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From: info-vax@ucbvax.ARPA
Newsgroups: fa.info-vax
Subject: re: More memory for VMS V4
Message-ID: <6672@ucbvax.ARPA>
Date: Wed, 1-May-85 19:44:13 EDT
Article-I.D.: ucbvax.6672
Posted: Wed May  1 19:44:13 1985
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From: sasaki@harvard.ARPA (Marty Sasaki)

When we went from version 3.7 to version 4.0 of VMS the kernel used up
70% more memory. We fortunately have 8Mbytes, but I could see some
problems with a smaller system.

My subjective impression is much like engvax!KVC@cit-vax's, overall
there isn't much change. However, there are times when things do seem to
slow down considerably. This seems to be due to two things: 1) I haven't
had the experience with V4.0 to really do a good job on tuning the
system, experience I did have (and used extensively) on V3.x, and 2)
there are occasionally degradations having to do with the disk ACP being
part of the user's address space and not a separate process.

I have been told that the second problem shows up because the disk
handling is accomplished at the process's priority rather than at the
ACP's priority in V3.x systems. The ACP usually ran at a higher priority
than user processes, and could usually finish an i/o request without
interruption. Such interruptions are more likely on V4.x systems. I have
to admit to not totally understanding this explanation.

	Marty Sasaki (sasaki@harvard.arpa)