QEMU slowdown and portability

Posted Feb 6, 2007 19:37 UTC (Tue) by jreiser (subscriber, #11027)
In reply to: KQEMU 1.3.0pre10 released - under the GPL by mikov
Parent article: KQEMU 1.3.0pre10 released - under the GPL

It is actually possible to run Windows in QEMU ... and it is completely usable.

QEMU and KQEMU are impressively good, but not that good. Installing TurboTax onto WindowsXP Pro running under Win4Lin Pro 3.0-0.7 [uses KQEMU] took around two hours, versus just a few minutes under native WindowsXP Pro running on the same hardware: a Pentium4 with 1GB RAM and "nothing" else running. Also, CPU utilization for (K)QEMU usually exceeds 90% even for simple things such as actually running TurboTax. WinXP graphics such as progress bars frequently do not get updated at all under Win4Lin. This shows that there is very little CPU power available for background tasks. TurboTax downloading updates thinks that something has gone wrong because the slowdown is excessive.

QEMU uses GCC ... (almost) trivially ported to any architecture supported by GCC

Except that QEMU's strategy requires a GCC version less than 4.0.

QEMU slowdown and portability

Posted Feb 7, 2007 0:19 UTC (Wed) by mikov (guest, #33179) [Link]

I am not closely familiar Win4Lin, but I am pretty sure that you cannot draw conclusions about QEMU from Win4Lin. They are completely different products, so I don't really see the relevance. AFAIK, Win4Lin does not use QEMU's user mode component, which is quite important.

I suggest you test with QEMU and install Win2K instead of WinXP before you form an opinion. I have never experienced such terrible performance as you are describing even without the accelerator. When running with full kernel virtualization (which was added recently,AFAIK), I found the performance comparable to VMWare. Plus, it certainly did not take me many hours to install Windows itself, and it is much larger than TurboTax.

I fail to see your point about GCC 4: this is not a fundamental technological limitation. Plus, there are no significant host architectures supported only by GCC4 and not by GCC3 (are there any at all?).

BTW, I am not affiliated with QEMU in any way, except by being a happy user. It has literally enabled me to do things that I didn't think possible, like running Windows-only applications as software appliances on a headless Linux box, which I find to be incredibly cool.

I will grant you that QEMU is not perfect though - for example saving and loading the virtual machine state doesn't work well yet, as of version 0.9.

QEMU slowdown and portability

Posted Feb 7, 2007 1:18 UTC (Wed) by mgalgoci (guest, #24168) [Link] (1 responses)

I believe you are mistaken about Win4Lin. Win4Lin is a linux port of ancient SCO software called "Merge". It even goes so far as to replace windows DLLs with special versions that attach to hooks inside linux, so it's not really virtualization as much as it is running two OS at the same time.

http://www.sco.com/products/merge/

Of course that was last time I looked, which was like three years ago. Maybe Win4Lin swapped out their core technology for something more sane.

QEMU slowdown and portability

Posted Feb 7, 2007 5:59 UTC (Wed) by rloomans (subscriber, #759) [Link]

That, indeed, was the previous version. It only supported up to Win98/Me. The current version
appears to be based on QEMU and supports Win2k and up.