linux-kernel - Re: [PATCH V3 1/4] Sched: Scheduler time slice extension

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Message-ID: <20250506091328.32696fe6@gandalf.local.home>
Date: Tue, 6 May 2025 09:13:28 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Prakash Sangappa <prakash.sangappa@...cle.com>
Cc: Peter Zijlstra <peterz@...radead.org>, "linux-kernel@...r.kernel.org"
 <linux-kernel@...r.kernel.org>, "mathieu.desnoyers@...icios.com"
 <mathieu.desnoyers@...icios.com>, "tglx@...utronix.de"
 <tglx@...utronix.de>, "bigeasy@...utronix.de" <bigeasy@...utronix.de>,
 "kprateek.nayak@....com" <kprateek.nayak@....com>
Subject: Re: [PATCH V3 1/4] Sched: Scheduler time slice extension

On Tue, 6 May 2025 01:23:55 +0000
Prakash Sangappa <prakash.sangappa@...cle.com> wrote:

> Does it have to be sched_yield()? Or can the application call some other (fast)system call to yield the cpu
> (getppid(2) ) if extended time was granted?

It can be anything we decide I guess. yield() just seemed to be the most
appropriate, because in essence, that's exactly what it's doing.
 
> 
> It appears by default sched feature HRTICK/HRTICK_DL is disabled so
> hrtick_clear() Will not get called from __schedule().  I have noticed
> that enabling these sched feature to let hrtick_clear() get called from
> __schedule(), adds overhead.
> 
> So not sure if we need to enable the sched_feat(HRTICK//HRTICK_DL) to use
> the scheduler time extension.
> 
> Maybe rseq_delay_resched_tick() with this support,  would have to be
> called in __schedule() path but not thru hrtick_clear(),

I think that's more of a question for Peter.

-- Steve