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SubjectRe: [bug, bisected] pfifo_fast causes packet reordering
Date
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

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