Re: Lua as a scripting language in NetBSD

[Marc Balmer <marc%msys.ch@localhost>]

Lourival,

> I'm computer science msc student and I'm working in Lua embedded in
> Linux kernel (which I call Lunatik) under the guidance of professor
> Roberto Ierusalimschy. We already have a functional port of Lua core
> to Linux kernel, which allows us to run arbitrary Lua code inside the
> kernel. We have also created a small example application for this,
> that allows users to write cpufreq governors purely in Lua.
>
> I don't know if you are conversant with Linux cpufreq mechanism, but
> it basically controls the frequency of laptop-like CPUs. Through the
> cpufreq it is possible to switch the CPU clock dynamically to save
> battery with a tolerable loss of performance. Through cpufreq
> governors written in Lua it is possible to users create them own
> policies to manage the CPU frequency. Here are some examples of
> governors written in Lua:
>
> -- simplified version of cpufreq ondemand governor
> function governor()
>    cpu_load = getLoad()
>
>    if ( cpu_load > 80 ) then
>
>        target( tab_freq.getMax() )
>
>    elseif ( cpu_load < 30 ) then
>
>        target( tab_freq.getPrev() )
>    end
> end
>
> -- modified version of ondemand with temperature concerns
> function governor()
>    cpu_load = getLoad()
>    cpu_temp = getTemp()
>
>    if ( cpu_load > 80 and cpu_temp < 65 ) then
>
>        target( tab_freq.getMax() )
>
>    elseif ( cpu_load < 30 or cpu_temp > 75 ) then
>
>        target( tab_freq.getPrev() )
>    end
> end
>
> Lunaitk is still only a concept proof and a lab to study extensible
> operating systems, but we are currently writing a paper and working on
> a first public release. I will be glad to share my experience with
> Lunatik and join you to port Lua to NetBSD kernel too.

This is a nice application and imo it shows the power of Lua embedded  
in an OS.  Please be aware, however, that we are currently in the  
process of discussing wheter we want to include Lua into NetBSD, this  
has not yet been decided, although we had quite some positive  
reactions to the idea.

Integration of Lua into the kernel is even a different story than  
adding Lua to the base system.  We have to think in which form to do,  
what services to expose etc. etc.  And then I think personally that  
Lunatik is a bit of a misnomer... ;)

Well, since you work at the heart of Lua and with one of ots  
inevntors, you can possible help us with a technical question:  Number  
format.  I am well aware that I can compile Lua for different number  
formats, which is good, since there is no floating point math in BSD  
kernels usually.  But what about 64 Bit integers?  Can Lua be built to  
support 64 bit integers as number format?

Thanks for your feedback,
Marc Balmer