Re: [PATCH] nvmet: make nvmet_wq visible in sysfs

[Chaitanya Kulkarni <chaitanyak@nvidia.com>]

On 10/29/24 18:44, Guixin Liu wrote:
>
> 在 2024/10/30 03:52, Chaitanya Kulkarni 写道:
>> On 10/28/24 23:46, Guixin Liu wrote:
>>> 在 2024/10/29 13:04, Chaitanya Kulkarni 写道:
>>>> On 10/28/24 18:49, Guixin Liu wrote:
>>>>> Make nvmet_wq visible in sysfs, allowing for tuning the it's attr
>>>>> through sysfs.
>>>>>
>>>>> Signed-off-by: Guixin Liu<kanie@linux.alibaba.com>
>>>>> ---
>>>> do you happened have a usecase for this?
>>>>
>>>> -ck
>>> Sometimes, in order to respond promptly to certain events or
>>>
>>> manage commands, we need to reserve resources and partition
>>>
>>> the CPU cores. For example, if there are 4 cores available,
>>>
>>> we can initially allocate them by dedicating one core for
>>>
>>> management while the remaining 3 cores are specifically for handling 
>>> IO.
>>>
>>> Best Regards,
>>>
>>> Guixin Liu
>>>
>> I'm aware of exposing tunables through sysfs and it's benefits, my 
>> question
>> was do you have a setup where this setting is needed currently ?
>>
>> I've always been asked to for the usecase on a patch when we expose
>> something
>> out of kernel that is solving the problem in the deployment ...
>>
>> -ck
>
> I need serverve some cpu core to do other things, such as handle events
>
> and managements, so that the nvmet_wq can't running on all cpu cores,
>
> currently, I restrict it by setting the cpumask of nvmet_wq（that's why
>
> I expose nvmet_wq to sysfs）.
>
> Best Regards,
>
> Guixin Liu
>
>>

Can you please explain your setup ? e.g. transport tcp/rdma/fc, device
backend file/block etc ?

so nvmet_wq's CPU consumption is so high, that it doesn't have bandwidth
to handle events and managements ?

Can you please explain the workload and what kind of events and managements
handling is needed where you need to restrict the nvmet_wq with CPUMASK ?

The only reason I'm asking that I've not seen this scenario so far in 
the many
many deployments since we've added the nvmet_wq and I'd really like to learn
about scenario.

-ck