Re: [PATCH] Convert pgtable cache to slab

Robin Holt
2005-02-15T20:08:56Z

On Tue, Feb 15, 2005 at 12:03:22PM -0800, David Mosberger wrote:
> >>>>> On Tue, 15 Feb 2005 13:59:45 -0600, Robin Holt <holt@sgi.com> said:
>
> >> I certainly don't want to switch my machines to 4-levels. There
> >> is zero need for that on the machines I use, so why pay the
> >> overhead of an extra level?
>
> Robin> I missed the why the extra level question. That part is
> Robin> motivated by some large MPI jobs need a fourth level to get a
> Robin> large enough single mapping to cover their entire dataset.
> Robin> We have already tripped this limitation for a couple of our
> Robin> really large customers.
>
> What I'm saying is that the default probably should stay at 3-levels.
> Optimizing ia64 linux _just_ for "really large customers" would be
> a bad direction to go in.

I agree. What I am asking is if we turn on the 4th level of page tables,
does anybody have an objection to 4/16k levels as opposed to 3/PAGE_SIZE
plus a 4th cleanup to cover the entire address space?

Thanks,
Robin