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Date:      Fri, 24 Apr 1998 21:32:19 +0200 (MET DST)
From:      Luigi Rizzo <luigi@labinfo.iet.unipi.it>
To:        benedict@echonyc.com (Snob Art Genre)
Cc:        kjc@csl.sony.co.jp, current@FreeBSD.ORG
Subject:   Re: Bandwidth throttling etc.
Message-ID:  <199804241932.VAA22011@labinfo.iet.unipi.it>
In-Reply-To: <Pine.GSO.3.96.980424165606.18437A-100000@echonyc.com> from "Snob Art Genre" at Apr 24, 98 05:00:53 pm

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> Stevens suggests on p. 297 of TCP/IPv3 that "It appears that an mbuf
> cluster should be used sooner (e.g.for the 100-byte point) to reduce the
> processing time."
> 
> What are the relative merits of increasing the size of mbufs vs. going
> right to clusters?

a cluster is 2 KB, an mbuf is 8-16 times smaller. 
Moreover, a cluster also requires an associated mbuf, so you lose in
locality of references, etc.

I may be completely wrong, but I'd say that the most effective thing
would be to have mbufs large enough to hold the whole packet in most
cases. It remains to see how much memory you can afford to waste.

	cheers
	luigi
-----------------------------+--------------------------------------
Luigi Rizzo                  |  Dip. di Ingegneria dell'Informazione
email: luigi@iet.unipi.it    |  Universita' di Pisa
tel: +39-50-568533           |  via Diotisalvi 2, 56126 PISA (Italy)
fax: +39-50-568522           |  http://www.iet.unipi.it/~luigi/
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