linux-kernel - Re: [PATCH 0/6] blk-mq: optimize the queue

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Message-ID: <c48a294c-a8a9-63ae-182f-e1d757f6179e@acm.org>
Date:   Sat, 26 Aug 2023 17:45:53 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Chengming Zhou <chengming.zhou@...ux.dev>, axboe@...nel.dk,
        hch@....de, ming.lei@...hat.com, kbusch@...nel.org
Cc:     mst@...hat.com, sagi@...mberg.me, damien.lemoal@...nsource.wdc.com,
        kch@...dia.com, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, zhouchengming@...edance.com
Subject: Re: [PATCH 0/6] blk-mq: optimize the queue_rqs() support

On 8/25/23 01:24, Chengming Zhou wrote:
> I don't know the details of the UFS devices bad performance problem.
> But I feel it maybe caused by the too lazy queue idle handling, which
> is now only handled in queue timeout work.

Hi Chengming,

The root cause of the UFS performance problem is the fair sharing
algorithm itself: reducing the active queue count only happens after
the request queue timeout has expired. This is way too slow. Last time
it was proposed to remove that algorithm Yu Kuai promised to replace it
by a better algorithm. Since progress on the replacement algorithm has
stalled I'm asking again whether everyone agrees to remove the fairness
algorithm.

Thanks,

Bart.