Currently we as a company are evaluating KVM over XEN. So far KVM has been winning as far as performance particularly in disk I/O since our infrastructure will include iscsi/iser over infiniband. One problem we have run into is the cpu cache size is reported as being 4096 KB When in fact it should be reporting 15360 KB We have concluded that this is adversely affecting the performance on one of our J2EE applications that use lots of cpu. Identical Testing on XEN which does correct cpu passthrough show increased performance of the cpu compared to KVM. Is there any workaround or patch for this feature or possible something I'm missing when starting the vm to enable the additional cache? #this command is supposed to do direct cpu passthrough. qemu-kvm -S -M rhel6.3.0 -cpu host -enable-kvm -m 20480 -smp 8,sockets=8,cores=1,threads=1 #results from cat /proc/cpuinfo on the host processor : 23 vendor_id : GenuineIntel cpu family : 6 model : 45 model name : Intel(R) Xeon(R) CPU E5-2630 0 @ 2.30GHz stepping : 7 cpu MHz : 2294.231 cache size : 15360 KB physical id : 1 siblings : 12 core id : 5 cpu cores : 6 apicid : 43 initial apicid : 43 fpu : yes fpu_exception : yes cpuid level : 13 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm dca sse4_1 sse4_2 x2apic popcnt aes xsave avx lahf_lm arat xsaveopt pln pts dts tpr_shadow vnmi flexpriority ept vpid bogomips : 4588.30 clflush size : 64 cache_alignment : 64 address sizes : 46 bits physical, 48 bits virtual power management: # results from cat /proc/cpuinfo on the guest processor : 7 vendor_id : GenuineIntel cpu family : 6 model : 45 model name : Intel(R) Xeon(R) CPU E5-2630 0 @ 2.30GHz stepping : 7 cpu MHz : 2294.470 cache size : 4096 KB fpu : yes fpu_exception : yes cpuid level : 13 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss syscall nx lm constant_tsc arch_perfmon unfair_spinlock pni pclmulqdq ssse3 cx16 sse4_1 sse4_2 x2apic popcnt aes xsave avx hypervisor lahf_lm xsaveopt bogomips : 4588.94 clflush size : 64 cache_alignment : 64 address sizes : 46 bits physical, 48 bits virtual power management: Regards, Benjamin Rizkowsky ben@xxxxxxxxxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
