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 <algorithm>
+#include "webrtc/base/cpu_time.h"
+#include "webrtc/base/platform_thread.h"
+#include "webrtc/base/timeutils.h"
+#include "webrtc/test/gtest.h"
+#include "webrtc/system_wrappers/include/cpu_info.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 = GetProcessCpuTimeNanos();
+  int64_t counter;
+  WorkingFunction(reinterpret_cast<void*>(&counter));
+  EXPECT_GT(counter, 0);
+  int64_t duration_nanos = GetProcessCpuTimeNanos() - start_time_nanos;
+  //  Should be about kProcessingTimeMillisecs.
+  EXPECT_NEAR(duration_nanos,
+              kProcessingTimeMillisecs * kNumNanosecsPerMillisec,
+              kAllowedErrorMillisecs * kNumNanosecsPerMillisec);
+}
+
+TEST(GetProcessCpuTimeTest, TwoThreads) {
+  int64_t start_time_nanos = GetProcessCpuTimeNanos();
+  int64_t counter1;
+  int64_t counter2;
+  PlatformThread thread1(WorkingFunction, reinterpret_cast<void*>(&counter1),
+                         "Thread1");
+  PlatformThread thread2(WorkingFunction, reinterpret_cast<void*>(&counter2),
+                         "Thread2");
+  thread1.Start();
+  thread2.Start();
+  thread1.Stop();
+  thread2.Stop();
+
+  EXPECT_GE(counter1, 0);
+  EXPECT_GE(counter2, 0);
+  int64_t duration_nanos = GetProcessCpuTimeNanos() - start_time_nanos;
+  const uint32_t kWorkingThreads = 2;
+  uint32_t used_cores =
+      std::min(webrtc::CpuInfo::DetectNumberOfCores(), kWorkingThreads);
+  // Two working threads for kProcessingTimeMillisecs consume double CPU time
+  // if there are at least 2 cores.
+  EXPECT_NEAR(duration_nanos,
+              used_cores * kProcessingTimeMillisecs * kNumNanosecsPerMillisec,
+              used_cores * kAllowedErrorMillisecs * kNumNanosecsPerMillisec);
+}
+
+TEST(GetThreadCpuTimeTest, SingleThread) {
+  int64_t start_times_nanos = GetThreadCpuTimeNanos();
+  int64_t counter;
+  WorkingFunction(reinterpret_cast<void*>(&counter));
+  EXPECT_GT(counter, 0);
+  int64_t duration_nanos = GetThreadCpuTimeNanos() - start_times_nanos;
+  EXPECT_NEAR(duration_nanos,
+              kProcessingTimeMillisecs * kNumNanosecsPerMillisec,
+              kAllowedErrorMillisecs * kNumNanosecsPerMillisec);
+}
+
+TEST(GetThreadCpuTimeTest, TwoThreads) {
+  int64_t start_time_nanos = GetThreadCpuTimeNanos();
+  int64_t counter1;
+  int64_t counter2;
+  PlatformThread thread1(WorkingFunction, reinterpret_cast<void*>(&counter1),
+                         "Thread1");
+  PlatformThread thread2(WorkingFunction, reinterpret_cast<void*>(&counter2),
+                         "Thread2");
+  thread1.Start();
+  thread2.Start();
+  thread1.Stop();
+  thread2.Stop();
+
+  EXPECT_GE(counter1, 0);
+  EXPECT_GE(counter2, 0);
+  int64_t duration_nanos = GetThreadCpuTimeNanos() - start_time_nanos;
+  // This thread didn't do any work.
+  EXPECT_NEAR(duration_nanos, 0,
+              kAllowedErrorMillisecs * kNumNanosecsPerMillisec);
+}
+
+}  // namespace rtc