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Commit 20dc3811 authored by Neil Horman's avatar Neil Horman Committed by James Bottomley
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[SCSI] fcoe: reduce contention for fcoe_rx_list lock [v2] 



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: default avatarNeil Horman <nhorman@tuxdriver.com>
Acked-by: default avatarVasu Dev <vasu.dev@intel.com>
Signed-off-by: default avatarRobert Love <robert.w.love@intel.com>
Signed-off-by: default avatarJames Bottomley <JBottomley@Parallels.com>
parent dd060e74

drivers/scsi/fcoe/fcoe.c

+14 −8
Original line number Original line Diff line number Diff line
@@ -1471,7 +1471,7 @@ static int fcoe_rcv(struct sk_buff *skb, struct net_device *netdev, 
	 * in softirq context.

	 * in softirq context.

	 */

	 */

	__skb_queue_tail(&fps->fcoe_rx_list, skb);

	__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);

		wake_up_process(fps->thread);

	spin_unlock(&fps->fcoe_rx_list.lock);

	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 fcoe_percpu_s *p = arg;

	struct sk_buff *skb;

	struct sk_buff *skb;

	struct sk_buff_head tmp;



	skb_queue_head_init(&tmp);





	set_user_nice(current, -20);

	set_user_nice(current, -20);





	while (!kthread_should_stop()) {

	while (!kthread_should_stop()) {





		spin_lock_bh(&p->fcoe_rx_list.lock);

		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);

			set_current_state(TASK_INTERRUPTIBLE);

			spin_unlock_bh(&p->fcoe_rx_list.lock);

			spin_unlock_bh(&p->fcoe_rx_list.lock);

			schedule();

			schedule();

			set_current_state(TASK_RUNNING);

			set_current_state(TASK_RUNNING);

			if (kthread_should_stop())

		} else

				return 0;

			spin_lock_bh(&p->fcoe_rx_list.lock);

		}

			spin_unlock_bh(&p->fcoe_rx_list.lock);

			spin_unlock_bh(&p->fcoe_rx_list.lock);

		fcoe_recv_frame(skb);

	}

	}

	return 0;

	return 0;

}

}