block: move queue run on unplug to kblockd
There are worries that we are now consuming a lot more stack in
some cases, since we potentially call into IO dispatch from
schedule() or io_schedule(). We can reduce this problem by moving
the running of the queue to kblockd, like the old plugging scheme
did as well.
This may or may not be a good idea from a performance perspective,
depending on how many tasks have queue plugs running at the same
time. For even the slightly contended case, doing just a single
queue run from kblockd instead of multiple runs directly from the
unpluggers will be faster.
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/block/blk-core.c b/block/blk-core.c
index c6eaa1f..36b1a75 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2665,7 +2665,7 @@
static void queue_unplugged(struct request_queue *q, unsigned int depth)
{
trace_block_unplug_io(q, depth);
- __blk_run_queue(q, false);
+ __blk_run_queue(q, true);
if (q->unplugged_fn)
q->unplugged_fn(q);