From 95fdd5e980e6eea4579c15043f7a9be6ad63012c Mon Sep 17 00:00:00 2001
From: Neil Horman <nhorman@tuxdriver.com>
Date: Fri, 6 Jul 2012 10:40:05 -0700
Subject: [PATCH] [SCSI] fcoe: Cleanup locking on fcoe_percpu_receive_thread
Noticed that we can shuffle the code around in fcoe_percpu_receive_thread a bit
and avoid taking the fcoe_rx_list lock twice per iteration. This should improve
throughput somewhat. With this change we take the lock, and check for new
frames in a single critical section. Only if the list is empty do we drop the
lock and re-acquire it after being signaled to wake up.
Change Notes:
v2) did some further cleanup on the patch by replacing the 2nd call of
spin_lock/splice_init with a goto to the top of the outer loop. This allows me
to change the inner while loop to an if conditional and remove the sencond check
of kthread_should_stop. Based on suggestion from Vasu Dev.
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 | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)
diff --git a/drivers/scsi/fcoe/fcoe.c b/drivers/scsi/fcoe/fcoe.c
index 2b065d26a5ae21..078d262ac7ccf5 100644
--- a/drivers/scsi/fcoe/fcoe.c
+++ b/drivers/scsi/fcoe/fcoe.c
@@ -1851,23 +1851,25 @@ static int fcoe_percpu_receive_thread(void *arg)
set_user_nice(current, -20);
+retry:
while (!kthread_should_stop()) {
spin_lock_bh(&p->fcoe_rx_list.lock);
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)) {
+ if (!skb_queue_len(&tmp)) {
set_current_state(TASK_INTERRUPTIBLE);
spin_unlock_bh(&p->fcoe_rx_list.lock);
schedule();
set_current_state(TASK_RUNNING);
- } else
- spin_unlock_bh(&p->fcoe_rx_list.lock);
+ goto retry;
+ }
+
+ spin_unlock_bh(&p->fcoe_rx_list.lock);
+
+ while ((skb = __skb_dequeue(&tmp)) != NULL)
+ fcoe_recv_frame(skb);
+
}
return 0;
}
--
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