Messages in this thread | ![/](/images/icornerl.gif) | | Date | Wed, 7 Sep 2005 08:42:22 -0700 (PDT) | From | Christoph Lameter <> | Subject | Re: Hugh's alternate page fault scalability approach on 512p Altix |
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On Wed, 7 Sep 2005, Martin J. Bligh wrote:
> > Anticipatory prefaulting raises the highest fault rate obtainable three-fold > > through gang scheduling faults but may allocate some pages to a task that are > > not needed. > > IIRC that costed more than it saved, at least for forky workloads like a > kernel compile - extra cost in zap_pte_range etc. If things have changed > substantially in that path, I guess we could run the numbers again - has > been a couple of years.
Right. The costs come about through wrong anticipations installing useless mappings. The patches that I posted have this feature off by default. Gang scheduling can be enabled by modifying a value in /proc. But I guess the approach is essentially dead unless others want this feature too. The current page fault scalability approach should be fine for a couple of years and who knows what direction mmu technology has taken then.
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