[libvirt-users] QEMU-KVM and bare metal performance impact

Hi, My name is Rajiv Nishtala and I am a PhD student in UPC. I am trying to investigate the performance (instructions per second (IPS)) impact of an application on QEMU-KVM and bare metal using the performance monitoring tools perfmon and perf. The performance counter used for measuring this is "instructions" and "instructions_retired" on perf and perfmon, respectively. The application is a *stress* microbenchmark that does not produce any cache misses (LLC). I account for the performance of the application on QEMU-KVM using the following procedure: A) Record the IPS of the QEMU-KVM (using its PID) on perf and perfmon when idle. B) Launch the stress benchmark and record IPS. C) the difference between *B* and *A* should give the performance of the application since the KVM does not inherently provide a technique to collect this statistic. However the performance of the application on bare metal is recorded as is using the per-thread session available in perfmon and perf. The sampling frequency to collect the statistics is 1 second. The result obtained on bare metal are in the order of magnitude of billions. On the other hand, results from KVM do not show any difference in performance when idle or when an application is running and is in the order of magnitude of 100's of thousands. IPS_KVM_IDLE LLC_KVM_IDLE IPS_KVM_STRESS LLC_KVM_STRESS IPS_bare metal_STRESS LLC_bare metal_STRESS 47902 2495 25157 600 8116556011 3805 23437 758 48762 1032 8166564000 2140 834370 9954 543690 2379 8326333629 234 25261 662 49139 997 8057453733 1399 47998 2767 23773 600 8214761042 494 542039 2299 843266 2231 8075529487 4593 47982 2781 25249 603 8327678364 443 23833 794 49138 622 8058893864 1870 832913 9978 544567 2204 8210889659 394 I also tried using perf-kvm using the following command: sudo perf kvm --guest --guestkallsyms=guest-kallsyms --guestmodules=guest-modules record -a -o perf.data but failed with the following error: *Couldn't record guest kernel [0]'s reference relocation symbol. *and no events were recorded. I describe details of QEMU and the host machine (bare metal) below. QEMU emulator version 2.0.0 in conjunction with KVM as the virtual environment and libvirt 1.2.2 The guest machine is running kernel version 3.19.0-15-generic and the host machine is running version 3.14.5-031405-generic on a x86_64 machine I setup the guest machine with Intel SandyBridge processor (model name:Intel Xeon E312xx) with the following flags: sockets=2,cores=2,threads=1 and 4mb cache. More details: cpu family : 6 model : 42 max freq : 2394.560 MHz flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss ht syscall nx rdtscp lm constant_tsc rep_good nopl eagerfpu pni pclmulqdq vmx ssse3 cx16 pcid sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave avx hypervisor lahf_lm vnmi ept xsaveopt The host machine is an Intel Sandy Bridge processor (Intel(R) Core(TM) i7-2760QM CPU @ 2.40GHz) with 4 cores and 6mb cache. cpu family : 6 model : 42 flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf eagerfpu pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave avx lahf_lm ida arat epb xsaveopt pln pts dtherm tpr_shadow vnmi flexpriority ept vpid Thanks Rajiv Nishtala WARNING / LEGAL TEXT: This message is intended only for the use of the individual or entity to which it is addressed and may contain information which is privileged, confidential, proprietary, or exempt from disclosure under applicable law. If you are not the intended recipient or the person responsible for delivering the message to the intended recipient, you are strictly prohibited from disclosing, distributing, copying, or in any way using this message. If you have received this communication in error, please notify the sender and destroy and delete any copies you may have received. http://www.bsc.es/disclaimer