Hi Rik!

On Fri, Dec 30, 2005 at 08:22:12PM -0500, Rik van Riel wrote:

On Fri, 30 Dec 2005, Marcelo Tosatti wrote:

quoted

I think that final objective should be to abstract it away completly,
making it possible to select between different policies, allowing
further experimentation and implementations such as energy efficient
algorithms.

I'm not convinced.  That might just make vmscan.c harder to read ;)

Are you serious or just joking? :) 

Sure it might make it harder to read, but allowing selectable policies
is very interesting. Peter's patches go half-way into that direction.

Lets say, if CLOCK-Pro underperforms for a given workload (take into
account that its simply optimizing reclaim for a subset of all existing
access patterns, ie. heuristics), it would be easier for people to
develop/use different policies.

quoted

About CLOCK-Pro itself, I think that a small document with a short
introduction would be very useful...

http://linux-mm.org/AdvancedPageReplacement

I meant something more like Documentation/vm/clockpro.txt, for easier
reading of patch reviewers and community in general. 

quoted

quoted

The HandCold rotation is driven by page reclaim needs. HandCold in turn
drives HandHot, for every page HandCold promotes to hot HandHot needs to
degrade one hot page to cold.

Why do you use only two clock hands and not three (HandHot, HandCold and 
HandTest) as in the original paper?

Because the non-resident pages cannot be in the clock.
This is both because of space overhead, and because the
non-resident list cannot be per zone.

I see - that is a fundamental change from the original CLOCK-Pro
algorithm, right? 

Do you have a clear idea about the consequences of not having           
non-resident pages in the clock? 

I agree though, Peter's patch could use a lot more
documentation.

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