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Commit 6e583ce5 authored by Stephen Hemminger's avatar Stephen Hemminger Committed by David S. Miller
Browse files

net: eliminate refcounting in backlog queue 



Avoid the overhead of atomic increment/decrement on each received packet.
This helps performance of non-NAPI devices (like loopback).
Use cleanup function to walk queue on each cpu and clean out any
left over packets.

Signed-off-by: default avatarStephen Hemminger <shemminger@vyatta.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 283d07ac

net/core/dev.c

+16 −7
Original line number Diff line number Diff line
@@ -1909,7 +1909,6 @@ int netif_rx(struct sk_buff *skb) 
	if (queue->input_pkt_queue.qlen <= netdev_max_backlog) {

		if (queue->input_pkt_queue.qlen) {

enqueue:

			dev_hold(skb->dev);

			__skb_queue_tail(&queue->input_pkt_queue, skb);

			local_irq_restore(flags);

			return NET_RX_SUCCESS;
@@ -2270,6 +2269,20 @@ int netif_receive_skb(struct sk_buff *skb) 
	return ret;

}



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

static void flush_backlog(void *arg)

{

	struct net_device *dev = arg;

	struct softnet_data *queue = &__get_cpu_var(softnet_data);

	struct sk_buff *skb, *tmp;



	skb_queue_walk_safe(&queue->input_pkt_queue, skb, tmp)

		if (skb->dev == dev) {

			__skb_unlink(skb, &queue->input_pkt_queue);

			kfree_skb(skb);

		}

}



static int process_backlog(struct napi_struct *napi, int quota)

{

	int work = 0;
@@ -2279,7 +2292,6 @@ static int process_backlog(struct napi_struct *napi, int quota) 
	napi->weight = weight_p;

	do {

		struct sk_buff *skb;

		struct net_device *dev;



		local_irq_disable();

		skb = __skb_dequeue(&queue->input_pkt_queue);
@@ -2288,14 +2300,9 @@ static int process_backlog(struct napi_struct *napi, int quota) 
			local_irq_enable();

			break;

		}



		local_irq_enable();



		dev = skb->dev;



		netif_receive_skb(skb);



		dev_put(dev);

	} while (++work < quota && jiffies == start_time);



	return work;
@@ -4169,6 +4176,8 @@ void netdev_run_todo(void) 


		dev->reg_state = NETREG_UNREGISTERED;



		on_each_cpu(flush_backlog, dev, 1);



		netdev_wait_allrefs(dev);



		/* paranoia */