Re: [PATCH v3 00/10] tcp: Fix throughput issues with non-local peers

[Max Chernoff <git@maxchernoff.ca>]

Hi Stefano,

On Mon, 2025-12-08 at 08:20 +0100, Stefano Brivio wrote:
> With this series, I'm getting the expected (wirespeed) throughput for
> transfers between peers with varying non-local RTTs: I checked
> different guests bridged on the same machine (~500 us) and hosts with
> increasing distance using iperf3, as well as HTTP transfers only for
> some hosts I have control over (500 us and 5 ms case).
>
> With increasing RTTs, I can finally see the throughput converging to
> the available bandwidth reasonably fast:

Thanks for the patch, but this unfortunately seems to make things worse
in my testing (with curl/https). Using my benchmarking script from the
earlier thread, with a 10MB file size and a 30s timeout:

    $ pasta --version  # Using the stock pasta in F43
    pasta 0^20250919.g623dbf6-1.fc43.x86_64

    $ ./pasta-upload-test.sh
    network ping_time       wmem_max        rmem_max        tcp_notsent_lowat       tcp_congestion_control  default_qdisc        download_time   upload_time
    host    50ms    custom  custom  custom  custom  custom  1.508751        1.656876
    pasta   50ms    custom  custom  custom  custom  custom  1.548367        2.184099
    host    170ms   custom  custom  custom  custom  custom  9.313611        3.055348
    pasta   170ms   custom  custom  custom  custom  custom  13.300405       25.046154

    $ sudo dnf install <freshly built pasta rpms>
    $ pasta --version
    pasta 0^20251208.g5943ea4-1.fc43.x86_64

    $ ./pasta-upload-test.sh
    network ping_time       wmem_max        rmem_max        tcp_notsent_lowat       tcp_congestion_control  default_qdisc        download_time   upload_time
    host    50ms    custom  custom  custom  custom  custom  1.490700        1.666525
    pasta   50ms    custom  custom  custom  custom  custom  1.474725        30.000000
    host    170ms   custom  custom  custom  custom  custom  9.618929        3.221314
    pasta   170ms   custom  custom  custom  custom  custom  10.475894       30.000000

    $ sudo dnf downgrade pasta
    $ pasta --version  # Back to the stock pasta in F43
    pasta 0^20250919.g623dbf6-1.fc43.x86_64

    $ ./pasta-upload-test.sh
    network ping_time       wmem_max        rmem_max        tcp_notsent_lowat       tcp_congestion_control  default_qdisc        download_time   upload_time
    host    50ms    custom  custom  custom  custom  custom  1.407653        1.686541
    pasta   50ms    custom  custom  custom  custom  custom  1.558330        2.481097
    host    170ms   custom  custom  custom  custom  custom  8.951508        3.191743
    pasta   170ms   custom  custom  custom  custom  custom  9.891349        30.000000

    $ sudo dnf install <freshly built pasta rpms>
    $ pasta --version  # Try the patched version again in case the last test was an anomaly
    pasta 0^20251208.g5943ea4-1.fc43.x86_64

    $ ./pasta-upload-test.sh
    network ping_time       wmem_max        rmem_max        tcp_notsent_lowat       tcp_congestion_control  default_qdisc        download_time   upload_time
    host    50ms    custom  custom  custom  custom  custom  1.450695        1.689421
    pasta   50ms    custom  custom  custom  custom  custom  1.605941        30.000000
    host    170ms   custom  custom  custom  custom  custom  5.610433        3.034058
    pasta   170ms   custom  custom  custom  custom  custom  5.544638        30.000000

Thanks,
-- Max