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Date:      Sun, 29 Oct 1995 01:47:02 -0400 (EDT)
From:      Brian Tao <taob@io.org>
To:        David Greenman <davidg@Root.COM>
Cc:        FREEBSD-HACKERS-L <freebsd-hackers@freebsd.org>
Subject:   Re: panic: free vnode isn't 
Message-ID:  <Pine.BSI.3.91.951028233436.5278A-100000@trepan.io.org>
In-Reply-To: <199510250616.XAA28141@corbin.Root.COM>

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On Tue, 24 Oct 1995, David Greenman wrote:
> 
>    Okay...but for DDB this really isn't necessary and only results in you
> losing about 4-6MB of memory for all the unused gdb debugging symbols.

    So I noticed... sysctl -a reported 20 megs of hw.usermem on a
32-meg machine.  :(

> I think your problem is caused by bug(s) in the NFS client code. While
> we do test it relatively thoroughly, we don't pond on it in the way
> that you are doing and that likely explains why the bug hasn't been
> seen before and fixed. :-)

    At least it has been isolated to an NFS-related bug.  :)  The
server died again today (2.0.5R was installed on it), but this time it
managed to send a message to the console before keeling over
completely:

biodone: page busy < 0, off: 3162112, foff: 3162112, resid: 4096, index: 0
iozone: 8192, lblkno: 386
valid: 0xff, dirty: 0x0, mapped: 0
panic: biodone: page busy < 0

    Then a bunch of attempts at syncing which eventually failed, then
it rebooted.  I'm in the process of installing 2.1.0-951026-SNAP right
now.  I'm also going to move our FTP server over to another machine,
and mount only the staff home directories (a single 2-gig drive).
Since I'm really the only person who uses this machine for interactive
use, NFS traffic will be significantly reduced.  If it is a problem
with NFS load, the machine should be stable.  My machines back in
Taiwan had everything but the base FreeBSD distribution NFS-mounted
from an SGI server (including user home directories and work
directories) without encountering this problem.

    If this incarnation survives for a week, then I'll try moving the
FTP service back on and take it from there.  Oh, I'm getting "nfs send
error 55" in syslog quite often... is this a symptom of an overrun
buffer?  I should add that the collision rate on our LAN averages 50%
and can spike above 100%.  It's absolutely horrid, but I hope it isn't
the cause of the kernel panics.

> Debugging this problem will almost certainly be quite difficult. ...
> Unfortunately, without a lot more information, it's unlikely that I'll
> be able solve this problem.

    *sigh*  I'll try the latest snapshot and see what happens then.
--
Brian Tao (BT300, taob@io.org)
Systems Administrator, Internex Online Inc.
"Though this be madness, yet there is method in't"





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