linux-kernel - Re: [PATCH v3] sched/fair: Skip sched_balance

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Message-ID: <4fc95e1409d3218171a54e3baaa2e2a37d724add.camel@linux.intel.com>
Date: Fri, 07 Nov 2025 09:43:42 -0800
From: Tim Chen <tim.c.chen@...ux.intel.com>
To: Shrikanth Hegde <sshegde@...ux.ibm.com>, K Prateek Nayak
	 <kprateek.nayak@....com>, Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...nel.org>, Chen Yu <yu.c.chen@...el.com>, Doug
 Nelson	 <doug.nelson@...el.com>, Mohini Narkhede
 <mohini.narkhede@...el.com>, 	linux-kernel@...r.kernel.org, Vincent Guittot
 <vincent.guittot@...aro.org>
Subject: Re: [PATCH v3] sched/fair: Skip sched_balance_running cmpxchg when
 balance is not due

On Fri, 2025-11-07 at 14:27 +0530, Shrikanth Hegde wrote:
> 
> On 11/7/25 8:27 AM, K Prateek Nayak wrote:
> > Hello Tim,
> > 
> > On 11/7/2025 4:57 AM, Tim Chen wrote:
> > > @@ -11757,6 +11772,7 @@ static int sched_balance_rq(int this_cpu, struct rq *this_rq,
> > >   		.fbq_type	= all,
> > >   		.tasks		= LIST_HEAD_INIT(env.tasks),
> > >   	};
> > > +	int need_unlock = false;
> > >   
> > >   	cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask);
> > >   
> > > @@ -11768,6 +11784,13 @@ static int sched_balance_rq(int this_cpu, struct rq *this_rq,
> > >   		goto out_balanced;
> > >   	}
> > >   
> > > +	if (idle != CPU_NEWLY_IDLE && (sd->flags & SD_SERIALIZE)) {
> 
> Can you also try removing "idle != CPU_NEWLY_IDLE" and see the workload behavior?
> If workloads don't observe regression, it might be worth serializing it too.

Let me ask my colleague running OLTP to give it a try.

Tim