🚀 go-pugleaf

In article <19633.2b5f18fd@levels.unisa.edu.au>, ccbjs@levels.unisa.edu.au writes:
>
>Is it possible to configure an Ultrix 4.3 system to use 3 disks
>for swap?   The documentation for swapon  sort of suggests it is.
>We have found from experience that swapon  doesn't work unless
>the kernal was configured to use it, eg two partitions:

As far as I know more than two is supported and works.  I'm not sure
what the limit is.  I was able to pretty quickly configure a system
with five for a reply to this.  Below is a cut and paste transcript
of what I did.  The command "swapdev" is something I wrote ages ago
to walk through the "_swdevt" data structure and put names to the
device numbers.

>
>When we added the 3rd partition to fstab it would boot OK, but strange
>things happened:
>  pstat -s returned
>  -8k    (Thats minus!) for swap configured.
>

The only thing intesting I saw as I added each swap device was that
the amount missing got smaller and the amount "reserved" got larger.
It looks like the space not turned on is reserved.

>  and top failed to execute.

It would be tacky if top only expected a limited number of devices.

It's also possible that one of the devices has a strange size and
is causing problems.  You should be able to look at the kernel swap
device table with dbx:

# dbx -k /vmunix /dev/mem
(dbx) print swdevt[0]
(dbx) print swdevt[...]
(dbx) print swdevt[n-1]

Here's my transcript.

# swapdev
/dev/ra0b:
        Freed: 1
        NBlks: 190464
/dev/ra4b:
        Freed: 1
        NBlks: 190464
/dev/ra8b:
        Freed: 0
        NBlks: 190464
/dev/ra129b:
        Freed: 0
        NBlks: 190464
/dev/ra60b:
        Freed: 0
        NBlks: 190464

# swapon /dev/ra8b
# pstat -s
476158k swap configured
197909k reserved virtual address space
        15k used (0k text, 0k smem)
        285679k free, 0k wasted, 190464k missing
avail: 8927*32k 15*1k

# swapon /dev/ra129b
# pstat -s
476158k swap configured
102679k reserved virtual address space
        15k used (0k text, 0k smem)
        380911k free, 0k wasted, 95232k missing
avail: 11903*32k 15*1k

# swapon /dev/ra60b
# pstat -s
476158k swap configured
7449k reserved virtual address space
        15k used (0k text, 0k smem)
        476143k free, 0k wasted, 0k missing
avail: 14879*32k 15*1k


>
>Thanks for your help, Bevin Steer, Unix Systems Manager,
>------------                                                      ------------
>ccbjs@levels.unisa.edu.au
>Phone:  +61-8-302-3271                                           Fax: 302 3385
>Computer Centre, University of South Australia, The Levels, SA 5095, Australia
>
--
Alan Rollow				alan@nabeth.cxo.dec.com