linux-kernel - Re: [RFC PATCH 07/13] sched: Add core wide task selection and scheduling.

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Message-ID: <20200417111805.GA20730@hirez.programming.kicks-ass.net>
Date:   Fri, 17 Apr 2020 13:18:05 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Chen Yu <yu.chen.surf@...il.com>
Cc:     vpillai <vpillai@...italocean.com>,
        Nishanth Aravamudan <naravamudan@...italocean.com>,
        Julien Desfossez <jdesfossez@...italocean.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>, mingo@...nel.org,
        tglx@...utronix.de, pjt@...gle.com, torvalds@...ux-foundation.org,
        linux-kernel@...r.kernel.org, fweisbec@...il.com,
        keescook@...omium.org, kerrnel@...gle.com,
        Phil Auld <pauld@...hat.com>, Aaron Lu <aaron.lwe@...il.com>,
        Aubrey Li <aubrey.intel@...il.com>, aubrey.li@...ux.intel.com,
        Valentin Schneider <valentin.schneider@....com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Joel Fernandes <joelaf@...gle.com>, joel@...lfernandes.org,
        Aaron Lu <aaron.lu@...ux.alibaba.com>,
        Long Cui <long.cui@...el.com>
Subject: Re: [RFC PATCH 07/13] sched: Add core wide task selection and
 scheduling.

On Thu, Apr 16, 2020 at 11:39:05AM +0800, Chen Yu wrote:

> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 02495d44870f..ef101a3ef583 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -4477,9 +4477,14 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
>  		return next;
>  	}
>  
> -	prev->sched_class->put_prev_task(rq, prev);
> -	if (!rq->nr_running)
> -		newidle_balance(rq, rf);
> +
> +#ifdef CONFIG_SMP
> +	for_class_range(class, prev->sched_class, &idle_sched_class) {
> +		if (class->balance(rq, prev, rf))
> +			break;
> +	}
> +#endif
> +	put_prev_task(rq, prev);
>  
>  	smt_mask = cpu_smt_mask(cpu);

Instead of duplicating that, how about you put the existing copy in a
function to share? finish_prev_task() perhaps?

Also, can you please make newidle_balance() static again; I forgot doing
that in 6e2df0581f56, which would've made you notice this sooner I
suppose.