linux-kernel - Re: [PATCH V6 1/7] Sched: Scheduler time slice extension

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Message-ID: <87plehwu6z.ffs@tglx>
Date: Thu, 03 Jul 2025 10:32:36 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: Prakash Sangappa <prakash.sangappa@...cle.com>
Cc: Peter Zijlstra <peterz@...radead.org>, "linux-kernel@...r.kernel.org"
 <linux-kernel@...r.kernel.org>, "rostedt@...dmis.org"
 <rostedt@...dmis.org>, "mathieu.desnoyers@...icios.com"
 <mathieu.desnoyers@...icios.com>, "bigeasy@...utronix.de"
 <bigeasy@...utronix.de>, "kprateek.nayak@....com"
 <kprateek.nayak@....com>, "vineethr@...ux.ibm.com"
 <vineethr@...ux.ibm.com>
Subject: Re: [PATCH V6 1/7] Sched: Scheduler time slice extension

On Thu, Jul 03 2025 at 05:38, Prakash Sangappa wrote:
>> On Jul 1, 2025, at 5:36 AM, Thomas Gleixner <tglx@...utronix.de> wrote:
>>
>> Also if we go there and allow non-RT tasks to delay scheduling, then we
>> need a control mechanism to enable/disable this mechanism on a per task
>> or process basis. That way a RT system designer can prevent random
>> user space tasks, which think they are the most important piece, from
>> interfering with truly relevant RT tasks w/o going to chase down source
>> code and hack it into submission.
>
> Could the per task  control mechanism be thru /proc?

Is that a serious question?

> Wonder how easy it will be to administer such control.

Obviously it's horrible.

That's what prctl() is for. Plus a proper inheritance mechanism on
fork/exec along with a system wide default which can be controlled via
the kernel command line.

> Alternatively, can we have a config option to apply to LAZY only?
> This will not provide the finer  control as you suggested. 

A config option is not solving anything; it's just a lazy hack to avoid
the hard work of a proper and future proof ABI design.

Thanks,

        tglx