Re: [PATCH 0/8] x86, acpi: Move acpi_initrd_override() earlier.

Tejun Heo
2013-08-22T20:22:08Z

Hello,

On Thu, Aug 22, 2013 at 02:11:32PM -0600, Toshi Kani wrote:
> It's too late for the kernel image itself, but it prevents allocating
> kernel memory from movable ranges after that. I'd say it solves a half
> of the issue this time.

That works if such half solution eventually leads to the full
solution. This is just a distraction. You are already too late in
the boot sequence. It doesn't even qualify as a half solution. It's
like obsessing about a speck on your shirt without your trousers on.
If you want to solve this, do that from a place where it actually is
solvable.

> > > Also, how do you support local page tables without pursing SRAT early?
> >
> > Does it even matter with huge mappings? It's gonna be contained in a
> > single page anyway, right?
>
> Are the huge mappings always used? We cannot force user programs to use
> huge pages, can we?

Everything is a trade-off. Should we do all this just to support the
off chance someone tries to use memory hotplug on a machine which
doesn't support huge mapping when virtually all CPUs on market
supports it?

> As for the maintainability, I am far more concerned with your suggestion
> of having a separate page table init code when SRAT is used. This kind
> of divergence is a recipe of breakage.

I don't buy that. The only thing which needs to change is the
directionality of allocation and we probably don't even need to do
that if huge mapping is in use.

Thanks.

--
tejun