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net: batch skb dequeueing from softnet input_pkt_queue 

batch skb dequeueing from softnet input_pkt_queue to reduce potential lock
contention when RPS is enabled.

Note: in the worst case, the number of packets in a softnet_data may
be double of netdev_max_backlog.

Signed-off-by: Changli Gao <xiaosuo@gmail.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Changli Gao 2010-04-27 15:07:33 -07:00 committed by David S. Miller
parent c58dc01bab
commit 6e7676c1a7
2 changed files with 44 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
include/linux/netdevice.h
View File

@ -1388,6 +1388,7 @@ struct softnet_data {
struct Qdisc **output_queue_tailp;
struct list_head poll_list;
struct sk_buff *completion_queue;
struct sk_buff_head process_queue;
#ifdef CONFIG_RPS
struct softnet_data *rps_ipi_list;
@ -1402,10 +1403,11 @@ struct softnet_data {
struct napi_struct backlog;
};
static inline void input_queue_head_incr(struct softnet_data *sd)
static inline void input_queue_head_add(struct softnet_data *sd,
unsigned int len)
{
#ifdef CONFIG_RPS
sd->input_queue_head++;
sd->input_queue_head += len;
#endif
}

59
net/core/dev.c
View File

@ -2408,12 +2408,13 @@ static int enqueue_to_backlog(struct sk_buff *skb, int cpu,
__get_cpu_var(netdev_rx_stat).total++;
rps_lock(sd);
if (sd->input_pkt_queue.qlen <= netdev_max_backlog) {
if (sd->input_pkt_queue.qlen) {
if (skb_queue_len(&sd->input_pkt_queue) <= netdev_max_backlog) {
if (skb_queue_len(&sd->input_pkt_queue)) {
enqueue:
__skb_queue_tail(&sd->input_pkt_queue, skb);
#ifdef CONFIG_RPS
*qtail = sd->input_queue_head + sd->input_pkt_queue.qlen;
*qtail = sd->input_queue_head +
skb_queue_len(&sd->input_pkt_queue);
#endif
rps_unlock(sd);
local_irq_restore(flags);
@ -2934,13 +2935,21 @@ static void flush_backlog(void *arg)
struct sk_buff *skb, *tmp;
rps_lock(sd);
skb_queue_walk_safe(&sd->input_pkt_queue, skb, tmp)
skb_queue_walk_safe(&sd->input_pkt_queue, skb, tmp) {
if (skb->dev == dev) {
__skb_unlink(skb, &sd->input_pkt_queue);
kfree_skb(skb);
input_queue_head_incr(sd);
input_queue_head_add(sd, 1);
}
}
rps_unlock(sd);
skb_queue_walk_safe(&sd->process_queue, skb, tmp) {
if (skb->dev == dev) {
__skb_unlink(skb, &sd->process_queue);
kfree_skb(skb);
}
}
}
static int napi_gro_complete(struct sk_buff *skb)
@ -3286,24 +3295,33 @@ static int process_backlog(struct napi_struct *napi, int quota)
}
#endif
napi->weight = weight_p;
do {
local_irq_disable();
while (work < quota) {
struct sk_buff *skb;
unsigned int qlen;
local_irq_disable();
rps_lock(sd);
skb = __skb_dequeue(&sd->input_pkt_queue);
if (!skb) {
__napi_complete(napi);
rps_unlock(sd);
while ((skb = __skb_dequeue(&sd->process_queue))) {
local_irq_enable();
break;
__netif_receive_skb(skb);
if (++work >= quota)
return work;
local_irq_disable();
}
input_queue_head_incr(sd);
rps_unlock(sd);
local_irq_enable();
__netif_receive_skb(skb);
} while (++work < quota);
rps_lock(sd);
qlen = skb_queue_len(&sd->input_pkt_queue);
if (qlen) {
input_queue_head_add(sd, qlen);
skb_queue_splice_tail_init(&sd->input_pkt_queue,
&sd->process_queue);
}
if (qlen < quota - work) {
__napi_complete(napi);
quota = work + qlen;
}
rps_unlock(sd);
}
local_irq_enable();
return work;
}
@ -5630,8 +5648,10 @@ static int dev_cpu_callback(struct notifier_block *nfb,
/* Process offline CPU's input_pkt_queue */
while ((skb = __skb_dequeue(&oldsd->input_pkt_queue))) {
netif_rx(skb);
input_queue_head_incr(oldsd);
input_queue_head_add(oldsd, 1);
}
while ((skb = __skb_dequeue(&oldsd->process_queue)))
netif_rx(skb);
return NOTIFY_OK;
}
@ -5850,6 +5870,7 @@ static int __init net_dev_init(void)
struct softnet_data *sd = &per_cpu(softnet_data, i);
skb_queue_head_init(&sd->input_pkt_queue);
skb_queue_head_init(&sd->process_queue);
sd->completion_queue = NULL;
INIT_LIST_HEAD(&sd->poll_list);
sd->output_queue = NULL;