On Thursday 03 January 2008 23:07:07 you wrote: > > Does anyone have an idea on how I can measure performance in qemu to a > > somewhat accurate level? I have modified qemu (the memory handling) and > > the linux kernel and want to find out the penalty this introduced... does > > anyone have any comments / ideas on this? > > Short answer is you probably can't. And even if you can I won't believe > tyour results unless you've verified them on real hardware :-) > > With the exception of some very small embedded cores, Modern CPUs have > complex out of order execution pipelines and multi-level cache hierarchies. > It's common for performance to be dominated by these secondary factors > rather than raw instruction throughput. > > Exactly what features dominate performance is very application specific. > Determining which factor dominates is unlikely to be something qemu can > help with. > > However if e.g. you know that for your application there's a good > correlation was between performance and L2 cache misses you could > instrument qemu to and a L1/L2 cache model. The overhead will be fairly > severe (easily 10x slower), and completely screw up any realtime > measurements. However it would produce some useful cache use statistics > that you could use to guesstimate actual performance. This is similar to > how cachegrind works. Obviously if your application isn't cache bound then > these figures will be meaningless.
Well, the measuring I had in mind partly concentrats on TLB misses, page faults, etc. (in addition to the cycle measuring). guess i'll have to implement something for myself in qemu :-/ But thanks a lot for helping me out!