On Thu, 3 Jun 2010 21:07:07 -0700
Arve Hjønnevåg <arve@xxxxxxxxxxx> wrote:
> On Thu, Jun 3, 2010 at 2:05 PM, Rafael J. Wysocki <rjw@xxxxxxx> wrote:
> > On Thursday 03 June 2010, James Bottomley wrote:
> >> On Thu, 2010-06-03 at 00:10 -0700, Arve Hjønnevåg wrote:
> >> > A request update then becomes something like this:
> >> > if on primary list {
> >> > unlink from primary list
> >> > if secondary list is not empty
> >> > get next secondary entry and add in same spot on primary list
> >> > }
> >> > unlink from secondary list
> >> > find new spot on primary list
> >> > if already there
> >> > add to secondary list
> >> > else
> >> > add to primary list
> >>
> >> This is just reinventing hash bucketed lists. To get the benefits, all
> >> we do is implement an N state constraint as backed by an N bucketed hash
> >> list, which the kernel already has all the internal mechanics for.
> >
> > Agreed.
> >
>
> No, a hash is used for quick lookup of a specific value, not to find
> an extreme value. It is however extremely similar to plists. The only
> difference is that plists link all the secondary lists together. If we
> want to have constraints that autoexpire, then keeping the secondary
> lists separate allows the same optimization as I did for
> wakelock/suspend_blocker timeouts where no timer is active if an
> (equal or stricter) non-expiring constraint is active.
Can you give an example for the optimization or elaborate about the
negative effect of linking the secondary lists together? I don't
understand right now.
Would be hlist from list.h better? (I think that is what James is
referring to?) That is a (single-linked-)list of double-linked-lists.
Cheers,
Flo
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