| From: | Kenneth Marshall <ktm(at)it(dot)is(dot)rice(dot)edu> |
|---|---|
| To: | Manfred Koizar <mkoi-pg(at)aon(dot)at> |
| Cc: | Hannu Krosing <hannu(at)tm(dot)ee>, Neil Conway <neilc(at)samurai(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>, Jeff Davis <jdavis-pgsql(at)empires(dot)org>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: ARC patent |
| Date: | 2005-01-21 14:57:28 |
| Message-ID: | 20050121145728.GE6207@it.is.rice.edu |
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| Lists: | pgsql-hackers |
On Fri, Jan 21, 2005 at 03:42:38PM +0100, Manfred Koizar wrote:
> On Fri, 21 Jan 2005 02:31:40 +0200, Hannu Krosing <hannu(at)tm(dot)ee> wrote:
> >2) Another simple, but nondeterministic, hack would be using randomness,
> >i.e.
> >
> > 2.1) select a random buffer in LR side half (or 30% or 60%) of
> > for replacement.
> >
> > 2.2) dont last accessed pages to top of LRU list immediately,
> > just push them uphill some amount, either random, or
> > perhaps 1/2 the way to top at each access.
>
> Sounds good, but how do find the middle of a linked list? Or the other
> way round: Given a list element, how do you find out its position in a
> linked list? So the only approach that is easily implementable is
>
> 2.3) If a sequential scan hint flag is set, put the buffer into the
> free list at a random position.
>
If we use the clock algorithm as an approximation to LRU, we can avoid
a lot of the MRU/LRU churn. Then the seq. scan hint could just be another
type of clock bit.
Ken
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