linux-kernel - Re: [PATCH] pci: derive nearby CPUs from device's instead of bus' NUMA information

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Date:	Fri, 17 Apr 2009 18:21:15 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Andreas Herrmann <andreas.herrmann3@....com>
Cc:	jbarnes@...tuousgeek.org, "H. Peter Anvin" <hpa@...or.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH]  pci: derive nearby CPUs from device's instead of bus'
	NUMA information


* Andreas Herrmann <andreas.herrmann3@....com> wrote:

> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index a7eb1b4..9360f3d 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -74,7 +74,11 @@ static ssize_t local_cpus_show(struct device *dev,
>  	const struct cpumask *mask;
>  	int len;
>  
> +#ifdef CONFIG_NUMA
> +	mask = cpumask_of_node(dev_to_node(dev));
> +#else
>  	mask = cpumask_of_pcibus(to_pci_dev(dev)->bus);
> +#endif
>  	len = cpumask_scnprintf(buf, PAGE_SIZE-2, mask);
>  	buf[len++] = '\n';
>  	buf[len] = '\0';
> @@ -88,7 +92,11 @@ static ssize_t local_cpulist_show(struct device *dev,
>  	const struct cpumask *mask;
>  	int len;
>  
> +#ifdef CONFIG_NUMA
> +	mask = cpumask_of_node(dev_to_node(dev));
> +#else
>  	mask = cpumask_of_pcibus(to_pci_dev(dev)->bus);
> +#endif

No objections against the change (at all), but this pattern cries 
out for a different, cleaner solution.

Shouldnt there be a cpumask_of_pcidev(dev) helper instead, which 
[recognizing that most PCI devices dont get their node info 
initialized in practice] would do something like:

const struct cpumask * cpumask_of_pcidev(struct pci_dev *dev)
{
	if (dev->numa_node == -1)
		return cpumask_of_pcibus(to_pci_dev(dev)->bus);

	return cpumask_of_node(dev_to_node(dev));
}

? This would work fine in all cases.

Which you could thus use in both cases above, cleanly.

	Ingo
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