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Date:      Thu, 15 Apr 1999 14:50:02 -0500 (CDT)
From:      Anthony Kimball <alk@pobox.com>
To:        chuckr@picnic.mat.net
Cc:        dcs@newsguy.com, chat@FreeBSD.ORG
Subject:   Re: swap-related problems
Message-ID:  <14102.16644.178732.291963@avalon.east>
References:  <14102.8184.91918.375800@avalon.east> <Pine.BSF.4.10.9904151428030.18456-100000@picnic.mat.net>

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Quoth Chuck Robey on Thu, 15 April:

: > I understand this.  I concieve the purpose of this thread as being
: > a clear determination of the best known way to allow correctly 
: > written code to run reliably when, for reasons perhaps out of the
: > control of the application, memory becomes overcommitted.
: 
: It might have been that, if on the second line of your original post you
: didn't claim we were ANSI incompatible.  As it was, it sounded much like
: chicken little yelling the sky was falling.  Your position now seems to
: have changed quite a bit.

I'm glad to be corrected where I err.  But we are ANSI incompatible
if one cannot configure the system so that malloc failure semantics
conform to the C spec.  Being able to rely upon ANSI C malloc failure
semantics is a contributory factor in being able to run a correctly
written application reliably.  It is not sufficient, however, as
others have noted.  In order to respond properly to the practical
inadequacy of mere ANSI conformance, the scope of the discussion has
expanded.  

My understanding of the state of play is this:  While mmap-backed
malloc suffices to provide ANSI C conformant malloc failure semantics,
and this can be handled best at the library level, the best proposed 
solution to the broader practical problem is to provide a kernel-level
facility to specify that a fork (and all children, recursively?) are
to be backed by a specific file.  

In my opinion, this is not detectably better (in the sense of being
less intrusive to implement) than a kernel facility to reserve swap
for a fork (and all children, recursively?).




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