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Subject: Re: [hwloc-devel] How to get information about hwloc objects?
From: Jirka Hladky (jhladky_at_[hidden])
Date: 2010-07-08 05:18:29


On Wednesday, July 07, 2010 04:56:54 pm Brice Goglin wrote:
> Le 07/07/2010 13:48, Jirka Hladky a écrit :
> > I know that such mapping is artificial. However, it enables me to see
> > that hyper threading is enabled. I use it in my reports only.
>
> Just compare the number of cores and the number of PUs. It should be
> enough to know if each core has multiple threads. On some architectures
> (power7), this may require recent kernels before everything shows up
> properly. But on x86 and ia64, I think things should be fine.
Yes, I'm already doing this:-)

>
> > I wonder if some similar concept exists in hwloc. To be honest, I don't
> > know what the future of "thread id" in /proc/cpuinfo file is. It seems
> > to be only in /proc/cpuinfo for ia64.
>
> We currently have no room to store this thread id since it would likely
> to go in the physical index of PU objects but we already store the
> logical processor index there. But we could add some PU-specific
> attributes to store it if somebody really needs this thread id.
>
> /proc/cpuinfo is highly non portable anyway, so it's not clear we really
> want to look closely at what it contains. And parsing /sys is much
> easier than /proc/cpuinfo. Do you see this thread_id in
> /sys/devices/system/cpu/cpu%d/topology/ ?

I agree that /proc/cpuinfo is non portable. That's why we are moving to
hwloc:-)

I have checked
/sys/devices/system/cpu/cpu%d/topology/
and there is no thread_id.

So I my conclusion is that that it does not make sense to look into it
further.

Thanks!
Jirka