linux-kernel - Re: [tip: sched/core] sched/balance: Skip unnecessary updates to idle load balancer's flags

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Date: Wed, 05 Jun 2024 10:07:33 -0700
From: Tim Chen <tim.c.chen@...ux.intel.com>
To: linux-kernel@...r.kernel.org, linux-tip-commits@...r.kernel.org
Cc: "Peter Zijlstra (Intel)" <peterz@...radead.org>, Chen Yu
	 <yu.c.chen@...el.com>, Vincent Guittot <vincent.guittot@...aro.org>, 
	x86@...nel.org, Mohini Narkhede <mohini.narkhede@...el.com>
Subject: Re: [tip: sched/core] sched/balance: Skip unnecessary updates to
 idle load balancer's flags

On Wed, 2024-06-05 at 14:54 +0000, tip-bot2 for Tim Chen wrote:
> 
> Signed-off-by: Tim Chen <tim.c.chen@...ux.intel.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Reviewed-by: Chen Yu <yu.c.chen@...el.com>
> Reviewed-by: Vincent Guittot <vincent.guittot@...aro.org>
> Link: https://lore.kernel.org/r/20240531205452.65781-1-tim.c.chen@linux.intel.com

Peter,

Thanks for putting the patch in tip.

Can you also also add 

Tested-by: Mohini Narkhede <mohini.narkhede@...el.com>

Thanks.

Tim

> ---
>  kernel/sched/fair.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 63113dc..41b5838 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -11892,6 +11892,13 @@ static void kick_ilb(unsigned int flags)
>  		return;
>  
>  	/*
> +	 * Don't bother if no new NOHZ balance work items for ilb_cpu,
> +	 * i.e. all bits in flags are already set in ilb_cpu.
> +	 */
> +	if ((atomic_read(nohz_flags(ilb_cpu)) & flags) == flags)
> +		return;
> +
> +	/*
>  	 * Access to rq::nohz_csd is serialized by NOHZ_KICK_MASK; he who sets
>  	 * the first flag owns it; cleared by nohz_csd_func().
>  	 */