Klaus, I understand your frustration, but I think you misread my question. I wasn't asking if the vbox emulates instructions that are not supported by the host CPU, I was asking if the number of instructions on 386 vs. 686 which require workarounds (i.e patch manager) is different.
Assuming that 386 has less problematic instructions than 686, I should be able to get an improved performance if I compile the Linux kernel to target 386. On Mon, Jun 18, 2012 at 12:36 PM, Klaus Espenlaub < [email protected]> wrote: > On 18.06.2012 17:56, Ribhi Kamal wrote: > > I'm worried that some of these relatively new instructions might add > > more instructions that are troublesome to virtualize. So I'm inclined to > > using the arch with the smallest feature set, 386, rather than 686. Does > > that sound right? > > You expect detailed answers without giving the minimal set of facts - > what virtualization mode are you talking about? VirtualBoxe effectively > has 3 of them - the recompiler, raw mode and hardware virtualization. In > the last two effectively all "normal" instructions are executed usually > without significant overhead (ignoring interrupts/faults or unrelated > instructions which need attention by the hypervisor). In general, > VirtualBox tries to stay as much as possible in those two virtualization > modes (if available - there are conditions which may force going to the > recompiler). > > In any case, VirtualBox doesn't offer instructions which the host CPU > doesn't have (and actually might disable the CPUID feature bits for some > instruction set extensions which the CPU might have), and thus there is > no need for completely emulating something in software (the recompiler > often does it nevertheless, just to have everything under control). > > So don't worry too much about those fuzzy "relatively new instructions". > > Klaus > > > On Mon, Jun 18, 2012 at 10:58 AM, Alexey Eromenko <[email protected] > > <mailto:[email protected]>> wrote: > > > > On Mon, Jun 18, 2012 at 5:51 PM, Ribhi Kamal <[email protected] > > <mailto:[email protected]>> wrote: > > > >From a Virtualbox point of view, would a Linux kernel be > > easier/faster > > > to virtualize if it was targeted for a 386 CPU architecture, 486 > > or 686? > > > Would it make a difference at all? > > > > I think 686 would be faster, as more instructions are available > > (MMX, cmov, ...) > > > > -- > > -Alexey Eromenko "Technologov" > > > > _______________________________________________ > > vbox-dev mailing list > > [email protected] <mailto:[email protected]> > > https://www.virtualbox.org/mailman/listinfo/vbox-dev > > > > > > > > > > -- > > -- Ribhi > > > > > > _______________________________________________ > > vbox-dev mailing list > > [email protected] > > https://www.virtualbox.org/mailman/listinfo/vbox-dev > > > -- > Oracle <http://www.oracle.com> > Dr. Klaus Espenlaub | Snr. Manager Software Development Desktop > Virtualization > Phone: +49 7151 60405 205 <tel:+49715160405205> > Oracle VM VirtualBox > > ORACLE Deutschland B.V. & Co. KG | Werkstr. 24 | 71384 Weinstadt > > ORACLE Deutschland B.V. & Co. KG > Hauptverwaltung: Riesstr. 25, D-80992 München > Registergericht: Amtsgericht München, HRA 95603 > Geschäftsführer: Jürgen Kunz > > Komplementärin: ORACLE Deutschland Verwaltung B.V. > Hertogswetering 163/167, 3543 AS Utrecht, Niederlande > Handelsregister der Handelskammer Midden-Niederlande, Nr. 30143697 > Geschäftsführer: Alexander van der Ven, Astrid Kepper, Val Maher > > Green Oracle <http://www.oracle.com/commitment> Oracle is > committed to > developing practices and products that help protect the environment > > > _______________________________________________ > vbox-dev mailing list > [email protected] > https://www.virtualbox.org/mailman/listinfo/vbox-dev > -- -- Ribhi
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