Setting up swap on macppc

With Martin Husemann's advice, I've got a more-or-less working
NetBSD 9.3 system on my PowerMac G4 Cube.  However, I've had
two seeming kernel hangs while stress-testing it today, one
while using the 9.3 GENERIC kernel and one while using
HEAD-from-a-couple-days-ago kernel.  The second time around,
I was watching the test with "top" and noted that it got down
to about zero free RAM just before freezing.  So I'm theorizing
that there is something going wrong when the system tries to
use swap, and the most likely cause is that I did something
wrong while configuring that.  I thought I'd followed the
INSTALL document's advice carefully, but ...

I've got a suitable swap partition according to pdisk:

# pdisk /dev/wd0c
Edit /dev/wd0c -
Command (? for help): p

Partition map (with 512 byte blocks) on '/dev/wd0c'
 #:                type name           length   base      ( size )
 1: Apple_partition_map Apple              63 @ 1        
 2:           Apple_HFS Boot            20480 @ 64        ( 10.0M)
 3:     Apple_UNIX_SVR2 NetBSD_root 153092096 @ 20544     ( 73.0G) S0 RUFS k0  /
 4:     Apple_UNIX_SVR2 NetBSD_swap   2097152 @ 153112640 (  1.0G) S1  SFS k0  (swap)
 5:          Apple_Free Extra         1091696 @ 155209792 (533.1M)

Device block size=512, Number of Blocks=156301488 (74.5G)
DeviceType=0x0, DeviceId=0x0

Command (? for help): q

and swapctl says it's in use:

# swapctl -l
Device      512-blocks     Used    Avail Capacity  Priority
/dev/wd0b      2097152        0  2097152     0%    0

and the /etc/fstab entries seem OK:

/dev/wd0a               /       ffs     rw               1 1
/dev/wd0b               none    swap    sw,dp            0 0

But I didn't do anything particular about initializing the
contents of the partition.  Are you supposed to zero it out
or anything like that?

			regards, tom lane