Re: [uml-devel] memory

[Blaisorblade <blaisorblade@yahoo.it>]

On Sunday 23 January 2005 10:51, Rob Landley wrote:
> On Sunday 23 January 2005 03:28 am, Doug Dumitru wrote:
> > Mr. Sharma,
> >
> > What you are trying to do will work, but not for large amounts of
> > memory.  UML runs the client using a single user mode memory block as
> > the entire client's core.  Thus the clients core size is limited to what
> > a single task can allocate as plain memory.  With x86 architechure cpus,
> > this is 2G or 3G depending on how you build a kernel (but usually 2G).
> > There are no paging mechanism here so there is no way to make it
> > "gigabytes"
> >
> > Others can correct me if I have the exact numbers wrong.
>
> UML uses mmap (generally of a /tmp file) as physical memory.  This can be
> way bigger than physical memory on the machine, sure, and the parent kernel
> will transparently use the mmaped file as backing store, demand paged and
> all that.  (Just like it would for any other application.)
>
> You could run out of virtual address space, though.  Trying to map more
> than a few gigabytes on a 32 bit machine is unlikely to work.
>
> Might I suggest buying a cheap x86-64 system (you can get 'em at Fry's a
> couple hundred bucks), feed it a cheap 300 gigabyte IDE drive, and have
> fun.

This is not (yet) exactly supported... a lot of work is going on this, and 
somebody was even able to compile and run (successfully?) some x86_64 umls... 
However, consider it still as a developer-only tool for now. 2.6.11 could 
effectively be a good x86_64 tree, but do not yet use it for anything 
critical.

Clearly, 32-bit UMLs run well on x86_64 boxes, but don't have the 64-bit 
advantages...
-- 
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729
http://www.user-mode-linux.org/~blaisorblade


-------------------------------------------------------
This SF.Net email is sponsored by: IntelliVIEW -- Interactive Reporting
Tool for open source databases. Create drag-&-drop reports. Save time
by over 75%! Publish reports on the web. Export to DOC, XLS, RTF, etc.
Download a FREE copy at http://www.intelliview.com/go/osdn_nl
_______________________________________________
User-mode-linux-devel mailing list
User-mode-linux-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel