From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefan Wahren Subject: Packet loss when txqueuelen is zero Date: Sat, 28 Jun 2014 12:59:27 +0200 Message-ID: <53AEA00F.6060500@lategoodbye.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Cc: arnd@arndb.de To: netdev@vger.kernel.org Return-path: Received: from www.augenpunkt.de ([213.239.207.9]:44429 "EHLO www.augenpunkt.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751460AbaF1LLW (ORCPT ); Sat, 28 Jun 2014 07:11:22 -0400 Sender: netdev-owner@vger.kernel.org List-ID: Hi, i'm new to Linux network driver development and currently i want to port the QCA7000 network driver to mainline [1]. I concentrate my tests on tx buffering since my last QCA7000 patch RFC [2]. Now i've found a test scenario which leads to packet loss: host A Powerline host B (QCA7000) Ethernet Ethernet 192.168.1.3 adaptor 192.168.1.5 |------------------|---------------| Homeplug Ethernet 10 Mbit 100 Mbit 1. Reduce the txqueuelen from 100 (default value) to 0 2. Run ping in flood mode on host A to host B ping -c 200 -s 10000 -f 192.168.1.5 3. ping reports a high packet loss Additional information: - QCA7000 network driver has a tx ring size of 10 packets - the packet loss doesn't appear when txqueuelen is 100 Here are my questions: Is the packet loss a expected result for this scenario? If not what could be the cause of the packet loss? [1] - https://github.com/I2SE/qca7000/tree/linux-mainline [2] - http://www.spinics.net/lists/netdev/msg280751.html