Re: [libvirt] Paradox cpu topology in capabilities outputs

On Wed, Jan 11, 2017 at 06:52:45AM +0000, Qiao, Liyong wrote: > Hi, > > I observe that virsh capabilities give wrong cpu topology on a multiple sockets host > > taget@jfz1r04h13:~/libvirt$ lscpu > Architecture: x86_64 > CPU op-mode(s): 32-bit, 64-bit > Byte Order: Little Endian > CPU(s): 72 > On-line CPU(s) list: 0-71 > Thread(s) per core: 2 > Core(s) per socket: 18 > Socket(s): 2 <------------------------ > NUMA node(s): 2 > Vendor ID: GenuineIntel > CPU family: 6 > Model: 63 > Model name: Intel(R) Xeon(R) CPU E5-2699 v3 @ 2.30GHz > Stepping: 2 > CPU MHz: 1201.660 > CPU max MHz: 3600.0000 > CPU min MHz: 1200.0000 > BogoMIPS: 4590.78 > Virtualization: VT-x > L1d cache: 32K > L1i cache: 32K > L2 cache: 256K > L3 cache: 46080K > NUMA node0 CPU(s): 0-17,36-53 > NUMA node1 CPU(s): 18-35,54-71 > > But output of virsh capabilities only gives. > > <topology sockets='1' cores='18' threads='2'/> The 'sockets' value is basically "sockets-per-NUMA-node". > > looking into code and got this: > https://libvirt.org/git/?p=libvirt.git;a=blob;f=src/util/virhostcpu.c;h= f29f3122acee018b9fd7dca06fd7ae1fc118b210;hb=HEAD#l703 > > should we change it into > > 704<https://libvirt.org/git/?p=libvirt.git;a=blob;f=src/ util/virhostcpu.c;h=f29f3122acee018b9fd7dca06fd7ae1fc118b210;hb=HEAD#l704> *sockets += nodesockets; > > > This also affect nodeinfo.sockets. BOth the <topology> summary and nodeinfo data is really a broken design as it can't cope with asymetric topologies. We recommend apps to completely ignore this data, and instead look at the fine grained topology info in the capabilities: <topology> <cells num='2'> <cell id='0'> ... <cpus num='6'> <cpu id='0' socket_id='0' core_id='0' siblings='0'/> <cpu id='1' socket_id='0' core_id='2' siblings='1'/> <cpu id='2' socket_id='0' core_id='4' siblings='2'/> <cpu id='6' socket_id='0' core_id='1' siblings='6'/> <cpu id='7' socket_id='0' core_id='3' siblings='7'/> <cpu id='8' socket_id='0' core_id='5' siblings='8'/> </cpus> </cell> ... </cells> </topology>

Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://entangle-photo.org -o- http://search.cpan.org/~danberr/ :| -- libvir-list mailing list libvir-list(a)redhat.com https://www.redhat.com/mailman/listinfo/libvir-list