Re: [PATCH v2 5/5] block/null_blk: add queue_rqs() support

Ming Lei
2023-09-22T08:55:52Z

On Wed, Sep 13, 2023 at 03:16:16PM +0000, chengming.zhou@linux.dev wrote:
> From: Chengming Zhou <zhouchengming@bytedance.com>
>
> Add batched mq_ops.queue_rqs() support in null_blk for testing. The
> implementation is much easy since null_blk doesn't have commit_rqs().
>
> We simply handle each request one by one, if errors are encountered,
> leave them in the passed in list and return back.
>
> There is about 3.6% improvement in IOPS of fio/t/io_uring on null_blk
> with hw_queue_depth=256 on my test VM, from 1.09M to 1.13M.

I guess you pass 'shared_tags' to null_blk for the verification?

>
> Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
> ---
> drivers/block/null_blk/main.c | 20 ++++++++++++++++++++
> 1 file changed, 20 insertions(+)
>
> diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
> index 968090935eb2..79d6cd3c3d41 100644
> --- a/drivers/block/null_blk/main.c
> +++ b/drivers/block/null_blk/main.c
> @@ -1750,6 +1750,25 @@ static blk_status_t null_queue_rq(struct blk_mq_hw_ctx *hctx,
> return null_handle_cmd(cmd, sector, nr_sectors, req_op(rq));
> }
>
> +static void null_queue_rqs(struct request **rqlist)
> +{
> + struct request *requeue_list = NULL;
> + struct request **requeue_lastp = &requeue_list;
> + struct blk_mq_queue_data bd = { };
> + blk_status_t ret;
> +
> + do {
> + struct request *rq = rq_list_pop(rqlist);
> +
> + bd.rq = rq;
> + ret = null_queue_rq(rq->mq_hctx, &bd);
> + if (ret != BLK_STS_OK)
> + rq_list_add_tail(&requeue_lastp, rq);
> + } while (!rq_list_empty(*rqlist));
> +
> + *rqlist = requeue_list;
> +}
> +

null_blk may not be one perfect example for showing queue_rqs()
which is usually for handling request in batch, but for test or
demo purpose, it is fine:

Reviewed-by: Ming Lei <ming.lei@redhat.com>

Thanks
Ming