From owner-freebsd-net@FreeBSD.ORG Thu Dec 1 06:26:50 2011 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 2714C1065670 for ; Thu, 1 Dec 2011 06:26:50 +0000 (UTC) (envelope-from hapvbk@yahoo.co.uk) Received: from nm22-vm1.bullet.mail.ukl.yahoo.com (nm22-vm1.bullet.mail.ukl.yahoo.com [217.12.10.75]) by mx1.freebsd.org (Postfix) with SMTP id 9063C8FC18 for ; Thu, 1 Dec 2011 06:26:49 +0000 (UTC) Received: from [217.146.183.211] by nm22.bullet.mail.ukl.yahoo.com with NNFMP; 01 Dec 2011 06:26:47 -0000 Received: from [77.238.184.53] by tm4.bullet.mail.ukl.yahoo.com with NNFMP; 01 Dec 2011 06:26:47 -0000 Received: from [127.0.0.1] by smtp122.mail.ukl.yahoo.com with NNFMP; 01 Dec 2011 06:26:47 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.co.uk; s=s1024; t=1322720807; bh=0TbTSPBxIBvBK4buHYamrLzD5OVR0q4OulfE6AFPGnY=; h=X-Yahoo-Newman-Id:X-Yahoo-Newman-Property:X-YMail-OSG:X-Yahoo-SMTP:Received:Message-ID:From:To:Cc:References:In-Reply-To:Subject:Date:MIME-Version:Content-Type:Content-Transfer-Encoding:X-Priority:X-MSMail-Priority:Importance:X-Mailer:X-MimeOLE; b=G9iU5WrDT1ut2BIqP6gyY1K0BDt1pvrSgzxMKBv0rnuqZVoX1/KjD7XwQpkOyci2jVBNWRmW9kJzDv9KzgPYm9QEGiMk83JFFwPIawGmbZIieKSg1NDGpjHmv6EtcUMiPcWlh5VTuPs8EH3r45DmBW8gPEKsGnVcCIvJiSn2z7E= X-Yahoo-Newman-Id: 609098.44574.bm@smtp122.mail.ukl.yahoo.com X-Yahoo-Newman-Property: ymail-3 X-YMail-OSG: TdfWzvwVM1mDJNE8TqhcWQCAK5C23R9k.CPmZzDgeh2YPQg 27tKklfTtehDHQHZjINO848mqdaAZSNnAT8Dqsn0_iW5LfF5Q.lfjQNOLgnZ S.PnJ6s07WuYg7fjEUAXnTg8YzYDpWnAfENuE45d2o6jhANyVZN2BfjxbPtA NsnqIsC4oIrry7qlqfUHccbOdDxVw9PcSv00p9LItywDBHoP7PvRKdgueMB_ LN2epmsF8F5St7x6xTVrlV1NUzWXd55wGNATjh3D5foS0ogPmoRj6h3VIbm5 v5OiGQSrIBj2WZHsnYmMxFkSGu2mdJeEYbkq9m53rkToTbU8cdI4Pt4V5z6O MslibtfQttd9_Fptz.89oRzoBm2Nvn8PbsXsVy54- X-Yahoo-SMTP: xBpCc9iswBApASleyiIs9lcZMA-- Received: from PC (hapvbk@66.11.191.2 with login) by smtp122.mail.ukl.yahoo.com with SMTP; 01 Dec 2011 06:26:47 +0000 GMT Message-ID: From: "Viet-Ha Pham" To: "Adrian Chadd" References: <69C75F6ECC9646C79374299EDF0E4304@PC><5939430EC6AF43B79CB9BE99940E9B91@PC> In-Reply-To: Date: Thu, 1 Dec 2011 01:26:43 -0500 MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 15.4.3538.513 X-MimeOLE: Produced By Microsoft MimeOLE V15.4.3538.513 Cc: freebsd-net@freebsd.org, Bernhard Schmidt Subject: Re: Wifi throughput test issue (FreeBSD 8.2) X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 01 Dec 2011 06:26:50 -0000 Hi Adrian, Thanks for your reply. I will try the sysctl today. Let me clarify what we are doing and our objectives. We want to investigate the relationship between SNR and throughput at each transmission rate. So we fix the rate, vary the input noise and measure the throughput at that noise level for that rate. We repeat this procedure for all transmission rates. The issue that I described happened even with no-noise scenario. For the samplerate source code, we have read it since we are working also on rate adaptation algorithm. I'll update the dmesg result. Thanks. HAPV -----Original Message----- From: Adrian Chadd Sent: Wednesday, November 30, 2011 11:06 AM To: Viet-Ha Pham Cc: freebsd-net@freebsd.org ; Bernhard Schmidt Subject: Re: Wifi throughput test issue (FreeBSD 8.2) Hi, Hm. Selecting a static rate would mean that you'd end up populating the rate control statistics with more "wins" for that particular TX rate, so when you go back to "any", it will choose 54mbit more often. I suggest looking at the code in sys/dev/ath/ath_rate/sample/sample.[ch] and see what's going on. You can investigate the current statistics by "sysctl dev.ath.X.sample_stats=1" and then check dmesg. It sounds like your noise is causing some tx failures to occur at higher rates, which makes sample back off very quickly. It may not then sample the higher rates often enough if it sees failures early on. Adrian _______________________________________________ freebsd-net@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org"