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Subject: Re: [PATCH RFC 0/7] blk-mq: improve tag fair sharing
To:     Bart Van Assche <bvanassche@acm.org>,
        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>
References: <20230618160738.54385-1-yukuai1@huaweicloud.com>
 <4c9fea33-9c30-4ab9-c210-95e09d323837@acm.org>
 <82d44ba1-4389-079c-935a-cbb49203ca27@huaweicloud.com>
 <c4de836a-a2a1-847f-1525-1accb814e45e@acm.org>
From:   Yu Kuai <yukuai1@huaweicloud.com>
Message-ID: <84f9bfb4-293b-ad55-97e4-e8c611c5e9ca@huaweicloud.com>
Date:   Wed, 5 Jul 2023 11:17:48 +0800
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Hi,

在 2023/07/04 2:08, Bart Van Assche 写道:
> On 7/3/23 06:29, Yu Kuai wrote:
>> 在 2023/06/20 23:20, Bart Van Assche 写道:
>>> On 6/18/23 09:07, Yu Kuai wrote:
>>>> This is not a formal version and not fully tested, I send this RFC
>>>> because I want to make sure if people think doing this is meaningful,
>>>> before I spend too much time on this.
>>> The approach looks good to me but I'd like to hear from Jens and 
>>> Christoph what their opinion is about the approach of this patch 
>>> series before doing an in-depth review.
>>>
>> Any suggestions on this topic? It'll be great to hear that if anyone
>> thinks it's meaningful to refactor tag fair sharing.
> 
> The cover letter of this patch series says "This is not a formal version 
> and not fully tested". If a fully tested version will be posted, I will 
> help with an in-depth review.

Thanks for taking time on this patchset, do you think I need to do
following for the formal version, or these improvements can be done
later?

- current algorithm to borrow tags in patch 7 is very easy and
straightforward, it should work fine on simple caces like the case you
reported for ufs, but this algorithm should be improved for more
complicated cases.
- 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.

Thanks,
Kuai

> 
> Thanks,
> 
> Bart.
> 
> 
> .
>