netdev - Re: debugging TCP stalls on high-speed wifi

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Date:   Thu, 12 Dec 2019 10:11:14 -0500
From:   Neal Cardwell <ncardwell@...gle.com>
To:     Johannes Berg <johannes@...solutions.net>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        linux-wireless@...r.kernel.org, Netdev <netdev@...r.kernel.org>
Subject: Re: debugging TCP stalls on high-speed wifi

On Thu, Dec 12, 2019 at 9:50 AM Johannes Berg <johannes@...solutions.net> wrote:
> If you have any thoughts on this, I'd appreciate it.

Thanks for the detailed report!

I was curious:

o What's the sender's qdisc configuration?

o Would you be able to log periodic dumps (e.g. every 50ms or 100ms)
of the test connection using a recent "ss" binary and "ss -tinm", to
hopefully get a sense of buffer parameters, and whether the flow in
these cases is being cwnd-limited, pacing-limited,
send-buffer-limited, or receive-window-limited?

o Would you be able to share a headers-only tcpdump pcap trace?

thanks,
neal