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For Shared Processor LPARs, the POWER Hypervisor maintains a relatively static mapping of the LPAR processors (vcpus) to physical processor chips (representing the "home" node) and tries to always dispatch vcpus on their associated physical processor chip. However, under certain scenarios, vcpus may be dispatched on a different processor chip (away from its home node). The actual physical processor number on which a certain vcpu is dispatched is available to the guest in the 'processor_id' field of each DTL entry. The guest can discover the home node of each vcpu through the H_HOME_NODE_ASSOCIATIVITY(flags=1) hcall. The guest can also discover the associativity of physical processors, as represented in the DTL entry, through the H_HOME_NODE_ASSOCIATIVITY(flags=2) hcall. These can then be compared to determine if the vcpu was dispatched on its home node or not. If the vcpu was not dispatched on the home node, it is possible to determine if the vcpu was dispatched in a different chip, socket or drawer. Introduce a procfs file /proc/powerpc/vcpudispatch_stats that can be used to obtain these statistics. Writing '1' to this file enables collecting the statistics, while writing '0' disables the statistics. The statistics themselves are available by reading the procfs file. By default, the DTLB log for each vcpu is processed 50 times a second so as not to miss any entries. This processing frequency can be changed through /proc/powerpc/vcpudispatch_stats_freq. Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> |
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