[okl4-developer] SMP in OKL4

[Nelson Tam]

Hi Xiang Fei,

On 18/03/2008, at 9:38 AM, Xiangfei Jia wrote:

> Hi Nelson,
>
> As far as I know, OKL4 uses L4Ka::Pistachio microkernel. I compiled  
> Pistachio long time ago and it seemed SMP was supported under beta  
> testing. How come OKL4 doesn't support SMP? Are there any major  
> modification?


L4Ka::Pistachio has traditionally been optimised for high-end, memory- 
rich machines, and in addition, the SMP support was optimized for very  
high (Intel-style) cross-CPU communication costs.

OKL4, on the other hand, is built with embedded systems in mind.  Many  
assumptions about SMP in Pistachio does not hold for embedded systems,  
and to a certain extent, modern multi-cores.  In addition, OKL4 has in  
many ways significantly deviated from Pistachio, to the point that  
there isn't a lot of common code left.

Correspondingly, SMP in OKL4 had to be redone completely.

We have OKL4 running on multi-threaded and multi-processor hardware  
for well over a year.  We have been running para-virtualised guest  
OSes on top of this kernel, and have yield very satisfying performance  
results.  Over this time, it has been evaluated by several customers  
who are providing feedback.

In an ideal world, sometime in the future we would release a proper  
performance benchmark report, along with an OKL4 that contains SMP  
support so the benchmark numbers can be verified independently by the  
OKL4 community.

For reasons I mentioned above (reengineering SMP etc), we are not able  
to make such a release for the time being.

--
(nt)

Nelson Tam
nelson at ok-labs.com