On Wed, Jul 29, 2020 at 03:24:49PM +0800, 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.
>
> Cc: Bart Van Assche <bvanassche@xxxxxxx>
> Cc: Mike Snitzer <snitzer@xxxxxxxxxx>
> Fixes: c616cbee97ae ("blk-mq: punt failed direct issue to dispatch list")
> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
> ---
> block/blk-mq.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index c3856377b961..b356d4d3ca0b 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -2016,7 +2016,8 @@ static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
> if (bypass_insert)
> return BLK_STS_RESOURCE;
>
> - blk_mq_request_bypass_insert(rq, false, run_queue);
> + blk_mq_sched_insert_request(rq, false, run_queue, false);
> +
> return BLK_STS_OK;
> }
>
Hello Guys,
Ping...
thanks,
Ming
