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Message-Id: <1272010378-2955-1-git-send-email-xiaosuo@gmail.com>
Date: Fri, 23 Apr 2010 16:12:58 +0800
From: Changli Gao <xiaosuo@...il.com>
To: "David S. Miller" <davem@...emloft.net>
Cc: jamal <hadi@...erus.ca>, Tom Herbert <therbert@...gle.com>,
Eric Dumazet <eric.dumazet@...il.com>,
Stephen Hemminger <shemminger@...tta.com>,
netdev@...r.kernel.org, Changli Gao <xiaosuo@...il.com>
Subject: [PATCH v6] net: batch skb dequeueing from softnet input_pkt_queue
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@...il.com>
----
include/linux/netdevice.h | 6 +++--
net/core/dev.c | 50 +++++++++++++++++++++++++++++++---------------
2 files changed, 38 insertions(+), 18 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 3c5ed5f..6ae9f2b 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1387,6 +1387,7 @@ struct softnet_data {
struct Qdisc *output_queue;
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;
@@ -1401,10 +1402,11 @@ 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
}
diff --git a/net/core/dev.c b/net/core/dev.c
index a4a7c36..c1585f9 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2409,12 +2409,13 @@ 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 +3295,30 @@ static int process_backlog(struct napi_struct *napi, int quota)
}
#endif
napi->weight = weight_p;
- do {
+ local_irq_disable();
+ while (1) {
struct sk_buff *skb;
- local_irq_disable();
+ while ((skb = __skb_dequeue(&sd->process_queue))) {
+ local_irq_enable();
+ __netif_receive_skb(skb);
+ if (++work >= quota)
+ return work;
+ local_irq_disable();
+ }
+
rps_lock(sd);
- skb = __skb_dequeue(&sd->input_pkt_queue);
- if (!skb) {
+ input_queue_head_add(sd, skb_queue_len(&sd->input_pkt_queue));
+ skb_queue_splice_tail_init(&sd->input_pkt_queue,
+ &sd->process_queue);
+ if (skb_queue_empty(&sd->process_queue)) {
__napi_complete(napi);
rps_unlock(sd);
- local_irq_enable();
break;
}
- input_queue_head_incr(sd);
rps_unlock(sd);
- local_irq_enable();
-
- __netif_receive_skb(skb);
- } while (++work < quota);
+ }
+ local_irq_enable();
return work;
}
@@ -5631,8 +5646,10 @@ 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;
}
@@ -5851,6 +5868,7 @@ 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);
--
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