[RFC/PATCH] powerpc: Dynamically allocate pacas

[Michael Ellerman]

On Thu, 2010-01-14 at 11:26 +1100, Michael Neuling wrote:
> > On 64-bit kernels we currently have a 512 byte struct paca_struct for
> > each cpu (usually just called "the paca"). Currently they are statically
> > allocated, which means a kernel built for a large number of cpus will
> > waste a lot of space if it's booted on a machine with few cpus.
> > 
> > We can avoid that by only allocating the number of pacas we need at
> > boot. However this is complicated by the fact that we need to access
> > the paca before we know how many cpus there are in the system.
> > 
> > The solution is to dynamically allocate enough space for NR_CPUS pacas,
> > but then later in boot when we know how many cpus we have, we free any
> > unused pacas.
> > 
> > Lightly booted on Legacy iSeries & pSeries LPAR.
> > 
> > Signed-off-by: Michael Ellerman <michael at ellerman.id.au>
> 
> Nice!
> 
> <snip>
> 
> > +	lmb_free(__pa(paca) + new_size, paca_size - new_size);
> 
> You didn't explicitly mention this above but this depends on your
> lmb_free patch...

Ah yes, good point :)

> FYI boots bare metal

Sweet! Thanks for testing.

cheers

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