linux-kernel - Re: [PATCH v2 1/9] sched: Add a generic function to return the preemption string.

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Message-ID: <b7740edc-ea89-488d-9d6e-d31f5f1dcae1@linux.ibm.com>
Date: Mon, 10 Feb 2025 19:51:33 +0530
From: Shrikanth Hegde <sshegde@...ux.ibm.com>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: linux-kernel@...r.kernel.org, linux-rt-devel@...ts.linux.dev,
        Ben Segall <bsegall@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Ingo Molnar <mingo@...hat.com>, Juri Lelli <juri.lelli@...hat.com>,
        Mel Gorman <mgorman@...e.de>, Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Valentin Schneider <vschneid@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Will Deacon <will@...nel.org>
Subject: Re: [PATCH v2 1/9] sched: Add a generic function to return the
 preemption string.



On 2/10/25 16:22, Sebastian Andrzej Siewior wrote:
> On 2025-02-08 13:31:27 [+0530], Shrikanth Hegde wrote:
>>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>>> index 165c90ba64ea9..bd2664755b09a 100644
>>> --- a/kernel/sched/core.c
>>> +++ b/kernel/sched/core.c

[...]

>> nit: This means when it preempt=full, it is going to show PREEMPT or
>> PREEMPT_RT. Maybe that could be put into changelog or add code similar to
>> lazy for full as well, so it is easier for user to know if it is in
>> preempt=full model. In all other models, there is a suffix like PREEMPTLAZY.
>> Dynamic modes looks good.
> 
> Sorry, I can't follow. With PREEMPT_RT enabled, it will show einer
> PREEMPT or PREEMPT_RT. It will add lazy if you pass preempt=lazy. It is
> either 'full' or 'lazy'.
> You can't have VOLUNTARY+lazy or VOLUNTARY+RT.
> 
> What do I miss?

No No. That's not what i meant.

I was saying, as peter mentioned in the previous discussion, can we put 
something like below in changelog/comment for a easier understanding.?

"
RT+DYN:	 PREEMPT_{RT,(dyn_mode)}
RT+LAZY: PREEMPT_{RT,LAZY}
RT+FULL: PREEMPT_RT

DYN:       PREEMPT_(dyn_mode)
FULL:      PREEMPT
LAZY:      PREEMPTLAZY
VOLUNTARY: VOLUNTARY
NONE:      NONE
"

> 
> Sebastian