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Issue 1555553002: [profiler] Implement POC Sampling Heap Profiler (Closed) Base URL: https://chromium.googlesource.com/v8/v8.git@master
Patch Set: remove unused variable Created 4 years, 11 months ago
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1 // Copyright 2015 the V8 project 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 "src/profiler/sampling-heap-profiler.h"
6
7 #include <stdint.h>
8 #include <memory>
9 #include "src/api.h"
10 #include "src/base/utils/random-number-generator.h"
11 #include "src/frames-inl.h"
12 #include "src/heap/heap.h"
13 #include "src/isolate.h"
14 #include "src/profiler/strings-storage.h"
15
16 namespace v8 {
17 namespace internal {
18
19 SamplingHeapProfiler::SamplingHeapProfiler(Heap* heap, StringsStorage* names,
20 uint64_t rate, int stack_depth)
21 : InlineAllocationObserver(GetNextSampleInterval(
22 heap->isolate()->random_number_generator(), rate)),
23 isolate_(heap->isolate()),
24 heap_(heap),
25 random_(isolate_->random_number_generator()),
26 names_(names),
27 samples_(),
28 rate_(rate),
29 stack_depth_(stack_depth) {
30 heap->new_space()->AddInlineAllocationObserver(this);
31 }
32
33
34 SamplingHeapProfiler::~SamplingHeapProfiler() {
35 heap_->new_space()->RemoveInlineAllocationObserver(this);
36
37 // Clear samples and drop all the weak references we are keeping.
38 std::set<SampledAllocation*>::iterator it;
39 for (it = samples_.begin(); it != samples_.end(); ++it) {
40 delete *it;
41 }
42 std::set<SampledAllocation*> empty;
43 samples_.swap(empty);
44 }
45
46 void SamplingHeapProfiler::Step(int bytes_allocated, Address soon_object,
47 size_t size) {
48 DCHECK(heap_->gc_state() == Heap::NOT_IN_GC);
49 DCHECK(soon_object);
50 SampleObject(soon_object, size);
51 }
52
53
54 void SamplingHeapProfiler::SampleObject(Address soon_object, size_t size) {
55 DisallowHeapAllocation no_allocation;
56
57 HandleScope scope(isolate_);
58 HeapObject* heap_object = HeapObject::FromAddress(soon_object);
59 Handle<Object> obj(heap_object, isolate_);
60
61 // Mark the new block as FreeSpace to make sure the heap is iterable while we
62 // are taking the sample.
63 heap()->CreateFillerObjectAt(soon_object, static_cast<int>(size));
64
65 Local<v8::Value> loc = v8::Utils::ToLocal(obj);
66
67 SampledAllocation* sample =
68 new SampledAllocation(this, isolate_, loc, size, stack_depth_);
69 samples_.insert(sample);
70 }
71
72
73 // We sample with a Poisson process, with constant average sampling interval.
74 // This follows the exponential probability distribution with parameter
75 // λ = 1/rate where rate is the average number of bytes between samples.
76 //
77 // Let u be a uniformly distributed random number between 0 and 1, then
78 // next_sample = (- ln u) / λ
79 intptr_t SamplingHeapProfiler::GetNextSampleInterval(
80 base::RandomNumberGenerator* random, uint64_t rate) {
81 double u = random->NextDouble();
82 double next = (-std::log(u)) * rate;
83 return next < kPointerSize
84 ? kPointerSize
85 : (next > INT_MAX ? INT_MAX : static_cast<intptr_t>(next));
86 }
87
88
89 void SamplingHeapProfiler::SampledAllocation::OnWeakCallback(
90 const WeakCallbackInfo<SampledAllocation>& data) {
91 SampledAllocation* sample = data.GetParameter();
92 sample->sampling_heap_profiler_->samples_.erase(sample);
93 delete sample;
94 }
95
96
97 SamplingHeapProfiler::FunctionInfo::FunctionInfo(SharedFunctionInfo* shared,
98 StringsStorage* names)
99 : name_(names->GetFunctionName(shared->DebugName())),
100 script_name_(""),
101 script_id_(v8::UnboundScript::kNoScriptId),
102 start_position_(shared->start_position()) {
103 if (shared->script()->IsScript()) {
104 Script* script = Script::cast(shared->script());
105 script_id_ = script->id();
106 if (script->name()->IsName()) {
107 Name* name = Name::cast(script->name());
108 script_name_ = names->GetName(name);
109 }
110 }
111 }
112
113
114 SamplingHeapProfiler::SampledAllocation::SampledAllocation(
115 SamplingHeapProfiler* sampling_heap_profiler, Isolate* isolate,
116 Local<Value> local, size_t size, int max_frames)
117 : sampling_heap_profiler_(sampling_heap_profiler),
118 global_(reinterpret_cast<v8::Isolate*>(isolate), local),
119 size_(size) {
