[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-users] Dual Core processor options
Simon <greminn@xxxxxxxxx> wrote on 12/07/2005 05:31:59 PM: > Hi There, Having read about this somewhere recently, am i correct in > assuming that if you have a (say) dual processor server with dual core > processors, that you can assign domU's to individual cores? for > example: > > 2 domUs on 1 core of one processor > 1 domU on the other core of the same processor > 1 domU to both cores of the other processor > > This allocation would of couse reflect the indented usage of domUs In Xen 3.0 you can use the "cpus=" option in the domain configuration file to set which cpus the domain's vcpus should map to. As far as I know, you can't map the vcpus to cores or processors directly; you map vcpus to cpus. In my experience, you have to know ahead of time which processor and core a CPU is on in order to know what the vcpu should map to. And the assignment of CPU numbers is not necessarily in a linear fashion, e.g. with hyperthreading, CPU 0 ->core 0 -> processor 0, CPU 1 ->core 0 -> processor 0, CPU 2 ->core 1 -> processor 0, ... , CPU 4 ->core 0 -> processor 1, etc. The only way I have found so far to discover Xen's mapping of CPUS to processors and cores is to examine the output of "xm dmesg". I wrote a little script to parse the output of "xm dmesg", extract the CPU information, and print it out in a simpler format. Here is some sample output from my 4 processor, dual core, hyperthreaded machine. Processor 0, Core 0, CPU 0 Processor 0, Core 0, CPU 10 Processor 0, Core 1, CPU 6 Processor 0, Core 1, CPU 14 Processor 1, Core 2, CPU 7 Processor 1, Core 2, CPU 15 Processor 1, Core 3, CPU 3 Processor 1, Core 3, CPU 11 Processor 2, Core 4, CPU 1 Processor 2, Core 4, CPU 8 Processor 2, Core 5, CPU 4 Processor 2, Core 5, CPU 12 Processor 3, Core 6, CPU 5 Processor 3, Core 6, CPU 13 Processor 3, Core 7, CPU 2 Processor 3, Core 7, CPU 9 As you can see the assignments are not linear according to IDs. If dom0 is running on cpu 0 and I want to put my domU on another processor, I can set "cpus=1-5,7-9,11-13,15". Not very straight forward, but it works. Anyone with better knowledge or experience, feel free to comment and correct. Steve D. _______________________________________________ Xen-users mailing list Xen-users@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-users
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