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From: jackg@sequent.UUCP (Jack Griffith)
Newsgroups: comp.sys.sequent
Subject: Re: Memory on Symmetry's
Keywords: memory, s27
Message-ID: <22260@sequent.UUCP>
Date: 26 Sep 89 10:05:37 GMT
References: <509@ariel.unm.edu>
Reply-To: jackg@sequent.UUCP (Jack Griffith)
Organization: Sequent Computer Systems, Inc
Lines: 35

In article <509@ariel.unm.edu> smorgan@ariel.unm.edu writes:
>
>   We have a Symmetry S27 with 6 CPUs that's used for general class
>instruction (compile/link/go users with a few math/stats packages
>thrown in on the side).  We've recently run into problems with
>interactive response (we average somewhere around twenty to forty
>concurrent users). From looking at `vmstat` output, we're apparently
>swapping a fair amount.
>
>   So, it looks like we're in need of memory. We currently have 8Mbytes

	When swapping it is useful to take a look at your "ps" output
	RSS column which is the Resident Set Size in memory of the
	processes running.  It may be that processes are exceeding 
	what you really require them to have for RSS. vmtune(8) can be used
	to dial down the maxRS (maximum resident set size) to top off the
	maximum RSS to allow enough memory for all of the processes.

	For example, if you had 5 processes whose RSS was at 3.5 Mbytes,
	then you would begin to swap and performance would degrade
	(with only 8Mbytes of memory).  Now if you were to dial down the
	maxRS to 1Mbyte (using vmtune -R 1000), then each process could
	only grow to 1Mbyte and you would still have memory left.  Paging
	MAY increase (if the processes are always paging into pages not in
	the resident set, then you may not even be increasing the page
	fault frequency (pff) of the process), but the response time is
	more reasonable.
________________________________________________________________________________

		Jack Griffith
		Customer Service Technical Support Engineer Specialist
		Sequent Computer Systems
		uunet!sequent!jackg
		(800) 854-9969
________________________________________________________________________________