On Sun, 7 Oct 2007 10:17:47 -0700
Jeremy Fitzhardinge <[email protected]> wrote:
>
> On Oct 7, 2007, at 9:58 AM, Arjan van de Ven wrote:
>
> > On Sat, 06 Oct 2007 23:31:33 -0700
> >
> >> I'm presume I'm the first person to try holding multiple pte locks
> >> at once, so there's no existing locking order for these locks. I'm
> >> always traversing and locking the pagetable in virtual address
> >> order (and this seems like a sane-enough rule for anyone else who
> >> wants to hold multiple pte locks).
> >
> > I'm not sure that's a valid assumption in light of things like
> > sharing pagetables between processes etc etc..
> > (granted, that one is out of tree right now but I still hope it'll
> > go in some day:)
>
> Well, yes, but that will take some thought about how split pte locks
> will work anyway (or more specifically, fork will probably just end
> up reusing the pte pages and avoid the need to do any
> cross-pagetable pte locking anyway, though I guess that will be
> deferred to COW handling).
>
> So are you saying I should pass up the opportunity to optimise a
> relatively hot path (fork/exec/exit) because it will need some
> further thought if/when shared ptes get implemented?
s/implemented/merged/ :)
IN fact shared pagetables are already there for hugepages.
For small pages it's a patch at this point.
> Doesn't seem
> like a good tradeoff...
no I'm not saying that. I'm just saying that I'm worried about the
locking robustness of your trick in general.
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