Re: [PATCH] block: limit request dispatch loop duration

[Jens Axboe <axboe@xxxxxxxxx>]

On 3/16/22 12:11 AM, Shin'ichiro Kawasaki wrote:
> diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
> index 55488ba97823..64941615befc 100644
> --- a/block/blk-mq-sched.c
> +++ b/block/blk-mq-sched.c
> @@ -181,9 +181,15 @@ static int __blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx)
>  static int blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx)
>  {
>  	int ret;
> +	unsigned long end = jiffies + HZ;
>  
>  	do {
>  		ret = __blk_mq_do_dispatch_sched(hctx);
> +		if (ret == 1 &&
> +		    (need_resched() || time_is_after_jiffies(end))) {
> +			blk_mq_delay_run_hw_queue(hctx, 0);
> +			break;
> +		}
>  	} while (ret == 1);
>  
>  	return ret;

I think it'd look cleaner as:

static int blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx)
{
	unsigned long end = jiffies + HZ;
	int ret;

	do {
		ret = __blk_mq_do_dispatch_sched(hctx);
		if (ret != 1)
			break;
		if (need_resched() || time_is_after_jiffies(end)) {
			blk_mq_delay_run_hw_queue(hctx, 0);
			break;
		}
	} while (1);

	return ret;
}

-- 
Jens Axboe