[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 <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>
diff --git a/drivers/scsi/fcoe/fcoe.c b/drivers/scsi/fcoe/fcoe.c
index d86ca37..58c88b0 100644
--- a/drivers/scsi/fcoe/fcoe.c
+++ b/drivers/scsi/fcoe/fcoe.c
@@ -1471,7 +1471,7 @@
* 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 @@
{
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;
}