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[SCSI] fcoe: Cleanup locking on fcoe_percpu_receive_thread

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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>
This commit is contained in:
Neil Horman 2012-07-06 10:40:05 -07:00 committed by James Bottomley
parent 902a45af5c
commit 95fdd5e980
1 changed files with 10 additions and 8 deletions
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18
drivers/scsi/fcoe/fcoe.c
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@ -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);
if (!skb_queue_len(&tmp)) {
set_current_state(TASK_INTERRUPTIBLE);
spin_unlock_bh(&p->fcoe_rx_list.lock);
schedule();
set_current_state(TASK_RUNNING);
goto retry;
}
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);
} else
spin_unlock_bh(&p->fcoe_rx_list.lock);
}
return 0;
}