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SubjectRe: HOLES_IN_ZONE...
On Thu, Feb 05, 2009 at 02:14:29AM -0800, David Miller wrote:
> From: Mel Gorman <mel@csn.ul.ie>
> Date: Thu, 5 Feb 2009 10:10:23 +0000
>
> > On Wed, Feb 04, 2009 at 10:26:51PM -0800, David Miller wrote:
> > > As a suggestion, it would have been a lot more pleasant if the code
> > > validated this requirement (in the !HOLES_IN_ZONE case) at boot time
> > > instead of after 2 hours of stress testing :-(
> > >
> >
> > Nice maybe, but we'd take a hit on pfn_valid_within() which goes from
> > being compiled-away on architectures that don't need it to being
> > a read of a shared cacheline and a branch.
>
> I said at boot time Mel, not in the fast paths.

pfn_valid_within() is not used in any critical paths, but it's used in
the page free path so it would be a hit there.

> Meaning, we'd
> check it after all the available ranges get registered and
> tossed into the free page lists.
>

It's not a free-list problem, it's walkers of PFN ranges. Anyway, it's
not important to the current problem.

> Anyways, it appears we have a fix already, read the rest of
> the thread.
>

Yes. Thanks Kamezawa Hiroyu for the fix.

--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab


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