linux-kernel - Re: stalling IO regression since linux 5.12, through 5.18

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Date:   Wed, 17 Aug 2022 20:21:39 +0200
From:   Holger Hoffstätte <holger@...lied-asynchrony.com>
To:     Jan Kara <jack@...e.cz>, Chris Murphy <lists@...orremedies.com>
Cc:     Nikolay Borisov <nborisov@...e.com>, Jens Axboe <axboe@...nel.dk>,
        Paolo Valente <paolo.valente@...aro.org>,
        Linux-RAID <linux-raid@...r.kernel.org>,
        linux-block <linux-block@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Josef Bacik <josef@...icpanda.com>
Subject: Re: stalling IO regression since linux 5.12, through 5.18

On 2022-08-17 20:15, Jan Kara wrote:
> On Wed 17-08-22 13:57:00, Chris Murphy wrote:
>> On Wed, Aug 17, 2022, at 12:47 PM, Chris Murphy wrote:
>> Can you boot with
>>>> "megaraid_sas.host_tagset_enable = 0" kernel option and see whether the
>>>> issue reproduces?
>>
>> This has been running an hour without symptoms. It's strongly suggestive,
>> but needs to run overnight to be sure. Anecdotally, the max write IO is
>> less than what I'm used to seeing.
> 
> OK, if this indeed passes then b6e68ee82585 ("blk-mq: Improve performance
> of non-mq IO schedulers with multiple HW queues") might be what's causing
> issues (although I don't know how yet...).
> 
> 								Honza

Certainly explains why BFQ turned up as a suspect, considering it's still
single-queue (fair MQ scheduling is .. complicated).

-h