Re: [PATCH 0/4] Demand faunting for huge pages

[Andi Kleen <ak@suse.de>]

On Thu, Aug 18, 2005 at 10:33:02AM +1000, David Gibson wrote:
> On Wed, Aug 17, 2005 at 11:04:32PM +0200, Andi Kleen wrote:
> > 
> > What about the overcommit issue Ken noted? It needs to be solved
> > in some way at least, either with the full check or the lazy simple
> > check.
> 
> Hrm... I'm not 100% convinced that just allowing overcommit isn't the
> right thing to do.  Overcommit has some unfortunate consequences, but
> the semantics are clearly defined and trivial to implement.

I disagree. With Linux's primitive hugepage allocation scheme (static
pool that is usually too small) at least simple overcommit check
is absolutely essential.

> Strict accounting leads to nicer behaviour in some cases - you'll tend
> to die early rather than late - but it seems an awful lot of work for
> a fairly small improvement in behaviour.

Strict is a lot of work, but a simple "right in 99% of all cases, but racy" 
check is quite easy.

-Andi
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