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Subject: Re: debugging TCP stalls on high-speed wifi
From:   Johannes Berg <johannes@sipsolutions.net>
To:     Eric Dumazet <eric.dumazet@gmail.com>,
        Neal Cardwell <ncardwell@google.com>
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Date:   Thu, 12 Dec 2019 22:53:47 +0100
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On Thu, 2019-12-12 at 13:50 -0800, Eric Dumazet wrote:

> I presume you could hack TCP to no longer care about bufferbloat and you'll
> probably match Windows 'performance' on a single flow and a lossless network.
> 
> Ie always send ~64KB TSO packets and fill the queues, inflating RTT.
> 
> Then, in presence of losses, you get a problem because the retransmit packets
> can only be sent _after_ the huge queue that has been put on the sender.

Sure, I'll do it as an experiment. Got any suggestions on how to do
that?

I tried to decrease sk_pacing_shift even further with no effect, I've
also tried many more TCP streams with no effect.

I don't even care about a single flow that much, honestly. The default
test is like 10 or 20 flows anyway.

> If only TCP could predict the future ;)

:)

johannes