Re: [PATCH iwl-next v4] igb: Retrieve Tx timestamp from BH workqueue

[Kurt Kanzenbach <kurt@linutronix.de>]

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On Tue Mar 03 2026, Paul Menzel wrote:
> Dear Kurt,
>
>
> Thank you for the patch.
>
> Am 03.03.26 um 12:48 schrieb Kurt Kanzenbach:
>> Retrieve Tx timestamp from system BH instead of regular system workqueue.
>> 
>> The current implementation uses schedule_work() which is executed by the
>> system work queue and kworkers to retrieve Tx timestamps. This increases
>> latency and can lead to timeouts in case of heavy system load. i210 is
>> often used in industrial systems, where timestamp timeouts can be fatal.
>> 
>> Therefore, switch to the system BH workqueues which are executed directly
>> at the end of the IRQ handler.
>
> Thank you for implementing this.
>
>> Tested on Intel i210 and i350 with ptp4l.
>
> It would be great, if you shared the numbers. Did Miroslav already test 
> this?

Great question. I did test with ptp4l and synchronization looks fine <
below 10ns back to back as expected. I did not test with ntpperf,
because I was never able to reproduce the NTP regression to the same
extent as Miroslav reported. Therefore, Miroslav is on Cc in case he
wants to test it. Let's see.

Thanks,
Kurt

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