From owner-svn-src-stable-7@FreeBSD.ORG Fri Jun 10 18:51:33 2011 Return-Path: <owner-svn-src-stable-7@FreeBSD.ORG> Delivered-To: svn-src-stable-7@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id D532F1065670; Fri, 10 Jun 2011 18:51:33 +0000 (UTC) (envelope-from jhb@FreeBSD.org) Received: from svn.freebsd.org (svn.freebsd.org [IPv6:2001:4f8:fff6::2c]) by mx1.freebsd.org (Postfix) with ESMTP id C48A58FC13; Fri, 10 Jun 2011 18:51:33 +0000 (UTC) Received: from svn.freebsd.org (localhost [127.0.0.1]) by svn.freebsd.org (8.14.4/8.14.4) with ESMTP id p5AIpXxX038555; Fri, 10 Jun 2011 18:51:33 GMT (envelope-from jhb@svn.freebsd.org) Received: (from jhb@localhost) by svn.freebsd.org (8.14.4/8.14.4/Submit) id p5AIpXmx038553; Fri, 10 Jun 2011 18:51:33 GMT (envelope-from jhb@svn.freebsd.org) Message-Id: <201106101851.p5AIpXmx038553@svn.freebsd.org> From: John Baldwin <jhb@FreeBSD.org> Date: Fri, 10 Jun 2011 18:51:33 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-7@freebsd.org X-SVN-Group: stable-7 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Cc: Subject: svn commit: r222937 - stable/7/sys/netinet X-BeenThere: svn-src-stable-7@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: SVN commit messages for only the 7-stable src tree <svn-src-stable-7.freebsd.org> List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/svn-src-stable-7>, <mailto:svn-src-stable-7-request@freebsd.org?subject=unsubscribe> List-Archive: <http://lists.freebsd.org/pipermail/svn-src-stable-7> List-Post: <mailto:svn-src-stable-7@freebsd.org> List-Help: <mailto:svn-src-stable-7-request@freebsd.org?subject=help> List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/svn-src-stable-7>, <mailto:svn-src-stable-7-request@freebsd.org?subject=subscribe> X-List-Received-Date: Fri, 10 Jun 2011 18:51:33 -0000 Author: jhb Date: Fri Jun 10 18:51:33 2011 New Revision: 222937 URL: http://svn.freebsd.org/changeset/base/222937 Log: MFC 220794: When checking to see if a window update should be sent to the remote peer, don't force a window update if the window would not actually grow due to window scaling. Specifically, if the window scaling factor is larger than 2 * MSS, then after the local reader has drained 2 * MSS bytes from the socket, a window update can end up advertising the same window. If this happens, the supposed window update actually ends up being a duplicate ACK. This can result in an excessive number of duplicate ACKs when using a higher maximum socket buffer size. Modified: stable/7/sys/netinet/tcp_output.c Directory Properties: stable/7/sys/ (props changed) stable/7/sys/cddl/contrib/opensolaris/ (props changed) stable/7/sys/contrib/dev/acpica/ (props changed) stable/7/sys/contrib/pf/ (props changed) Modified: stable/7/sys/netinet/tcp_output.c ============================================================================== --- stable/7/sys/netinet/tcp_output.c Fri Jun 10 18:51:22 2011 (r222936) +++ stable/7/sys/netinet/tcp_output.c Fri Jun 10 18:51:33 2011 (r222937) @@ -560,11 +560,19 @@ after_sack_rexmit: long adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale) - (tp->rcv_adv - tp->rcv_nxt); + /* + * If the new window size ends up being the same as the old + * size when it is scaled, then don't force a window update. + */ + if ((tp->rcv_adv - tp->rcv_nxt) >> tp->rcv_scale == + (adv + tp->rcv_adv - tp->rcv_nxt) >> tp->rcv_scale) + goto dontupdate; if (adv >= (long) (2 * tp->t_maxseg)) goto send; if (2 * adv >= (long) so->so_rcv.sb_hiwat) goto send; } +dontupdate: /* * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW