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Date: Mon, 21 Apr 2003 03:49:32 -0700
From: David Schultz <das@freebsd.org>
To: Matthew Dillon <dillon@apollo.backplane.com>
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cc: freebsd-current@freebsd.org
Subject: Re: Broken memory management on system with no swap
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On Sun, Apr 20, 2003, Matthew Dillon wrote:
>     note (1): normally act_count protects against thrashing.  It is the
>     active queue's act_count algorithm which gives FreeBSD's such a nice
>     smooth degredation curve when memory loads become extreme by preventing
>     a frequently accessed page from being freed too early, so we don't
>     want to just turn it off.  Maybe we need a test for 'too many active
>     pages', aka when > 80% of available pages are in the active queue
>     to temporarily disable the act_count test.

Another possibility is to increase act_count's decay constant
ACT_DECLINE in proportion to the size of the active queue.
However, I don't know whether six bits would provide enough
resolution for this strategy to have any advantage over your
proposal.