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Date:      Thu, 5 Sep 2002 02:04:05 +0400 (MSD)
From:      Dmitry Morozovsky <marck@rinet.ru>
To:        Dominic Marks <dominic_marks@btinternet.com>
Cc:        Mike Hoskins <mike@adept.org>, Charles Sprickman <spork@inch.com>, <stable@FreeBSD.ORG>
Subject:   Re: interpreting netstat -m output
Message-ID:  <20020905014934.J56943-100000@woozle.rinet.ru>
In-Reply-To: <20020904212032.GA1688@gallium>

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On Wed, 4 Sep 2002, Dominic Marks wrote:

DM> An mbuf is a fixed length structure which contains network data.
DM>
DM> An mbuf cluster is associated with an area of memory which is used for
DM> storing more data than you can fit in a single mbuf.
DM>
DM> According the D&I 4.4 an mbuf is 128 bytes and (not all of this is
DM> available for data storage), an mbuf cluster varies in size, but
DM> defaults to 1024 bytes (but according to the book this may be different
DM> depending on CPU architecture).

AFAIK according to /usr/src/sys/*/param.h, mbuf size if 256 (at least for
i386, see /usr/src/sys/i386/include/param.h, and is not defined for
Alphas);

and mbcluster size defaults to 2k (I suppose the smallest 2^x to
cover standard Ethernet frame)

however, in /usr/src/sys/i386/boot/dosboot/param.h, MCLBYTES defined as
2^12 (4k). Don't know whether this value is really used.

Sincerely,
D.Marck                                   [DM5020, DM268-RIPE, DM3-RIPN]
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*** Dmitry Morozovsky --- D.Marck --- Wild Woozle --- marck@rinet.ru ***
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