linux-kernel - Re: [PATCH 02/13] genirq/affinity: Provide smarter irq spreading infrastructure

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Date:   Wed, 21 Sep 2016 14:29:44 +0200
From:   Alexander Gordeev <agordeev@...hat.com>
To:     Christoph Hellwig <hch@....de>
Cc:     axboe@...com, tglx@...utronix.de, keith.busch@...el.com,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/13] genirq/affinity: Provide smarter irq spreading
 infrastructure

On Wed, Sep 14, 2016 at 04:18:48PM +0200, Christoph Hellwig wrote:
> +/**
> + * irq_calc_affinity_vectors - Calculate to optimal number of vectors for a given affinity mask
> + * @affinity:		The affinity mask to spread. If NULL cpu_online_mask
> + *			is used
> + * @maxvec:		The maximum number of vectors available
> + */
> +int irq_calc_affinity_vectors(const struct cpumask *affinity, int maxvec)
> +{
> +	int cpus, ret;
> +
> +	/* Stabilize the cpumasks */
> +	get_online_cpus();
> +	/* If the supplied affinity mask is NULL, use cpu online mask */
> +	if (!affinity)
> +		affinity = cpu_online_mask;
> +
> +	cpus = cpumask_weight(affinity);

Should not we consider the result of AND of affinity and cpu_online_mask?

> +	ret = (cpus < maxvec) ? cpus : maxvec;
> +
> +	put_online_cpus();
> +	return ret;
> +}
> +
>  static int get_first_sibling(unsigned int cpu)
>  {
>  	unsigned int ret;
> -- 
> 2.1.4
>