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Finding Allocations

Side note: There is a new testing approach: TBDD = Test n' Benchmark Driven Development.

On the first run we got this result:

$ go test -run=😶 -bench=Benchmark_WithInitStoreByToken .
PASS
Benchmark_WithInitStoreByToken-4	  100000	     17297 ns/op	    9112 B/op	     203 allocs/op
ok  	github.com/corestoreio/pkg/store	2.569s

Quite shocking to use 203 allocs for just figuring out the current store view within a request.

Now compile your tests into an executable binary:

$ go test -c

This compilation reduces the noise in the below output trace log.

$ GODEBUG=allocfreetrace=1 ./store -test.run=😶 -test.bench=Benchmark_WithInitStoreByToken -test.benchtime=10ms 2>trace.log

Now open the trace.log file (around 26MB) and investigate all the allocations and refactor your code. Once finished you can achieve results like:

$ go test -run=NONE -bench=Benchmark_WithInitStoreByToken .
PASS
Benchmark_WithInitStoreByToken-4	 2000000	       826 ns/op	     128 B/op	       5 allocs/op
ok  	github.com/corestoreio/pkg/store	2.569s

Profiling

$ go test -cpuprofile=cpu.out -benchmem -memprofile=mem.out -run=NONE -bench=NameOfBenchmark -v
$ go tool pprof packageName.test cpu.out
Entering interactive mode (type "help" for commands)
(pprof) top5
560ms of 1540ms total (36.36%)
Showing top 5 nodes out of 112 (cum >= 60ms)
      flat  flat%   sum%        cum   cum%
     180ms 11.69% 11.69%      400ms 25.97%  runtime.mallocgc
  • flat is how much time is spent inside of a function.
  • cum shows how much time is spent in a function, and also in any code called by a function.

For memory profile:

Sample value selection option (for heap profiles):
  -inuse_space      Display in-use memory size
  -inuse_objects    Display in-use object counts
  -alloc_space      Display allocated memory size
  -alloc_objects    Display allocated object counts

$ go tool pprof -alloc_objects packageName.test mem.out

Bound Check Elimination

http://klauspost-talks.appspot.com/2016/go17-compiler.slide

$ go build -gcflags="-d=ssa/check_bce/debug=1" bounds.go
or
$ go test -gcflags="-d=ssa/check_bce/debug=1" .

Success - Check bounds outside the loop.

Running Benchmark

Assuming we have already an existing file called bm_baseline.txt.

$ go test -v -run=🤐 -bench=. -count=10 . > bm_baseline_new.txt

After running above command to generate the second benchmark statistics file we run:

$ benchstat bm_baseline.txt bm_baseline_new.txt

https://godoc.org/rsc.io/benchstat

Other development helpers

A preconfigured linter file lint has been included in this repoistory.