OTOH, maybe this is a bad test on purpose? the blogger doesn't like running these tests, so do a bad one and hope someone else is baited into running a better test?

Also it doesn't look like they enabled sendfile() in the nginx conf: https://nginx.org/en/docs/http/ngx_http_core_module.html#sen...

The combination of sendfile and kTLS should avoid round-trips to userland while sending files.

are you making the request from a single IP address source? are you aware of the limit of using the same source IP address for the same destination IP address ( and port )? ( each connection can have only a unique source address and source port to the destination, maxing out in source 65535 ports ) for the same destination