Re: Hwloc with Xen host topology

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 02/01/14 21:24, Samuel Thibault wrote:
> Hello,
>
> Andrew Cooper, le Thu 02 Jan 2014 20:26:49 +0000, a écrit :
>> Cores are numbered per-socket in Xen, while sockets,
>> numa nodes and cpus are numbered on an absolute scale.  There is
>> currently a gross hack in my hwloc code which adds (socket_id *
>> cores_per_socket * threads_per_core) onto each core id to make them
>> similarly numbered on an absolute scale.  This is fine for a homogeneous
>> system, but not for a hetrogeneous system.
> BTW, hwloc does not need these physical ids to be unique, it can cope
> with duplication and whatnot.  That said, having a coherent interface at
> the Xen layer would be a good thing, indeed :)
>
> Samuel

If I take out the described hack, I am presented with

****************************************************************************
* hwloc has encountered what looks like an error from the operating system.
*
* object (Core P#0 cpuset 0x30000003) intersection without inclusion!
* Error occurred in topology.c line 853
*
* Please report this error message to the hwloc user's mailing list,
* along with the output from the hwloc-gather-topology.sh script.
****************************************************************************

Which I took to mean "I have done something stupid".  I looked and saw
that I was attempting to insert a second Core P#0 object with a
different cpuset and decided to renumber the cores so they didn't
overlap in physical ids.

If you believe that this should indeed work, then I guess I need to
raise a bug...

~Andrew