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| 1 // Copyright (c) 2013 The Chromium Authors. All rights reserved. |
| 2 // Use of this source code is governed by a BSD-style license that can be |
| 3 // found in the LICENSE file. |
| 4 |
| 5 #include "chrome/browser/metrics/time_ticks_experiment_win.h" |
| 6 |
| 7 #if defined(OS_WIN) |
| 8 |
| 9 #include "base/cpu.h" |
| 10 #include "base/metrics/histogram.h" |
| 11 #include "base/win/windows_version.h" |
| 12 |
| 13 #include <windows.h> |
| 14 |
| 15 namespace chrome { |
| 16 |
| 17 namespace { |
| 18 |
| 19 const int kNumIterations = 1000; |
| 20 |
| 21 } // anonymous namespace |
| 22 |
| 23 void CollectTimeTicksStats() { |
| 24 // This bit is supposed to indicate that rdtsc is safe across cores. If so, we |
| 25 // can use QPC as long as it uses rdtsc. |
| 26 // TODO(simonjam): We should look for other signals that QPC might be safe and |
| 27 // test them out here. |
| 28 base::CPU cpu; |
| 29 UMA_HISTOGRAM_BOOLEAN("WinTimeTicks.NonStopTsc", |
| 30 cpu.has_non_stop_time_stamp_counter()); |
| 31 if (!cpu.has_non_stop_time_stamp_counter()) { |
| 32 return; |
| 33 } |
| 34 |
| 35 DWORD_PTR default_mask; |
| 36 DWORD_PTR system_mask; |
| 37 if (!GetProcessAffinityMask(GetCurrentProcess(), |
| 38 &default_mask, &system_mask)) { |
| 39 return; |
| 40 } |
| 41 |
| 42 SYSTEM_INFO sys_info; |
| 43 GetSystemInfo(&sys_info); |
| 44 DWORD num_cores = sys_info.dwNumberOfProcessors; |
| 45 DWORD current_core = 0; |
| 46 bool failed_to_change_cores = false; |
| 47 |
| 48 base::win::OSInfo* info = base::win::OSInfo::GetInstance(); |
| 49 UMA_HISTOGRAM_ENUMERATION("WinTimeTicks.VersionTotal", info->version(), |
| 50 base::win::VERSION_WIN_LAST); |
| 51 |
| 52 LARGE_INTEGER qpc_frequency; |
| 53 QueryPerformanceFrequency(&qpc_frequency); |
| 54 |
| 55 int min_delta = 1e9; |
| 56 LARGE_INTEGER qpc_last; |
| 57 QueryPerformanceCounter(&qpc_last); |
| 58 for (int i = 0; i < kNumIterations; ++i) { |
| 59 LARGE_INTEGER qpc_now; |
| 60 QueryPerformanceCounter(&qpc_now); |
| 61 int delta = static_cast<int>(qpc_now.QuadPart - qpc_last.QuadPart); |
| 62 if (delta != 0) { |
| 63 min_delta = std::min(min_delta, delta); |
| 64 } |
| 65 qpc_last = qpc_now; |
| 66 |
| 67 if (num_cores > 1 && (i % 100) == 0) { |
| 68 ++current_core; |
| 69 if (current_core > num_cores) { |
| 70 current_core = 0; |
| 71 } |
| 72 if (!SetThreadAffinityMask(GetCurrentThread(), 1 << current_core)) { |
| 73 failed_to_change_cores = true; |
| 74 break; |
| 75 } |
| 76 } |
| 77 } |
| 78 |
| 79 if (num_cores > 1) { |
| 80 SetThreadAffinityMask(GetCurrentThread(), default_mask); |
| 81 if (failed_to_change_cores) { |
| 82 UMA_HISTOGRAM_ENUMERATION("WinTimeTicks.FailedToChangeCores", |
| 83 info->version(), base::win::VERSION_WIN_LAST); |
| 84 return; |
| 85 } |
| 86 } |
| 87 |
| 88 if (min_delta < 0) { |
| 89 UMA_HISTOGRAM_ENUMERATION("WinTimeTicks.TickedBackwards", info->version(), |
| 90 base::win::VERSION_WIN_LAST); |
| 91 return; |
| 92 } |
| 93 |
| 94 int min_delta_ns = static_cast<int>( |
| 95 min_delta * (1e9 / qpc_frequency.QuadPart)); |
| 96 UMA_HISTOGRAM_CUSTOM_COUNTS("WinTimeTicks.MinResolutionNanoseconds", |
| 97 min_delta_ns, 1, 1000000, 50); |
| 98 |
| 99 bool success = min_delta_ns <= 10000; |
| 100 if (success) { |
| 101 UMA_HISTOGRAM_ENUMERATION("WinTimeTicks.VersionSuccessful", |
| 102 info->version(), base::win::VERSION_WIN_LAST); |
| 103 } |
| 104 } |
| 105 |
| 106 } // namespace chrome |
| 107 |
| 108 #endif // defined(OS_WIN) |
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