Re: [PATCH 00/16] blk-mq: introduce new queue attribute asyc_dpeth

[Ming Lei]

On Thu, Aug 14, 2025 at 11:35:06AM +0800, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@xxxxxxxxxx>
> 
> 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

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


Thanks,
Ming