Some questions about L4 operating system

Adam Lackorzynski adam at os.inf.tu-dresden.de
Thu Jul 16 23:55:54 CEST 2015


On Thu Jul 16, 2015 at 19:31:42 +0800, Qing Wei wrote:
>   I am a beginner to L4, and very interested in it. I think it is great in 
> terms of its minimality and security. However, I have some questions
> about it,
> (1) How is its performance compared to other monolithic kernel,
> say, Linux. Could it make use of multicore, multiprocessor to
> enjoy the performance scalability?

L4Re supports SMP just fine. The system is actually less, so it less in
the way of applications and thus leaves them more of the bare metal.

> (2) How is its ecosystem, fox example, how to support new hardware,
> does it need write the driver from scratch or could it make use of
> Linux driver?

Regarding new devices/hardare and drivers the full scale of approaches
is possible. Writing drivers yourself, what you might want to do for
certain use cases such as driver size, trustworthiness, licensing, fun,
requirements etc. However, reusing some existing drivers is more
popular. Again, several approaches possible, but using some
virtualization tech for running drivers is the most obvious one.

> And how to write application on it, or, could it run
> Linux application without modification?

L4Re has POSIX (subset) support, so POSIX programs can work without or
small modifications, e.g. see
http://svn.tudos.org/repos/oc/tudos/trunk/l4/pkg/examples/misc/cat/cat.c
But L4Re is not Linux, so Linux-specific programs will not work by just
recompiling.

> (3) How is its virtualization support, could it run Linux vm, and
> does it need any modification to the guest os?

We do both hardware-assisted full virtualization and
para-virtualization. L4Linux is popular for the para-virtualization
approach and it is adapted to run as an application on the system.



Adam
-- 
Adam                 adam at os.inf.tu-dresden.de
  Lackorzynski         http://os.inf.tu-dresden.de/~adam/



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