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

[Damien Le Moal]

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 ?

Do you set a block I/O scheduler for the drive, e.g. mq-deadline. If not, does
setting a scheduler resolve the issue ?

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.

-- 
Damien Le Moal
Western Digital Research