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>
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index c04ca24..40d4c20 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1388,6 +1388,7 @@
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 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
}
diff --git a/net/core/dev.c b/net/core/dev.c
index 3d31491..100dcbd 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2408,12 +2408,13 @@
__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 @@
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 @@
}
#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 @@
/* 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 @@
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;