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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_browser_metrics { | |
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 default_mask; | |
36 DWORD 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); | |
Sigurður Ásgeirsson
2013/04/19 12:59:17
ah - great catch :)
| |
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_browser_net | |
107 | |
108 #endif // defined(OS_WIN) | |
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