Re: stalling IO regression since linux 5.12, through 5.18

[Holger Hoffstätte]

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