Re: [PATCH] sched: Further restrict the preemption modes

[Shrikanth Hegde <sshegde@linux.ibm.com>]

Hi Steve.

On 2/27/26 8:23 PM, Steven Rostedt wrote:
> On Fri, 27 Feb 2026 14:39:42 +0530
> Shrikanth Hegde <sshegde@linux.ibm.com> wrote:
> 
>> I am afraid we will have trace all functions to begin with (which is expensive), but filter
>> out those which took minimal time (like less than a 1s or so). that would eventually leave only a
>> few functions that actually took more than 1s(that should have limited overhead).
> 
> Well, I think the detection can be done with timings between schedules.
> What's the longest running task without any voluntary schedule. Then you
> can add function graph tracing to it where it can possibly trigger in the
> location that detected the issue.
> 
> On a detection of a long schedule, a stack trace can be recorded. Using
> that stack trace, you could use the function graph tracer to see what is
> happening.
> 
> Anyway, something to think about, and this could be a topic at this years
> Linux Plumbers Tracing MC ;-)
> 

Yep. Will try to do this.

Someone from our tracing team wanted to give this a try too. Lets see.

> -- Steve