Return-path: Received: from mail-iy0-f174.google.com ([209.85.210.174]:53276 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755722Ab1EQQex (ORCPT ); Tue, 17 May 2011 12:34:53 -0400 Received: by iyb14 with SMTP id 14so557984iyb.19 for ; Tue, 17 May 2011 09:34:53 -0700 (PDT) Message-ID: <4DD2A3A9.90003@lwfinger.net> (sfid-20110517_183456_836520_99E95F3C) Date: Tue, 17 May 2011 11:34:49 -0500 From: Larry Finger MIME-Version: 1.0 To: Rob Browning CC: linux-wireless@vger.kernel.org Subject: Re: Slow receive with rtl8192cu (usb ew-7811Un) References: <87pqnl5i81.fsf@raven.defaultvalue.org> <4DD074E3.3090502@lwfinger.net> <87vcxbe5xz.fsf@trouble.defaultvalue.org> <4DD09C78.2010304@lwfinger.net> <8762pbkytq.fsf@trouble.defaultvalue.org> <4DD13EF0.2070803@lwfinger.net> <87iptaj8nf.fsf@trouble.defaultvalue.org> <87fwoehtd7.fsf@trouble.defaultvalue.org> In-Reply-To: <87fwoehtd7.fsf@trouble.defaultvalue.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sender: linux-wireless-owner@vger.kernel.org List-ID: On 05/16/2011 10:57 PM, Rob Browning wrote: > Rob Browning writes: > >> So that command ran at essentially the rates you report for 10-20 >> seconds. Then I killed it and tried another test I'd been using, which >> was to lftp to ftp.kernel.org and get -c linux-2.6.39-rc7.tar.bz2. That >> transfer started at a high rate, but settled fairly quickly at about >> 60KB/s. So I killed that transfer and restarted the wget, and it ran >> steadily at ~60KB/s. > > In case it helps, it also looks like the 60KB/s is an aggregate limit. > Once it gets into the "lower bandwidth" state, if I run multiple > transfers, the total won't go above that. I can duplicate your result. To me, it appears to be a problem with bufferbloat. If that is correct, then there is little I can do with rtl8192cu to fix the problem. I see exactly the same slow rate with rt2800usb using an Ralink RT3070 device. In addition, I see that rate when connected to my router with a wired 100 Mbps connection. What up/down rates do you see if you test with www.speedtest.net? I get 0.48 Mbps up and 12.03 Mbps down. The up rate is a little slower than the 512 Kbps that my ISP provides. My nominal down rate is 7 Mbps with burst rates above 10 if the bandwidth is available. Apparently it was this morning. Larry