linux-kernel - Re: [PATCH 2/4] sched,numa: weigh nearby nodes for task placement on complex NUMA topologies

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Message-ID: <20140509095324.GQ30445@twins.programming.kicks-ass.net>
Date:	Fri, 9 May 2014 11:53:24 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	riel@...hat.com
Cc:	linux-kernel@...r.kernel.org, mingo@...nel.org, mgorman@...e.de,
	chegu_vinod@...com
Subject: Re: [PATCH 2/4] sched,numa: weigh nearby nodes for task placement on
 complex NUMA topologies

On Thu, May 08, 2014 at 01:23:29PM -0400, riel@...hat.com wrote:
> +		/*
> +		 * For nodes with distances in-between LOCAL_DISTANCE
> +		 * and max_distance, we count the faults on those nodes
> +		 * in proportion to their distance, using this formula:
> +		 *
> +		 * max_distance - node_distance
> +		 * -----------------------------
> +		 * max_distance - LOCAL_DISTANCE
> +		 */
> +		if (task)
> +			faults = task_faults(p, node);
> +		else
> +			faults = group_faults(p, node);
> +
> +		score += 1000 * faults *
> +				(max_distance - distance) /
> +				(max_distance - LOCAL_DISTANCE);

OK that makes sense, except I would suggest you use a power-of-two scale
factor :-)

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