benchmark: ByteString append and builder (#30313)

akka-bench-jmh/src/main/scala/akka/util/ByteString_append_Benchmark.scala

@@ -0,0 +1,105 @@
+/*
+ * Copyright (C) 2021 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.util
+
+import java.util.concurrent.TimeUnit
+
+import org.openjdk.jmh.annotations._
+import org.openjdk.jmh.infra.Blackhole
+
+@State(Scope.Benchmark)
+@OutputTimeUnit(TimeUnit.MILLISECONDS)
+@BenchmarkMode(Array(Mode.Throughput))
+@Fork(2)
+@Warmup(iterations = 4)
+@Measurement(iterations = 10)
+class ByteString_append_Benchmark {
+
+  private val bs = ByteString(Array.ofDim[Byte](10))
+
+  @Benchmark
+  @OperationsPerInvocation(10000)
+  def appendThree(bh: Blackhole): Unit = {
+    var result = ByteString.empty
+    var i = 0
+    while (i < 10000) {
+      result = result ++ bs
+      if (i % 3 == 0) {
+        bh.consume(result)
+        result = ByteString.empty
+      }
+      i += 1
+    }
+    bh.consume(result)
+  }
+
+  @Benchmark
+  @OperationsPerInvocation(10000)
+  def appendMany(bh: Blackhole): Unit = {
+    var result = ByteString.empty
+    var i = 0
+    while (i < 10000) {
+      result = result ++ bs
+      i += 1
+    }
+    bh.consume(result)
+  }
+  @Benchmark
+  @OperationsPerInvocation(10000)
+  def builderOne(bh: Blackhole): Unit = {
+    val builder = ByteString.newBuilder
+    var i = 0
+    while (i < 10000) {
+      builder ++= bs
+      bh.consume(builder.result())
+      builder.clear()
+      i += 1
+    }
+  }
+
+  @Benchmark
+  @OperationsPerInvocation(10000)
+  def builderThree(bh: Blackhole): Unit = {
+    val builder = ByteString.newBuilder
+    var i = 0
+    while (i < 10000) {
+      builder ++= bs
+      if (i % 3 == 0) {
+        bh.consume(builder.result())
+        builder.clear()
+      }
+      i += 1
+    }
+    bh.consume(builder.result())
+  }
+
+  @Benchmark
+  @OperationsPerInvocation(10000)
+  def builderFive(bh: Blackhole): Unit = {
+    val builder = ByteString.newBuilder
+    var i = 0
+    while (i < 10000) {
+      builder ++= bs
+      if (i % 5 == 0) {
+        bh.consume(builder.result())
+        builder.clear()
+      }
+      i += 1
+    }
+    bh.consume(builder.result())
+  }
+
+  @Benchmark
+  @OperationsPerInvocation(10000)
+  def builderMany(bh: Blackhole): Unit = {
+    val builder = ByteString.newBuilder
+    var i = 0
+    while (i < 10000) {
+      builder ++= bs
+      i += 1
+    }
+    bh.consume(builder.result())
+  }
+}