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Date:      Tue, 29 Jan 2002 08:22:09 -0500
From:      talist@vif.com
To:        stable@freebsd.org
Subject:   Re: Crashing Freebsd + Dummynet + heavy traffic + workaround
Message-ID:  <1012310529.3c56a2017d4d4@email.vif.com>

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I noticed that the box can be made much more resilient by boosting the following
kernel variable:
options         HZ=1000 # granularity was 100

After rebuilding the kernel, freebsd did not freeze but I am sure this is only a
workaround.  Dummynet should not be able to lock-out the machine.
 

> I am using a freebsd box as a gateway in order to throttle down bandwidth for 
> some particular traffic.
> The box freezes under high load and the only way to recover is through a power 
> cycle.  
> The crash does not generate any logs, but I have ruled out hardware causes.  I 
> can repeat the lock-out with 2 different hardware and with xl(4) and dc(4)
NIC's
> 
> I am suspecting a problem with DUMMYNET's PIPE and QUEUE.
> 
> I have collected all the config information about the machine with a small 
> script that helps in crashing the box after a few minutes of alternating the 
> dummynet pipe's size.
> http://www.geocities.com/dummynetus/ipfw.txt
> 
> In summary, I have tried the following:
> - Boost maxusers to 128
> - Boost NMBCLUSTERS to 10240
> - monitor netstat -m gives normal readings even before freeze
> 

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