Re: [Xen-devel] Hwloc with Xen host topology

[Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>]

Andrew Cooper, le Thu 02 Jan 2014 21:50:06 +0000, a écrit :
> On 02/01/14 21:24, Samuel Thibault wrote:
> > 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 :)
> 
> 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...

Well, logical processor physical ids, i.e. what is used for indexing
physical cpusets, have to be unique. The core/socket/node IDs don't have
to.

Samuel

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