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

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Date: Thu, 8 Feb 2024 10:49:51 -0700
From: Jens Axboe <axboe@...nel.dk>
To: "zhaoyang.huang" <zhaoyang.huang@...soc.com>,
 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 2:31 AM, 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"
>  
>  #include <trace/events/block.h>
>  
> @@ -802,6 +803,7 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
>  	u8 ioprio_class = IOPRIO_PRIO_CLASS(ioprio);
>  	struct dd_per_prio *per_prio;
>  	enum dd_prio prio;
> +	int fifo_expire;
>  
>  	lockdep_assert_held(&dd->lock);
>  
> @@ -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
>  		/*

Hard pass on this blatant layering violation. Just like the priority
changes, this utterly fails to understand how things are properly
designed.

-- 
Jens Axboe