Re: Virtual memory and pager

On Sun, Oct 10, 2010 at 7:52 PM, BERTRAND Joel
<[email protected]> wrote:
>        Hello,
>
>        I'm trying to understand how L4 manages system memory. I have read a
> lot of docs, but I'm not sure that I have understood very well.
>
>        On my system, I have installed L4, default sigma0 and a hand made
> roottask. Roottask must use sigma0 to map virtual addresses to real ones. If
> I want to use virtual memory, I have to write a new memory manager. Right ?

Yes, you need your own VM manager.

I've tried to use NetBSD's VM subsystem in a L4Ka-based setup,
but quickly stumbled across the lack of mutexes (esp. of the NetBSD
or Solaris-like flavor, i.e. the adaptive mutexes).

You need a lot of patience and perseverance here, before you can
get a working virtual memory system. ;-)

>        This memory manager has to be split in two parts, a L4 server
> launched by roottask (that includes pagefault management) and a client
> library. Is there anywhere some memory management examples ? I have found
> http://www.lg2.de/vm.html but I'm not sure that sources are available.

I still think that NetBSD's VM subsystem would be a great fit, once the
(lack of) mutex problem is solved (ideally in BSD-licensed code!). UVM
is reasonably well self-contained, and doesn't depend on too many other
parts (at least, nothing you couldn't replace with function stubs):

http://www.netbsd.org/docs/kernel/uvm.html

>        Any URL or exhaustive documentation are welcome.
>
>        Regards,
>
>        JKB

Kind regards,
-Farid.