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Date: Mon, 31 Mar 2003 01:05:14 -0800
From: David Schultz <das@FreeBSD.ORG>
To: Poul-Henning Kamp <phk@phk.freebsd.dk>
Message-ID: <20030331090514.GB32360@HAL9000.homeunix.com>
Mail-Followup-To: Poul-Henning Kamp <phk@phk.freebsd.dk>,
	Wes Peters <wes@softweyr.com>, Garance A Drosihn <drosih@rpi.edu>,
	Dan Nelson <dnelson@allantgroup.com>, freebsd-arch@FreeBSD.ORG
References: <200303280910.32307.wes@softweyr.com>
	<10261.1048975354@critter.freebsd.dk>
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cc: freebsd-arch@FreeBSD.ORG
Subject: Re: Patch to protect process from pageout killing
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Thus spake Poul-Henning Kamp <phk@phk.freebsd.dk>:
> In message <200303280910.32307.wes@softweyr.com>, Wes Peters writes:
> 
> >I've reworked my patch to use the madvise(2) syscall, like the original 
> >4.x patch did.  I've even documented it, in a man page of all places.  
> >Please see attached patch.  If nobody objects, I'll commit sometime this 
> >weekend.
> 
> I'm still not certain about the inheritance of this, do we want/is it
> inherited ?
> 
> Also, thinking about it, on at least a handful of machines I would
> have more use for MADV_KILLMEFIRST having the exact opposite
> behaviour.

KILLMEFIRST is more of an advisory mechanism.  See relevant
discussions of SIGDANGER, priority systems, etc.  These are all
good ideas, but I think they belong in a domain of cooperation and
altruism, whereas MADV_PROTECT is the memory equivalent of rtprio.
At some level, there is generally a set of processes that should
never, ever be killed, e.g. postgres, sshd, apache.  So you're
right that KILLMEFIRST would be useful, but MADV_PROTECT is a very
nice first step.