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

Florian Mickler
2010-06-03T15:17:42Z

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.

Cheers,
Flo