[Ecn-sane] SCE pacing (was: a data point on syn and dscp)

[Pete Heist]

Not sure if this covers it, but there was a brief time before we had
enabled pacing programmatically in our TCP CCAs. There's a sysctl with
default:

net.ipv4.tcp_sce_pacing = 1

and in each CCA:

if (sock_net(sk)->ipv4.sysctl_tcp_sce_pacing)
    cmpxchg(&sk->sk_pacing_status, SK_PACING_NONE, SK_PACING_NEEDED);

This should enable the internal pacing mechanism in the kernel, which
is different from the one used by the fq qdisc, iirc.

On Tue, 2021-03-09 at 10:58 -0800, Dave Taht wrote:
> 
> this leads to my final question in that early sce and l4s experiments
> did have a lot of trouble with having to pace the initial burst, and I
> don't know what is actually done there, now, in current oses.
>