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authorKen Chen <kenneth.w.chen@intel.com>2005-04-16 15:25:43 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:25:43 -0700
commita299738283a654544c75167d190d9e87b77e5fb7 (patch)
tree653e92ba3b9b19cbfe0d86d64d573eab7886b193 /drivers/block
parent975e046cc06005bafe0c5ce81d55a1b1eb84f5a1 (diff)
[PATCH] use cheaper elv_queue_empty when unplug a device
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>
Diffstat (limited to 'drivers/block')
-rw-r--r--drivers/block/ll_rw_blk.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/drivers/block/ll_rw_blk.c b/drivers/block/ll_rw_blk.c
index 2d6934a0286..46e54b44166 100644
--- a/drivers/block/ll_rw_blk.c
+++ b/drivers/block/ll_rw_blk.c
@@ -1589,7 +1589,8 @@ void blk_run_queue(struct request_queue *q)
spin_lock_irqsave(q->queue_lock, flags);
blk_remove_plug(q);
- q->request_fn(q);
+ if (!elv_queue_empty(q))
+ q->request_fn(q);
spin_unlock_irqrestore(q->queue_lock, flags);
}
EXPORT_SYMBOL(blk_run_queue);