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

On Thu, 5 Jan 2006, IWAMOTO Toshihiro wrote:

quoted

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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