[raggi]

Hi! Tailscaler here, one of the folks who worked on the recent throughput improvements. One of the machines I was testing with during our work on segment offloading was a Haswell. I absolutely understand your concern if we're using 40% of CPU at 4MiB/s, we should be doing substantially better than that on efficiency. In our various testbeds which include CPUs like yours, we see higher performance. If you'd like us to look into the issue, do email [e-mail] - we'd be really happy to dig in and find the cause.

We have continued our work on performance improvements, and along that path, as an example, we recently diagnosed an issue with a change in the kernel frequency scaling governor that has a regression that Tailscale can tickle and we have an ongoing discussion with the kernel maintainers about that problem. I'm not at all assuming this particular thing is the key source of the performance you're observing, it is more to provide an anecdote that we're still digging deep into areas where we aren't performing well and finding the root cause, and working both inside and outside to address those and where appropriate to add workarounds as well.