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

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Message-ID: <20100603155552.24c38afc@schatten.dmk.lab>
Date:	Thu, 3 Jun 2010 15:55:52 +0200
From:	Florian Mickler <florian@...kler.org>
To:	Arve Hjønnevåg <arve@...roid.com>
Cc:	markgross@...gnar.org, Brian Swetland <swetland@...gle.com>,
	640e9920@...il.com, "Rafael J. Wysocki" <rjw@...k.pl>,
	Alan Stern <stern@...land.harvard.edu>,
	Peter Zijlstra <peterz@...radead.org>,
	Linux PM <linux-pm@...ts.linux-foundation.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>
Subject: Re: [linux-pm] [PATCH 0/8] Suspend block api (version 8)

On Thu, 3 Jun 2010 00:10:03 -0700
Arve Hjønnevåg <arve@...roid.com> wrote:

> On Wed, Jun 2, 2010 at 10:40 PM, mark gross <640e9920@...il.com> wrote:

> > 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
> 

Yes. I think that would be good. If we keep the primary list sorted,
then this becomes a nice priority queue implementation which does 
GetMax in constant time and Insert and Delete in logarithmic
complexity to the number of different values.

Cheers,
Flo
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