Re: Bug: Discontigmem virt_to_page() [Alpha,ARM,Mips64?]

[Martin J. Bligh]

> Have you done testing with 64GB? What sort of failure modes are you
> seeing with it? I've been hearing about more severe failure modes in
> practice on 32GB, Martin, could you comment on this?

I've never gone above 32Gb (yet ;-)). We don't have an SMP platform
that I know of that'll support 64Gb, only the NUMA platforms.

32Gb will boot and work with 1GB KVA, but if you actually want to
use the memory for something, a 2GB KVA seems imperative. It depends
on the workload you're using, but the things we tend to see are:

1. struct page.
2. buffer heads (will look at -aa tree)
3. user page tables (need highpte)
4. LDTs for threads filling the vmalloc space (seems to be fixed in 2.5)

I think the whole struct page issue needs some (complex, hard) work,
but in general, we're getting there. Fast ;-)

M.

PS. BTW, Andrea, your latest highpte looks like you obliterated the
kmap problem I was complaing of, but I've been having massive problems 
with other things which are blocking much of the real testing ... 
sorry about the time lag ;-)