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

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Message-ID: <3e9e42aa-9a0d-2b73-194b-5c229e9ed533@huaweicloud.com>
Date:   Wed, 14 Jun 2023 09:58:22 +0800
From:   Yu Kuai <yukuai1@...weicloud.com>
To:     Bart Van Assche <bvanassche@....org>,
        Yu Kuai <yukuai1@...weicloud.com>,
        Christoph Hellwig <hch@...radead.org>
Cc:     Ed Tsai <ed.tsai@...iatek.com>, axboe@...nel.dk,
        linux-block@...r.kernel.org, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org, martin.petersen@...cle.com,
        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, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH 2/2] ufs: don't use the fair tag sharings

Hi,

在 2023/06/13 22:07, Bart Van Assche 写道:
> On 5/18/23 00:55, Yu Kuai wrote:
>> 在 2023/05/18 10:23, Bart Van Assche 写道:
>>> On 5/17/23 18:49, Yu Kuai wrote:
>>>> Currently, fair share from hctx_may_queue() requires two
>>>> atomic_read(active_queues and active_requests), I think this smoothing
>>>> method can be placed into get_tag fail path, for example, the more 
>>>> times
>>>> a disk failed to get tag in a period of time, the more tag this disk 
>>>> can
>>>> get, and all the information can be updated here(perhaps directly
>>>> record how many tags a disk can get, then hctx_may_queue() still only
>>>> require 2 atomic_read()).
>>>
>>> That sounds interesting to me. Do you perhaps plan to implement this 
>>> approach and to post it as a patch?
>>
>> Of course, I'll try to send a RFC patch.
> 
> Hi Kuai,
> 
> Has this RFC patch already been posted or did I perhaps miss it?

Sorry for the delay, I finished switch from not share to fair share
directly verion, however, I found that it's not that simple to add a
smoothing method, and I'm stuck here for now.

I'll try to send a RFC verion soon, the smoothing method may not be
flexible, but I'll make sure it can work for your simple case that
2 device share tags, and one only issue few io while the other issue
lots of io.

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