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Date:      Fri, 14 Mar 2003 11:40:25 -0500
From:      Garance A Drosihn <drosih@rpi.edu>
To:        Juli Mallett <jmallett@FreeBSD.org>, Eivind Eklund <eivind@FreeBSD.org>
Cc:        Mike Silbersack <silby@silby.com>, David Schultz <das@FreeBSD.org>, src-committers@FreeBSD.org, cvs-src@FreeBSD.org, cvs-all@FreeBSD.org
Subject:   Re: cvs commit: src/sys/vm ... SIGDANGER
Message-ID:  <p05200f28ba97b4007dab@[128.113.24.47]>
In-Reply-To: <20030314101857.A98861@FreeBSD.org>
References:  <200303122313.h2CNDHMU046431@repoman.freebsd.org> <20030312175458.J32334@odysseus.silby.com> <20030313005115.GA11794@HAL9000.homeunix.com> <20030313154226.X682@odysseus.silby.com> <20030314012954.A42430@FreeBSD.org> <20030314101857.A98861@FreeBSD.org>

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At 10:18 AM -0600 3/14/03, Juli Mallett wrote:
>* De: Eivind Eklund <eivind@FreeBSD.org> [ Data: 2003-03-14 ]
>  >
>  > Having had as my workstation a FreeBSD machine with X, netscape,
>  > and too little RAM, I think it would be very useful for some
>  > situations.  You have no idea how annoying it is when netscape
>  > eats all your memory and FreeBSD decide that the solution to
>  > this is to kill *X*.
>
>I've had that happen for me (though the combinations required are a
>lot lower, as my RAM is a lot lower :>), and that's why I started
>looking into this. ...
>
>Basically I was adding a new signal, SIGVM (or SIGNOMEM), and the
>semantics were as such:

AIX (and maybe some other systems?) have a signal called SIGDANGER,
which is meant for this kind of situation.  If we implement some
new signal, then perhaps it would be good to use that signal name
and mimic their implementation of it.

This has been talked about in the past, but has stalled out
because there was "no room for new signals" (at the time).
Something about a problem with adding any new signal number,
although obviously I'm foggy on the details.  And I don't know
if that issue has been addressed in 5.0.

I would like to see this happen.  No matter how much memory you have,
it would be nice to have some kind of control over which processes
will be killed when the system does run out of VM!

[mind you, I know about SIGDANGER because several years ago we had
some AIX systems which would keep killing 'lpd' if they got low on
memory, so I had to use SIGDANGER to protect lpd!]

-- 
Garance Alistair Drosehn            =   gad@gilead.netel.rpi.edu
Senior Systems Programmer           or  gad@freebsd.org
Rensselaer Polytechnic Institute    or  drosih@rpi.edu

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