Test memory consumption

Question

I need to verify how much memory a specific function consumes during execution, and make sure that it stays under a specific limit.

Ideally I'd like to do this in a test or benchmark. As far as I can see the only way to do this is to create a separate test binary and use the BenchmarkResult from

func Benchmark(f func(b *B)) BenchmarkResult

Is this the correct way to do this?

Answer 1

Actually it's very simple:

1. Read memstats with runtime.ReadMemStats(&m) into m
2. Invoke f()
3. Read memstats again into m2
4. Calculate diff between m and m2

For example:

var m1, m2 runtime.MemStats
runtime.GC()
runtime.ReadMemStats(&m1)
f()
runtime.ReadMemStats(&m2)
fmt.Println("total:", m2.TotalAlloc - m1.TotalAlloc)
fmt.Println("mallocs:", m2.Mallocs - m1.Mallocs)

Answer 2

That's not really how you use the testing package. Just create a file called something_test.go and write a function called func BenchmarkSomething(b *testing.B) and you're good to go.

The documentation of the testing package goes into a lot more detail, but basically after you write your _test.go files, you just run them, enable benchmarks, and specific to your question, turn on -benchmem:

go test -bench=. -benchmem

That should give you what you're looking for.