds time elapsed

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Acked-by: default avatarHannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ae3cb8cb

net/core/dev.c

+12 −20
Original line number Diff line number Diff line
@@ -4282,18 +4282,11 @@ int netif_receive_skb(struct sk_buff *skb) 
}

EXPORT_SYMBOL(netif_receive_skb);



struct flush_work {

	struct net_device *dev;

	struct work_struct work;

};



DEFINE_PER_CPU(struct flush_work, flush_works);

DEFINE_PER_CPU(struct work_struct, flush_works);



/* Network device is going away, flush any packets still pending */

static void flush_backlog(struct work_struct *work)

{

	struct flush_work *flush = container_of(work, typeof(*flush), work);

	struct net_device *dev = flush->dev;

	struct sk_buff *skb, *tmp;

	struct softnet_data *sd;
@@ -4303,7 +4296,7 @@ static void flush_backlog(struct work_struct *work) 
	local_irq_disable();

	rps_lock(sd);

	skb_queue_walk_safe(&sd->input_pkt_queue, skb, tmp) {

		if (skb->dev == dev) {

		if (skb->dev->reg_state == NETREG_UNREGISTERING) {

			__skb_unlink(skb, &sd->input_pkt_queue);

			kfree_skb(skb);

			input_queue_head_incr(sd);
@@ -4313,7 +4306,7 @@ static void flush_backlog(struct work_struct *work) 
	local_irq_enable();



	skb_queue_walk_safe(&sd->process_queue, skb, tmp) {

		if (skb->dev == dev) {

		if (skb->dev->reg_state == NETREG_UNREGISTERING) {

			__skb_unlink(skb, &sd->process_queue);

			kfree_skb(skb);

			input_queue_head_incr(sd);
@@ -4322,22 +4315,18 @@ static void flush_backlog(struct work_struct *work) 
	local_bh_enable();

}



static void flush_all_backlogs(struct net_device *dev)

static void flush_all_backlogs(void)

{

	unsigned int cpu;



	get_online_cpus();



	for_each_online_cpu(cpu) {

		struct flush_work *flush = per_cpu_ptr(&flush_works, cpu);



		INIT_WORK(&flush->work, flush_backlog);

		flush->dev = dev;

		queue_work_on(cpu, system_highpri_wq, &flush->work);

	}

	for_each_online_cpu(cpu)

		queue_work_on(cpu, system_highpri_wq,

			      per_cpu_ptr(&flush_works, cpu));



	for_each_online_cpu(cpu)

		flush_work(&per_cpu_ptr(&flush_works, cpu)->work);

		flush_work(per_cpu_ptr(&flush_works, cpu));



	put_online_cpus();

}
@@ -6725,8 +6714,8 @@ static void rollback_registered_many(struct list_head *head) 
		unlist_netdevice(dev);



		dev->reg_state = NETREG_UNREGISTERING;

		flush_all_backlogs(dev);

	}

	flush_all_backlogs();



	synchronize_net();
@@ -8291,8 +8280,11 @@ static int __init net_dev_init(void) 
	 */



	for_each_possible_cpu(i) {

		struct work_struct *flush = per_cpu_ptr(&flush_works, i);

		struct softnet_data *sd = &per_cpu(softnet_data, i);



		INIT_WORK(flush, flush_backlog);



		skb_queue_head_init(&sd->input_pkt_queue);

		skb_queue_head_init(&sd->process_queue);

		INIT_LIST_HEAD(&sd->poll_list);

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