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Date:      Mon, 13 Jul 1998 16:58:19 -0700 (PDT)
From:      Tom Wadlow <wadlow@tw.com>
To:        hackers@FreeBSD.ORG
Subject:   Problem with swap under 3.0-980524-SNAP
Message-ID:  <Pine.SUN.3.95P.980713162308.8130A-100000@hotspur.tw.com>

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I've got an odd problem with swap space on my machine, namely, it doesn't
seem to be using any.

Machine:	HP Kayak (Pentium II)
Memory:		128M
Disk:		4.3 GB SCSI

/etc/fstab (with allocations shown in parens):
/dev/sd0s1b    none            swap    sw  0       0   (500MB)
/dev/sd0s1a    /               ufs     rw  1       1   (100MB)
/dev/sd0s1g    /export/home    ufs     rw  2       2   (2.1GB)
/dev/sd0s1f    /usr            ufs     rw  2       2   (1.4GB)
/dev/sd0s1e    /var            ufs     rw  2       2   (200MB)
proc           /proc           procfs  rw  0       0

Unusual things about this workstation:
	Two-headed display (two Matrox Millenium II's)
	XIG Multiheaded X11R6 instead of XFree86 (which doesn't support
	multihead)

Kernel config:	GENERIC with the mods described below

FAQ:		Yes, I looked, but I couldn't find anything helpful for
		this.

Description:

I'm just in the process of finalizing the setup of this system for my
primary use (moving off Sun boxes for the first time in more than a
decade, for whatever that's worth).  Got most things working, but then
ran into a problem where I ran out of pseudo-ttys.   Looking through the
FAQ, I figured out how to up them to the (documented) max of 64 in the
kernel.  Did so.  Made more pseudo-ttys in /dev via MAKEDEV.  Rebooted.
Everything seemed to work.

Ran a little script to start creating rxvts one per second to see how much
stress I could put on the system.  I expected this to get up into the 50s
or low 60s with the kernel mods.  Instead, it went up from 16 (the
previous limit) to about 24, then started getting "Cannot fork" errors.

I stopped the script, and everything else I tried could not fork either.
Killed a few windows, enough to see that it looked like a swap problem,
as in, "I am out of swap".  This surprised me.  So I did a "pstat -T"

136/1320 files
0M/499M swap space

Hmmmm, not touching the swap space.... So I ran the test again, this time
with "top" running.  Turns out that the system starts hanging when mem
usage gets up near the 128M border, which is the amount of RAM I have in
the system.  The pstat output never lifts off 0, which says to me that 
the system isn't using any of the 500MB of swap that I built into it.
"pstat -s" says this:

Device      1K-blocks     Used    Avail Capacity  Type
/dev/sd0s1b    512000        0   511872     0%    Interleaved

which seems to imply that the system knows about my swap space at some
level as that is the correct swap volume.  It is just not choosing to
use that space as swap space.

Any thoughts?  --Tom

P.S.  Is the max ptys still 64 (as it says in the FAQ)?  The MAKEDEV seems
to imply 240 are trivially possible, with more requiring a little edit of
MAKEDEV.  I may try it in the kernel just to see what happens, but while
I'm addressing this august body, I might as well do a little pre-emptive
lobbying for more if need be.


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