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Subject: Re: [hwloc-devel] restricted topology (& topology changes)
From: Fawzi Mohamed (fawzi_at_[hidden])
Date: 2009-09-27 09:26:40


On 27-set-09, at 14:37, Samuel Thibault wrote:

> Brice Goglin, le Sun 27 Sep 2009 14:18:54 +0200, a écrit :
>> Samuel Thibault wrote:
>>>> but shouldn't it return the restricted topology (or have a method
>>>> that
>>>> returns the restricted topology).
>>>>
>>>
>>> It should already be the default. To get the whole system, see
>>> lstopo
>>> --help: --whole-system
>>
>> Maybe he's referring to when the process launcher does a
>> sched_setaffinity/numatcl to restrict this process, as opposed to
>> administrator-wide restriction with linux cpusets or so. We could add
>> another topology flag for such restrictions.
>
> Ah, right.

thanks for the quick answers, so I think that the answer is for now
you can on linux 2.6 if you use cpusets.
Having my app starting a a restricted subtask that will see it in its
topology in a portable way is not possible at the moment, if I
understood correctly.
Still it is already something.

>>> I've wondered how to implement topology changes indeed. AIX does
>>> have a
>>> SIGRECONFIG signal for this, I don't know any support from other
>>> OSes.
>>
>> Maybe there's a inotify way to get such changes in Linux.
>
> There is usually no inotify support for virtual files. I've just
> tested
> that it doesn't work for /sys/bus/usb/devices for instance. We'll have
> to ask kernel developers for it.

ok just as information osx has such a callback if possible it would be
nice to have such functionality abstracted away...

thanks

Fawzi