linux-kernel - Re: [PATCH v2] blk-ioprio: Introduce promote-to-rt policy

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Message-ID: <5ff2b68a-a8fb-7901-2c38-1056a2c59f70@gmail.com>
Date:   Wed, 22 Feb 2023 14:38:01 +0700
From:   Bagas Sanjaya <bagasdotme@...il.com>
To:     Hou Tao <houtao@...weicloud.com>, linux-block@...r.kernel.org
Cc:     Bart Van Assche <bvanassche@....org>, Jan Kara <jack@...e.cz>,
        Jens Axboe <axboe@...nel.dk>, cgroups@...r.kernel.org,
        Tejun Heo <tj@...nel.org>, Zefan Li <lizefan.x@...edance.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Jonathan Corbet <corbet@....net>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, houtao1@...wei.com
Subject: Re: [PATCH v2] blk-ioprio: Introduce promote-to-rt policy

On 2/20/23 20:54, Hou Tao wrote:
> diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
> index 74cec76be9f2..ccfb9fdfbc16 100644
> --- a/Documentation/admin-guide/cgroup-v2.rst
> +++ b/Documentation/admin-guide/cgroup-v2.rst
> @@ -2021,31 +2021,33 @@ that attribute:
>    no-change
>  	Do not modify the I/O priority class.
>  
> -  none-to-rt
> -	For requests that do not have an I/O priority class (NONE),
> -	change the I/O priority class into RT. Do not modify
> -	the I/O priority class of other requests.
> +  promote-to-rt
> +	For requests that have a no-RT I/O priority class, change it into RT.
"non-RT" maybe? Or the original wording is better?
> +	Also change the priority level of these requests to 4. Do not modify
> +	the I/O priority of requests that have priority class RT.>  
>    restrict-to-be
>  	For requests that do not have an I/O priority class or that have I/O
> -	priority class RT, change it into BE. Do not modify the I/O priority
> -	class of requests that have priority class IDLE.
> +	priority class RT, change it into BE. Also change the priority level
> +	of these requests to 0. Do not modify the I/O priority class of
> +	requests that have priority class IDLE.
>  
>    idle
>  	Change the I/O priority class of all requests into IDLE, the lowest
>  	I/O priority class.
>  
> +  none-to-rt
> +	Deprecated. Just an alias for promote-to-rt.
> +
>  The following numerical values are associated with the I/O priority policies:
>  
> -+-------------+---+
> -| no-change   | 0 |
> -+-------------+---+
> -| none-to-rt  | 1 |
> -+-------------+---+
> -| rt-to-be    | 2 |
> -+-------------+---+
> -| all-to-idle | 3 |
> -+-------------+---+
> ++----------------+---+
> +| no-change      | 0 |
> ++----------------+---+
> +| rt-to-be       | 2 |
> ++----------------+---+
> +| all-to-idle    | 3 |
> ++----------------+---+
>  
>  The numerical value that corresponds to each I/O priority class is as follows:
>  
> @@ -2061,9 +2063,13 @@ The numerical value that corresponds to each I/O priority class is as follows:
>  
>  The algorithm to set the I/O priority class for a request is as follows:
>  
> -- Translate the I/O priority class policy into a number.
> -- Change the request I/O priority class into the maximum of the I/O priority
> -  class policy number and the numerical I/O priority class.
> +- If I/O priority class policy is promote-to-rt, change the request I/O
> +  priority class to IOPRIO_CLASS_RT and change the request I/O priority
> +  level to 4.
> +- If I/O priorityt class is not promote-to-rt, translate the I/O priority
> +  class policy into a number, then change the request I/O priority class
> +  into the maximum of the I/O priority class policy number and the numerical
> +  I/O priority class.
>  
>  PID
>  ---

The rest is LGTM.

-- 
An old man doll... just what I always wanted! - Clara