Tuning L4Linux on Fiasco

Frank Mehnert fm3 at os.inf.tu-dresden.de
Tue Oct 1 14:50:07 CEST 2002

Hi Jacob,

On Tuesday 24 September 2002 23:53, Jacob Gorm Hansen wrote:

> the original l4linux papers mention performance about 4% lower than
> native linux. When running l4linux on top of Fiasco, performance seems
> to be more like 50% of what we get with native 2.2. For example,
> encoding a .wav-file to ogg-vorbis takes 2 minutes native, and almost 4
> minutes with l4linux. LMBench also gives way-different figures.

Encoding of 185MB .wav-file into mp3/128kBit/s with lame 3.92
on Pentium III Coppermine 800 MHz:

Plain Linux 2.2.21
  real    6m32.000s
  user    4m16.290s
  sys     0m7.360s

L4Linux 2.2.21 on Fiasco (current CVS version):
  real    6m46.943s
  user    0m0.010s
  sys     0m0.000s

Don't depend on the usr/sys times! The only time you can believe in
is the time after "real". L4Linux doesn't have its own scheduler but
L4Linux tasks are scheduled by the scheduler of the underlaying L4 
implementation. The time a L4Linux task is running is determined by
the l4_thread_schedule() system call. But thread time accounting is
disabled by default in Fiasco because of the additional costs. You
can enable it by setting config::fine_grained_cputime to TRUE (but
it isn't fully tested yet so without any warranty :-)).

BTW: What about your L4Linux migration? Do you have a website?
We are very interested ...

Frank Mehnert
## 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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