Re: [bug report] block: Non-NCQ commands will never be executed while fio is continuously running

[yangxingui]

On 2024/9/10 12:45, Damien Le Moal wrote:
> On 9/10/24 10:09 AM, yangxingui wrote:
> > On 2024/9/9 21:21, Damien Le Moal wrote:
> > > On 9/9/24 22:10, yangxingui wrote:
> > > > Hello axboe & John,
> > > >
> > > > After the driver exposes all HW queues to the block layer, non-NCQ
> > > > commands will never be executed while fio is continuously running, such
> > > > as a smartctl command.
> > > >
> > > > The cause of the problem is that other hctx used by the NCQ command is
> > > > still active and can continue to issue NCQ commands to the sata disk.
> > > > And the pio command keeps retrying in its corresponding hctx because
> > > > qc_defer() always returns true.
> > > >
> > > > hctx0: ncq, pio, ncq
> > > > hctx1：ncq, ncq, ...
> > > > ...
> > > > hctxn: ncq, ncq, ...
> > > >
> > > > Is there any good solution for this?
> > >
> > > SATA devices are single queue so how can you have multiple queues ?
> > > What adapter are you using ?
> >
> > In the following patch, we expose the host's 16 hardware queues to the block
> > layer. And when connecting to a sata disk, 16 hctx are used.
> >
> > 8d98416a55eb ("scsi: hisi_sas: Switch v3 hw to MQ")
>
> OK, so the HBA is a hisi one, using libsas...
> What is the device ? An SSD ? and HDD ?
Both SATA SSD and SATA HDD have this problem.

> Do you set a block I/O scheduler for the drive, e.g. mq-deadline. If not, does
> setting a scheduler resolve the issue ?
Currently, the default configuration mq-deadline is used, and the same 
phenomenon occurs when I try setting it to none. It seems to have 
nothing to do with the scheduling strategy.

> I do not have any hisi HBA. I use a lot of mpt3sas and mpi3mr HBAs which also
> have multiple queues with a shared tagset. Never seen the issue you are
> reporting though using HDDs with mq-deadline or bfq as the scheduler.
Unlike libsas, as these hosts don't use qc_defer()?

Thanks,
Xingui
.