misc/103455: "swap_pager: indefinite wait buffer" with page file enabled (causes lockups)

[Nick Withers]

>Number:         103455
>Category:       misc
>Synopsis:       "swap_pager: indefinite wait buffer" with page file enabled (causes lockups)
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Thu Sep 21 11:40:20 GMT 2006
>Closed-Date:
>Last-Modified:
>Originator:     Nick Withers
>Release:        6.2-PRERELEASE
>Organization:
>Environment:
FreeBSD unixserv3.shmon.net 6.2-PRERELEASE FreeBSD 6.2-PRERELEASE #1: Sat Sep 16 02:22:39 EST 2006     nick at unixserv3.shmon.net:/usr/obj/usr/src/sys/UNIXSERV3  i386
>Description:
This bug was (and still is) noted on the 6.1-RELEASE Release Engineering "to do" page ("http://www.freebsd.org/releases/6.1R/todo.html"), but I'm filing this because I have been unable to find a PR for the issue, nor anyone else who does (I emailed Don Lewis about it a few days ago but have yet to hear back).

With a page _file_ enabled on one of my servers (which routinely, if not pretty well always, has to use the page file), I occasionally get messages similar to these:
____

swap_pager: indefinite wait buffer: bufobj: 0, blkno: 43638, size: 4096
swap_pager: indefinite wait buffer: bufobj: 0, blkno: 43947, size: 32768
swap_pager: indefinite wait buffer: bufobj: 0, blkno: 44007, size: 4096
swap_pager: indefinite wait buffer: bufobj: 0, blkno: 47939, size: 32768
____

Often enough, they're just "here and there", and nothing I worry too much about. However, they're often also relatively frequently accompanied by system lockups: The console will be chock full of messages similar to the above and the machine will have to be powered off nastily.

The system is still responsive to pings during these lockups and the "swap_pager" messages do not make it to "/var/log/messages"

The system in question has 64 MB of physical RAM, a 102 MB swap partition and a 128 MB swap file (I know this is a pretty shoddy configuration... unfortunately, the machine in question doesn't have an abundance of hard disk space at its disposal, and I don't have an abundance of money :-))
>How-To-Repeat:
If I run something particularly memory intensive such as a "make -j2 buildworld" I can generally reproduce the issue fairly reliably.

>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted: