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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>
Cc:        freebsd-current@freebsd.org
Subject:   Re: Broken memory management on system with no swap
Message-ID:  <20030421104932.GA3658@HAL9000.homeunix.com>
In-Reply-To: <200304201924.h3KJOxWo090302@apollo.backplane.com>
References:  <000501c30682$4e5e64b0$6601a8c0@VAIO650> <20030420002940.GB46590@HAL9000.homeunix.com> <20030420191744.G19683@gamplex.bde.org> <20030420101401.GA2821@HAL9000.homeunix.com> <200304201828.h3KISlKq090099@apollo.backplane.com> <20030420191029.GA4803@HAL9000.homeunix.com> <200304201924.h3KJOxWo090302@apollo.backplane.com>

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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.



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