On 8/18/20 2:07 AM, Ming Lei wrote:
> c616cbee97ae ("blk-mq: punt failed direct issue to dispatch list") supposed
> to add request which has been through ->queue_rq() to the hw queue dispatch
> list, however it adds request running out of budget or driver tag to hw queue
> too. This way basically bypasses request merge, and causes too many request
> dispatched to LLD, and system% is unnecessary increased.
>
> Fixes this issue by adding request not through ->queue_rq into sw/scheduler
> queue, and this way is safe because no ->queue_rq is called on this request
> yet.
>
> High %system can be observed on Azure storvsc device, and even soft lock
> is observed. This patch reduces %system during heavy sequential IO,
> meantime decreases soft lockup risk.
Applied, thanks Ming.
--
Jens Axboe
