On Tuesday 12 September 2006 14:19, Markus Schiltknecht wrote: > Paul Brook wrote: > > Modern CPUs are complicated, with many factors effecting execution speed > > (pipeline interlocks, multiple levels of cache). A cycle accurate > > simulator will generally be orders of magnitude slower than qemu. > > Would it be feasible to just limit the number of instructions qemu > simulates? Of course that's not very precise and most probably far from > cycle accurate. But it would allow to easily scale down a virtual > machine. Which then would allow comparable benchmarks or such. > > One step, somewhat more accurate would be to weight all the different > assembler commands with known (measured) average execution times. Taking > into account 40% cache misses, for example. (Hm.. but since cache misses > are very expensive, that might not lead to a much better approximation, > I guess)
I'd be surprised if you managed to get any sort of reliable results. Most of what you described can be achieved with profiling and static analysis. You could maybe get order-of-magnitude estimates (ie. do you need a 20MHz cpu or a 2GHz cpu), but I certainly wouldn't trust the results for deciding between eg. 500MHz and 200MHz cores. IMHO a benchmarking setup that doesn't reliably correspond to real system performance is worse than useless. Paul _______________________________________________ Qemu-devel mailing list Qemu-devel@nongnu.org http://lists.nongnu.org/mailman/listinfo/qemu-devel
