Re: RFC: COW for hugepages

[David Gibson]

On Wed, Apr 07, 2004 at 02:34:47PM +0200, Andi Kleen wrote:
> On Wed, 7 Apr 2004 17:42:39 +1000
> David Gibson <david@xxxxxxxxxxxxxxxxxxxxx> wrote:
> 
> > Currently the kernel does not implement copy-on-write for huge pages -
> > in fact any sort of page fault on a hugepage results in a SIGBUS.
> > This means that hugepages *always* have MAP_SHARED semantics, even if
> > MAP_PRIVATE is requested, and in particular that they are always
> > shared across a fork().  Particularly when using hugetlbfs as just a
> > source of quasi-anonymous memory, those are rather strange semantics.
> 
> [...]
> 
> Implementing this for ppc64 only is just wrong. Before you do this 
> I would suggest to factor out the common code in the various hugetlbpage
> implementations and then implement it in common code.

Yes, I know it needs to be implemented for the other archs, but I
wanted to get some feedback on the concept before diving into the
other arch details to figure out how to implement it there.

-- 
David Gibson			| For every complex problem there is a
david AT gibson.dropbear.id.au	| solution which is simple, neat and
				| wrong.
http://www.ozlabs.org/people/dgibson
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