Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!xanth!lll-winken!uunet!nfsun!libove!root
From: root@libove.UUCP (Jay M. Libove)
Newsgroups: comp.unix.wizards
Subject: Re: A Danger Message From UNIX
Message-ID: <252@libove.UUCP>
Date: 23 Apr 89 14:37:49 GMT
References: <3320@homxb.ATT.COM>
Distribution: usa
Organization: Libove.UUCP
Lines: 33

From article <3320@homxb.ATT.COM>, by cjn@homxb.ATT.COM (C.NORTHRUP):

> 	for(i=0;i<4096;++i)
> 		if( (memptr[i] = malloc(80540)) == (char *) NULL)
> 		{
> 			perror("mt");
> 			break;
> 		}

> 	While running multiple versions of this in the background, 
> 	(loged on as a general user) the following message started 
> 	appearing on the system console:
> 	DANGER: out of swap space.

> 	Since the five (or so) invocations of the program consumed
> 	minimal space prior to the mallocs, how should the OS
> 	have handled this?  Should the mallocs have failed?
> 	Or is this considered acceptable.

I think you'll find that the malloc() calls _did_ fail, and that
the warning message occurs because an attempt to grab that much
swap space failed - not that the system alloc'd all of the
remaining space, and now has zero free space in the swap area.

Serious counter question: What kind of application needs to
allocate 4000 chunks of 80Kbytes each, and be run five times
simultaneously?

------------- 
Jay Libove		jl42@andrew.cmu.edu, libove@cs.cmu.edu,
5731 Centre Ave, Apt 3	gateway.sei.cmu.edu!libove!libove, jl42@andrew.BITnet,
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