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linux-sg2042
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rps: keep the old behavior on SMP without rps 

keep the old behavior on SMP without rps

RPS introduces a lock operation to per cpu variable input_pkt_queue on
SMP whenever rps is enabled or not. On SMP without RPS, this lock isn't
needed at all.

Signed-off-by: Changli Gao <xiaosuo@gmail.com>
----
net/core/dev.c | 42 ++++++++++++++++++++++++++++--------------
1 file changed, 28 insertions(+), 14 deletions(-)
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Changli Gao 2010-03-30 20:16:22 +00:00 committed by David S. Miller
parent 630b943c18
commit 152102c7f2
1 changed files with 28 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

42
net/core/dev.c
View File

@ -206,6 +206,20 @@ static inline struct hlist_head *dev_index_hash(struct net *net, int ifindex)
return &net->dev_index_head[ifindex & (NETDEV_HASHENTRIES - 1)];
}
static inline void rps_lock(struct softnet_data *queue)
{
#ifdef CONFIG_RPS
spin_lock(&queue->input_pkt_queue.lock);
#endif
}
static inline void rps_unlock(struct softnet_data *queue)
{
#ifdef CONFIG_RPS
spin_unlock(&queue->input_pkt_queue.lock);
#endif
}
/* Device list insertion */
static int list_netdevice(struct net_device *dev)
{
@ -2313,13 +2327,13 @@ static int enqueue_to_backlog(struct sk_buff *skb, int cpu)
local_irq_save(flags);
__get_cpu_var(netdev_rx_stat).total++;
spin_lock(&queue->input_pkt_queue.lock);
rps_lock(queue);
if (queue->input_pkt_queue.qlen <= netdev_max_backlog) {
if (queue->input_pkt_queue.qlen) {
enqueue:
__skb_queue_tail(&queue->input_pkt_queue, skb);
spin_unlock_irqrestore(&queue->input_pkt_queue.lock,
flags);
rps_unlock(queue);
local_irq_restore(flags);
return NET_RX_SUCCESS;
}
@ -2341,7 +2355,7 @@ enqueue:
goto enqueue;
}
spin_unlock(&queue->input_pkt_queue.lock);
rps_unlock(queue);
__get_cpu_var(netdev_rx_stat).dropped++;
local_irq_restore(flags);
@ -2766,19 +2780,19 @@ int netif_receive_skb(struct sk_buff *skb)
EXPORT_SYMBOL(netif_receive_skb);
/* Network device is going away, flush any packets still pending */
static void flush_backlog(struct net_device *dev, int cpu)
static void flush_backlog(void *arg)
{
struct softnet_data *queue = &per_cpu(softnet_data, cpu);
struct net_device *dev = arg;
struct softnet_data *queue = &__get_cpu_var(softnet_data);
struct sk_buff *skb, *tmp;
unsigned long flags;
spin_lock_irqsave(&queue->input_pkt_queue.lock, flags);
rps_lock(queue);
skb_queue_walk_safe(&queue->input_pkt_queue, skb, tmp)
if (skb->dev == dev) {
__skb_unlink(skb, &queue->input_pkt_queue);
kfree_skb(skb);
}
spin_unlock_irqrestore(&queue->input_pkt_queue.lock, flags);
rps_unlock(queue);
}
static int napi_gro_complete(struct sk_buff *skb)
@ -3091,14 +3105,16 @@ static int process_backlog(struct napi_struct *napi, int quota)
do {
struct sk_buff *skb;
spin_lock_irq(&queue->input_pkt_queue.lock);
local_irq_disable();
rps_lock(queue);
skb = __skb_dequeue(&queue->input_pkt_queue);
if (!skb) {
__napi_complete(napi);
spin_unlock_irq(&queue->input_pkt_queue.lock);
break;
}
spin_unlock_irq(&queue->input_pkt_queue.lock);
rps_unlock(queue);
local_irq_enable();
__netif_receive_skb(skb);
} while (++work < quota && jiffies == start_time);
@ -5548,7 +5564,6 @@ void netdev_run_todo(void)
while (!list_empty(&list)) {
struct net_device *dev
= list_first_entry(&list, struct net_device, todo_list);
int i;
list_del(&dev->todo_list);
if (unlikely(dev->reg_state != NETREG_UNREGISTERING)) {
@ -5560,8 +5575,7 @@ void netdev_run_todo(void)
dev->reg_state = NETREG_UNREGISTERED;
for_each_online_cpu(i)
flush_backlog(dev, i);
on_each_cpu(flush_backlog, dev, 1);
netdev_wait_allrefs(dev);