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

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Message-ID: <80120491-7F90-4171-9FB8-9FE89B09F728@oracle.com>
Date: Wed, 4 Jun 2025 17:29:44 +0000
From: Prakash Sangappa <prakash.sangappa@...cle.com>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
CC: Steven Rostedt <rostedt@...dmis.org>,
        "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 4, 2025, at 7:54 AM, Sebastian Andrzej Siewior <bigeasy@...utronix.de> wrote:
> 
> On 2025-06-04 10:31:06 [-0400], Steven Rostedt wrote:
>> On Tue,  3 Jun 2025 23:36:49 +0000
>> Prakash Sangappa <prakash.sangappa@...cle.com> wrote:
>> 
>>> @@ -2249,6 +2251,20 @@ static inline bool owner_on_cpu(struct task_struct *owner)
>>> unsigned long sched_cpu_util(int cpu);
>>> #endif /* CONFIG_SMP */
>>> 
>>> +#ifdef CONFIG_RSEQ
>>> +
>>> +extern bool rseq_delay_resched(void);
>>> +extern void rseq_delay_resched_fini(void);
>>> +extern void rseq_delay_resched_tick(void);
>>> +
>>> +#else
>>> +
>>> +static inline bool rseq_delay_resched(void) { return false; }
>>> +static inline void rseq_delay_resched_fini(void) { }
>>> +static inline void rseq_delay_resched_tick(void) { }
>>> +
>>> +#endif
>>> +
>> 
>> Can we add a config to make this optional. I don't want to allow any task
>> to have an extended timeslice over RT tasks regardless of how small the
>> delay is.
> 
> I asked to get RT tasks excluded from this extensions and it is ignored.
> Maybe they were benefits mentioned somewhere…

Don’t know if there were benefits mentioned when RT tasks are involved.

I had shared some benchmark results in this thread showing benefit of using scheduler time extension.
https://lore.kernel.org/all/20241113000126.967713-1-prakash.sangappa@oracle.com/
The workload did not include RT tasks.

-Prakash


> 
>> -- Steve
> 
> Sebastian