Re: [RFC] The meaning of local_cpulist and local_cpus

[Mike Travis <travis@sgi.com>]

On 4/24/2013 9:48 AM, Bjorn Helgaas wrote:
> [+cc linux-pci, Mike]
> 
> On Wed, Apr 24, 2013 at 4:06 AM, Bian LuLu <helianthus.lu@gmail.com> wrote:
>> Hi all,
>>
>> Recently, i read some codes of PCI portions. I think
>> local_cpulist is a list about one kind of CPU and
>> local_cpus is a mask of CPU. But i am not sure when
>> and how i should use these two parameters.
>>
>> See http://lxr.linux.no/linux+v3.5.4/drivers/pci/pci-sysfs.c#L390 for
>> details.
>>
>> Would anyone please give me some suggestions?
>> Thanks in advance ;-)
> 
> I don't know off-hand, but maybe Mike or somebody on linux-pci does.
> It looks like Mike added local_cpulist with 39106dcf85.
> 

It primarily comes into play when you have a large # of cpus.
Here's the difference on a system that has 1024 cpu threads:

harp31-sys:/sys/devices/system/node/node20 # cat cpulist
160-167,672-679
harp31-sys:/sys/devices/system/node/node20 # cat cpumap
00000000,00000000,00000000,00000000,00000000,00000000,00000000,
00000000,00000000,00000000,000000ff,00000000,00000000,00000000,
00000000,00000000,00000000,00000000,00000000,00000000,00000000,
00000000,00000000,00000000,00000000,00000000,000000ff,00000000,
00000000,00000000,00000000,00000000

Which is easier to interpret?  :)

But there are some older user side utilities that still
use the mask format.