All, I am performing a study about KVM. (Shame on me, I did not check the version of kvm module. All I know is that I was using the last Red Hat EL 5.4. Anyway). I used a DELL server 2950, with: - 1 processor Xeon L5240 (3 Ghz, 6 Mo cache) - 8 GB of RAM - 4 disks SAS 15k in RAID-1 I created a procedure consist to launch a benchmark on several virtual machine at the same time. Each session consist in testing X VM, where X comes from 1 to 8. With nbench, I collected all results and extracted an average value of results for each VM. Then, I multiplied these average values by the number of VM in test, getting one unique and generic value per session of test. I did nearly the same with unixbench. On the host side, I launched the same tests, except that instead of running them in separate VM, I just launched several threads at the same time thanks to a script. My main purpose is watching the overhead due to these different hypervisors, according bechmark results. I am not really in trouble with KVM itself, but results of my benchmarks: -> http://img121.imageshack.us/img121/9279/nbench.png -> http://img704.imageshack.us/img704/953/unixbench.png Indeed, where I have all results growing from 1 VM tested to 8 VM, we can see the host growing from 1 to 8 VM. which seems good. But KVM only increases from 1 to 4 VM, and then stays on the same order of results, without growing anymore. The situation is inverse on Unixbench, where KVM seems to follow host's performances. So now I wonder which test is reliable. Is unixbench right? It is possible, I don't know why KVM could be so different from the host since it can use hardware CPU instructions for virtualization. In the other hand, nbench is in fact doing 3 tests(Fourrier, Neural Net, LU decomposition) and unixbench only 1 (whetstone). This last test could be outdated and therefore nbench in the truth? I've got nearly the same problems with integers tests (nbench vs unixbench) and cache memory (nbench vs cachebench). Anyone have got an idea? -- Matthieu Olivier -- 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
