Re: stalling IO regression since linux 5.12, through 5.18

Holger Hoffstätte
2022-08-17T18:21:44Z

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