linux-kernel - Re: [PATCH 2/2] ufs: don't use the fair tag sharings

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Message-ID: <ZF0K7A6G2cYBjSgn@infradead.org>
Date:   Thu, 11 May 2023 08:34:04 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Ed Tsai <ed.tsai@...iatek.com>
Cc:     axboe@...nel.dk, linux-block@...r.kernel.org,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        martin.petersen@...cle.com, bvanassche@....org,
        stanley.chu@...iatek.com, peter.wang@...iatek.com,
        chun-hung.wu@...iatek.com, alice.chao@...iatek.com,
        powen.kao@...iatek.com, naomi.chu@...iatek.com,
        wsd_upstream@...iatek.com
Subject: Re: [PATCH 2/2] ufs: don't use the fair tag sharings

On Tue, May 09, 2023 at 02:52:30PM +0800, Ed Tsai wrote:
> The tags allocation is limited by the fair sharing algorithm. It hurts
> the performance for UFS devices, because the queue depth of general I/O
> is reduced by half once the UFS send a control command.

But it is there for a reason.  You completely fail to explain why you
think your change is safe, and also why you did not try to even explain
where the overhead is and how else you tried to mitigate it.