[base] Precise CPU usage by default on Windows.

Now that we're confident that QueryProcessCycleTime provides more
accurate CPU measurements than GetProcessTimes, use it by default in
ProcessMetrics::GetCumulativeCPUUsage and remove
ProcessMetrics::GetPreciseCumulativeCPUUsage.

Bug: 1313216
Change-Id: I5e22f1c18069bacd1199a14b4ab1ba6b811166b9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4943814
Commit-Queue: Francois Pierre Doray <fdoray@chromium.org>
Reviewed-by: Patrick Monette <pmonette@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Joe Mason <joenotcharles@google.com>
Auto-Submit: Francois Pierre Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1218355}

base/process/process_metrics.cc

@@ -128,34 +128,6 @@ double ProcessMetrics::GetPlatformIndependentCPUUsage() {
 }
 #endif
 
-#if BUILDFLAG(IS_WIN)
-double ProcessMetrics::GetPreciseCPUUsage(TimeDelta cumulative_cpu) {
-  TimeTicks time = TimeTicks::Now();
-
-  if (last_precise_cumulative_cpu_.is_zero()) {
-    // First call, just set the last values.
-    last_precise_cumulative_cpu_ = cumulative_cpu;
-    last_cpu_time_for_precise_cpu_usage_ = time;
-    return 0;
-  }
-
-  TimeDelta cpu_time_delta = cumulative_cpu - last_precise_cumulative_cpu_;
-  TimeDelta time_delta = time - last_cpu_time_for_precise_cpu_usage_;
-  DCHECK(!time_delta.is_zero());
-  if (time_delta.is_zero())
-    return 0;
-
-  last_precise_cumulative_cpu_ = cumulative_cpu;
-  last_cpu_time_for_precise_cpu_usage_ = time;
-
-  return 100.0 * cpu_time_delta / time_delta;
-}
-
-double ProcessMetrics::GetPreciseCPUUsage() {
-  return GetPreciseCPUUsage(GetPreciseCumulativeCPUUsage());
-}
-#endif  // BUILDFLAG(IS_WIN)
-
 #if BUILDFLAG(IS_APPLE) || BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) || \
     BUILDFLAG(IS_AIX)
 int ProcessMetrics::CalculateIdleWakeupsPerSecond(

base/process/process_metrics.h

@@ -136,32 +136,6 @@ class BASE_EXPORT ProcessMetrics {
   // will result in a time delta of 2 seconds/per 1 wall-clock second.
   [[nodiscard]] TimeDelta GetCumulativeCPUUsage();
 
-#if BUILDFLAG(IS_WIN)
-  // TODO(pmonette): Remove the precise version of the CPU usage functions once
-  // we're validated that they are indeed better than the regular version above
-  // and that they can replace the old implementation.
-
-  // Returns the percentage of time spent executing, across all threads of the
-  // process, in the interval since the last time the method was called, using
-  // the current |cumulative_cpu|.
-  //
-  // Same as GetPlatformIndependentCPUUSage() but implemented using
-  // `QueryProcessCycleTime` for higher precision.
-  [[nodiscard]] double GetPreciseCPUUsage(TimeDelta cumulative_cpu);
-
-  // Same as the above, but automatically calls GetPreciseCumulativeCPUUsage()
-  // to determine the current cumulative CPU.
-  [[nodiscard]] double GetPreciseCPUUsage();
-
-  // Returns the cumulative CPU usage across all threads of the process since
-  // process start. In case of multi-core processors, a process can consume CPU
-  // at a rate higher than wall-clock time, e.g. two cores at full utilization
-  // will result in a time delta of 2 seconds/per 1 wall-clock second.
-  //
-  // This is implemented using `QueryProcessCycleTime` for higher precision.
-  [[nodiscard]] TimeDelta GetPreciseCumulativeCPUUsage();
-#endif  // BUILDFLAG(IS_WIN)
-
 #if BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) || BUILDFLAG(IS_ANDROID) || \
     BUILDFLAG(IS_AIX)
   // Emits the cumulative CPU usage for all currently active threads since they
@@ -266,11 +240,6 @@ class BASE_EXPORT ProcessMetrics {
   TimeDelta last_cumulative_cpu_;
 #endif
 
-#if BUILDFLAG(IS_WIN)
-  TimeTicks last_cpu_time_for_precise_cpu_usage_;
-  TimeDelta last_precise_cumulative_cpu_;
-#endif
-
 #if BUILDFLAG(IS_APPLE) || BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) || \
     BUILDFLAG(IS_AIX)
   // Same thing for idle wakeups.

