On 6/12/26 19:21, Jonas Köppeler wrote:

On 6/12/26 16:10, Simon Schippers wrote:

quoted

On 6/12/26 10:35, hawk@kernel.org wrote:

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From: Jesper Dangaard Brouer <hawk@kernel.org>

This series adds BQL (Byte Queue Limits) to the veth driver, reducing
latency by dynamically limiting in-flight packets in the ptr_ring and
moving buffering into the qdisc where AQM algorithms can act on it.

LGTM, thanks for the detailed changelog :)

Maybe we should stop searching for the perfect tx-usecs value.
100us is probably fine for most hardware to not have a performance
regression. And lowering it does not really improve the RTT anyways.
Do you agree?

I agree, I already thought that it just might be a very lucky case when using 50us where something accidentally aligns nicely. Interestingly, I could also reproduce that 50us was consistently a little better compared to 100us on an Intel CPU. Maybe if I get the time, I'll have another look at it, but in general I think 50us or 100us does not really matter.

Interesting.

I ran the benchmarks again, the results are at [1].
I tested values between 0-9us, 10-90us, 100, 500, 1000, 5000 and 10000us.

TLDR: Throughput is fine for everything > 0us. RTT only improves
      slightly for < 100us. So 100us is fine.

[1] https://github.com/simoschip2000/veth-backpressure-performance-testing/blob/v7/results/tx-usecs/text_sweep.txt

quoted

Nevertheless, I will compile and run the benchmarks again.

I will go on vacation from 15th to 24th of June, so I will not be able
to contribute code or run benchmarks then.

Thanks,
Simon