Path: utzoo!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!uunet!samsung!gca!beaulieu
From: beaulieu@gca.UUCP (Larry Beaulieu)
Newsgroups: comp.unix.ultrix
Subject: Re: Missing swap space?
Summary: you need a few minor changes
Message-ID: <444@gca.UUCP>
Date: 9 Aug 90 12:46:06 GMT
References: <1990Aug8.143813.16876@cs.wayne.edu>
Distribution: na
Organization: GCA Corporation, Andover Mass
Lines: 90

> to argdev.  Seems like rather a lot of space.  I wonder if I missed 
> something when I configured the system for interleaved swap??

	Yup.  You did.

	In your file /usr/sys/conf/systemname, you have the
	line:

> config        vmunix  root on ra0a  swap on ra0b size 66690 \
> and ra1b size 66880

	As root:

	Change the configuration line to read:

config	vmunix root on ra0a swap on ra0b and ra1b

	without specifying the size. 

	You then need to make an entry in /etc/fstab to reflect
	the additional swap partition:

/dev/ra1b::sw:0:1:ufs::

	Issuing the command 

	swapon -a 

	will cause the system to scan fstab and add any appropriate
	entries (file systems designated by sw) as additional
	interleaved swap partitions, so you don't have to reboot to
	effect the changes.  You should get a messge indicating
	that additional swap spaces have been added.

	The file /etc/rc by default already contains the swapon -a
	command.

	Also, note that you can use any available partition for
	your second swap space; use of partition b is not
	a prerequisite.


 	Instead of:

> pandora[27] %pstat -s
> 66785k swap configured
>         8272k used (1456k text, 0k smem)
>         25071k free, 2959k wasted, 33442k missing
>         avail: 46*512k 2*256k 3*128k 3*64k 5*32k 5*16k 191*1k
> 

	You should get something like the following.

	On our 11/780 (w/3.1) configured this way pstat gives the
	following output:

altair> pstat -s
24662k swap configured
        8450k used (1088k text, 0k smem)
        16210k free, 2795k wasted, 2k missing
avail: 29*512k 3*256k 3*64k 5*32k 5*16k 162*1k
altair>

> The number of pages missing is suspiciously close to the size
> of ra1b, and a previous incarnation of the kernel, with a smaller
> ra1b partition exhibited similar behavior -- the missing pages were
> almost equal in size to the size of the second swap partition.  TFM

	I suspect that it is because the kernel expects to have
	the additional swap space available but doesn't actually 
	doesn't, since it wasn't specified in /etc/fstab; ergo the 
	kernel treats the expected pages from the 2nd swap
	space as 'missing'.

******

	As I understand it, most 4.2 BSD based systems should be 
	able to interleave swap spaces using a similar procedure.

	The method here is similar to that used for SunOS; the major
	difference is that the SunOS kernel uses a slightly
	different (and SUPPOSEDLY more efficient) algorithm to 
	interleave, and by default it supports multiple 
	swap partitions without requiring listing them in 
	the configuration file.  
-- 
Larry Beaulieu				The usual disclaimers apply.
GCA/Ultratech Corporation, 	
Andover, MA						
beaulieu@gca.com (or ...uunet!gca!beaulieu, if you prefer)