linux-kernel - Re: [PATCH v2] kyber: introduce kyber_depth

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Message-ID: <1f94990f-2732-547a-09f4-42d5a6ab77d7@kernel.dk>
Date:   Mon, 22 Feb 2021 12:38:07 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Yang Yang <yang.yang@...o.com>,
        Omar Sandoval <osandov@...ndov.com>,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     onlyfever@...oud.com
Subject: Re: [PATCH v2] kyber: introduce kyber_depth_updated()

On 2/5/21 2:13 AM, Yang Yang wrote:
> Hang occurs when user changes the scheduler queue depth, by writing to
> the 'nr_requests' sysfs file of that device.
> 
> The details of the environment that we found the problem are as follows:
>   an eMMC block device
>   total driver tags: 16
>   default queue_depth: 32
>   kqd->async_depth initialized in kyber_init_sched() with queue_depth=32
> 
> Then we change queue_depth to 256, by writing to the 'nr_requests' sysfs
> file. But kqd->async_depth don't be updated after queue_depth changes.
> Now the value of async depth is too small for queue_depth=256, this may
> cause hang.
> 
> This patch introduces kyber_depth_updated(), so that kyber can update
> async depth when queue depth changes.

Applied, thanks.

-- 
Jens Axboe