Where or where has my memory gone? (UNIX pc)

[Bill Mayhew]

I have 2 meg on the motherboard and a 67 meg drive on my 3b1.
According to sysinfo, the smallest I've seen the free store drop is
497K; even when I've tried to excessively load the machine.  I'm
not sure if the machine is sensing a low water mark at 512K and
starting to page to disk at that point or what.  Heaven only knows
what algorithm the kernel is using.

At work, we use a 7300 with a 40 meg disk with 1 meg on the
motherboard and 1.5 on cards.  We have three serial ports going.
We use tty000 to drive a trailblazer and tty000 connected to a dz
port on a vax 750.  The 7300 is our news server since we've had a
lot of problems with SILO overruns on the vax ports talking to the
trailbalzer.  I've noticed that about every two weeks the 7300 at
work goes brain-dead with a normal console display and working
mouse, but ignores any input via the keyboard or tty.  It would
seem that all the jobs in the ready queue, except for smgr, are hung
becaue anything such as sysinfo does not update the display, but
the time and date in W5 at the top of the screen keep updating.
We're running HDB uucp.  Unfortunately, since the machine is locked
up it is rather difficult to tell what is going on.

At home, I had a LOT of problems running version 3.51 and the stock
uucp.  My machine crashed at least once a day.  After considerable
consultation with ye olde hotline, AT&T replaced the motherboard
after trying a recompiled uucico that they downloaded to my
machine.  Even with the new motherboard, I still had crashing.  The
HDB uucp solved the problems I was having.  The crashes that I got
at home were the same in symptom that we get on occasion at work.
The difference is that at work we transfer about 4 megs in and 4
megs of data out of the 7300 every day.  At home, my input is about
400 to 750K per day.

We can live with the occasional crashes at work, since once every
two weeks or so isn't that awful :-).  I built a little box with a
6502 CPU chip that monitors the serial line going to the vax.  If
the monitor doesn't see a uucico from the 7300 at least once an
hour, it picks a relay to reboot the 7300.

What I have noticed on my machine is that big chunks of memory
erode over the course of two or three days and then reappear.  The
free store is about 900K right after booting the mahcine, and this
usually drops to aobut 625K over a couple of days, after which the
memory seems to return from limbo.

As someone mentioned a while ago, the clist buffers seem to slowly
go away too.  My machine starts out with about 130, and that drops
to about 120 after a while, but seems to stabilize at 120.

One last item.  I've talked to people that had tons of problems
with the 3.51 uucp such as myself, while other people have had no
problmes at all.  One person speculated that use of /dev/ph* for
uucp was a factor in the crashing.

Bill
wtm at neoucom.edu