[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] VT-d scalability issue
Keir, I have found a VT-d scalability issue and want to some feed backs. When I assign a pass-through NIC to a linux VM and increase the num of VMs, the iperf throughput for each VM drops greatly. Say, start 8 VM running on a machine with 8 physical cpus, start 8 iperf client to connect each of them, the final result is only 60% of 1 VM. Further investigation shows vcpu migration cause "cold" cache for pass-through domain. following code in vmx_do_resume try to invalidate orig processor's cache when 14 migration if this domain has pass-through device and no support for wbinvd vmexit. 16 if ( has_arch_pdevs(v->domain) && !cpu_has_wbinvd_exiting ) { int cpu = v->arch.hvm_vmx.active_cpu; if ( cpu != -1 ) on_selected_cpus(cpumask_of_cpu(cpu), wbinvd_ipi, NULL, 1, } So we want to pin vcpu to free processor for domains with pass-through device in creation process, just like what we did for NUMA system. What do you think of it? Or have other ideas? Thanks, -- best rgds, edwin _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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