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Subject: Re: [hwloc-devel] How to get information about hwloc objects?
From: Jirka Hladky (jhladky_at_[hidden])
Date: 2010-07-07 07:48:51

Hi Brice,

I have one question regarding thread id:
./hwloc-calc --physical --list core proc:60
is matching with
core id : 11 from /proc/cpuinfo

./hwloc-calc --physical --list socket proc:60
is matching with
physical id : 0 from /proc/cpuinfo

and obviously --physical proc:60 corresponds to
processor : 60 from /proc/cpuinfo

On Itanium there is also
thread id : 0
line in /proc/cpuinfo

In our current code (based solely on /proc/cpuinfo, we are moving it to use
hwloc instead) we are using "thread id". Currently, on boxes with hyper
threading enabled I parse lstopo output and map "physical thread id" following

  NUMANode #2 (phys=3 2048MB) + Socket #3 + L3 #3 (24MB)
    L2 #24 (256KB) + L1 #24 (32KB) + Core #24
      PU #48 (phys=3) => thread id 0
      PU #49 (phys=35) => thread id 1
    L2 #25 (256KB) + L1 #25 (32KB) + Core #25
      PU #50 (phys=7) => thread id 0
      PU #51 (phys=39) => thread id 1

(You can think of it as doing logical_CPU modulo <number of HW threads on
given Core>)

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.

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.

Thanks for your opinion!

PS: I have included /proc/cpuinfo from IA64 box.