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Subject: Re: [hwloc-devel] restricted topology (& topology changes)
From: Brice Goglin (Brice.Goglin_at_[hidden])
Date: 2009-09-27 08:18:54


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.

>> Another thing that would be nice to have (but much less important for
>> me) is having a callback that can be called when/if the topology
>> changes.
>>
>
> 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.
> that'd mean having to poll for changes, how often, and in which context?
> (another thread? an explicit polling request from the application?). I'd
> rather avoid the thread usage and just let the application decide both
> how often and in which context. In other words, actually maybe all we
> need is a function to compare two topologies?
>

Maybe there's a inotify way to get such changes in Linux.

Brice