Benchmarking Golang with benchstat

go-bench.sh

#!/bin/bash

#
# Generate benchmark files in a Git repository.
#
# Usage: TIMES=1 go-bench [prefix]
#

# Number of times to run the benchmark; useful for benchstat.
TIMES=${TIMES:-1}

# Prefix of the output file; useful for placing in a subdirectory.
PREFIX=${1:-benchmark.}

# Assume we're in a git repository, so we can remember which commit
# was the result of a benchmark.
REF=$(git rev-parse --short HEAD)

# Generate a file with a timestamp so that we can easily sort the
# benchmarks during comparison.
FILE="${PREFIX}$(date '+%Y%m%d%H%M')-${REF}.txt"

function do_bench {
    for i in $(seq 1 $TIMES); do
        go test -run=NONE -bench=. -benchmem ./...
    done
}

do_bench > ${FILE}

session.txt

$ go get golang.org/x/perf/cmd/benchstat
$ TIMES=5 go-bench out/
... make changes to code ...
$ TIMES=5 go-bench out/
$ find out -type f | tail -2 | xargs benchstat
name             old time/op    new time/op    delta
Parse-4             124µs ± 2%     122µs ± 1%    ~     (p=0.421 n=5+5)