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

keith
2004-11-18T02:08:44Z

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