linux-kernel - Re: [PATCH 0/3] block: device frequency PM QoS tuning

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Message-ID: <de099236-8c97-4ecc-9af7-740f09c2b0b2@acm.org>
Date: Mon, 15 Sep 2025 14:13:22 -0700
From: Bart Van Assche <bvanassche@....org>
To: Wang Jianzheng <wangjianzheng@...o.com>, Jens Axboe <axboe@...nel.dk>,
 Alim Akhtar <alim.akhtar@...sung.com>, Avri Altman <avri.altman@....com>,
 "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
 "Martin K. Petersen" <martin.petersen@...cle.com>,
 "Rafael J. Wysocki" <rafael@...nel.org>, Peter Wang
 <peter.wang@...iatek.com>, Bean Huo <beanhuo@...ron.com>,
 "Bao D. Nguyen" <quic_nguyenb@...cinc.com>,
 Adrian Hunter <adrian.hunter@...el.com>, linux-block@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
 linux-pm@...r.kernel.org
Subject: Re: [PATCH 0/3] block: device frequency PM QoS tuning

On 9/14/25 4:45 AM, Wang Jianzheng wrote:
> Now, the patches provided here intruduce a mechanism for the block layer
> to add constraints to device frequecny through PM QoS framework, with
> configurable sysfs knobs per block device. Doing following config in my
> test system:
> 
>    /sys/block/sda/dev_freq_timeout_ms = 30
> 
> This constraints is removed if there is no block IO for 30ms.

Why a new sysfs attribute? Is this attribute really necessary? How are
users expected to determine what value to write into that attribute to
achieve optimal results?

Thanks,

Bart.