[SCSI] fcoe: reduce contention for fcoe_rx_list lock [v2] (20dc3811) · Commits · 戴 / test

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>

drivers/scsi/fcoe/fcoe.c

+14 −8

Original line number	Diff line number	Diff line
		@@ -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);
		}
		} else
		spin_unlock_bh(&p->fcoe_rx_list.lock);
		fcoe_recv_frame(skb);
		}
		return 0;
		}

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