On ven, 2013-12-20 at 09:09 +0000, Wangyufei (James) wrote:
hi , I am confused by pinvcpu before migration.
I have two physical machine. One has 12 CPUs (E5645 2*6 ) as src and the other has 8 CPUs (2*4) as des.
Step 1 : VM is running on src host (E5645 2*6 CPUs) with its VCPUs pinned on some PCPUs
Step 2 :Because PCPU count is different between src and des , I should pin VCPUs to all PCPUs . virsh vcpupin vmname 0 0-11 --config --live
Step 3: Do migrate ,and it failed with error in des libvirt log "Unable to set cpuset.cpus: Invalid argument"
I find that VM's cpu bitmap on src turns to <vcpupin vcpu='0' cpuset='0-11'/> . vm start fails on des due to its pin info cpuset='0-11' in vm->def.
In usual case, after I pin VCPU to all PCPU, vcpupin info will be deleted in vm->def.
Is that the case? AFAICT, reset happens upon explicit request, e.g., something like: # virsh vcpupin vmname 0 r --config --live This is at least what works for me with both QEMU and libxl drivers.
-- qemuDomainPinVcpuFlags -- if (virBitmapIsAllSet(pcpumap, pCpuCount)) doReset = true; -- if (doReset) if (virDomainVcpuPinDel(vm->def, vcpu) < 0)
Exactly, and that virBitmapIsAllSet() is true when you pass 'r' as cpulist to the `virsh vcpupin' command, rather than some actual set of pcpus, even if the latter spans all the pcpus on your host.
I debug libvirt and find that on src which PCPU count is 12 (2*6) virBitmapIsAllSet(pcpumap, pCpuCount) return false
Probably because the bitmap is not 12 bits wide! ;-P
pcpumap->max_bit is 16. pcpumap = virBitmapNewData(cpumap, maplen) --> bitmap = virBitmapNew(len * CHAR_BIT); //here len is 2.
Although my physical machine only has 12 PCPUs , but here pcpumap->max_bit is len*CHAR_BIT . So bitmap is 0000 1111 1111 1111 ,and it's not ALL SET (ALL SET is 1111 1111 1111 1111).
Exactly.
I tried to fix the bug in this case , but I have not found a good solution.
That's because it's not wrong. I do agree that there may be tricky cases, but this one of yours doesn't look like one. Just use 'r'. Regards, Dario -- <<This happens because I choose it to happen!>> (Raistlin Majere) ----------------------------------------------------------------- Dario Faggioli, Ph.D, http://about.me/dario.faggioli Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)