[Cbe-oss-dev] Only 86MB of RAM available running Ubuntu 8.04 powerpc64-smp kernel on PS3

[Michael Ellerman]

On Mon, 2008-05-05 at 01:50 +0100, Dan Munckton wrote:
> Hi all
> 
> Quick intro - I've recently taken it upon myself to do something about
> getting Ubuntu Hardy running on the PS3. Unfortunately for most of the
> Hardy development cycle there was no one working on the PS3 port
> consequently the kernel is a bit broken.

Awesome, we'd all love it to work, we're just all a bit busy doing
"real" work :/

> Although I have the motivation I am quite new to kernel work so please
> be gentle with me.
> 
> Basically I think most of the issues we have can be solved by using the
> correct configuration. Building and running a kernel using just the
> options from ps3_defconfig makes all issues go away. Where I'm going to
> need help is in identifying which options need to be changed and
> hopefully understanding why.
> 
> The first issue on my list is this: only 86MB of RAM appear to be
> available. We're tracking this issue at [0] where I've uploaded all
> configs and logs.
> 
> There is a backtrace in the dmesg output from the failing kernel which I
> think maybe related (attached). It starts with ...
> 
> swapper: page allocation failure. order:12, mode:0x80d0

I think that's caused by the VMEMMAP stuff. The PS3 boots with some
memory (128MB?) and then the rest is hot-plugged later on. The VMEMMAP
stuff has introduced an issue (bug), where the rest of memory can't be
hotplugged because the VMEMMAP can't be allocated. (correct me if I'm
wrong Ben or Geoff).

The end result is you have jack all memory. That should be fixed by
either Ben's patch or something similar, see the patch here:
http://patchwork.ozlabs.org/linuxppc/patch?q=vmemmap&id=18232

cheers

-- 
Michael Ellerman
OzLabs, IBM Australia Development Lab

wwweb: http://michael.ellerman.id.au
phone: +61 2 6212 1183 (tie line 70 21183)

We do not inherit the earth from our ancestors,
we borrow it from our children. - S.M.A.R.T Person
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