From owner-freebsd-current@FreeBSD.ORG Sat Mar 3 18:38:29 2007 Return-Path: X-Original-To: freebsd-current@freebsd.org Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id CBE7F16A402 for ; Sat, 3 Mar 2007 18:38:29 +0000 (UTC) (envelope-from andy@siliconlandmark.com) Received: from lexi.siliconlandmark.com (lexi.siliconlandmark.com [209.69.98.4]) by mx1.freebsd.org (Postfix) with ESMTP id 771FF13C491 for ; Sat, 3 Mar 2007 18:38:29 +0000 (UTC) (envelope-from andy@siliconlandmark.com) Received: from [10.0.1.5] (cpe-24-33-245-212.twmi.res.rr.com [24.33.245.212]) by lexi.siliconlandmark.com (8.13.8/8.13.3) with ESMTP id l23IcIC4099459; Sat, 3 Mar 2007 13:38:18 -0500 (EST) (envelope-from andy@siliconlandmark.com) In-Reply-To: <20070303000125.GA9918@turion.vk2pj.dyndns.org> References: <17850.13146.266196.499166@grasshopper.cs.duke.edu> <20070303000125.GA9918@turion.vk2pj.dyndns.org> Mime-Version: 1.0 (Apple Message framework v752.3) Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Message-Id: <20DDE355-5F52-4E1F-B316-D933C816DE3B@siliconlandmark.com> Content-Transfer-Encoding: 7bit From: Andre Guibert de Bruet Date: Sat, 3 Mar 2007 13:38:23 -0500 To: Peter Jeremy X-Mailer: Apple Mail (2.752.3) X-Virus-Scanned: ClamAV 0.88.7/2713/Sat Mar 3 10:57:58 2007 on lexi.siliconlandmark.com X-Virus-Status: Clean X-Information: Please contact the ISP for more information X-SL-MailScanner: Not scanned: please contact your Internet E-Mail Service Provider for details X-SL-SpamCheck: not spam, SpamAssassin (not cached, score=-0.042, required 6, AWL 0.51, BAYES_00 -2.60, RCVD_IN_SORBS_DUL 2.05, SPF_PASS -0.00) X-MailScanner-From: andy@siliconlandmark.com Cc: freebsd-current@freebsd.org, Andrew Gallatin Subject: Re: excessive TCP duplicate acks? X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 03 Mar 2007 18:38:29 -0000 On Mar 2, 2007, at 7:01 PM, Peter Jeremy wrote: > On 2007-Jan-26 11:59:06 -0500, Andrew Gallatin > wrote: >> When running some benchmarks, I noticed tons of duplicate acks >> showing >> up in systat -tcp (thousands, or tens of thousands per second). > > Whilst investigating other problems, I've just seen the same on 6.2. > The following trace was taken on 192.168.234.1, which is running > 6.2-RELEASE/i386 (with ipfilter enabled) with fxp (Intel 82559) NICs. > 192.168.234.64 is running 6.2-STABLE/amd64 from late January (no > firewall active) with a bge (Broadcom BCM5705 A3, ASIC rev. 0x3003) > NIC and checksum offloading enabled. > > The multiple SYN packets are due to a bug in the IPfilter state > management, though it eventually allows a SYN through. (And it is not > totally unrealistic for multiple SYNs to be required before a SYN-ACK > is received so this does not excuse the ACK flood). Note that the > duplicate ACKs are being sent from the host without a firewall so this > does not appear to be related to ipfilter (or kern/102653). > > The common factor seems to be amd64. I am seeing this problem on a machine with dual 64-bit Xeons in i386 mode: Vendor ID: "GenuineIntel"; CPUID level 5 Intel-specific functions: Version 00000f34: Type 0 - Original OEM Family 15 - Pentium 4 Extended family 0 Model 3 - Intel Pentium 4 processor (generic) or newer Stepping 4 Reserved 0 Extended brand string: " Intel(R) Xeon(TM) CPU 3.00GHz" CLFLUSH instruction cache line size: 8 Hyper threading siblings: 1 Andy /* Andre Guibert de Bruet * 6f43 6564 7020 656f 2e74 4220 7469 6a20 */ /* Code poet / Sysadmin * 636f 656b 2e79 5320 7379 6461 696d 2e6e */ /* GSM: +1 734 846 8758 * 5520 494e 2058 6c73 7565 6874 002e 0000 */ /* WWW: siliconlandmark.com * C/C++, Java, Perl, PHP, SQL, XHTML, XML */