howto/benchmark.md

@@ -5,6 +5,9 @@ TPA.
 
 # HTTP load testing
 
+Those procedures were quickly established to compare various caching
+software as part of the [cache service](howto/cache) setup.
+
 ## Common procedure
 
  1. punch a hole in the firewall to allow the test server to access
@@ -55,10 +58,15 @@ Classic commandline:
 
     ab2 -n 1000 -c 100 -X cache01.torproject.org https://example.com/
 
-`-X` also doesn't work with ATS, hacked `/etc/hosts`.
+`-X` also doesn't work with ATS, modify `/etc/hosts` instead.
 
 ## bombardier
 
+We tested bombardier as an alternative to `go-wrk` in previous
+benchmarks. The goal of using `go-wrk` was that it supported HTTP/2
+(while `wrk` didn't), but `go-wrk` had performance issues, so we went
+with the next best (and similar) thing.
+
 Unfortunately, the [bombardier package in Debian](https://tracker.debian.org/pkg/bombardier) is *not* the HTTP
 benchmarking tool but a commandline game. It's still possible to
 install it in Debian with:
@@ -116,6 +124,9 @@ the advantage of being already packaged in Debian. Simple cheat sheet:
     echo "10.0.0.0 target.example.com" >> /etc/hosts
     wrk --latency -c 100 --duration 2m https://target.example.com/
 
+The main disadvantage is that it doesn't (seem to) support HTTP/2 or
+similarly advanced protocols.
+
 ## Other tools
 
 Siege has trouble going above ~100 concurrent clients because of its
@@ -138,3 +149,9 @@ limited, here's a set of interesting alternatives:
 Note that the Proto(col) and Features columns are not exhaustive: a
 tool *might* support (say) HTTPS, HTTP/2, or HTTP/3 even if it doesn't
 explicitly mention it, although it's unlikely.
+
+It should be noted that very few (if any) benchmarking tools seem to
+support HTTP/3 (or even QUIC) at this point. Even HTTP/2 support is
+spotty: for example, while bombardier supports HTTP/2, it only does so
+with the slower `net/http` library at the time of writing (2021). It's
+unclear how many (if any) other projects to support HTTP/2 as well.