linux-kernel - Re: [RFC PATCH v3 00/16] Core scheduling v3

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Date:   Thu, 18 Jul 2019 16:27:19 -0700
From:   Tim Chen <tim.c.chen@...ux.intel.com>
To:     Aaron Lu <aaron.lu@...ux.alibaba.com>,
        Julien Desfossez <jdesfossez@...italocean.com>
Cc:     Aubrey Li <aubrey.intel@...il.com>,
        Subhra Mazumdar <subhra.mazumdar@...cle.com>,
        Vineeth Remanan Pillai <vpillai@...italocean.com>,
        Nishanth Aravamudan <naravamudan@...italocean.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Paul Turner <pjt@...gle.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        Frédéric Weisbecker <fweisbec@...il.com>,
        Kees Cook <keescook@...omium.org>,
        Greg Kerr <kerrnel@...gle.com>, Phil Auld <pauld@...hat.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [RFC PATCH v3 00/16] Core scheduling v3



On 7/18/19 3:07 AM, Aaron Lu wrote:
> On Wed, Jun 19, 2019 at 02:33:02PM -0400, Julien Desfossez wrote:

> 
> With the below patch on top of v3 that makes use of util_avg to decide
> which task win, I can do all 8 steps and the final scores of the 2
> workloads are: 1796191 and 2199586. The score number are not close,
> suggesting some unfairness, but I can finish the test now...

Aaron,

Do you still see high variance in terms of workload throughput that
was a problem with the previous version?

>
>  
>  }
> +
> +bool cfs_prio_less(struct task_struct *a, struct task_struct *b)
> +{
> +	struct sched_entity *sea = &a->se;
> +	struct sched_entity *seb = &b->se;
> +	bool samecore = task_cpu(a) == task_cpu(b);


Probably "samecpu" instead of "samecore" will be more accurate.
I think task_cpu(a) and task_cpu(b)
can be different, but still belong to the same cpu core.

> +	struct task_struct *p;
> +	s64 delta;
> +
> +	if (samecore) {
> +		/* vruntime is per cfs_rq */
> +		while (!is_same_group(sea, seb)) {
> +			int sea_depth = sea->depth;
> +			int seb_depth = seb->depth;
> +
> +			if (sea_depth >= seb_depth)

Should this be strictly ">" instead of ">=" ?

> +				sea = parent_entity(sea);
> +			if (sea_depth <= seb_depth)

Should use "<" ?

> +				seb = parent_entity(seb);
> +		}
> +
> +		delta = (s64)(sea->vruntime - seb->vruntime);
> +	}
> +

Thanks.

Tim