On 10/17/2012 03:06 PM, Dusty Mabe wrote:
Hi,
Would it be possible to augment the output produced in virsh capabilities to also provide the hyperthreaded sibling of a processor? For example the information would look something like:
<topology>
<cells num='2'> <cell id='0'> <cpus num='8'> <cpu id='1' sibling='9'/>
Indeed, that sounds useful, and it is strictly additive so there is no technical reason preventing that addition.
I notice that you guys are actually using some of the numactl stuff (numa.h) to query for the cpus on a given node and I have combed through that code to see if it provided any info about hyperthreaded siblings but from what I can tell it does not. I have tinkered around with the hwloc libraries (http://www.open-mpi.org/projects/hwloc/) and have written a short program to print out each logical cpu and its hyperthreaded sibling (see attached)
We haven't used hwloc before, but if that is the only way to get at the sibling information, it sounds like it might be a reasonable additional requirement for libvirt. On Fedora 17, I see: hwloc x86_64 1.4.1-2.fc17 updates 1.1 M hwloc-devel x86_64 1.4.1-2.fc17 updates 150 k so it looks like -lhwloc is currently bundled alongside the hwloc command line executable; the library itself is decently small: -rwxr-xr-x. 1 root root 163168 Apr 18 16:27 /usr/lib64/libhwloc.so.5.0.1 so I wonder if Fedora packaging should split that up so we only drag in the library instead of the whole command line utility. But that's a concern for Fedora, not this list.
Would you guys ever consider adding something like this? I would be willing to help create a patch if I had some guidance.
Absolutely! It sounds like there's several major places to touch to add this in: configure.ac - check for presence of hwloc libvirt.spec.in - require hwloc on new-enough Fedora docs - document the new XML docs/schemas - accept the new XML during RNG validation src/nodeinfo.c - use the new library, when availalble, to get at the new information tests - add a new xml file that demonstrates the RNG changes accept the new XML You may find it helpful to read http://libvirt.org/hacking.html -- Eric Blake eblake@redhat.com +1-919-301-3266 Libvirt virtualization library http://libvirt.org