// Copyright 2015 The Bazel Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package com.google.devtools.build.lib.profiler;

import com.google.caliper.BeforeExperiment;
import com.google.caliper.Benchmark;
import com.google.devtools.build.lib.clock.BlazeClock;
import com.google.devtools.build.lib.profiler.Profiler.ProfiledTaskKinds;
import com.google.devtools.build.lib.vfs.inmemoryfs.InMemoryFileSystem;

/**
 * Microbenchmarks for the overhead of {@link AutoProfiler} over using {@link Profiler} manually.
 */
public class AutoProfilerBenchmark {

  private final Object obj = new Object();
  private final ProfilerTask profilerTaskType = ProfilerTask.TEST;

  @BeforeExperiment
  void startProfiler() throws Exception {
    Profiler.instance().start(ProfiledTaskKinds.ALL,
        new InMemoryFileSystem().getPath("/out.dat").getOutputStream(), "benchmark", false,
        BlazeClock.instance(), BlazeClock.instance().nanoTime());
  }

  @BeforeExperiment
  void stopProfiler() throws Exception {
    Profiler.instance().stop();
  }

  @Benchmark
  void profiledWithAutoProfiler(int reps) {
    for (int i = 0; i < reps; i++) {
      try (AutoProfiler p = AutoProfiler.profiled(obj, profilerTaskType)) {
      }
    }
  }

  @Benchmark
  void profiledManually(int reps) {
    for (int i = 0; i < reps; i++) {
      long startTime = Profiler.nanoTimeMaybe();
      Profiler.instance().logSimpleTask(startTime, profilerTaskType, obj);
    }
  }
}