Subject: Re: easy ways to crash your NetBSD system
To: Jukka Marin <>
From: Brett Lymn <>
List: current-users
Date: 04/08/1996 17:45:30
According to Jukka Marin:
>> I'm sure I've seen this behaviour with swap space and processes being
>> killed in commercial Unixes...
>Wouldn't it be a good idea to kill the most recently started, largest
>user processes in case the system runs out of swap?  This would protect
>the system processes like init and inetd.

Ummm only if you can arrange for the bad sector on the disk to be
mapped to that last process run ;-)  Things don't work like that - if
the swapper managed to be convinced the data hit the disk but when it
goes to get it back it finds it cannot what do you do?  return null?
return an error that makes the process die?  OK, so if you do the last
then what happens?  do you have a mechanism for locking that disk
block out of the swap pool?  otherwise the block will get used
somewhere else causing more problems - sort of a roving/random process

This has become very focussed on just handling bad swap - the start of
this thread was someone claiming that panic'ing was taking the easy
way out.  I still instist that there are situations where it is better
to have the machine go toes up in no uncertain manner than try to cope
with something that is hopelessly broken only to limp on into more
damage.  This is what a panic is for.... if in danger or in doubt, run
in circles, scream and shout :-)

Brett Lymn, Computer Systems Administrator, AWA Defence Industries
  "Upgrading your memory gives you MORE RAM!" - ad in MacWAREHOUSE catalogue.