From owner-svn-src-all@FreeBSD.ORG Tue Nov 19 18:04:27 2013 Return-Path: Delivered-To: svn-src-all@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 7D72BD37; Tue, 19 Nov 2013 18:04:27 +0000 (UTC) Received: from h2.funkthat.com (gate2.funkthat.com [208.87.223.18]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id 43337211F; Tue, 19 Nov 2013 18:04:27 +0000 (UTC) Received: from h2.funkthat.com (localhost [127.0.0.1]) by h2.funkthat.com (8.14.3/8.14.3) with ESMTP id rAJI4QZ0065948 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Tue, 19 Nov 2013 10:04:26 -0800 (PST) (envelope-from jmg@h2.funkthat.com) Received: (from jmg@localhost) by h2.funkthat.com (8.14.3/8.14.3/Submit) id rAJI4QjH065947; Tue, 19 Nov 2013 10:04:26 -0800 (PST) (envelope-from jmg) Date: Tue, 19 Nov 2013 10:04:26 -0800 From: John-Mark Gurney To: Robert Watson Subject: Re: svn commit: r258328 - head/sys/net Message-ID: <20131119180426.GC2279@funkthat.com> References: <201311182258.rAIMwEFd048783@svn.freebsd.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.3i X-Operating-System: FreeBSD 7.2-RELEASE i386 X-PGP-Fingerprint: 54BA 873B 6515 3F10 9E88 9322 9CB1 8F74 6D3F A396 X-Files: The truth is out there X-URL: http://resnet.uoregon.edu/~gurney_j/ X-Resume: http://resnet.uoregon.edu/~gurney_j/resume.html X-to-the-FBI-CIA-and-NSA: HI! HOW YA DOIN? can i haz chizburger? X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.2 (h2.funkthat.com [127.0.0.1]); Tue, 19 Nov 2013 10:04:26 -0800 (PST) Cc: svn-src-head@FreeBSD.org, "George V. Neville-Neil" , svn-src-all@FreeBSD.org, src-committers@FreeBSD.org X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.16 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 19 Nov 2013 18:04:27 -0000 Robert Watson wrote this message on Tue, Nov 19, 2013 at 11:04 +0000: > On Mon, 18 Nov 2013, George V. Neville-Neil wrote: > > > Allow ethernet drivers to pass in packets connected via the nextpkt > > pointer. > > Handling packets in this way allows drivers to amortize work during > > packet reception. > > > > Submitted by: Vijay Singh > > Sponsored by: NetApp > > Currently, it is quite easy to make mistakes regarding individual mbuf > chains vs. lists of mbuf chains. This leads me to wonder whether a new > type, perhaps simply constructed on the stack before passing in, should be > used for KPIs that accept lists of packets. E.g., > > /* > * This structure is almost always allocated on a caller stack, so > * cannot itself be queued without memory allocation in most cases. > */ > struct mbuf_queue { > struct mbuf *mq_head; > }; > > int > ether_input(struct ifnet *ifp, struct mbuf_queue *m) Why not pass in the structure (not a pointer to the struct) if the struct really is the above? It would even be able to save the stack allocation (not that it's that expensive)... so instead: int ether_input(struct ifnet *ifp, struct mbuf_queue m) You can also create the struct via a macro like: #define MAKE_MQ(mbuf) ((struct mbuf_queue){ (mbuf) }) so below would become: return (ether_input(ifp, MAKE_MQ(m))); Just a thought... But I do like using the compiler for this... The above makes the compiler do the work, and it be transparent from the code side... > { > > ... > } > > ... > struct mbuf_queue mq = { m }; > > return (ether_input(ifp, &mq)); > ... > > That way the compiler can help us figure out where we expect an individual > packet but have accidentally leaked a queue. Functions that accept only a > single packet could also more agressively assert that m->m_nextpkt is NULL: > > M_ASSERT_ONEPACKET(m); -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."