Date: Thu, 25 Oct 2001 14:08:30 -0700 From: Bill Fenner <fenner@research.att.com> To: rizzo@aciri.org Cc: wollman@khavrinen.lcs.mit.edu, net@freebsd.org Subject: Re: performance issues with M_PREPEND on clusters Message-ID: <200110252108.OAA26017@windsor.research.att.com> References: <20011023110307.A34494@iguana.aciri.org> <200110231917.f9NJH4T32996@khavrinen.lcs.mit.edu> <20011023140318.A35869@iguana.aciri.org>
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Luigi Rizzo <rizzo@aciri.org> said: >On Tue, Oct 23, 2001 at 03:17:04PM -0400, Garrett Wollman wrote: >> ... the whole purpose of m_pullup is to >> *guarantee* that the data in question will never be shared. > >Technically, it is correct that m_pullup guarantees that the data >in question will never be shared, but it seems to me more an artifact >of its implementation than a real goal. It was not a design goal (in fact, the 4.4 daemon book actually claims "If the dtom() macro is eventually removed, m_pullup() will no longer be forced to move data from mbuf clusters." However, the "ensure that the data is not shared" side effect is heavily in at least the multicast code; the bridge code seem to also rely on it. I wouldn't be surprised if there were more. Bill To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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