Date: Thu, 1 Dec 2011 01:26:43 -0500 From: "Viet-Ha Pham" <hapvbk@yahoo.co.uk> To: "Adrian Chadd" <adrian@freebsd.org> Cc: freebsd-net@freebsd.org, Bernhard Schmidt <bschmidt@freebsd.org> Subject: Re: Wifi throughput test issue (FreeBSD 8.2) Message-ID: <CB7EB42661084A168C508C6A2AC07BF2@PC> In-Reply-To: <CAJ-Vmo=B3H3_Wefhq4fKQQ7LiYF27oQ06osm4QzuWKT2a3wDxA@mail.gmail.com> References: <69C75F6ECC9646C79374299EDF0E4304@PC><CAAgh0_Ym0Np4Py-aaxH=bEJcSJPAKcx2CFECMtgSD=%2B%2BVhUvLQ@mail.gmail.com><5939430EC6AF43B79CB9BE99940E9B91@PC> <CAJ-Vmo=B3H3_Wefhq4fKQQ7LiYF27oQ06osm4QzuWKT2a3wDxA@mail.gmail.com>
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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"
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