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To: Thor Clark <thor@tab012.tabula.com>
cc: questions@freebsd.org
Subject: Re: system hangs? after resetting rtq_reallyold 
In-reply-to: Your message of "Sun, 14 Jul 1996 20:31:11 PDT."
             <Pine.SOL.3.91.960714195300.27434A-100000@tab012.tabula.com> 
From: David Greenman <davidg@root.com>
Reply-To: davidg@root.com
Date: Sun, 14 Jul 1996 22:21:45 -0700
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>running 2.1 Release, straight off the cd
>
>The system doesn't actually hang - it just becomes unresponsive, while 
>continuing to run some processes: eg will respond to a ping, and continue 
>to run some background processes, but will not respond to 
>telnet,ftp,http, or console input.
>
>I can (and did several times ;) reliably reproduce this by mailing ~1500 
>messages, with ~150 of them going to non-responsive or non-existant 
>servers.  
>
>from the log
>830:Jul 14 15:21:50 trex /kernel: in_rtqtimo: adjusted rtq_reallyold to 2400
>836:Jul 14 15:31:50 trex /kernel: in_rtqtimo: adjusted rtq_reallyold to 1600
>846:Jul 14 15:41:50 trex /kernel: in_rtqtimo: adjusted rtq_reallyold to 1066
>853:Jul 14 15:51:50 trex /kernel: in_rtqtimo: adjusted rtq_reallyold to 710
>863:Jul 14 16:01:57 trex /kernel: in_rtqtimo: adjusted rtq_reallyold to 473
>875:Jul 14 16:11:58 trex /kernel: in_rtqtimo: adjusted rtq_reallyold to 315
>883:Jul 14 16:21:58 trex /kernel: in_rtqtimo: adjusted rtq_reallyold to 210

   The above messages can be completely ignored and aren't part of the
problem. They indicate that the system is adjusting the route expiration
time for "clone" routes.
   Look via dmesg or in /var/log/messages for a kernel message of the form
"Out of mbuf clusters - increase maxusers", or for older releases of FreeBSD,
"mb_map full". The message will only occur once. If this is happening (likely),
then you need to increase the number of mbuf clusters either by increasing
maxusers or by adding:

options "NMBCLUSTERS=<n>"

   ...to your kernel config file. Where <n> is some number in the area of 2000
and not more than 4000 (unless you know what you're doing).
   I believe this is covered in the FAQ. The question gets asked about once
a week, so it should be.

-DG

David Greenman
Core-team/Principal Architect, The FreeBSD Project