Re: [Qemu-devel] define desired speed?

["Laurent Desnogues" <laurent.desnogues@gmail.com>]

On Jan 15, 2008 10:34 PM, Jeremy C. Reed <reed@reedmedia.net> wrote:
> Any way to startup qemu with my own desired speed?

You can't as qemu emulated target speed is not constant.
qemu generates code on-the-fly and uses optimizations
that result in big variations.

Add to that there's no cycle accuracy at all.

> Bochs provides a CPU "IPS" (emulated Instructions Per Second)
> configuration that can be adjusted to get at least close to the desired
> speed.

IIRC Bochs is an interpreted simulator so it can count
instructions.  Counting instructions is only a crude
approximation as most processors have pipeline and
caches.

> I know that BogoMips is not a real benchmark, but the Linux system I am
> running in qemu says it is at 7497.31 BogoMIPS which is the probably same
> as if I booted the Linux system outside of qemu on same 1900Mhz hardware.
> (I was hoping to see the BogoMips in the 200 to 700 range.)

7.4 BGIPS is an indicator that the bogo loop was very
well optimized by qemu and/or the timer is wrong :-)


Laurent