kqemu runs 2x faster on i386 than amd64!?

RW fbsd06 at mlists.homeunix.com
Thu Oct 30 16:06:41 PDT 2008

On Thu, 30 Oct 2008 15:08:51 -0700
"Steve Franks" <stevefranks at ieee.org> wrote:

> > "Steve Franks" <stevefranks at ieee.org> writes:
> >
> >> Guess I should've mentioned the target is 32-bit win2k...
> >
> > If the target isn't the same as the host, I think it's going to have
> > to use (at least partial) emulation instead of direct execution...
> Yes, but isn't that the same for win2k regardless of wether the host
> is fbsdamd64 or fbsdi386?  Or are you talking 64 vs. 32 bit?

As I understand it, the performance advantage of kqemu over ordinary
qemu, comes from running many of the instructions in the emulation
directly on the host cpu. An amd64 compatible processor can't run
32-bit code in 64-bit mode and vice-versa, so it's either doing some
emulation or switching back and forth between 32/64-bit modes.

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