> No matter what load you have, P99 and especially P99.9 latency will be higher than any other language

I strongly call BS on that.

Strong claim and evidence seems to be a hallucination in your own head.

There are several writeups of large backends ported from node/python/ruby to Go which resulted in dramatic speedups, including drop in P99 and P99.9 latencies by 10x

That's empirical evidence your claim is BS.

What exactly is so unfair about Go scheduler and what do you compare it to?

Node's lack of multi-threading?

Python's and Ruby's GIL?

Just leaving this to OS thread scheduler which, unlike Go, has no idea about i/o and therefore cannot optimize for it?

Apparently the source of your claim is https://github.com/php/frankenphp/pull/2016

Which is optimizing for a very specific micro-benchmark of hammering std-lib http server with concurrent request. Which is not what 99% of go servers need to handle. And is exercising way more than a scheduler. And is not benchmarking against any other language, so the sweeping statement about "higher than any other language" is literally baseless.

And you were able to make a change that trades throughput for P99 latency without changing the scheduler, which kind of shows it wasn't the scheduler but an interaction between a specific implementation of HTTP server and Go scheduler.

And there are other HTTP servers in Go that focus on speed. It's just 99.9% of Go servers don't need any of that because the baseline is 10x faster than python/ruby/javascript and on-par with Java or C#.