| [email protected] | aa31281 | 2013-04-30 19:46:05 | [diff] [blame] | 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) |
