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From: friesen@psivax.UUCP (Stanley Friesen)
Newsgroups: net.unix-wizards
Subject: Re: Vax memory utilization on 4.2 BSD.
Message-ID: <881@psivax.UUCP>
Date: Wed, 27-Nov-85 16:36:00 EST
Article-I.D.: psivax.881
Posted: Wed Nov 27 16:36:00 1985
Date-Received: Tue, 10-Dec-85 05:07:56 EST
References: <2391@ukma.UUCP>
Reply-To: friesen@psivax.UUCP (Stanley Friesen)
Organization: Pacesetter Systems Inc., Sylmar, CA
Lines: 31

In article <2391@ukma.UUCP> sean@ukma.UUCP (Sean Casey) writes:
>I've noticed that our Vax 11/750 with 5 megs running 4.2 BSD almost never
>uses more than half of the physical memory.  Does anyone know of a simple
>way to retune the vm scheduler?  I've considered raising the virtual paging
>point by fiddling with some of the constants, but I'm not sure of all the
>consequences.  Is there anyone out there that can give me some help?  Any
>ideas at all would be helpful.
>
	Actually it is simpler than you think. The scheduler in 4.x is
controlled by three *variables*(not constants). If the variables are
initialized to zero(the default) the boot procedure calculates
standard values, if they are initialized to other values the boot
procedure leaves them alone. This means even a binary site can tune
the scheduler, by patching the values in vmunix.
The variables are: lotsfree - high water mark where paging is turned off
		   desfree  - desired minimum: turn page daemon on
		   minfree  - serious minimum: page daemon to overdrive
The default values are: lotsfree = 1/4 of available memory(excl. kernel)
			desfree = max(0x190, 1/8 available memory)
			minfree = max(0x80, 1/2 of desfree)
(Where the number specified is the number of core allocation units, which
is either pages or klusters, I don't have the time to figure out which)
Decreasing these values will slow down paging and lead to greater
memory utilization. I would not recomend reducing the values of
desfree and minfree below the stated minimums.
-- 

				Sarima (Stanley Friesen)

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