Re: Out of memory kernel deat

Tim Hollebeek (tim@franck.Princeton.EDU)
Mon, 12 May 1997 14:24:14 -0400 (EDT)

Mike Jagdis writes ...
> On Mon, 12 May 1997, Thomas Koenig wrote:
> > I'd propose a fairly simple solution: send a SIGURG signal to
> > whatever process has a signal handler for it installed.
> >
> > This process could then do whatever it wants to, such as allocating
> > more swap, killing off an errant process or send an E-Mail to
> > the admin to go out and buy more RAM.
> >
> > Policy is for userland.
> I seem to remember that AIX has a signal specifically for this
> situation (SIGDANGER?). I seem to remember that this came up
> last time the out of memory thread surfaced too.
> The bottom line is that there is no single algorithm, simple
> or complex, that will consistently pick a non-stupid process
> to kill for everyone.
> Might I suggest that SIGDANGER be introduced and used to warn
> everything that they damn well better try and sort themselves
> out? If things don't get better we can try killing things - perhaps
> starting with things that don't have a SIGDANGER handler, followed
> by things that didn't reduce their footprint in response to

AIX is a wonderful OS to bring up in this debate, and has been mentioned
several times before and IMO is an excellent example of what we should
*not* do.

SIGDANGER is essentially useless because it is AIX specific; >99% of
software ignores it so it gains you nothing. AIX then goes on to the
kill the largest process solution, which as several people have pointed
out from experience is a really bad solution. It is in fact on my list
of Top 10 Things I Dislike Most About AIX.

Tim Hollebeek | Disclaimer :=> Everything above is a true statement,
Electron Psychologist | for sufficiently false values of true.
Princeton University | email:
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