Subject: Re: Swap overcommit (was Re: Replacement for grep(1) (part 2))
To: None <freebsd-hackers@FreeBSD.ORG,>
From: John Nemeth <>
List: tech-userlevel
Date: 07/14/1999 10:53:27
On Jul 15, 12:20am, "Daniel C. Sobral" wrote:
} "Charles M. Hannum" wrote:
} > 
} > That's also objectively false.  Most such environments I've had
} > experience with are, in fact, multi-user systems.  As you've pointed
} > out yourself, there is no combination of resource limits and whatnot
} > that are guaranteed to prevent `crashing' a multi-user system due to
} > overcommit.  My simulation should not be axed because of a bug in
} > someone else's program.  (This is also not hypothetical.  There was a
} > bug in one version of bash that caused it to consume all the memory it
} > could and then fall over.)
} In which case the program that consumed all memory will be killed.
} The program killed is +NOT+ the one demanding memory, it's the one
} with most of it.

     On one system I administrate, the largest process is typically
rpc.nisd (the NIS+ server daemon).  Killing that process would be a
bad thing (TM).  You're talking about killing random processes.  This
is no way to run a system.  It is not possible for any arbitrary
decision to always hit the correct process.  That is a decision that
must be made by a competent admin.  This is the biggest argument
against overcommit:  there is no way to gracefully recover from an
out of memory situation, and that makes for an unreliable system.

}-- End of excerpt from "Daniel C. Sobral"