On Sat, 2005-04-16 at 22:58 -0700, Joe Luser wrote: > Hi folks, > > I've been using Qemu on the Mac for a few days now; Several OSes > running (including Windoze), and I'm impressed. The source looks pretty > clean, too. > > Has anyone done any profiling work to see where Qemu spends most of its > processing time? It is fast running x86 code on the PPC, but I'd like > to find ways to speed things up even more. > > If you know of areas that will make a big difference in speed, please > let me know. > > -Nathaniel G H > >
>From what I've read the Cirrus SVGA emulation probably deserves some attention. Read through the archives, there have been some recent discussions. Beyond that what will always be left is continually tweaking the dynamic code generator with whatever heuristics and host platform specific stuff you can conjure up. Pretty much no end to that sort of thing. QEMU takes executing machine instructions from one virtual computer and dynamically translates them to the working equivalent on another (the host), stores them in cache to save reprocessing time (that's the *big* time-saving heuristic over Bochs) and executes the dynamically generated code on the host. Think of it like this: aside from speed, the best generator of dynamic code would be an expert assembly language programmer on the platform you are translating code from and to. As you can imagine QEMU has tricks and leverages GCC but it will never attain the nirvana of being as good as the assembly language programmer. That's an asymptote. So that's why I say there will always be lots of things you can do on the dynamic code generator to speed it up. One thought would be to have a peephole optimizer that looks back over the just translated basic block (or a state machine that matches such sequences as an on-line algorithm) and match against common, known primitive sequences, and replaces them with optimized versions. The kind of profiling you would want to do here is to run, say, windows and take a snapshot of the dynamic code cache, and look for common instruction sequences. Ideally, you could write some software to do this automatically. Anyway, I'm sure there are lots of other ideas laying around. -- John. _______________________________________________ Qemu-devel mailing list Qemu-devel@nongnu.org http://lists.nongnu.org/mailman/listinfo/qemu-devel
