From owner-cvs-all Wed Dec 1 16:10:14 1999 Delivered-To: cvs-all@freebsd.org Received: from panzer.kdm.org (panzer.kdm.org [216.160.178.169]) by hub.freebsd.org (Postfix) with ESMTP id CA9321534A; Wed, 1 Dec 1999 16:10:02 -0800 (PST) (envelope-from ken@panzer.kdm.org) Received: (from ken@localhost) by panzer.kdm.org (8.9.3/8.9.1) id RAA45585; Wed, 1 Dec 1999 17:06:35 -0700 (MST) (envelope-from ken) Message-Id: <199912020006.RAA45585@panzer.kdm.org> Subject: Re: cvs commit: src/sys/kern uipc_mbuf.c src/sys/sys mbuf.h In-Reply-To: from Julian Elischer at "Dec 1, 1999 03:39:28 pm" To: julian@whistle.com (Julian Elischer) Date: Wed, 1 Dec 1999 17:06:35 -0700 (MST) Cc: archie@whistle.com (Archie Cobbs), gibbs@FreeBSD.org (Justin T. Gibbs), cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org From: "Kenneth D. Merry" X-Mailer: ELM [version 2.4ME+ PL54 (25)] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-cvs-all@FreeBSD.ORG Precedence: bulk Julian Elischer wrote... > basically it's not supposed to be in the hot path. > It's for debugging and tracing utilities. As long as m_dup() is not used in the standard network paths, it shouldn't cause any major problems. > On Wed, 1 Dec 1999, Archie Cobbs wrote: > > > Justin T. Gibbs writes: > > > > Modified files: > > > > sys/kern uipc_mbuf.c > > > > sys/sys mbuf.h > > > > Log: > > > > The functions m_copym() and m_copypacket() return read-only copies, > > > > because in the case of mbuf clusters they only increment the reference > > > > count rather than actually copying the data. > > > > > > > > Add comments to this effect, and add a new routine called m_dup() that > > > > returns a real, writable copy of an mbuf chain. > > > > > > How does this work in a 0 copy system? > > > > Not sure what a '0 copy system' is.. A zero copy system is a setup in which (at least on the send side) data is not copied into the kernel before DMAing it to the NIC. > > Basically all it does is create a completely new mbuf chain containing > > the same data as the original. Definitely at least 1 copy :-) > > > > You rarely need this, but 'ipfw tee' is one of those cases. I take it you need both copies to be writeable in that case? What are you writing to the copy? Ken -- Kenneth Merry ken@kdm.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message