On Tue, May 05, 2015 at 07:49:55PM +0800, Ming Lei wrote:
...
> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> index 3dc1598..1bee523 100644
> --- a/drivers/block/loop.c
> +++ b/drivers/block/loop.c
> @@ -725,7 +725,7 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
> goto out_putf;
> error = -ENOMEM;
> lo->wq = alloc_workqueue("kloopd%d",
> - WQ_MEM_RECLAIM | WQ_HIGHPRI | WQ_UNBOUND, 0,
> + WQ_MEM_RECLAIM | WQ_HIGHPRI | WQ_UNBOUND, 16,
It's a bit weird to hard code this to 16 as this effectively becomes a
hidden bottleneck for concurrency. For cases where 16 isn't a good
value, hunting down what's going on can be painful as it's not visible
anywhere. I still think the right knob to control concurrency is
nr_requests for the loop device. You said that for linear IOs, it's
better to have higher nr_requests than concurrency but can you
elaborate why?
Thanks.
--
tejun
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