1 //===-- TimeProfiler.cpp - Hierarchical Time Profiler ---------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements hierarchical time profiler.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "llvm/Support/TimeProfiler.h"
14 #include "llvm/ADT/StringMap.h"
15 #include "llvm/Support/CommandLine.h"
16 #include "llvm/Support/JSON.h"
17 #include "llvm/Support/Path.h"
18 #include <cassert>
19 #include <chrono>
20 #include <string>
21 #include <vector>
22 
23 using namespace std::chrono;
24 
25 namespace llvm {
26 
27 TimeTraceProfiler *TimeTraceProfilerInstance = nullptr;
28 
29 typedef duration<steady_clock::rep, steady_clock::period> DurationType;
30 typedef time_point<steady_clock> TimePointType;
31 typedef std::pair<size_t, DurationType> CountAndDurationType;
32 typedef std::pair<std::string, CountAndDurationType>
33     NameAndCountAndDurationType;
34 
35 struct Entry {
36   const TimePointType Start;
37   TimePointType End;
38   const std::string Name;
39   const std::string Detail;
40 
41   Entry(TimePointType &&S, TimePointType &&E, std::string &&N, std::string &&Dt)
42       : Start(std::move(S)), End(std::move(E)), Name(std::move(N)),
43         Detail(std::move(Dt)) {}
44 
45   // Calculate timings for FlameGraph. Cast time points to microsecond precision
46   // rather than casting duration. This avoid truncation issues causing inner
47   // scopes overruning outer scopes.
48   steady_clock::rep getFlameGraphStartUs(TimePointType StartTime) const {
49     return (time_point_cast<microseconds>(Start) -
50             time_point_cast<microseconds>(StartTime))
51         .count();
52   }
53 
54   steady_clock::rep getFlameGraphDurUs() const {
55     return (time_point_cast<microseconds>(End) -
56             time_point_cast<microseconds>(Start))
57         .count();
58   }
59 };
60 
61 struct TimeTraceProfiler {
62   TimeTraceProfiler(unsigned TimeTraceGranularity = 0, StringRef ProcName = "")
63       : StartTime(steady_clock::now()), ProcName(ProcName),
64         TimeTraceGranularity(TimeTraceGranularity) {}
65 
66   void begin(std::string Name, llvm::function_ref<std::string()> Detail) {
67     Stack.emplace_back(steady_clock::now(), TimePointType(), std::move(Name),
68                        Detail());
69   }
70 
71   void end() {
72     assert(!Stack.empty() && "Must call begin() first");
73     auto &E = Stack.back();
74     E.End = steady_clock::now();
75 
76     // Check that end times monotonically increase.
77     assert((Entries.empty() ||
78             (E.getFlameGraphStartUs(StartTime) + E.getFlameGraphDurUs() >=
79              Entries.back().getFlameGraphStartUs(StartTime) +
80                  Entries.back().getFlameGraphDurUs())) &&
81            "TimeProfiler scope ended earlier than previous scope");
82 
83     // Calculate duration at full precision for overall counts.
84     DurationType Duration = E.End - E.Start;
85 
86     // Only include sections longer or equal to TimeTraceGranularity msec.
87     if (duration_cast<microseconds>(Duration).count() >= TimeTraceGranularity)
88       Entries.emplace_back(E);
89 
90     // Track total time taken by each "name", but only the topmost levels of
91     // them; e.g. if there's a template instantiation that instantiates other
92     // templates from within, we only want to add the topmost one. "topmost"
93     // happens to be the ones that don't have any currently open entries above
94     // itself.
95     if (std::find_if(++Stack.rbegin(), Stack.rend(), [&](const Entry &Val) {
96           return Val.Name == E.Name;
97         }) == Stack.rend()) {
98       auto &CountAndTotal = CountAndTotalPerName[E.Name];
99       CountAndTotal.first++;
100       CountAndTotal.second += Duration;
101     }
102 
103     Stack.pop_back();
104   }
105 
106   void Write(raw_pwrite_stream &OS) {
107     assert(Stack.empty() &&
108            "All profiler sections should be ended when calling Write");
109     json::OStream J(OS);
110     J.objectBegin();
111     J.attributeBegin("traceEvents");
112     J.arrayBegin();
113 
114     // Emit all events for the main flame graph.
