netdev - Re: knob to disable locally-originating qdisc optimisation?

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Message-ID: <87y1loapvt.fsf@toke.dk>
Date: Wed, 17 May 2023 00:11:02 +0200
From: Toke Høiland-Jørgensen <toke@...e.dk>
To: Thorsten Glaser <t.glaser@...ent.de>
Cc: Stephen Hemminger <stephen@...workplumber.org>, Jakub Kicinski
 <kuba@...nel.org>, netdev@...r.kernel.org, Haye.Haehne@...ekom.de
Subject: Re: knob to disable locally-originating qdisc optimisation?

Thorsten Glaser <t.glaser@...ent.de> writes:

> On Tue, 16 May 2023, Toke Høiland-Jørgensen wrote:
>
>>Pushing stuff into a
>>qdisc so it can be ECN-marked is also nonsensical for locally generated
>>traffic; you don't need the ECN roundtrip, you can just directly tell
>>the local TCP sender to slow down (which is exactly what TSQ does).
>
> Yes, but the point of this exercise is to develop algorithms which
> react to ECN marking; in production, the RAN BTS will do the marking
> so the sender will not be at the place where congestion happens, so
> adding that kind of insight is not needed.
>
> Some people have asked for the ability to make Linux behave as if
> the sender was remote to ease the test setup (i.e. require one less
> machine), nothing more.

Well, if it's a custom qdisc you could just call skb_orphan() on the
skbs when enqueueing them?

-Toke