no core: help needed

[Alan's Home for Wayward Notes File.]

In article <1317 at eutrc3.urc.tue.nl>, rcpt at eutrc4.urc.tue.nl (Piet Tutelaers) writes:
> 
> We get regular the message `no core' on our uVAXII since we have recently
> upgraded our memory capacity from 5 to 13 MB. We use two swap disks, 
> the default on device /dev/ra0b and an extra on ra1b. The line in /etc/fstab
> is:
> 	/dev/ra1b::sw:0:0:ufs:: 
> 
> The partition data of both swap disks (RD53 and RD54) is:
> RD53: /dev/rra0a
> partition     bottom        top       size    overlap
>     b          15884      49323      33440    c,e
> RD54: /dev/rra1a
> partition     bottom        top       size    overlap
>     b          15884      49323      33440    c

	Every looks as expected so far...
> 
> Vmstat shows the following data:
>  procs     memory                       page      disk  faults          cpu
>  r b w   avm  fre  re at  pi  po  fr  de  sr r1 r2 r0 x3  in  sy  cs us sy id
>  0 1 0  1705 4931   0  0   0   0   0   0   0  0  0  1  0  11  16   3 10  5 86
>  0 0 0  1144 4866   0  0   0   0   0   0   0  0  0  0  0   2  20   1  1  0 99

	In almost every example I've seen "out of core" is due to
	a lack of swap space not a lack of memory.  After running
	out of swap space the next limit usually the "datasize"
	and "stacksize" limits enforced by the C-shell.

	Rather than vmstat(1) look at "pstat -s".  This prints the
	usage of swap space.

	The C-shell has a builtin command called limit.  You can
	use it look at what the various limits are.  Generally the
	stack is limited to 512 KBytes.  You can use "unlimit" to
	remove the limit.  The limit on "datasize" is controlled
	by the configuration parameters "dmmin" and "dmmax".  They
	are sufficiently described in the "Guide to System Configuration
	File Maintenance".
> 
> I have noticed that when the number of free pages is less than 3000 (column
> fre), I cannot start up SliTeX for example.
> 
> a) Does anyone have suggestions how we can reconfigure the uVAXII in order to
>    get more programs started?

	Determine which of the common two problems is occuring.

	1.  If it's swap space get more or get rid of an application
	    that is using a lot.

	2.  If it's the "datasize" or "stacksize" limit, raise them.
	    See what I said before about "dmmin" and "dmmax".
> 
> b) Is it possible to see on a running system which swap devices are active?

	Using adb you can look at a data structure called _swdevt.  The 
	format of this structure is defined in <sys/conf.h>.
> 
> c) Is it possible to find out what memory claim a program makes?

	You can use size(1) to find out what the startup memory	
	requirements are.  The text size limit in V3.x is either 
	6 MB or 12 MB.  In V3.x it might be something that can
	be configured.
> 
> Thanks for any help! Piet
> ------------------------------------------------------------------
> uucp:   rcpt at urc.tue.nl       | Piet Tutelaers        Room  RC 1.82


-- 
Alan Rollow				alan at nabeth.enet.dec.com