Re: wbt_lat_usec still set despite wbt disabled by BFQ

["Holger Hoffstätte" <holger@applied-asynchrony.com>]

On 2022-09-13 15:39, Yu Kuai wrote:
> Hi, Holger
> 
> 在 2022/08/18 1:12, Holger Hoffstätte 写道:
>>
>> I just noticed that my device configured with BFQ still shows wbt_lat_usec
>> as configured, despite the fact that BFQ disables WBT in bfq_init_queue [1]:
>>
>> $cat /sys/block/sdc/queue/scheduler
>> mq-deadline [bfq] none
>> $cat /sys/block/sdc/queue/wbt_lat_usec
>> 75000
>>
>> Is this supposed to be 0 (since it's disabled) or is sysfs confused?
>>
>> Thanks,
>> Holger
> 
> I'm reviewing wbt codes recently, and I found that this problem will
> happen if the default elevator is bfq. I'll try to fix this, do you mind
> if I add reported-by tag?

Do not mind at all - thank you for looking into it!
Let me know if I can test a patch or help in some other way.

Btw not sure what "default scheduler" means here, I set my schedulers via
udev rules. In this case:

ACTION=="add", KERNEL=="sd[a-z]", ATTR{queue/rotational}=="1", ATTR{queue/scheduler}="bfq"

cheers
Holger