linux-kernel - Re: [PATCH 00/16] blk-mq: introduce new queue attribute asyc

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Message-ID: <b6587204-9798-fcb0-c4b7-f00d5979d243@huaweicloud.com>
Date: Thu, 14 Aug 2025 16:22:27 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: Ming Lei <ming.lei@...hat.com>, Yu Kuai <yukuai1@...weicloud.com>
Cc: axboe@...nel.dk, bvanassche@....org, nilay@...ux.ibm.com, hare@...e.de,
 linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
 yi.zhang@...wei.com, yangerkun@...wei.com, johnny.chenyi@...wei.com,
 "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH 00/16] blk-mq: introduce new queue attribute asyc_dpeth

Hi,

在 2025/08/14 15:54, Ming Lei 写道:
> On Thu, Aug 14, 2025 at 11:35:06AM +0800, Yu Kuai wrote:
>> From: Yu Kuai <yukuai3@...wei.com>
>>
>> Backgroud and motivation:
>>
>> At first, we test a performance regression from 5.10 to 6.6 in
>> downstream kernel(described in patch 13), the regression is related to
>> async_depth in mq-dealine.
>>
>> While trying to fix this regression, Bart suggests add a new attribute
>> to request_queue, and I think this is a good idea because all elevators
>> have similar logical, however only mq-deadline allow user to configure
>> async_depth. And this is patch 9-16, where the performance problem is
>> fixed in patch 13;
>>
>> Because async_depth is related to nr_requests, while reviewing related
>> code, patch 2-7 are cleanups and fixes to nr_reqeusts.
>>
>> I was planning to send this set for the next merge window, however,
>> during test I found the last block pr(6.17-rc1) introduce a regression
>> if nr_reqeusts grows, exit elevator will panic, and I fix this by
>> patch 1,8.
> 
> Please split the patchset into two:
> 
> - one is for fixing recent regression on updating 'nr_requests', so this
>    can be merged to v6.17, and be backport easily for stable & downstream

There are actually two regressions, as fixed by patch 5 and patch 8, how
about the first patchset for patch 1-8? Are you good with those minor
prep cleanup patches?

> 
> - another one is for improving IO performance related with async_depth.

Sure, although patch 9-16 is still a performance regression :)

Thanks,
Kuai

> 
> 
> Thanks,
> Ming
> 
> 
> .
>