Has 10 Gbps through Linux tc qdiscs ever been solved?

I'm trying to use tc to shape traffic on a system with 10 Gbps NICs and I find that I can't get anywhere near 10 Gbps through any qdisc. When I do:

tc qdisc add dev $ifc root handle 1: htb default ffff
tc class add dev $ifc parent 1:0 classid 1:1 htb rate 32Gbit
tc class add dev $ifc parent 1:1 classid 1:ffff htb rate 1Gbit ceil 16Gbit burst 1G cburst 1G

My throughput gets capped around 3 Gbps. I've tried variations with CBQ and HFSC. No matter what I do I can't seem to get around that. Adding just the qdisc does *not* cause the problem (as I previously said). I've spent days reading everything I can find that mentions tc and qdisc and "10G". There seems to be a lot of mailing list activity 6-10 years ago (perhaps on the cusp as 10G became common, taking over from 1G) but no resolution. Am I missing something? Is it impossible to shape multiple gigabits/second on Linux?