Added GetCpuTime to base/ to get total CPU time consumed by process for perf tests.

webrtc/base/cpu_time_unittest.cc

+/*
+ *  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include <memory>
+
+#include "webrtc/base/cpu_time.h"
+#include "webrtc/base/platform_thread.h"
+#include "webrtc/base/timeutils.h"
+#include "webrtc/test/gtest.h"
+
+namespace {
+const int kAllowedErrorMillisecs = 30;
+const int kProcessingTimeMillisecs = 300;
+
+// Consumes approximately kProcessingTimeMillisecs of CPU time.
+bool WorkingFunction(void* counter_pointer) {
+  int64_t* counter = reinterpret_cast<int64_t*>(counter_pointer);
+  *counter = 0;
+  int64_t stop_time = rtc::SystemTimeNanos() +
+                      kProcessingTimeMillisecs * rtc::kNumNanosecsPerMillisec;
+  while (rtc::SystemTimeNanos() < stop_time) {
+    (*counter)++;
+  }
+  return false;
+}
+}  // namespace
+
+namespace rtc {
+
+TEST(GetProcessCpuTimeTest, SingleThread) {
+  int64_t start_time_nanos = GetProcessCpuTime();
+  std::unique_ptr<int64_t> counter(new int64_t);

[Taylor Brandstetter, 2017/02/16 18:49:19]

Is this because the int64_t needs to be on the heap?

[ilnik, 2017/02/17 09:17:10]

I was getting ASAN errors, but it wasn't because counter was on stack, yet I
thought it was. Fixed this now.

+  WorkingFunction(reinterpret_cast<void*>(counter.get()));
+  EXPECT_GT(*counter, 0);
+  int64_t duration_nanos = GetProcessCpuTime() - start_time_nanos;
+  //  Should be about kProcessingTimeMillisecs.
+  EXPECT_NEAR(static_cast<double>(duration_nanos) / kNumNanosecsPerMillisec,

[Taylor Brandstetter, 2017/02/16 18:49:19]

nit: I'd prefer no cast to double

[ilnik, 2017/02/17 09:17:10]

Done.

+            kProcessingTimeMillisecs, kAllowedErrorMillisecs);
+}
+
+TEST(GetProcessCpuTimeTest, TwoThreads) {
+  int64_t start_time_nanos = GetProcessCpuTime();
+  std::unique_ptr<int64_t> counter1(new int64_t);
+  std::unique_ptr<int64_t> counter2(new int64_t);
+  PlatformThread thread1(WorkingFunction,
+                         reinterpret_cast<void*>(counter1.get()), "Thread1");
+  PlatformThread thread2(WorkingFunction,
+                         reinterpret_cast<void*>(counter2.get()), "Thread2");
+  thread1.Start();
+  thread2.Start();
+  thread1.Stop();
+  thread2.Stop();
+
+  EXPECT_GE(*counter1, 0);
+  EXPECT_GE(*counter2, 0);
+  int64_t duration_nanos = GetProcessCpuTime() - start_time_nanos;
+  EXPECT_NEAR(static_cast<double>(duration_nanos) / kNumNanosecsPerMillisec,
+              2 * kProcessingTimeMillisecs, 2 * kAllowedErrorMillisecs);

[Taylor Brandstetter, 2017/02/16 18:49:19]

This test will fail if the system doesn't have multiple cores to run threads on.
May want to make a note of that, or call CpuInfo::DetectNumberOfCores at the top
of the test.

[ilnik, 2017/02/17 09:17:10]

Done.

+}
+
+TEST(GetThreadCpuTimeTest, SingleThread) {
+  int64_t start_times_nanos = GetThreadCpuTime();
+  std::unique_ptr<int64_t> counter(new int64_t);
+  WorkingFunction(reinterpret_cast<void*>(counter.get()));
+  EXPECT_GT(*counter, 0);
+  int64_t duration_nanos = GetThreadCpuTime() - start_times_nanos;
+  // Should be about kProcessingTimeMillisecs.
+  EXPECT_NEAR(static_cast<double>(duration_nanos) / kNumNanosecsPerMillisec,
+              kProcessingTimeMillisecs, kAllowedErrorMillisecs);
+}
+
+TEST(GetThreadCpuTimeTest, TwoThreads) {
+  int64_t start_time_nanos = GetThreadCpuTime();
+  std::unique_ptr<int64_t> counter1(new int64_t);
+  std::unique_ptr<int64_t> counter2(new int64_t);
+  PlatformThread thread1(WorkingFunction,
+                         reinterpret_cast<void*>(counter1.get()), "Thread1");
+  PlatformThread thread2(WorkingFunction,
+                         reinterpret_cast<void*>(counter2.get()), "Thread2");
+  thread1.Start();
+  thread2.Start();
+  thread1.Stop();
+  thread2.Stop();
+
+  EXPECT_GE(*counter1, 0);
+  EXPECT_GE(*counter2, 0);
+  int64_t duration_nanos = GetThreadCpuTime() - start_time_nanos;
+  // Should be about 0.
+  EXPECT_NEAR(static_cast<double>(duration_nanos) / kNumNanosecsPerMillisec, 0,
+              kAllowedErrorMillisecs);
+}
+
+}  // namespace rtc