L4Linux-2.6.14 perfomance question

Frank Mehnert fm3 at os.inf.tu-dresden.de
Mon Dec 12 09:07:57 CET 2005

Dear Prof. Mc Guire,

On Wednesday 07 December 2005 21:39, Der Herr Hofrat wrote:
>  I'm very new to L4Linux so my question might be obvious - anyway did not
>  find anything directly related in the archive. For a start I did a quick
>  performance comparison using lmbench-3.0.
> [...]
> The thing that supprises me is that the performance variation is much
> higher than on regular linux - in both cases the system was idle except
> for lmbench running, so I'm excluding any syslog parties or cron jobs
> fireing at inconvenient times (i.e bandwidth of UNIX sockets has a variance
> of almost 50% ?). Generally the performance difference is much larger
> than I would have expected, especially also in areas where I don't quite
> understand where the u-kenrel can impact the Linux system (i.e. bcopy,
> memory read-write)
> Are these values in the usual range or did I screw up fundamentally ?

L4Linux 2.6.14 is still a bit experimental. At least it still did not get
_that_ level of optimization that L4Linux 2.0 from the original SOSP'97
paper got. I assume that you used Fiasco as the underlaying L4 microkernel.
The development of that kernel had mainly good preemptablility in mind
and it is therefore not that performance tweaked as other L4 kernels.

It would be nice to get some more words about your hardware and software
configuration, e.g. which CPU and how many RAM, the configuration of Fiasco
and L4Linux. There are several points to optimize.

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