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Date:      Mon, 29 Nov 1999 18:17:34 -0800
From:      David Greenman <dg@root.com>
To:        Doug Barton <Doug@gorean.org>
Cc:        Colin Campbell <sgcccdc@citec.qld.gov.au>, freebsd-questions@FreeBSD.ORG
Subject:   Re: netstat -m confusion 
Message-ID:  <199911300217.SAA28138@implode.root.com>
In-Reply-To: Your message of "Mon, 29 Nov 1999 18:09:11 PST." <Pine.BSF.4.21.9911291801530.32747-100000@24-25-220-29.san.rr.com> 

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>On Mon, 29 Nov 1999, Colin Campbell wrote:
>
>> Hi,
>> 
>> I just had one box reboot because it ran out of mbufs, so I thought I'd
>> check another one and saw something quite confusing, namely:
>> 
>> 826/4724/4608 mbuf clusters in use (current/peak/max)
>> 
>> How can the peak be > max? (FreeBSD 3.2 off the WC CD set).
>
>	I've seen this myself in really high-load situations. The only
>answer I've ever come up with is that the value of "max" is slightly more
>conservative than what is really available in the kernel, and/or that it's
>rounded off to some factor of 8 which can be less than what's actually
>there. Notice for instance that 4608/1024=4.5, whereas 4724 is an
>"odd" number. I suspect that if you did the MAXUSERS multiplication that
>your actual number of mbufs is 4608 < x < 5120, but I haven't looked at
>the source to confirm my theory.
>
>	According to the figures that DG quoted way back in the 2.2.x days
>(by my recollection/experience anyways) the max should always be >= 1.5 x
>peak, so the point to all of this is that you need lots more
>NMBCLUSTERS. :)

   The max doesn't include additional space that was allocated for regular
mbufs (which we recently changed to be allocated out of the same kernel VM map
space), so if the peak is greater than the max, then this is telling you that
you ran out and used some other space as well that wasn't part of NMBCLUSTERS.
Anyway, increase the parameter to solve the problem.

-DG

David Greenman
Co-founder/Principal Architect, The FreeBSD Project - http://www.freebsd.org
Creator of high-performance Internet servers - http://www.terasolutions.com
Pave the road of life with opportunities.


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