linux-kernel - Re: [PATCH V5 1/6] Sched: Scheduler time slice extension

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Message-ID: <F2AEFF3B-15E4-489A-AA4C-0F829BBF32A5@oracle.com>
Date: Tue, 10 Jun 2025 15:40:09 +0000
From: Prakash Sangappa <prakash.sangappa@...cle.com>
To: Steven Rostedt <rostedt@...dmis.org>
CC: Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "mathieu.desnoyers@...icios.com" <mathieu.desnoyers@...icios.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "kprateek.nayak@....com"
	<kprateek.nayak@....com>,
        "vineethr@...ux.ibm.com" <vineethr@...ux.ibm.com>
Subject: Re: [PATCH V5 1/6] Sched: Scheduler time slice extension



> On Jun 9, 2025, at 2:52 PM, Steven Rostedt <rostedt@...dmis.org> wrote:
> 
> On Mon, 9 Jun 2025 16:55:32 -0400
> Steven Rostedt <rostedt@...dmis.org> wrote:
> 
>> So I applied your patches and fixed up my "extend-sched.c" program to use
>> your method. I booted on bare-metal PREEMPT_RT and ran:
> 
> In case anyone else wants to play, I'm attaching the source of extend-sched.c
> 
> I ran it with: sleep 5; ./extend-sched
> 
> Then switched over to cyclic test, counted to five and it was pretty
> noticeable when it triggered.
> 
> To build, simply do:
> 
>  $ cd linux.git
>  $ mkdir /tmp/extend
>  $ cp tools/testing/selftests/rseq/rseq-abi.h /tmp/extend
>  $ cd /tmp/extend
> 
>  [ download extend-sched.c here ]
> 
>  $ gcc extend-sched.c -o extend-sched
> 
> 
> -- Steve
> <extend-sched.c>

Thanks for sharing the test program.

In test program, unextend() should be slightly modified as follows.

101c101
< 	if (!(flags & (1 << 4)))
---
> 	if (flags & (1 << 3))
103,106c103,107
< 
< 	tracefs_printf(NULL, "Yield!\n");
< 	sched_yield();
< 		return 1;
---
> 	if (!(flags & (1 << 4))) {
> 		tracefs_printf(NULL, "Yield!\n");
> 		sched_yield();
> 	}
> 	return 1;