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[PATCH] use cheaper elv_queue_empty when unplug a device

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In function __generic_unplug_device(), kernel can use a cheaper function
elv_queue_empty() instead of more expensive elv_next_request to find
whether the queue is empty or not.  blk_run_queue can also made conditional
on whether queue's emptiness before calling request_fn().

Signed-off-by: Jens Axboe <axboe@suse.de>
Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Ken Chen 2005-04-16 15:25:43 -07:00 • committed by Linus Torvalds
parent 975e046cc0
commit a299738283
1 changed files with 2 additions and 1 deletions
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drivers/block/ll_rw_blk.c
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@ -1589,6 +1589,7 @@ void blk_run_queue(struct request_queue *q)
spin_lock_irqsave(q->queue_lock, flags); spin_lock_irqsave(q->queue_lock, flags);
blk_remove_plug(q); blk_remove_plug(q);
if (!elv_queue_empty(q))
q->request_fn(q); q->request_fn(q);
spin_unlock_irqrestore(q->queue_lock, flags); spin_unlock_irqrestore(q->queue_lock, flags);
} }