Re: [PATCH 6/9] clockpro-clockpro.patch

[IWAMOTO Toshihiro]

At Thu, 5 Jan 2006 08:32:19 -0500 (EST),
Rik van Riel wrote:
> 
> On Thu, 5 Jan 2006, IWAMOTO Toshihiro wrote:

> > In my understanding of CLOCK-Pro, such lapping causes sudden increase
> > in the distance between Hhot and Hcold.  As that distance is an
> > important parameter of page aging/replacement decisions, I'm afraid
> > that such lapping would result in incorrect page aging and bad
> > performance.
> 
> Hcold only manipulates cold pages, Hhot only manipulates hot
> pages and the test bit on cold pages.  Having one hand overtake
> the other should not disturb things at all, since they both do
> something different.

I don't think so.  Hhot turns unreferenced hot pages into cold ones,
and those are freed if they aren't referenced before Hcold passes.
So, the distance between those hands is a sort of "expiry timer" of
such pages.
The distance also affects aging of newly inserted pages.

--
IWAMOTO Toshihiro
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