netdev - Re: [PATCH net-next v2 0/3] add tx packets aggregation to ethtool and rmnet

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Date:   Wed, 30 Nov 2022 07:04:21 -0800
From:   Dave Taht <dave.taht@...il.com>
To:     Daniele Palmas <dnlplm@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Subash Abhinov Kasiviswanathan <quic_subashab@...cinc.com>,
        Sean Tranchetti <quic_stranche@...cinc.com>,
        Jonathan Corbet <corbet@....net>,
        Alexander Lobakin <alexandr.lobakin@...el.com>,
        Gal Pressman <gal@...dia.com>,
        Bjørn Mork <bjorn@...k.no>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        netdev@...r.kernel.org
Subject: Re: [PATCH net-next v2 0/3] add tx packets aggregation to ethtool and rmnet

On Wed, Nov 30, 2022 at 5:15 AM Daniele Palmas <dnlplm@...il.com> wrote:
>
> Hello maintainers and all,
>
> this patchset implements tx qmap packets aggregation in rmnet and generic
> ethtool support for that.
>
> Some low-cat Thread-x based modems are not capable of properly reaching the maximum
> allowed throughput both in tx and rx during a bidirectional test if tx packets
> aggregation is not enabled.
>
> I verified this problem with rmnet + qmi_wwan by using a MDM9207 Cat. 4 based modem
> (50Mbps/150Mbps max throughput). What is actually happening is pictured at
> https://drive.google.com/file/d/1gSbozrtd9h0X63i6vdkNpN68d-9sg8f9/view

Thank you for documenting which device this is. Is it still handing in
150ms of bufferbloat in good conditions,
and 25 seconds or so in bad?

> Testing with iperf TCP, when rx and tx flows are tested singularly there's no issue
> in tx and minor issues in rx (not able to reach max throughput). When there are concurrent
> tx and rx flows, tx throughput has an huge drop. rx a minor one, but still present.
>
> The same scenario with tx aggregation enabled is pictured at
> https://drive.google.com/file/d/1jcVIKNZD7K3lHtwKE5W02mpaloudYYih/view
> showing a regular graph.
>
> This issue does not happen with high-cat modems (e.g. SDX20), or at least it
> does not happen at the throughputs I'm able to test currently: maybe the same
> could happen when moving close to the maximum rates supported by those modems.
> Anyway, having the tx aggregation enabled should not hurt.
>
> The first attempt to solve this issue was in qmi_wwan qmap implementation,
> see the discussion at https://lore.kernel.org/netdev/20221019132503.6783-1-dnlplm@gmail.com/
>
> However, it turned out that rmnet was a better candidate for the implementation.
>
> Moreover, Greg and Jakub suggested also to use ethtool for the configuration:
> not sure if I got their advice right, but this patchset add also generic ethtool
> support for tx aggregation.
>
> The patches have been tested mainly against an MDM9207 based modem through USB
> and SDX55 through PCI (MHI).
>
> v2 should address the comments highlighted in the review: the implementation is
> still in rmnet, due to Subash's request of keeping tx aggregation there.
>
> Thanks,
> Daniele
>
> Daniele Palmas (3):
>   ethtool: add tx aggregation parameters
>   net: qualcomm: rmnet: add tx packets aggregation
>   net: qualcomm: rmnet: add ethtool support for configuring tx
>     aggregation
>
>  Documentation/networking/ethtool-netlink.rst  |  17 ++
>  .../ethernet/qualcomm/rmnet/rmnet_config.c    |   5 +
>  .../ethernet/qualcomm/rmnet/rmnet_config.h    |  20 ++
>  .../ethernet/qualcomm/rmnet/rmnet_handlers.c  |  18 +-
>  .../net/ethernet/qualcomm/rmnet/rmnet_map.h   |   6 +
>  .../ethernet/qualcomm/rmnet/rmnet_map_data.c  | 191 ++++++++++++++++++
>  .../net/ethernet/qualcomm/rmnet/rmnet_vnd.c   |  54 ++++-
>  .../net/ethernet/qualcomm/rmnet/rmnet_vnd.h   |   1 +
>  include/linux/ethtool.h                       |  12 +-
>  include/uapi/linux/ethtool_netlink.h          |   3 +
>  net/ethtool/coalesce.c                        |  22 +-
>  11 files changed, 342 insertions(+), 7 deletions(-)
>
> --
> 2.37.1
>


-- 
This song goes out to all the folk that thought Stadia would work:
https://www.linkedin.com/posts/dtaht_the-mushroom-song-activity-6981366665607352320-FXtz
Dave Täht CEO, TekLibre, LLC