linux-kernel - Re: [PATCH 3/3] block: introducing a bias over deadline's fifo

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Message-ID: <5f934ebf-4e2a-44f9-993f-8b2c8d358370@acm.org>
Date: Thu, 8 Feb 2024 09:46:06 -0800
From: Bart Van Assche <bvanassche@....org>
To: "zhaoyang.huang" <zhaoyang.huang@...soc.com>, Jens Axboe
 <axboe@...nel.dk>, Peter Zijlstra <peterz@...radead.org>,
 Ingo Molnar <mingo@...hat.com>, Juri Lelli <juri.lelli@...hat.com>,
 Vincent Guittot <vincent.guittot@...aro.org>, Yu Zhao <yuzhao@...gle.com>,
 linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
 Zhaoyang Huang <huangzhaoyang@...il.com>, steve.kang@...soc.com
Subject: Re: [PATCH 3/3] block: introducing a bias over deadline's fifo_time

On 2/8/24 01:31, zhaoyang.huang wrote:
> diff --git a/block/mq-deadline.c b/block/mq-deadline.c
> index f958e79277b8..43c08c3d6f18 100644
> --- a/block/mq-deadline.c
> +++ b/block/mq-deadline.c
> @@ -15,6 +15,7 @@
>   #include <linux/compiler.h>
>   #include <linux/rbtree.h>
>   #include <linux/sbitmap.h>
> +#include "../kernel/sched/sched.h"

Is kernel/sched/sched.h perhaps a private scheduler kernel header file? Shouldn't
block layer code only include public scheduler header files?

> @@ -840,7 +842,9 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
>   		/*
>   		 * set expire time and add to fifo list
>   		 */
> -		rq->fifo_time = jiffies + dd->fifo_expire[data_dir];
> +		fifo_expire = task_is_realtime(current) ? dd->fifo_expire[data_dir] :
> +			CFS_PROPORTION(current, dd->fifo_expire[data_dir]);
> +		rq->fifo_time = jiffies + fifo_expire;
>   		insert_before = &per_prio->fifo_list[data_dir];
>   #ifdef CONFIG_BLK_DEV_ZONED
>   		/*

Making the mq-deadline request expiry time dependent on the task priority seems wrong
to me.

Thanks,

Bart.