From: Ken Chen <[email protected]>
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 <[email protected]>
Signed-off-by: Ken Chen <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---
25-akpm/drivers/block/ll_rw_blk.c | 3 ++-
1 files changed, 2 insertions(+), 1 deletion(-)
diff -puN drivers/block/ll_rw_blk.c~use-cheaper-elv_queue_empty-when-unplug-a-device drivers/block/ll_rw_blk.c
--- 25/drivers/block/ll_rw_blk.c~use-cheaper-elv_queue_empty-when-unplug-a-device 2005-04-12 03:21:34.394908080 -0700
+++ 25-akpm/drivers/block/ll_rw_blk.c 2005-04-12 03:21:34.399907320 -0700
@@ -1589,7 +1589,8 @@ void blk_run_queue(struct request_queue
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);
_
-
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