Re: memory crash

William Burrow (
Tue, 10 Dec 1996 00:51:13 -0400 (AST)

On Mon, 9 Dec 1996, sheldon newhouse wrote:

> Just for the hell of it, I decided to see what would happen if I
> overloaded my system with cpu intensive programs which would cause the
> system to run out of memory and swap. The system started thrashing, and
> ultimately required a hard boot. I don't think this is healthy. Any user
> could do this.

Is this news to you guys? This ran by the newsgroups a few weeks ago. Do
you guys read the newsgroups? Do you want, say, two line summaries of the
latest brouhahas on the newsgroups and length of such threads?

> I have some questions:
> 1. Is it possible to set limits on accounts so that
> a. this kind of thing cannot be done ?

Under certain circumstances, the shell gets swapped out to make space for
the offending program, and cannot be swapped back to enforce ulimits. So
ulimits won't work. (This is the case on my machine, when I thought I
would be so smart to setup the ulimits fairly conservatively).

> 2. What should be done to insulate the system against this kind of thing?

Better swap scheme. Linux performs horribly under heavy swapping.
Memory is getting cheaper though, so maybe the impetus is slowly moving
away. (eg Imagine 200 meg Gaussian problems running on a system with 64
meg... apparently a lowly microVax can handle this but not Linux.)

[horrible complex code elided]

A simple malloc() bomb will do.

William Burrow  --  Fredericton Area Network, New Brunswick, Canada
Copyright 1996 William Burrow  
Canada's federal regulator says it may regulate content on the Internet to
provide for more Canadian content.   (Ottawa Citizen 15 Nov 96 D15)