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

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:

quoted

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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