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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: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Stephen Hemminger 2008-08-03 21:29:57 -07:00 committed by David S. Miller
parent 283d07ac20
commit 6e583ce524
1 changed files with 16 additions and 7 deletions
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23
net/core/dev.c
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@ -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 @@ out:
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 */