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

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Message-ID: <aJ2d3gtfi0aEaeEc@fedora>
Date: Thu, 14 Aug 2025 16:27:10 +0800
From: Ming Lei <ming.lei@...hat.com>
To: 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

On Thu, Aug 14, 2025 at 04:22:27PM +0800, Yu Kuai wrote:
> 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?

Then probably you need to make it into three by adding one extra bug fix for
`fix elevator depth_updated method`, which follows the philosophy of
"do one thing, do it better", also helps people to review.

Thanks, 
Ming