Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cbmvax!grr
From: grr@cbmvax.UUCP (George Robbins)
Newsgroups: comp.unix.wizards
Subject: Re: How much paging is "a lot?"
Message-ID: <7145@cbmvax.UUCP>
Date: 27 Jun 89 17:22:45 GMT
References: <3818@phri.UUCP>
Reply-To: grr@cbmvax.UUCP (George Robbins)
Organization: Commodore Technology, West Chester, PA
Lines: 34

In article <3818@phri.UUCP> roy@phri.UUCP (Roy Smith) writes:
> 
> 	I've been keeping an eye on our 4-Mbyte vax-11/750, trying to
> figure out if it would really help things if we added more memory...
>                                          ..Is 64 (1k) pages/second "a lot"?
>
> Over the past few minutes, it's been at or near 0 for perhaps half the
> time, with a few peaks up in the 30-50 range.  Is that "a lot"?

It depends on your work load.  If you have some mega-tasks that simply
won't fit in memory, it's no big deal.  On the other hand, if it's some
interactive task that has to be paged back in before the guy gets a
response to hitting return, or bopping some editing key then it might
seem pretty horrible.

I'm sure you'll get some horror stories from some of the educational
timesharing folks, but I'll suggest a simple alternative...

Used 750 memory boards (DEC) go for maybe $600/M-byte, you should be
able to get 4 for $2K with only a little haggling.  Do it, a 750 is
painful enough without adding wasted activity.

I'd think 8 M-byte is about right, unless you have a lot of tasks like
emacs, lisp or other virtual memory eaters.  Seems that 16-MB in a ~32
user 785 doesn't normally page at all, and you're about 1/3 to 1/2 of
that.

You might also want to look at the prices for used Microvax II's or the
like.  Unless you have some profound affection for that 750, you should
be able to do much better without spending much.
-- 
George Robbins - now working for,	uucp: {uunet|pyramid|rutgers}!cbmvax!grr
but no way officially representing	arpa: cbmvax!grr@uunet.uu.net
Commodore, Engineering Department	fone: 215-431-9255 (only by moonlite)