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From: Bill Fenner <fenner@research.att.com>
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To: bmilekic@technokratis.com
Subject: Re: performance issues with M_PREPEND on clusters
Cc: rizzo@aciri.org, keiichi@iij.ad.jp, dwmalone@maths.tcd.ie,
	bright@mu.org, net@freebsd.org
References:  <20011023110307.A34494@iguana.aciri.org> <20011023132813.I15052@elvis.mu.org> <20011023114650.C34494@iguana.aciri.org> <20011023140034.M15052@elvis.mu.org> <20011023140628.A36095@iguana.aciri.org> <20011023185759.A328@technokratis.com> <20011026110635.B14635@walton.maths.tcd.ie> <86u1wmlj1s.wl@keiichi01.osaka.iij.ad.jp> <20011026121724.A21512@technokratis.com> <20011026092840.F64631@iguana.aciri.org> <20011026133827.A22096@technokratis.com>
Date: Fri, 26 Oct 2001 13:28:37 -0700
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>  The M_LEADINGSPACE macro always had the line of code that would return
>the leading space even for ext_bufs commented out, suggesting that the
>code did exist in the original implementation or was intended to.

The M_LEADINGSPACE macro was introduced in rev 7.11 of mbuf.h, in
August 1988, at the same time as the "new" mbufs, i.e. when external
sotrage was introduced, m_act renamed to m_nextpkt, etc.

Perhaps the commented code is there to remind what the right thing
to do is once you can tell whether or not external storage is writable.
I don't think it's reasonable to say that the presence of the comment
makes it completely obvious what the intentions of this code were in
1988.

  Bill

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