Xref: utzoo unix-pc.general:4094 comp.sys.att:8006
Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!wuarchive!gem.mps.ohio-state.edu!tut.cis.ohio-state.edu!att!icus!limbic!gil
From: gil@limbic.UUCP (Gil Kloepfer Jr.)
Newsgroups: unix-pc.general,comp.sys.att
Subject: Re: Where or where has my memory gone? (UNIX pc)
Summary: Memory--okay to be fragmented
Keywords: memory, RAM, uptime, beta kernels
Message-ID: <577@limbic.UUCP>
Date: 9 Nov 89 05:45:20 GMT
References: <1020@icus.islp.ny.us>
Reply-To: gil@limbic.UUCP (Gil Kloepfer Jr.)
Organization: ICUS Software Systems, Islip, NY
Lines: 47

In article <1020@icus.islp.ny.us> lenny@icus.islp.ny.us (Lenny Tropiano) writes:
>Well my machine was up for 30 days, 20 hours, 14 minutes and it just 
>flipped out! Things were running slowly.  Does memory get fragmented 
>like disks do?

Okay, I'll bite.  Note that the following is definitely based on theory,
and not on documented experience, but it sounds reasonable.  The way
the UNIX-pc MM works, memory will probably be "fragmented" 99% of the
time, but the hardware page tables should map the memory into what
appears to be a "contiguous" section of memory.  What it can't get in
"real" memory, it will page off to disk as "virtual" memory by virtue
of the memory management system.

Now someone with a good working knowledge of the internals of the UNIX-pc
kernel (you know who you are ;-) could probably check the way that pages
are allocated and freed and whether the page table entries are being
maintained properly.  Someone mentioned in an earlier article that
he never saw his machine (via sysinfo) go below .5 meg free.  This
might (??) be a related problem.

> Should you reboot frequently, and what is the frequency?   

I would say that most of us would say that you should NEVER have
to reboot your machine.  The AT&T hotline would most certainly say
you should, every day if possible ;-)  [if that doesn't work, you
could always reformat the hard disk and reload the OS ;-) ;-) ]
Considering the number of daemons running on your machine, and
the nature of the devices you have, it might be a good idea to do
a "ps -lef" and check the SZ and RSZ fields (I think those are memory,
right folks?!) and see if any of them continuously increase from day to
day.  One of these daemons might be eating your memory to oblivion!

>The last dying word of my machine was:
>sysinfo: cannot read /dev/rfp002 

Hmmm....  System buffers maybe?

For those who find it necessary to flame for incorrect information, my
disclaimer here is that I don't claim to know all about this, but I'm
hoping that these comments will encourage some thought about what might
be happening.

Gil.
-----
| Gil Kloepfer, Jr.
| ICUS Software Systems/Bowne Management Systems (depending on where I am)
| ...ames!limbic!gil