115     for (const auto &E : Entries) {
116       auto StartUs = E.getFlameGraphStartUs(StartTime);
117       auto DurUs = E.getFlameGraphDurUs();
118 
119       J.object([&]{
120         J.attribute("pid", 1);
121         J.attribute("tid", 0);
122         J.attribute("ph", "X");
123         J.attribute("ts", StartUs);
124         J.attribute("dur", DurUs);
125         J.attribute("name", E.Name);
126         if (!E.Detail.empty()) {
127           J.attributeObject("args", [&] { J.attribute("detail", E.Detail); });
128         }
129       });
130     }
131 
132     // Emit totals by section name as additional "thread" events, sorted from
133     // longest one.
134     int Tid = 1;
135     std::vector<NameAndCountAndDurationType> SortedTotals;
136     SortedTotals.reserve(CountAndTotalPerName.size());
137     for (const auto &E : CountAndTotalPerName)
138       SortedTotals.emplace_back(E.getKey(), E.getValue());
139 
140     llvm::sort(SortedTotals.begin(), SortedTotals.end(),
141                [](const NameAndCountAndDurationType &A,
142                   const NameAndCountAndDurationType &B) {
143                  return A.second.second > B.second.second;
144                });
145     for (const auto &E : SortedTotals) {
146       auto DurUs = duration_cast<microseconds>(E.second.second).count();
147       auto Count = CountAndTotalPerName[E.first].first;
148 
149       J.object([&]{
150         J.attribute("pid", 1);
151         J.attribute("tid", Tid);
152         J.attribute("ph", "X");
153         J.attribute("ts", 0);
154         J.attribute("dur", DurUs);
155         J.attribute("name", "Total " + E.first);
156         J.attributeObject("args", [&] {
157           J.attribute("count", int64_t(Count));
158           J.attribute("avg ms", int64_t(DurUs / Count / 1000));
159         });
160       });
161 
162       ++Tid;
163     }
164 
165     // Emit metadata event with process name.
166     J.object([&] {
167       J.attribute("cat", "");
168       J.attribute("pid", 1);
169       J.attribute("tid", 0);
170       J.attribute("ts", 0);
171       J.attribute("ph", "M");
172       J.attribute("name", "process_name");
173       J.attributeObject("args", [&] { J.attribute("name", ProcName); });
174     });
175 
176     J.arrayEnd();
177     J.attributeEnd();
178     J.objectEnd();
179   }
180 
181   SmallVector<Entry, 16> Stack;
182   SmallVector<Entry, 128> Entries;
183   StringMap<CountAndDurationType> CountAndTotalPerName;
184   const TimePointType StartTime;
185   const std::string ProcName;
186 
187   // Minimum time granularity (in microseconds)
188   const unsigned TimeTraceGranularity;
189 };
190 
191 void timeTraceProfilerInitialize(unsigned TimeTraceGranularity,
192                                  StringRef ProcName) {
193   assert(TimeTraceProfilerInstance == nullptr &&
194          "Profiler should not be initialized");
195   TimeTraceProfilerInstance = new TimeTraceProfiler(
196       TimeTraceGranularity, llvm::sys::path::filename(ProcName));
197 }
198 
199 void timeTraceProfilerCleanup() {
200   delete TimeTraceProfilerInstance;
201   TimeTraceProfilerInstance = nullptr;
202 }
203 
204 void timeTraceProfilerWrite(raw_pwrite_stream &OS) {
205   assert(TimeTraceProfilerInstance != nullptr &&
206          "Profiler object can't be null");
207   TimeTraceProfilerInstance->Write(OS);
208 }
209 
210 void timeTraceProfilerBegin(StringRef Name, StringRef Detail) {
211   if (TimeTraceProfilerInstance != nullptr)
212     TimeTraceProfilerInstance->begin(Name, [&]() { return Detail; });
213 }
214 
215 void timeTraceProfilerBegin(StringRef Name,
216                             llvm::function_ref<std::string()> Detail) {
217   if (TimeTraceProfilerInstance != nullptr)
218     TimeTraceProfilerInstance->begin(Name, Detail);
219 }
220 
221 void timeTraceProfilerEnd() {
222   if (TimeTraceProfilerInstance != nullptr)
223     TimeTraceProfilerInstance->end();
224 }
225 
226 } // namespace llvm
227