On Mon, 2005-08-29 at 17:59 -0400, Jim C. Brown wrote: > Um, KQEMU/qvm86 don't do dynamic translation. They are virtualizers. They run > the code given to them (more or less) unchanged.
Sorry, I was speaking more generally (and imprecisely) about the qemu/kqemu as a combination. As you state below, there is still dynamic translation going on, just not by the kqemu or qvm86 modules. (snip) > > Without them, there is no native code run by qemu - everything is translated. > Yep. But even in that situation, there will always be room for improvement in how the dynamic code generator works. I wonder, has anyone tried doing a peephole optimizer? Translate key instruction sequences to macro instructions? There have got to be a few such high-traffic sequences that run all the time in Windows or Linux that could be implemented in the dynamically generated dynamic code generator. The most difficult part of the analysis would be to find such sequences for interesting guest OSs and applications. I think the implementation part would be pretty straightforward. You would have to take a hit computing a hash the first time through a translation block so that you could match up the block with the macroinstructions. Actually if GCC is around on the machine, it could even be done automatically. Put QEMU into a maintenance mode, and it would start to collect statistics about the translation blocks. You do your normal work on the guest machine for a little bit, maybe do a few processor intensive things that typically take too much time.. Then tell QEMU to stop collecting data. It looks at the translation blocks, and finds the top ten most popular translation blocks. It generates a little C file with the macro instructions in it, compiles it with gcc and generates a extension to the code generator tailored to the particular guest environment. I guess it's an open question whether handing gcc instruction primitives globbed together into into macroinstrucions will provide much benefit. Depends on how smart gcc is, I guess. -- John. _______________________________________________ Qemu-devel mailing list Qemu-devel@nongnu.org http://lists.nongnu.org/mailman/listinfo/qemu-devel