120 global_.SetWeak(this, OnWeakCallback, WeakCallbackType::kParameter);
121
122 StackTraceFrameIterator it(isolate);
123 int frames_captured = 0;
124 while (!it.done() && frames_captured < max_frames) {
125 JavaScriptFrame* frame = it.frame();
126 SharedFunctionInfo* shared = frame->function()->shared();
127 stack_.push_back(new FunctionInfo(shared, sampling_heap_profiler->names()));
128
129 frames_captured++;
130 it.Advance();
131 }
132
133 if (frames_captured == 0) {
134 const char* name = nullptr;
135 switch (isolate->current_vm_state()) {
136 case GC:
137 name = "(GC)";
138 break;
139 case COMPILER:
140 name = "(COMPILER)";
141 break;
142 case OTHER:
143 name = "(V8 API)";
144 break;
145 case EXTERNAL:
146 name = "(EXTERNAL)";
147 break;
148 case IDLE:
149 name = "(IDLE)";
150 break;
151 case JS:
152 name = "(JS)";
153 break;
154 }
155 stack_.push_back(new FunctionInfo(name));
156 }
157 }
158
159
160 SamplingHeapProfiler::Node* SamplingHeapProfiler::AllocateNode(
161 AllocationProfile* profile, const std::map<int, Script*>& scripts,
162 FunctionInfo* function_info) {
163 DCHECK(function_info->get_name());
164 DCHECK(function_info->get_script_name());
165
166 int line = v8::AllocationProfile::kNoLineNumberInfo;
167 int column = v8::AllocationProfile::kNoColumnNumberInfo;
168
169 if (function_info->get_script_id() != v8::UnboundScript::kNoScriptId) {
170 // Cannot use std::map<T>::at because it is not available on android.
171 auto non_const_scripts = const_cast<std::map<int, Script*>&>(scripts);
172 Handle<Script> script(non_const_scripts[function_info->get_script_id()]);
173
174 line =
175 1 + Script::GetLineNumber(script, function_info->get_start_position());
176 column = 1 + Script::GetColumnNumber(script,
177 function_info->get_start_position());
178 }
179
180 profile->nodes().push_back(
181 Node({ToApiHandle<v8::String>(isolate_->factory()->InternalizeUtf8String(
182 function_info->get_name())),
183 ToApiHandle<v8::String>(isolate_->factory()->InternalizeUtf8String(
184 function_info->get_script_name())),
185 function_info->get_script_id(), function_info->get_start_position(),
186 line, column, std::vector<Node*>(),
187 std::vector<v8::AllocationProfile::Allocation>()}));
188
189 return &profile->nodes().back();
190 }
191
192
193 SamplingHeapProfiler::Node* SamplingHeapProfiler::FindOrAddChildNode(
194 AllocationProfile* profile, const std::map<int, Script*>& scripts,
195 Node* parent, FunctionInfo* function_info) {
196 for (Node* child : parent->children) {
197 if (child->script_id == function_info->get_script_id() &&
198 child->start_position == function_info->get_start_position())
199 return child;
200 }
201 Node* child = AllocateNode(profile, scripts, function_info);
202 parent->children.push_back(child);
203 return child;
204 }
205
206
207 SamplingHeapProfiler::Node* SamplingHeapProfiler::AddStack(
208 AllocationProfile* profile, const std::map<int, Script*>& scripts,
209 const std::vector<FunctionInfo*>& stack) {
210 Node* node = profile->GetRootNode();
211
212 // We need to process the stack in reverse order as the top of the stack is
213 // the first element in the list.
214 for (auto it = stack.rbegin(); it != stack.rend(); ++it) {
215 FunctionInfo* function_info = *it;
216 node = FindOrAddChildNode(profile, scripts, node, function_info);
217 }
218 return node;
219 }
220
221
222 v8::AllocationProfile* SamplingHeapProfiler::GetAllocationProfile() {
223 // To resolve positions to line/column numbers, we will need to look up
224 // scripts. Build a map to allow fast mapping from script id to script.
225 std::map<int, Script*> scripts;
226 {
227 Script::Iterator iterator(isolate_);
228 Script* script;
229 while ((script = iterator.Next())) {
230 scripts[script->id()] = script;
231 }
232 }
233
234 auto profile = new v8::internal::AllocationProfile();
235
236 // Create the root node.
237 FunctionInfo function_info("(root)");
238 AllocateNode(profile, scripts, &function_info);
239
240 for (SampledAllocation* allocation : samples_) {
241 Node* node = AddStack(profile, scripts, allocation->get_stack());
242 node->allocations.push_back({allocation->get_size(), 1});
243 }
244
245 return profile;
246 }
247
248
249 } // namespace internal
250 } // namespace v8
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