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Date:   Thu, 6 Jul 2023 11:43:01 -0700
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Subject: Re: [PATCH RFC 0/7] blk-mq: improve tag fair sharing
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To:     Yu Kuai <yukuai1@huaweicloud.com>, axboe@kernel.dk
Cc:     linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
        yi.zhang@huawei.com, yangerkun@huawei.com,
        Christoph Hellwig <hch@lst.de>,
        "yukuai (C)" <yukuai3@huawei.com>
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From:   Bart Van Assche <bvanassche@acm.org>
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On 7/4/23 20:17, Yu Kuai wrote:
> - currently borrowed tags will never be returned untill queue is idle,
> I should figure out a way to return borrowed tags if this queue is not
> busy, so that other queues can borrow tag from this queue.

At least for UFS this is a significant disadvantage. If e.g. one SCSI
command is sent to the UFS WLUN every 20 seconds and the request queue
timeout is 30 seconds then borrowed tags will never be returned.

The complexity of this patch series is a concern to me. The complexity
of this patch series may be a barrier towards merging this patch series
in the upstream kernel.

Thanks,

Bart.