*BSD News Article 60290


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From: lew@bnr.ca (Pierre Lewis)
Newsgroups: comp.unix.bsd.netbsd.misc,comp.unix.solaris,comp.unix.aix
Subject: Re: Memory overcommit (was Re: ISP hardware/software choices (performance comparison))
Date: 22 Jan 96 12:20:50 GMT
Organization: Bell Northern Research
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Distribution: inet
Message-ID: <lew.822313250@bmtlh538>
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blarson@sundry.hsc.usc.edu (Bob Larson) writes:

> Overcommit may have its uses, but does not belong on a production
> machine.  (AIX's habit of killing important processes least likly to
> be causing the problem first just makes it worse

I had a shock when I realized that AIX can kill you (a process) at
unpredictable times, just for trying to access some memory it (AIX)
has already granted you. The only valid place for a process to be
told it's out of memory is sbrk(2), typically inside malloc(3).

On the version of AIX I saw, one could set PSALLOC=early to prevent
the late allocation algorithm from catching you. See malloc(3).

---
Pierre LEWIS    +1 514 765-8207    (ESN: 852-8207)
lew@bnr.ca      http://47.64.3.171:8080/experimental/lew/Menu.html

Real programmers can write assembly code in any language. :-)  [Larry Wall]