Re: [uml-devel] Re: V=R

[BlaisorBlade <blaisorblade_spam@yahoo.it>]

Alle 16:50, sabato 10 aprile 2004, Michael Koehne ha scritto:
> Moin Jeff Dike,
>
> > On Sat, Apr 10, 2004 at 01:06:51PM +0200, Sven Köhler wrote:
> > > is there any way for the UML-kernel to allocate a non-swappable
> > > memore-region in the host's memory? this could be especially important
> > > for dedicated host-machines that are only to run UMLs.
> >
> > What I am going to do is make it possible to manage the host's memory
> > so that it doesn't swap, and the UMLs in effect are mlocked.
>
>   this reminds me on VM's V=R nucleus option. A V=R is a memory partition
>   dedicated to 1 user, e.g. an MVS guest running under VM who is doing its
>   own demand paging. To translate this to Linux could be the following :
>
>   e.g. a system with 1GB real ram could boot `linux mem=256m` with
>   only a quarter of ram for the hosting system. We now need two tricks:
>
>   1: add 768m of ram as V=R memory (dont use it for Linux processes,
>      buffers, ...) partition and offer it as /dev/v=r. (this would
>      be a host kernel patch)
>
>   2: use this V=R region for UML `linux mem=256m@256m` (this would
>      be a user kernel patch)

Well, if you mlock() the UML RAM, you already implement something such. The 
problem is that such a patch will never go inside the official UML kernel 
tree, so someone should maintain it outside. Anyway, what you say, i.e. the 
fact that some system (S/390?) support it, could make it easier for the 
"mlock" patch to be accepted.

Bye
-- 
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729



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