Re: [PATCH 1/2] block: add blk_time_get_ns() helper

[Yu Kuai <yukuai1@xxxxxxxxxxxxxxx>]

Hi,

在 2024/01/16 5:53, Jens Axboe 写道:
>   
> @@ -2810,7 +2810,7 @@ static void ioc_rqos_done(struct rq_qos *rqos, struct request *rq)
>   		return;
>   	}
>   
> -	on_q_ns = ktime_get_ns() - rq->alloc_time_ns;
> +	on_q_ns = blk_time_get_ns() - rq->alloc_time_ns;

Just notice that this is from io completion path, and the same as
blk_account_io_done(), where plug does not exist. Hence ktime_get_ns()
will still be called multiple times after patch 2.

Do you think will this worth to be optimized? For example, add a new
field in request so that each rq completion will only call
ktime_get_ns() once. Furthermore, we can optimize io_tices precision
from jiffies to ns.

Thanks,
Kuai