From owner-p4-projects@FreeBSD.ORG Tue Mar 25 09:14:37 2008 Return-Path: Delivered-To: p4-projects@freebsd.org Received: by hub.freebsd.org (Postfix, from userid 32767) id 149331065747; Tue, 25 Mar 2008 09:14:37 +0000 (UTC) Delivered-To: perforce@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id C7BE71065745 for ; Tue, 25 Mar 2008 09:14:36 +0000 (UTC) (envelope-from bb+lists.freebsd.perforce@cyrus.watson.org) Received: from repoman.freebsd.org (repoman.freebsd.org [IPv6:2001:4f8:fff6::29]) by mx1.freebsd.org (Postfix) with ESMTP id A826A8FC21 for ; Tue, 25 Mar 2008 09:14:36 +0000 (UTC) (envelope-from bb+lists.freebsd.perforce@cyrus.watson.org) Received: from repoman.freebsd.org (localhost [127.0.0.1]) by repoman.freebsd.org (8.14.1/8.14.1) with ESMTP id m2P9Ean1024088 for ; Tue, 25 Mar 2008 09:14:36 GMT (envelope-from bb+lists.freebsd.perforce@cyrus.watson.org) Received: (from perforce@localhost) by repoman.freebsd.org (8.14.1/8.14.1/Submit) id m2P9EaKo024086 for perforce@freebsd.org; Tue, 25 Mar 2008 09:14:36 GMT (envelope-from bb+lists.freebsd.perforce@cyrus.watson.org) Date: Tue, 25 Mar 2008 09:14:36 GMT Message-Id: <200803250914.m2P9EaKo024086@repoman.freebsd.org> X-Authentication-Warning: repoman.freebsd.org: perforce set sender to bb+lists.freebsd.perforce@cyrus.watson.org using -f From: Robert Watson To: Perforce Change Reviews Cc: Subject: PERFORCE change 138505 for review X-BeenThere: p4-projects@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: p4 projects tree changes List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 25 Mar 2008 09:14:37 -0000 http://perforce.freebsd.org/chv.cgi?CH=138505 Change 138505 by rwatson@rwatson_cinnamon on 2008/03/25 09:14:08 Update bpf.4 to reflect that both buffers may be owned by userspace at once; caution against assuming this. Affected files ... .. //depot/projects/zcopybpf/src/share/man/man4/bpf.4#12 edit Differences ... ==== //depot/projects/zcopybpf/src/share/man/man4/bpf.4#12 (text+ko) ==== @@ -259,14 +259,14 @@ They will return a readable file descriptor when ownership of the next buffer is assigned to user space. .Pp -In the current implementation, the kernel will assign ownership of at most -one buffer at a time to the user process. -The user processes must acknowledge the current buffer in order to be -notified that the next buffer is ready for processing. -Programs should not rely on this as an invariant, as it may change in future -versions; in particular, they must maintain their own notion of which buffer -is "next" so that if both buffers are owned by userspace, it can process them -in the correct order. +In the current implementation, the kernel may assign zero, one, or both +buffers to the user process; however, an earlier implementation maintained +the invariant that at most one buffer could be assigned to the user process +at a time. +In order to both ensure progress and high performance, user processes should +acknowledge a completely processed buffer as quickly as possible, returning +it for reuse, and not block waiting on a second buffer while holding another +buffer. .Sh IOCTLS The .Xr ioctl 2