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)
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