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

[yangxingui <yangxingui@huawei.com>]

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
.