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Date:      Wed, 2 Sep 1998 22:32:41 +0200 (CEST)
From:      Andrzej Bialecki <abial@nask.pl>
To:        freebsd-current@FreeBSD.ORG
Subject:   VM question
Message-ID:  <Pine.BSF.4.02A.9809022201100.22481-100000@korin.warman.org.pl>

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Hi,

I'd like to change the behaviour of VM management, and I'm not sure how to
do this.

Here's what the setup looks like:

* the system in question is running without swap, so all that VM subsystem
has to manage is in RAM only,

* all binaries are either on an MFS, or on some other media with very fast
access (like a silicon disk),

...and here's what I'd like to achieve:

* to free pages aggressively, so that only a very few pages (a fraction of
.text and .data, the stack and bss) are paged in, and then as soon as
possible freed - it's relatively cheap to do pagein when the media that
holds binaries is very fast,

(As a side note: probably what I'd like to use is execution in place,
especially in case of MFS, but I remember someone telling me it's very
difficult to do...)

* to limit killing of random user processes - instead the VM should try
first to free as much pages as possible (and it should try better than it
is doing now :-)

So, given the above scenario and the goals:

* which existing knobs (and which direction...) should I twist to help it?

* what changes in VM code this would require (code examples are very
welcome...).

And yet another related question: what does NO_SWAPPING define do to the
kernel? When should I use it? (Ok, I thought it sounds good and enabled
it, but I don't see any obvious results...).

Thanks in advance, and excuse me if some of these questions show only my
ignorance... :-)

Andrzej Bialecki

--------------------   ++-------++  -------------------------------------
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 Research & Academic   |+-------+|       "Small & Embedded FreeBSD"
 Network in Poland     | |TT~~~| |    http://www.freebsd.org/~picobsd/
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