Re: [PATCH] chrt: Make priority optional for policies that don't use it

[Madadi Vineeth Reddy <vineethr@linux.ibm.com>]

Hi Karel,

On 17/06/25 17:35, Karel Zak wrote:
> On Mon, Jun 16, 2025 at 12:52:18AM +0530, Madadi Vineeth Reddy wrote:
>> Currently, chrt requires a priority argument even for scheduling
>> policies like SCHED_OTHER and SCHED_BATCH, which ignore it.
>>
>> This change relaxes that requirement. Now, priority is only expected
>> for SCHED_FIFO and SCHED_RR. For other policies, a default value of 0
>> is set internally and no argument is required on the command line.
>>
>> This simplifies usage when modifying runtime parameters like
>> --sched-runtime for non-realtime tasks.
>>
>> For example, to change the EEVDF tunable base_slice, one currently
>> needs to run:
>> chrt -v -o -T 1000000 -p 0 $PID
>>
>> Passing '0' after -p is not intutive and not required as priority is
>> not applicable to SCHED_OTHER tasks. Now with this patch, one can do:
>> chrt -v -o -T 1000000 -p $PID
>>
>> Passing '0' still works ensuring ABI doesn't break.
> 
> Looks good. It would be nice to update the man page and add a note  
> that -p is not required since util-linux v2.42.
> 

I believe you meant that the priority argument is not required for some
scheduling policies. The -p / --pid option is still required.

I’ll update the man page accordingly.

>> +	bool policy_needs_priority = (ctl->policy == SCHED_FIFO || ctl->policy == SCHED_RR);
> 
> Nitpicking... can't we use a shorter name, for example "need_prio"? ;-)

Sure, will update it in v2. Thanks for taking a look.

Thanks,
Madadi Vineeth Reddy

> 
>     Karel
>