base/process/process_metrics_unittest.cc

@@ -68,19 +68,6 @@ TimeDelta TestCumulativeCPU(ProcessMetrics* metrics, TimeDelta prev_cpu_usage) {
   return current_cpu_usage;
 }
 
-TimeDelta TestPreciseCumulativeCPU(ProcessMetrics* metrics,
-                                   TimeDelta prev_cpu_usage) {
-#if BUILDFLAG(IS_WIN)
-  const TimeDelta current_cpu_usage = metrics->GetPreciseCumulativeCPUUsage();
-  EXPECT_GE(current_cpu_usage, prev_cpu_usage);
-  EXPECT_GE(metrics->GetPreciseCPUUsage(), 0.0);
-  return current_cpu_usage;
-#else
-  // Do nothing. Not supported on this platform.
-  return base::TimeDelta();
-#endif
-}
-
 #endif  // ENABLE_CPU_TESTS
 
 std::unique_ptr<ProcessMetrics> CreateProcessMetricsForTest(
@@ -386,9 +373,6 @@ TEST_F(SystemMetricsTest, TestNoNegativeCpuUsage) {
   std::unique_ptr<ProcessMetrics> metrics(CreateProcessMetricsForTest(handle));
 
   EXPECT_GE(metrics->GetPlatformIndependentCPUUsage(), 0.0);
-#if BUILDFLAG(IS_WIN)
-  EXPECT_GE(metrics->GetPreciseCPUUsage(), 0.0);
-#endif
 
   Thread thread1("thread1");
   Thread thread2("thread2");
@@ -411,23 +395,15 @@ TEST_F(SystemMetricsTest, TestNoNegativeCpuUsage) {
   thread3.task_runner()->PostTask(FROM_HERE, BindOnce(&BusyWork, &vec3));
 
   TimeDelta prev_cpu_usage = TestCumulativeCPU(metrics.get(), TimeDelta());
-  TimeDelta prev_precise_cpu_usage =
-      TestPreciseCumulativeCPU(metrics.get(), TimeDelta());
 
   thread1.Stop();
   prev_cpu_usage = TestCumulativeCPU(metrics.get(), prev_cpu_usage);
-  prev_precise_cpu_usage =
-      TestPreciseCumulativeCPU(metrics.get(), prev_precise_cpu_usage);
 
   thread2.Stop();
   prev_cpu_usage = TestCumulativeCPU(metrics.get(), prev_cpu_usage);
-  prev_precise_cpu_usage =
-      TestPreciseCumulativeCPU(metrics.get(), prev_precise_cpu_usage);
 
   thread3.Stop();
   prev_cpu_usage = TestCumulativeCPU(metrics.get(), prev_cpu_usage);
-  prev_precise_cpu_usage =
-      TestPreciseCumulativeCPU(metrics.get(), prev_precise_cpu_usage);
 }
 #endif  // ENABLE_CPU_TESTS
 

base/process/process_metrics_win.cc

@@ -120,6 +120,28 @@ struct SYSTEM_PERFORMANCE_INFORMATION {
   ULONG SystemCalls;
 };
 
+TimeDelta GetImpreciseCumulativeCPUUsage(const win::ScopedHandle& process) {
+  FILETIME creation_time;
+  FILETIME exit_time;
+  FILETIME kernel_time;
+  FILETIME user_time;
+
+  if (!process.is_valid()) {
+    return TimeDelta();
+  }
+
+  if (!GetProcessTimes(process.get(), &creation_time, &exit_time, &kernel_time,
+                       &user_time)) {
+    // This should never fail because we duplicate the handle to guarantee it
+    // will remain valid.
+    DCHECK(false);
+    return TimeDelta();
+  }
+
+  return TimeDelta::FromFileTime(kernel_time) +
+         TimeDelta::FromFileTime(user_time);
+}
+
 }  // namespace
 
 size_t GetMaxFds() {
@@ -140,31 +162,10 @@ std::unique_ptr<ProcessMetrics> ProcessMetrics::CreateProcessMetrics(
 }
 
