Re: [PATCH 0/8] Suspend block api (version 8)

James Bottomley
2010-06-03T15:29:52Z

On Thu, 2010-06-03 at 17:17 +0200, Florian Mickler wrote:
> On Thu, 03 Jun 2010 09:36:34 -0500
> James Bottomley <James.Bottomley@suse.de> wrote:
>
> > On Thu, 2010-06-03 at 00:10 -0700, Arve Hjønnevåg wrote:
> > > On Wed, Jun 2, 2010 at 10:40 PM, mark gross <640e9920@gmail.com> wrote:
> > > > On Wed, Jun 02, 2010 at 09:54:15PM -0700, Brian Swetland wrote:
> > > >> On Wed, Jun 2, 2010 at 8:18 PM, mark gross <640e9920@gmail.com> wrote:
> > > >> > On Wed, Jun 02, 2010 at 02:58:30PM -0700, Arve Hjønnevåg wrote:
> > > >> >>
> > > >> >> The list is not short. You have all the inactive and active
> > > >> >> constraints on the same list. If you change it to a two level list
> > > >> >> though, the list of unique values (which is the list you have to walk)
> > > >> >> may be short enough for a tree to be overkill.
> > > >> >
> > > >> > what have you seen in practice from the wake-lock stats?
> > > >> >
> > > >> > I'm having a hard time seeing where you could get more than just a
> > > >> > handfull. However; one could go to a dual list (like the scheduler) and
> > > >> > move inactive nodes from an active to inactive list, or we could simply
> > > >> > remove them from the list uppon inactivity. which would would well
> > > >> > after I change the api to have the client allocate the memory for the
> > > >> > nodes... BUT, if your moving things in and out of a list a lot, I'm not
> > > >> > sure the break even point where changing the structure helps.
> > > >> >
> > > >> > We'll need to try it.
> > > >> >
> > > >> > I think we will almost never see more than 10 list elements.
> > > >> >
> > > >> > --mgross
> > > >> >
> > > >> >
> > > >>
> > > >> I see about 80 (based on the batteryinfo dump) on my Nexus One
> > > >> (QSD8250, Android Froyo):
> > > >
> > > > shucks.
> > > >
> > > > well I think for a pm_qos class that has boolean dynamic range we can
> > > > get away with not walking the list on every request update. we can use
> > > > a counter, and the list will be for mostly for stats.
> > > >
> > >
> > > Did you give any thought to my suggestion to only use one entry per
> > > unique value on the first level list and then use secondary lists of
> > > identical values. That way if you only have two constraints values the
> > > list you have to walk when updating a request will never have more
> > > than two entries regardless of how many total request you have.
> > >
> > > 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.
> >
> > James
> >
>
> http://www.itl.nist.gov/div897/sqg/dads/HTML/priorityque.html
>
> So no reinvention. Just using a common scheme.

By reinvention I meant open coding a common pattern for which the kernel
already has an API. (Whether we go with hash buckets or plists).

James

_______________________________________________
linux-pm mailing list
linux-pm@lists.linux-foundation.org