Date: Wed, 1 Dec 1999 17:06:35 -0700 (MST) From: "Kenneth D. Merry" <ken@kdm.org> To: julian@whistle.com (Julian Elischer) Cc: archie@whistle.com (Archie Cobbs), gibbs@FreeBSD.org (Justin T. Gibbs), cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/kern uipc_mbuf.c src/sys/sys mbuf.h Message-ID: <199912020006.RAA45585@panzer.kdm.org> In-Reply-To: <Pine.BSF.4.10.9912011538100.11380-100000@current1.whistle.com> from Julian Elischer at "Dec 1, 1999 03:39:28 pm"
next in thread | previous in thread | raw e-mail | index | archive | help
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
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199912020006.RAA45585>