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Date: Tue, 27 Apr 2010 11:16:44 -0400
From: Andrew Gallatin <gallatin@cs.duke.edu>
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Subject: Is swap on ZFS supposed to work?
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I have a machine where I enabled swap on ZFS somewhat accidentally
(really wanted to dump to ZFS, but that didn't pan out) and then
forgot about it.  A month later, under a heavy load (make
-j8 buildworld) it hung with:

swap_pager: indefinite wait buffer: bufobj: 0, blkno: 289218, size: 4096
swap_pager: indefinite wait buffer: bufobj: 0, blkno: 290789, size: 4096
swap_pager: indefinite wait buffer: bufobj: 0, blkno: 305343, size: 4096
<...>

scrolling on console.  I made 2 more attempts to buildworld before
I finally remembered the ZFS swap partition and removed it, which
allowed the buildworld to complete without hanging the machine.

It is running 8.0-STABLE #1 r205446M (amd64) and has very little (512MB) 
RAM.

Drew