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[SCSI] fcoe: reduce contention for fcoe_rx_list lock [v2]

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There is potentially lots of contention for the rx_list_lock.  On a cpu that is
receiving lots of fcoe traffic, the softirq context has to add and release the
lock for every frame it receives, as does the receiving per-cpu thread.  We can
reduce this contention somewhat by altering the per-cpu threads loop such that
when traffic is detected on the fcoe_rx_list, we splice it to a temporary list.
In this way, we can process multiple skbs while only having to acquire and
release the fcoe_rx_list lock once.

[ Braces around single statement while loop removed by Robert Love
  to satisfy checkpath.pl. ]

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Vasu Dev <vasu.dev@intel.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
This commit is contained in:
Neil Horman 2012-03-09 14:50:24 -08:00 committed by James Bottomley
parent dd060e74fb
commit 20dc3811a2
1 changed files with 14 additions and 8 deletions
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22
drivers/scsi/fcoe/fcoe.c
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@ -1471,7 +1471,7 @@ static int fcoe_rcv(struct sk_buff *skb, struct net_device *netdev,
* in softirq context.
*/
__skb_queue_tail(&fps->fcoe_rx_list, skb);
if (fps->fcoe_rx_list.qlen == 1)
if (fps->thread->state == TASK_INTERRUPTIBLE)
wake_up_process(fps->thread);
spin_unlock(&fps->fcoe_rx_list.lock);
@ -1790,23 +1790,29 @@ static int fcoe_percpu_receive_thread(void *arg)
{
struct fcoe_percpu_s *p = arg;
struct sk_buff *skb;
struct sk_buff_head tmp;
skb_queue_head_init(&tmp);
set_user_nice(current, -20);
while (!kthread_should_stop()) {
spin_lock_bh(&p->fcoe_rx_list.lock);
while ((skb = __skb_dequeue(&p->fcoe_rx_list)) == NULL) {
skb_queue_splice_init(&p->fcoe_rx_list, &tmp);
spin_unlock_bh(&p->fcoe_rx_list.lock);
while ((skb = __skb_dequeue(&tmp)) != NULL)
fcoe_recv_frame(skb);
spin_lock_bh(&p->fcoe_rx_list.lock);
if (!skb_queue_len(&p->fcoe_rx_list)) {
set_current_state(TASK_INTERRUPTIBLE);
spin_unlock_bh(&p->fcoe_rx_list.lock);
schedule();
set_current_state(TASK_RUNNING);
if (kthread_should_stop())
return 0;
spin_lock_bh(&p->fcoe_rx_list.lock);
}
spin_unlock_bh(&p->fcoe_rx_list.lock);
fcoe_recv_frame(skb);
} else
spin_unlock_bh(&p->fcoe_rx_list.lock);
}
return 0;
}