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Date: Mon, 16 Nov 1998 23:48:41 +1100
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199811161248.XAA18427@godzilla.zeta.org.au>
To: bugs@FreeBSD.ORG
Subject: deadlock when swap is exhausted
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Configure a system with 32MB of memory and 64MB of swap.
`dd if=/dev/zero of=/dev/null bs=104m count=1' on an otherwise
idle system then causes deadlock.  The pageout daemon runs and
keeps killing dd, but dd can't run because a critical part of
it is paged out, and the pagefault handler doesn't do anything
because of a shortage of resources (pages or pbufs, I think).

This is a fairly old bug.  I first saw it when attempting to
duplicate the dying daemons problem -- make the memory hogs too
large and you get deadlock instead of possibly dying daemons.
Deadlock doesn't always occur -- sometimes there are enough free
or freeable resources.

Bruce

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