[erlang-questions] FreeBSD cpu topology detection

[Raimo Niskanen]

On Thu, Oct 16, 2014 at 06:04:44PM -0700, Garret Smith wrote:
> CPU topology detection seems broken (at least incomplete) on FreeBSD.
> erlang:system_info(cpu_topology) returns 'undefined' on the few machines I
> have at my disposal.
> 
> I'm going to take a stab at a patch, but I'd like some help from other
> FreeBSD users out there first.
> 
> Can any FreeBSD users please send me:
>     a) the output of 'sysctl kern.sched.topology_spec'
>     b) a few lines from your 'dmesg' about the processor configuration like:
> FreeBSD/SMP: Multiprocessor System Detected: 8 CPUs
> FreeBSD/SMP: 1 package(s) x 4 core(s) x 2 SMT threads
> 
> Even if your topology is correctly determined, this info will help me
> ensure I don't introduce a regression.
> 
> Thanks,
> Garret

Here are 5 machines, not much variation but anyway...

kern.sched.topology_spec: <groups>
 <group level="1" cache-level="0">
  <cpu count="8" mask="ff">0, 1, 2, 3, 4, 5, 6, 7</cpu>
  <children>
   <group level="2" cache-level="2">
    <cpu count="4" mask="f">0, 1, 2, 3</cpu>
   </group>
   <group level="2" cache-level="2">
    <cpu count="4" mask="f0">4, 5, 6, 7</cpu>
   </group>
  </children>
 </group>
</groups>

FreeBSD/SMP: Multiprocessor System Detected: 8 CPUs
FreeBSD/SMP: 2 package(s) x 4 core(s)



kern.sched.topology_spec: <groups>
 <group level="1" cache-level="0">
  <cpu count="4" mask="f">0, 1, 2, 3</cpu>
  <children>
   <group level="2" cache-level="2">
    <cpu count="4" mask="f">0, 1, 2, 3</cpu>
   </group>
  </children>
 </group>
</groups>

FreeBSD/SMP: Multiprocessor System Detected: 4 CPUs
FreeBSD/SMP: 1 package(s) x 4 core(s)



kern.sched.topology_spec: <groups>
 <group level="1" cache-level="0">
  <cpu count="4" mask="0xf">0, 1, 2, 3</cpu>
  <children>
   <group level="2" cache-level="2">
    <cpu count="4" mask="0xf">0, 1, 2, 3</cpu>
   </group>
  </children>
 </group>
</groups>

FreeBSD/SMP: Multiprocessor System Detected: 4 CPUs
FreeBSD/SMP: 1 package(s) x 4 core(s)



kern.sched.topology_spec: <groups>
 <group level="1" cache-level="0">
  <cpu count="4" mask="f">0, 1, 2, 3</cpu>
  <children>
   <group level="2" cache-level="2">
    <cpu count="4" mask="f">0, 1, 2, 3</cpu>
   </group>
  </children>
 </group>
</groups>

FreeBSD/SMP: Multiprocessor System Detected: 4 CPUs
FreeBSD/SMP: 1 package(s) x 4 core(s)



kern.sched.topology_spec: <groups>
 <group level="1" cache-level="0">
  <cpu count="2" mask="3">0, 1</cpu>
  <children>
   <group level="2" cache-level="2">
    <cpu count="2" mask="3">0, 1</cpu>
   </group>
  </children>
 </group>
</groups>

FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs
FreeBSD/SMP: 1 package(s) x 2 core(s)


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-- 

/ Raimo Niskanen, Erlang/OTP, Ericsson AB