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Unified Diff: chrome/browser/metrics/time_ticks_field_trial_win.cc

Issue 13583007: Create a field trial to test if we can detect good QPC implementations. (Closed) Base URL: svn://svn.chromium.org/chrome/trunk/src
Patch Set: Try to force a core change Created 7 years, 8 months ago
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Index: chrome/browser/metrics/time_ticks_field_trial_win.cc
diff --git a/chrome/browser/metrics/time_ticks_field_trial_win.cc b/chrome/browser/metrics/time_ticks_field_trial_win.cc
new file mode 100644
index 0000000000000000000000000000000000000000..80085e5c5befd2e628032d4654d802f60ead3813
--- /dev/null
+++ b/chrome/browser/metrics/time_ticks_field_trial_win.cc
@@ -0,0 +1,102 @@
+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/metrics/time_ticks_field_trial_win.h"
+
+#if defined(OS_WIN)
+
+#include "base/cpu.h"
+#include "base/metrics/field_trial.h"
jar (doing other things) 2013/04/12 02:14:54 Is this actually a field trial? I don't think you
James Simonsen 2013/04/12 02:29:46 Good point. No it's not a field trial in the sense
+#include "base/metrics/histogram.h"
+#include "base/win/windows_version.h"
+
+#include <windows.h>
+
+namespace chrome_browser_metrics {
+
+namespace {
+
+const int kNumIterations = 1000;
+
+} // anonymous namespace
+
+void CollectTimeTicksStats() {
+ // This bit is supposed to indicate that rdtsc is safe across cores. If so, we
+ // can use QPC as long as it uses rdtsc.
+ // TODO(simonjam): We should look for other signals that QPC might be safe and
+ // test them out here.
+ base::CPU cpu;
+ UMA_HISTOGRAM_BOOLEAN("WinTimeTicks.NonStopTsc",
+ cpu.has_non_stop_time_stamp_counter());
+ if (!cpu.has_non_stop_time_stamp_counter()) {
+ return;
+ }
+
+ SYSTEM_INFO sys_info;
+ GetSystemInfo(&sys_info);
+ DWORD num_cores = sys_info.dwNumberOfProcessors;
+ DWORD current_core = GetCurrentProcessorNumber();
+
+ base::win::OSInfo* info = base::win::OSInfo::GetInstance();
+ UMA_HISTOGRAM_ENUMERATION("WinTimeTicks.VersionTotal", info->version(),
+ base::win::VERSION_WIN_LAST);
+
+ DWORD starting_core = GetCurrentProcessorNumber();
+ bool did_change_cores = false;
+
+ LARGE_INTEGER qpc_frequency;
+ QueryPerformanceFrequency(&qpc_frequency);
+
+ int min_delta = 1e9;
+ LARGE_INTEGER qpc_last;
+ QueryPerformanceCounter(&qpc_last);
+ for (int i = 0; i < kNumIterations; ++i) {
+ LARGE_INTEGER qpc_now;
+ QueryPerformanceCounter(&qpc_now);
+ int delta = static_cast<int>(qpc_now.QuadPart - qpc_last.QuadPart);
+ if (delta != 0) {
+ min_delta = std::min(min_delta, delta);
+ }
+ qpc_last = qpc_now;
+
+ if (num_cores > 1 && (i % 100) == 0) {
+ ++current_core;
+ if (current_core > num_cores) {
+ current_core = 0;
+ }
+ SetThreadAffinityMask(GetCurrentThread(), 1 << current_core);
+ if (!did_change_cores &&
+ GetCurrentProcessorNumber() != starting_core) {
+ did_change_cores = true;
+ }
+ }
+ }
+
+ if (did_change_cores) {
+ UMA_HISTOGRAM_ENUMERATION("WinTimeTicks.ChangedCores", info->version(),
+ base::win::VERSION_WIN_LAST);
+ }
+
+ if (min_delta >= 0) {
+ UMA_HISTOGRAM_ENUMERATION("WinTimeTicks.NonDecreasing", info->version(),
+ base::win::VERSION_WIN_LAST);
+ } else {
+ return;
+ }
+
+ int min_delta_ns = static_cast<int>(
+ min_delta * (1e9 / qpc_frequency.QuadPart));
+ UMA_HISTOGRAM_CUSTOM_COUNTS("WinTimeTicks.MinResolutionNanoseconds",
+ min_delta_ns, 1, 1000000, 50);
+
+ bool success = min_delta_ns <= 1000;
+ if (success) {
+ UMA_HISTOGRAM_ENUMERATION("WinTimeTicks.VersionSuccessful",
+ info->version(), base::win::VERSION_WIN_LAST);
+ }
+}
+
+} // namespace chrome_browser_net
+
+#endif // defined(OS_WIN)

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