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SubjectRe: TCP and BBR: reproducibly low cwnd and bandwidth
Date
Hi.

On pátek 16. února 2018 17:25:58 CET Eric Dumazet wrote:
> The way TCP pacing works, it defaults to internal pacing using a hint
> stored in the socket.
>
> If you change the qdisc while flow is alive, result could be unexpected.

I don't change a qdisc while flow is alive. Either the VM is completely
restarted, or iperf3 is restarted on both sides.

> (TCP socket remembers that one FQ was supposed to handle the pacing)
>
> What results do you have if you use standard pfifo_fast ?

Almost the same as with fq_codel (see my previous email with numbers).

> I am asking because TCP pacing relies on High resolution timers, and
> that might be weak on your VM.

Also, I've switched to measuring things on a real HW only (also see previous
email with numbers).

Thanks.

Regards,
Oleksandr


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