Open MPI logo

Hardware Locality Development Mailing List Archives

  |   Home   |   Support   |   FAQ   |   all Hardware Locality Development mailing list

Subject: Re: [hwloc-devel] How to get information about hwloc objects?
From: Brice Goglin (Brice.Goglin_at_[hidden])
Date: 2010-07-07 10:56:54

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.

> 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/ ?