Re: [PATCH 01/16] mm: delayed page activation

[Peter Zijlstra]

On Wed, 2005-11-09 at 21:49 +0800, Wu Fengguang wrote:
> plain text document attachment (mm-delayed-activation.patch)
> When a page is referenced the second time in inactive_list, mark it with
> PG_activate instead of moving it into active_list immediately. The actual
> moving work is delayed to vmscan time.
> 
> This implies two essential changes:
> - keeps the adjecency of pages in lru;
> - lifts the page reference counter max from 1 to 3.
> 
> And leads to the following improvements:
> - read-ahead for a leading reader will not be disturbed by a following reader;
> - enables the thrashing protection logic to save pages for following readers;
> - keeping relavant pages together helps improve I/O efficiency;
> - and also helps decrease vm fragmantation;
> - increased refcnt space might help page replacement algorithms.

I'm working on a clockpro implementation that essentialy keeps all
resident pages on 1 clock. In this case readahead pages will also not
fragment over the active/inactive lists but stay in order. Would that
also satisfy your requirements?

Code can be found at:
  http://programming.kicks-ass.net/kernel-patches/clockpro-2/

Note however that this is work in progress and rather unstable, there
are some livelock scenarios in there.

Kind regards,

Peter Zijlstra


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