Tool for running benchmark comparison of 2 commits (#2161)

dist/benchmark/benchcmp.sh

@@ -0,0 +1,67 @@
+#!/bin/bash          
+
+# usage: ./benchcmp.sh <commit-sha1> <commit-sha2>
+# Exit on any non zero return value on execution of a command. 
+set -e 
+
+# path of benchcmp. 
+benchcmp=${GOPATH}/bin/benchcmp
+
+# function which runs the benchmark comparison. 
+RunBenchCmp () {
+	# Path for storing output of benchmark at commit 1. 
+	commit1Bench=/tmp/minio-$1.bench
+	# Path for storing output of benchmark at commit 2. 
+	commit2Bench=/tmp/minio-$2.bench
+	# switch to commit $1. 
+	git checkout $1
+	# Check if the benchmark results for given commit 1 already exists. 
+	# Benchmarks are time/resource consuming operations, run only if the the results doesn't exist. 
+	if [[ ! -f $commit1Bench  ]]
+	then
+
+		echo "Running benchmarks at $1"
+		go test -run=NONE -bench=. | tee $commit1Bench 
+	fi
+	# get back to the commit from which it was started. 
+	git checkout -
+	echo "Checking into commit $2"
+	# switch to commit $2 
+	git checkout $2
+	# Check if the benchmark results for given commit 2 already exists. 
+	# Benchmarks are time/resource consuming operations, run only if the the results doesn't exist. 
+	if [[ ! -f $commit2Bench  ]]
+	then
+	# Running benchmarks at $2.
+		echo "Running benchmarks at $2"
+		go test -run=NONE -bench=. | tee $commit2Bench 
+	fi
+	
+	# get back to the commit from which it was started. 
+	git checkout - 
+	# Comparing the benchmarks.
+	echo "Running benchmark comparison between $1 and $2 ..."
+	$benchcmp $commit1Bench $commit2Bench 
+	echo "Done."
+}
+
+# check if 2 commit SHA's of snapshots of code for which benchmp has to be done is provided. 
+if [ ! $# -eq 2 ]
+then
+	# exit if commit SHA's are not provided. 
+	echo $#
+	echo "Need Commit SHA's of 2 snapshots to be supplied to run benchmark comparision."
+	exit 1
+fi
+
+# check if benchcmp exists. 
+if [[ -x "$benchcmp" ]]
+then
+	RunBenchCmp $1 $2
+else
+	# install benchcmp if doesnt't exist. 
+	echo "fetching Benchcmp..."
+	go get -u golang.org/x/tools/cmd/benchcmp
+	echo "Done."
+	RunBenchCmp $1 $2
+fi