Re: page fault scalability patch final : i386 tested, x86_64

[Andrew Morton <akpm@osdl.org>]

Andi Kleen <ak@muc.de> wrote:
>
> > When can we reasonably expect someone to blow this out of the water? 
>  > Within the next couple of years, I suspect?
> 
>  With 4 level page tables x86-64 will support 47 bits virtual theoretical.
>  They cannot be used right now because the current x86-64 CPUs have
>  40 bits physical max and it is currently even hardcoded to 40bits,
>  but I planned to drop that in the 4 level patch (in fact I already did) 
>  so that the kernel will in theory support CPUs will more physical memory.
> 

hm.  What's the maximum virtual size on power5?

>  > It does look like we need a new type which is atomic64 on 64-bit and
>  > atomic32 on 32-bit.  That could be used to fix the
>  > mmaping-the-same-page-4G-times-kills-the-kernel bug too.
> 
>  Yep.  Good plan. atomic_long_t ? 

Sounds good.  Converting page->_count should be fairly straightforward now
too, as it's all done via wrappers.

>  > 
>  > > and this limit actually
>  > > mostly comes from the 3-level page table limits.
>  > 
>  > This reminds me - where's that 4-level pagetable patch got to?
> 
>  It exists on my HD, but is not really finished yet.
> 
>  I was on vacation and travelling and had some other things to do, so it got 
>  delayed a bit, but I hope to work on it soon again.

OK, thanks.  There's no rush on this one.