misc/benchcmp: show memory statistics, when available

R=minux.ma, dave, extraterrestrial.neighbour, rsc
CC=golang-dev
https://golang.org/cl/6587069

misc/benchcmp

@@ -7,8 +7,13 @@ case "$1" in
 -*)	
 	echo 'usage: benchcmp old.txt new.txt' >&2
 	echo >&2
-	echo 'Each input file should be go test -test.run=NONE -test.bench=. > [old,new].txt' >&2
+	echo 'Each input file should be from:' >&2
+	echo '	go test -test.run=NONE -test.bench=. > [old,new].txt' >&2
+	echo >&2
 	echo 'Benchcmp compares the first and last for each benchmark.' >&2
+	echo >&2
+	echo 'If -test.benchmem=true is added to the "go test" command' >&2
+	echo 'benchcmp will also compare memory allocations.' >&2
 	exit 2
 esac
 
@@ -27,10 +32,21 @@ $1 ~ /Benchmark/ && $4 == "ns/op" {
 		new[$1] = $3
 		if($6 == "MB/s")
 			newmb[$1] = $5
+
+		# allocs/op might be at $8 or $10 depending on if
+		# SetBytes was used or not.
+		if($8 == "allocs/op")
+			newalloc[$1] = $7
+		if($10 == "allocs/op")
+			newalloc[$1] = $9
 	} else {
 		old[$1] = $3
-		if($6 = "MB/s")
+		if($6 == "MB/s")
 			oldmb[$1] = $5
+		if($8 == "allocs/op")
+			oldalloc[$1] = $7
+		if($10 == "allocs/op")
+			oldalloc[$1] = $9
 	}
 }
 
@@ -62,5 +78,21 @@ END {
 			sprintf("%.2f", newmb[what]),
 			sprintf("%.2f", newmb[what]/oldmb[what]))
 	}
+
+	# print allocs
+	anyalloc = 0
+	for(i=0; i<n; i++) {
+		what = name[i]
+		if(!(what in newalloc))
+			continue
+		if(anyalloc++ == 0)
+			printf("\n%-*s %12s %12s  %7s\n", len, "benchmark", "old allocs", "new allocs", "delta")
+		if(oldalloc[what] == 0)
+			delta="n/a"
+		else
+			delta=sprintf("%.2f", 100*newalloc[what]/oldalloc[what]-100)
+		printf("%-*s %12d %12d  %6s%%\n", len, what,
+			oldalloc[what], newalloc[what], delta)
+	}
 }
 ' "$@"