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 12:26:54 -0700
From:	Yinghai Lu <yhlu.kernel@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Andreas Herrmann <andreas.herrmann3@....com>,
	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

On Fri, Apr 17, 2009 at 9:21 AM, Ingo Molnar <mingo@...e.hu> wrote:
>
> * 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.

you are right, dev_to_node(dev) could return -1 on 64bit, if there is
no memory on that node.

YH
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