From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751526AbeCNKJK (ORCPT ); Wed, 14 Mar 2018 06:09:10 -0400 Received: from vegas.theobroma-systems.com ([144.76.126.164]:35294 "EHLO mail.theobroma-systems.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750751AbeCNKJI (ORCPT ); Wed, 14 Mar 2018 06:09:08 -0400 From: Jakob Unterwurzacher Subject: Re: [bug, bisected] pfifo_fast causes packet reordering To: John Fastabend , Dave Taht Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, "David S. Miller" , "linux-can@vger.kernel.org" , Martin Elshuber References: <946dbe16-a2eb-eca8-8069-468859ccc78d@theobroma-systems.com> <95844480-d020-9000-53ef-0da8b965ce6e@gmail.com> Message-ID: <52581141-db46-8657-e0b5-161e236caa1b@theobroma-systems.com> Date: Wed, 14 Mar 2018 11:09:02 +0100 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <95844480-d020-9000-53ef-0da8b965ce6e@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 14.03.18 05:03, John Fastabend wrote: >>> During stress-testing our "ucan" USB/CAN adapter SocketCAN driver on Linux >>> v4.16-rc4-383-ged58d66f60b3 we observed that a small fraction of packets are >>> delivered out-of-order. >>> > > Is the stress-testing tool available somewhere? What type of packets > are being sent? Not public, no, the problem is that you'd need a CAN adapter as well. The test is simple, sending CAN frames with an increasing counter and a random length payload: [ tx thread rx thread ] | ^ v | [ interface 0 ] ---- cable ----> [ interface 1 ] I'll see if I can come up with a UDP testcase that works with normal ethernet interfaces. > Is this a single queue device or a multiqueue device? Running > 'tc -s qdisc show dev foo' would help some. Here you go: root@rk3399-q7:~# tc -s qdisc show dev can0 qdisc pfifo_fast 0: root refcnt 2 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1 Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0) backlog 0b 0p requeues 0 > If we introduced a OOO edge case somewhere that was not > intended so I'll take a look into it. But, if you can provide > a bit more details on how stress testing is done to cause the > issue that would help. Will do. Thanks, Jakob