Re: [Lhms-devel] [RFC] fix for hot-add enabled SRAT/BIOS and numa KVA areas

[keith <kmannth@us.ibm.com>]

On Wed, 2004-11-17 at 09:11, Dave Hansen wrote:
> On Tue, 2004-11-16 at 18:37, keith wrote:
> >   The numa KVA code used the node_start and node_end values (obtained
> > from the above memory ranges) to make it's lowmem reservations.  The
> > problem is that the lowmem area reserved is quite large.  It reserves
> > the entire a lmem_map large enough for 0x1000000 address space.  I don't
> > feel this is a great use of lowmem on my system :)
> 
> It does seem silly to waste all of that lowmem for memory that *might*
> be there, but what do you plan to do for contiguous address space (for
> mem_map) once the memory addition occurs?  We've always talked about
> having to preallocate mem_map space on 32-bit platforms and by your
> patch it appears that this isn't what you want to do.  
> 
> -- Dave

  I am not anticipating to support hot-add without config_nonlinear or
something similar which should provide more flexibility in allocation of
smaller section mem_maps.  This is only a issue when booted as a
discontig system.  We don't even consult the SRAT when we boot flat
(contiguous address space) so it is a non-issue.

  Wasting 500k of lowmem for memory that "might" be there is no good.  I
don't think having to preallocate the mem_map for a hot-add is really
that good.  What if the system never adds memory?  What if it only adds
8gig not 49g?  The system is crippled because it reserves the lmem_map
it "might" do a hot add with?  

  I forgot the mention that without this patch my system does not boot
with the hot-add support enabled in the bios.  

Thanks,
  Keith 

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