Re: [RESEND][PATCH v2 1/3] sched/tp: Add new tracepoint to track uclamp set from user-space

Lukasz Luba
2023-07-19T13:18:01Z

On 7/6/23 12:14, Peter Zijlstra wrote:
> On Wed, May 31, 2023 at 07:26:29PM +0100, Qais Yousef wrote:
>> On 05/22/23 15:57, Lukasz Luba wrote:
>>> The user-space can set uclamp value for a given task. It impacts task
>>> placement decisions made by the scheduler. This is very useful information
>>> and helps to understand the system behavior or track improvements in
>>> middleware and applications which start using uclamp mechanisms and report
>>> better performance in tests.
>>
>> Do you mind adding a generic one instead please? And explain why we can't just
>> attach to the syscall via kprobes? I think you want to bypass the permission
>> checks, so maybe a generic tracepoint after that might be justifiable?
>> Then anyone can use it to track how userspace has changed any attributes for
>> a task, not just uclamp.
>
> Yeah, so I'm leaning towards the same, if you want to put a tracepoint
> in __sched_setscheduler(), just trace the whole attr and leave it at
> that:
>
> trace_update_sched_attr_tp(p, attr);
>
> or somesuch.
>

OK, fair enough, I'll do that. Thanks Peter!
(I'm sorry for the delay, I was on vacation)

Lukasz