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Date:      Sun, 24 Nov 2002 00:37:03 -0800 (PST)
From:      Julian Elischer <julian@elischer.org>
To:        Andrew Gallatin <gallatin@cs.duke.edu>
Cc:        Robert Watson <rwatson@freebsd.org>, Luigi Rizzo <rizzo@icir.org>, current@freebsd.org
Subject:   Re: mbuf header bloat ?
Message-ID:  <Pine.BSF.4.21.0211232306410.28833-100000@InterJet.elischer.org>
In-Reply-To: <15840.8629.324788.887872@grasshopper.cs.duke.edu>

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On Sat, 23 Nov 2002, Andrew Gallatin wrote:

> 
> As you eloquently state, there are a number of tradeoffs involved.  On
> a 64-bit platform, 99% of users are paying 40 bytes/pkt for something
> that they will never use.  On x86, 99.99% of users are paying 20
> bytes/pkt for a feature they will never use.  At least a signifigant
> fraction of nics make use of csum offloading (xl, ti, bge, em, myri).


the downside to the TAG stuff is that you need to allocate a separate
tag storage, and that is a malloc.. which has certain characteristics
vs the mbuf allocator.  We have a special allocator for mbufs for a
reason. (I'm not sure how many of the original reasons still apply).
so it's worth looking at whether malloc is a suitable method of
allocating all that stuff before we take it out of the mbuf.



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