netdev - Re: [PATCH net-next 2/3] net: qualcomm: rmnet: add tx packets aggregation

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Message-ID: <CAGRyCJHmNgzVVnGunUh7wwKxYA7GzSvfgqPDAxL+-NcO2P+1wg@mail.gmail.com>
Date:   Wed, 16 Nov 2022 16:19:48 +0100
From:   Daniele Palmas <dnlplm@...il.com>
To:     Alexander Lobakin <alexandr.lobakin@...el.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>,
        Bjørn Mork <bjorn@...k.no>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        netdev@...r.kernel.org
Subject: Re: [PATCH net-next 2/3] net: qualcomm: rmnet: add tx packets aggregation

Hello Alexander,

Il giorno gio 10 nov 2022 alle ore 18:35 Alexander Lobakin
<alexandr.lobakin@...el.com> ha scritto:
>
> Do I get the whole logics correctly, you allocate a new big skb and
> just copy several frames into it, then send as one chunk once its
> size reaches the threshold? Plus linearize every skb to be able to
> do that... That's too much of overhead I'd say, just handle S/G and
> fraglists and make long trains of frags from them without copying
> anything?

sorry for my question, for sure I'm lacking knowledge about this, but
I'm trying to understand how I can move forward.

Suppose I'm able to build the aggregated block as a train of
fragments, then I have to send it to the underlying netdevice that, in
my scenario, is created by the qmi_wwan driver: I could be wrong, but
my understanding is that it does not support fragments.

And, as far as I know, there's only another driver in mainline used
with rmnet (mhi_net) and that one also does not seem to support them
either.

Does this mean that once I have the aggregated block through fragments
it should be converted to a single linear skb before sending?

Thanks,
Daniele