From 20dc3811a2adfac65d5974e3b022a85fdbb9e205 Mon Sep 17 00:00:00 2001 From: Neil Horman Date: Fri, 9 Mar 2012 14:50:24 -0800 Subject: [PATCH] [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: Neil Horman Acked-by: Vasu Dev Signed-off-by: Robert Love Signed-off-by: James Bottomley --- drivers/scsi/fcoe/fcoe.c | 22 ++++++++++++++-------- 1 file changed, 14 insertions(+), 8 deletions(-) diff --git a/drivers/scsi/fcoe/fcoe.c b/drivers/scsi/fcoe/fcoe.c index d86ca37b3787..58c88b0e8792 100644 --- a/drivers/scsi/fcoe/fcoe.c +++ b/drivers/scsi/fcoe/fcoe.c @@ -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; }