 TimeDelta ProcessMetrics::GetCumulativeCPUUsage() {
-  FILETIME creation_time;
-  FILETIME exit_time;
-  FILETIME kernel_time;
-  FILETIME user_time;
-
-  if (!process_.is_valid())
-    return TimeDelta();
-
-  if (!GetProcessTimes(process_.get(), &creation_time, &exit_time, &kernel_time,
-                       &user_time)) {
-    // This should never fail because we duplicate the handle to guarantee it
-    // will remain valid.
-    DCHECK(false);
-    return TimeDelta();
-  }
-
-  return TimeDelta::FromFileTime(kernel_time) +
-         TimeDelta::FromFileTime(user_time);
-}
-
-TimeDelta ProcessMetrics::GetPreciseCumulativeCPUUsage() {
 #if defined(ARCH_CPU_ARM64)
   // Precise CPU usage is not available on Arm CPUs because they don't support
   // constant rate TSC.
-  return GetCumulativeCPUUsage();
+  return GetImpreciseCumulativeCPUUsage(process_);
 #else   // !defined(ARCH_CPU_ARM64)
   if (!time_internal::HasConstantRateTSC())
     return GetCumulativeCPUUsage();
@@ -172,10 +173,10 @@ TimeDelta ProcessMetrics::GetPreciseCumulativeCPUUsage() {
   const double tsc_ticks_per_second = time_internal::TSCTicksPerSecond();
   if (tsc_ticks_per_second == 0) {
     // TSC is only initialized once TSCTicksPerSecond() is called twice 50 ms
-    // apart on the same thread to get a baseline. This often doesn't happen in
-    // unit tests, and theoretically may happen in production if
-    // GetPreciseCumulativeCPUUsage() is called before any uses of ThreadTicks.
-    return GetCumulativeCPUUsage();
+    // apart on the same thread to get a baseline. In unit tests, it is frequent
+    // for the initialization not to be complete. In production, it can also
+    // theoretically happen.
+    return GetImpreciseCumulativeCPUUsage(process_);
   }
 
   ULONG64 process_cycle_time = 0;

chrome/browser/metrics/power/process_monitor.cc

@@ -58,11 +58,7 @@ std::unique_ptr<base::ProcessMetrics> CreateProcessMetrics(
 ProcessMonitor::Metrics SampleMetrics(base::ProcessMetrics& process_metrics) {
   ProcessMonitor::Metrics metrics;
 
-#if BUILDFLAG(IS_WIN)
-  metrics.cpu_usage = process_metrics.GetPreciseCPUUsage();
-#else
   metrics.cpu_usage = process_metrics.GetPlatformIndependentCPUUsage();
-#endif
 
 #if BUILDFLAG(IS_MAC) || BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) || \
     BUILDFLAG(IS_AIX)
@@ -94,16 +90,9 @@ ProcessMonitor::Metrics GetLastIntervalMetrics(
     base::ProcessMetrics& process_metrics,
     base::TimeDelta cumulative_cpu_usage) {
   ProcessMonitor::Metrics metrics;
-
-#if BUILDFLAG(IS_WIN)
-  metrics.cpu_usage = process_metrics.GetPreciseCPUUsage(cumulative_cpu_usage);
-#else
   metrics.cpu_usage =
       process_metrics.GetPlatformIndependentCPUUsage(cumulative_cpu_usage);
-#endif
-
   // TODO: Add other values in ProcessMonitor::Metrics.
-
   return metrics;
 }
 

chrome/browser/performance_manager/metrics/page_timeline_cpu_monitor.cc

@@ -67,11 +67,7 @@ CPUMeasurementDelegateImpl::CPUMeasurementDelegateImpl(
 }
 
 base::TimeDelta CPUMeasurementDelegateImpl::GetCumulativeCPUUsage() {
-#if BUILDFLAG(IS_WIN)
-  return process_metrics_->GetPreciseCumulativeCPUUsage();
-#else
   return process_metrics_->GetCumulativeCPUUsage();
-#endif
 }
 
 }  // namespace

components/performance_manager/resource_attribution/cpu_measurement_monitor.cc

@@ -68,11 +68,7 @@ CPUMeasurementDelegateImpl::CPUMeasurementDelegateImpl(
 }
 
 base::TimeDelta CPUMeasurementDelegateImpl::GetCumulativeCPUUsage() {
-#if BUILDFLAG(IS_WIN)
-  return process_metrics_->GetPreciseCumulativeCPUUsage();
-#else
   return process_metrics_->GetCumulativeCPUUsage();
-#endif
 }
 
 // Returns true if `result` is in the default-initialized state.

content/browser/child_process_launcher.cc

@@ -45,15 +45,7 @@ base::TimeDelta GetCPUUsage(base::ProcessHandle process_handle) {
   std::unique_ptr<base::ProcessMetrics> process_metrics =
       base::ProcessMetrics::CreateProcessMetrics(process_handle);
 #endif
-
-#if BUILDFLAG(IS_WIN)
-  // Use the precise version which is Windows specific.
-  // TODO(pmonette): Clean up this code when the precise version becomes the
-  //                 default.
-  return process_metrics->GetPreciseCumulativeCPUUsage();
-#else
   return process_metrics->GetCumulativeCPUUsage();
-#endif
 }
 #endif  // !BUILDFLAG(IS_ANDROID)