Add performance note

README.md

@@ -26,5 +26,25 @@ Additionally, add `-gc=custom` and `-tags=custommalloc` to your TinyGo build fla
 tinygo build -o main.wasm -gc=custom -tags=custommalloc -target=wasi -scheduler=none main.go
 ```
 
+## Performance
+
+Benchmarks are run against every commit in the [bench][4] workflow. GitHub action runners are highly
+virtualized and do not have stable performance across runs, but the relative numbers within a run
+should still be somewhat, though not precisely, informative.
+
+One run looks like this
+
+```
+BenchmarkGC/bench.wasm-2         	      52	 220294559 ns/op
+BenchmarkGC/benchref.wasm-2      	       6	2000167805 ns/op
+```
+
+The benchmark is very simple, allocating some large strings in a loop. We see nottinygc perform almost
+10x better in this benchmark. Note that just allocation / collection time is not the only aspect of
+GC performance, allocation locality and fragmentation can also affect performance of real-world
+applications. We have found that the default allocator can cause applications to run out of memory,
+possibly due to fragmentation, whereas this library will continue to run indefinitely.
+
 [1]: https://github.com/ivmai/bdwgc
 [2]: https://github.com/microsoft/mimalloc
+[4]: https://github.com/wasilibs/nottinygc/actions/workflows/bench.yaml