From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Stein Subject: Re: [bug, bisected] pfifo_fast causes packet reordering Date: Mon, 19 Mar 2018 07:07:05 +0100 Message-ID: <1950329.Eot9n0FZxY@ws-stein> References: <946dbe16-a2eb-eca8-8069-468859ccc78d@theobroma-systems.com> <5aeb54ba-2d96-4ab5-53c4-2d3691be7acc@gmail.com> <340a6c54-6031-5522-98f5-eafdd3a37a38@theobroma-systems.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Cc: John Fastabend , Dave Taht , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, "David S. Miller" , "linux-can@vger.kernel.org" , Martin Elshuber To: Jakob Unterwurzacher Return-path: In-Reply-To: <340a6c54-6031-5522-98f5-eafdd3a37a38@theobroma-systems.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Friday, March 16, 2018, 11:26:47 AM CET Jakob Unterwurzacher wrote: > On 15.03.18 23:30, John Fastabend wrote: > >> I have reproduced it using two USB network cards connected to each other. The test tool sends UDP packets containing a counter and listens on the other interface, it is available at > >> https://github.com/jakob-tsd/pfifo_stress/blob/master/pfifo_stress.py > >> > > > > Great thanks, can you also run this with taskset to bind to > > a single CPU, > > > > # taskset 0x1 ./pifof_stress.py > > > > And let me know if you still see the OOO. > > Interesting. Looks like it depends on which core it runs on. CPU0 is > clean, CPU1 is not. > > Clean: taskset --cpu-list 0 ./pfifo_stress.py > > Broken: taskset --cpu-list 1 ./pfifo_stress.py > > Maybe related: CPU0 is where USB interrupts are handled: > > > root@rk3399-q7:~# cat /proc/interrupts > > CPU0 CPU1 CPU2 CPU3 CPU4 CPU5 > > 217: 2175353 0 0 0 0 0 GICv3 142 Level xhci-hcd:usb5 This reminds me somewhat of this thread: https://marc.info/?l=linux-can&m=148007442317274&w=2 Best regards, Alexander