enabling/disabling trampoline

Frank Mehnert fm3 at os.inf.tu-dresden.de
Thu Mar 13 10:36:16 CET 2003

On Thursday 13 March 2003 01:24, Cristiano Ligieri Pereira wrote:
> thanks for answering. I'm really tight on my schedule to try such major
> change. I guess I will have to just forget about it for now.
> How was it done in the previous version of l4? The one written in
> assembly. And does the assembly version (hazelnut?) work fine on pentium 4
> machines?

Hazelnut is not the assembly version. Hazelnut from Karlsruhe (L4Ka project)
is written in C++ without using special C++ features. The assembly version
of L4 is not freely available.

> the problem is that Fiasco seems to be performing pretty bad on the same
> benchmarsk presented in the paper "The performance of micro-kernel Based
> Systems" and I'm wondering why. My first guess was the trampoline

Which benchmark do you talk about? AIM? Where from do you got it?
Which version of Fiasco do you use? What did you measure? Which compiler
did you use for compiling Fiasco? Please post your config file!

Please, could you give some more details about your test scenario?!

> mechanism. I using a Pentium 4 1.3Ghz machine and was expecting a smoother
> performance degradation (compared to the paper) even though executing a
> different version of l4 (fiasco instead of the assembly version

Why do you expect a smoother performance degradation?

We still have some minor problems building a libc for L4Linux without
using the trampoline mechanism. In fact we built such an libc but some
tests after the build process fail. However, you can only expect notable
better performance if you use the right benchmark, that is benchmarks using
many Linux system calls. You will not note a big difference in compiling
the Linux kernel since most work is done in userland.

## Dept. of Computer Science, Dresden University of Technology, Germany ##
## E-Mail: fm3 at os.inf.tu-dresden.de    http://os.inf.tu-dresden.de/~fm3 ##

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