Hello,
My testing machine has 2 quad-core CPU (It supports hyperthreading,
but i disable it in BIOS). I uses Xen 4.0.1 as the hypervisor. When I use 8
VMs to conduct a test, CPU affinity of the VMs is very strange. Like this:
vm_name vcpu_num cpu_affinity
Domain-0 8 any
VM1 4 1,3,5,7
VM2 4 1,3,5,7
VM3 4 1,3,5,7
VM4 4 1,3,5,7
VM5 4 1,3,5,7
VM6 4 0,2,4,6
VM7 4 0,2,4,6
VM8 4 0,2,4,6
I do not set the CPU affinity in the configuration file, and I cannot find
when the hypervisor set the CPU affinity in the source code. In this
situation, 4 VCPUs of each VM are binding to 4 PCPUs permanently, and 5 VMs
run on a set of PCPUs, and others run on the other set of PCPUs. It is
unfair to these VMs.
--
Like Zhou
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On 15.03.2013 10:08, 周理科 wrote:> Hello, > My testing machine has 2 quad-core CPU (It supports hyperthreading, but i > disable it in BIOS). I uses Xen 4.0.1 as the hypervisor. When I use 8 VMs to > conduct a test, CPU affinity of the VMs is very strange. Like this: > > vm_name vcpu_num cpu_affinity > Domain-0 8 any > VM1 4 1,3,5,7 > VM2 4 1,3,5,7 > VM3 4 1,3,5,7 > VM4 4 1,3,5,7 > VM5 4 1,3,5,7 > VM6 4 0,2,4,6 > VM7 4 0,2,4,6 > VM8 4 0,2,4,6 > > I do not set the CPU affinity in the configuration file, and I cannot find when > the hypervisor set the CPU affinity in the source code. In this situation, 4 > VCPUs of each VM are binding to 4 PCPUs permanently, and 5 VMs run on a set of > PCPUs, and others run on the other set of PCPUs. It is unfair to these VMs.I'd suspect NUMA optimization. xend tries to optimize domain placement by pinning the vcpus of the domains to cores in the same NUMA domain. Normally the overall performance is better with this optimization. You can disable it by specifying numa=off as an additional xen boot parameter for the hypervisor (not the dom0 kernel). You can see whether you have NUMA active with xm info It will display line(s) like: node_to_cpu : node0:0-3 If you see multiple nodes you have NUMA active. Juergen -- Juergen Gross Principal Developer Operating Systems PBG PDG ES&S SWE OS6 Telephone: +49 (0) 89 3222 2967 Fujitsu Technology Solutions e-mail: juergen.gross@ts.fujitsu.com Domagkstr. 28 Internet: ts.fujitsu.com D-80807 Muenchen Company details: ts.fujitsu.com/imprint.html _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
2013/3/15 Juergen Gross <juergen.gross@ts.fujitsu.com>> On 15.03.2013 10:08, 周理科 wrote: > >> Hello, >> My testing machine has 2 quad-core CPU (It supports hyperthreading, >> but i >> disable it in BIOS). I uses Xen 4.0.1 as the hypervisor. When I use 8 VMs >> to >> conduct a test, CPU affinity of the VMs is very strange. Like this: >> >> vm_name vcpu_num cpu_affinity >> Domain-0 8 any >> VM1 4 1,3,5,7 >> VM2 4 1,3,5,7 >> VM3 4 1,3,5,7 >> VM4 4 1,3,5,7 >> VM5 4 1,3,5,7 >> VM6 4 0,2,4,6 >> VM7 4 0,2,4,6 >> VM8 4 0,2,4,6 >> >> I do not set the CPU affinity in the configuration file, and I cannot >> find when >> the hypervisor set the CPU affinity in the source code. In this >> situation, 4 >> VCPUs of each VM are binding to 4 PCPUs permanently, and 5 VMs run on a >> set of >> PCPUs, and others run on the other set of PCPUs. It is unfair to these >> VMs. >> > > I''d suspect NUMA optimization. xend tries to optimize domain placement by > pinning the vcpus of the domains to cores in the same NUMA domain. Normally > the overall performance is better with this optimization. You can disable > it > by specifying > > numa=off > > as an additional xen boot parameter for the hypervisor (not the dom0 > kernel). > You can see whether you have NUMA active with > > xm info > > It will display line(s) like: > > node_to_cpu : node0:0-3 > > If you see multiple nodes you have NUMA active. > > > Juergen > > -- > Juergen Gross Principal Developer Operating Systems > PBG PDG ES&S SWE OS6 Telephone: +49 (0) 89 3222 2967 > Fujitsu Technology Solutions e-mail: > juergen.gross@ts.fujitsu.com > Domagkstr. 28 Internet: ts.fujitsu.com > D-80807 Muenchen Company details: > ts.fujitsu.com/imprint.html >Yes. When I disable NUMA optimization, CPU affinity of each VCPU becomes "any". Thanks. -- Like Zhou _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel