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Date:      Mon, 24 Nov 1997 08:55:56 -0800
From:      David Greenman <dg@root.com>
To:        "Gregory, Scott, SrA, SAF/AADXT" <gregorys@af.pentagon.mil>
Cc:        "'freebsd-questions@freebsd.org'" <freebsd-questions@FreeBSD.ORG>
Subject:   Re: Mbuf allocation or lack there of 
Message-ID:  <199711241655.IAA06743@implode.root.com>
In-Reply-To: Your message of "Mon, 24 Nov 1997 08:34:13 EST." <A1D69BFE912ED111A5BB00A0C95DDDDCA1F2@afp1.hq.af.mil> 

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>Thanks for the info, but now I have a few more questions.
>
>1.  I specified that "NMBCLUSTERS=4096".  Does this mean that the system
>has 4096 Mbuf clusters available?

   Yes.

>2.  If #1 is yes, then why did I get an "out of mbuf clusters" error
>when the system had only used 1136?  (I was reading the numbers
>correctly, I just explained it poorly :-) )

   It sounds like you either forgot to do a 'config' after changing the kernel
config file, or didn't install the new kernel after it was rebuilt.

>3.  Does the generic kernel (with max users set to 100 and maxmem set to
>96megs) allocate more mbufs than my custom kernel with maxusers set to
>128 and NMBCLUSTERS set to 4096?  The reason I ask this is because the
>slightly modified kernel was able to attain a maximum of 2318 mbufs
>where as the modified kernel was only able to get to 1136.

   No, GENERIC is set to 10 users which would yield about 672 mbuf clusters.
The formula in the absense of NMBCLUSTERS is (512 + maxusers * 16).

>4.  What would you suggest I set NMBCLUSTERS and/or maxusers to?

   4096 and 128 is probably fine for a medium loaded WWW server. It all
depends on how heavy the traffic is.

-DG

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



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