Line data Source code
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 :
10 : #include "src/api-inl.h"
11 : #include "src/base/ieee754.h"
12 : #include "src/base/template-utils.h"
13 : #include "src/base/utils/random-number-generator.h"
14 : #include "src/frames-inl.h"
15 : #include "src/heap/heap.h"
16 : #include "src/isolate.h"
17 : #include "src/profiler/strings-storage.h"
18 :
19 : namespace v8 {
20 : namespace internal {
21 :
22 : // We sample with a Poisson process, with constant average sampling interval.
23 : // This follows the exponential probability distribution with parameter
24 : // λ = 1/rate where rate is the average number of bytes between samples.
25 : //
26 : // Let u be a uniformly distributed random number between 0 and 1, then
27 : // next_sample = (- ln u) / λ
28 104788 : intptr_t SamplingAllocationObserver::GetNextSampleInterval(uint64_t rate) {
29 104788 : if (FLAG_sampling_heap_profiler_suppress_randomness) {
30 54652 : return static_cast<intptr_t>(rate);
31 : }
32 50136 : double u = random_->NextDouble();
33 50136 : double next = (-base::ieee754::log(u)) * rate;
34 : return next < kTaggedSize
35 : ? kTaggedSize
36 50136 : : (next > INT_MAX ? INT_MAX : static_cast<intptr_t>(next));
37 : }
38 :
39 : // Samples were collected according to a poisson process. Since we have not
40 : // recorded all allocations, we must approximate the shape of the underlying
41 : // space of allocations based on the samples we have collected. Given that
42 : // we sample at rate R, the probability that an allocation of size S will be
43 : // sampled is 1-exp(-S/R). This function uses the above probability to
44 : // approximate the true number of allocations with size *size* given that
45 : // *count* samples were observed.
46 44687 : v8::AllocationProfile::Allocation SamplingHeapProfiler::ScaleSample(
47 : size_t size, unsigned int count) const {
48 44687 : double scale = 1.0 / (1.0 - std::exp(-static_cast<double>(size) / rate_));
49 : // Round count instead of truncating.
50 44687 : return {size, static_cast<unsigned int>(count * scale + 0.5)};
51 : }
52 :
53 59 : SamplingHeapProfiler::SamplingHeapProfiler(
54 : Heap* heap, StringsStorage* names, uint64_t rate, int stack_depth,
55 : v8::HeapProfiler::SamplingFlags flags)
56 : : isolate_(heap->isolate()),
57 : heap_(heap),
58 : new_space_observer_(new SamplingAllocationObserver(
59 : heap_, static_cast<intptr_t>(rate), rate, this,
60 59 : heap->isolate()->random_number_generator())),
61 : other_spaces_observer_(new SamplingAllocationObserver(
62 : heap_, static_cast<intptr_t>(rate), rate, this,
63 59 : heap->isolate()->random_number_generator())),
64 : names_(names),
65 : profile_root_(nullptr, "(root)", v8::UnboundScript::kNoScriptId, 0,
66 : next_node_id()),
67 : stack_depth_(stack_depth),
68 : rate_(rate),
69 236 : flags_(flags) {
70 59 : CHECK_GT(rate_, 0u);
71 : heap_->AddAllocationObserversToAllSpaces(other_spaces_observer_.get(),
72 59 : new_space_observer_.get());
73 59 : }
74 :
75 118 : SamplingHeapProfiler::~SamplingHeapProfiler() {
76 : heap_->RemoveAllocationObserversFromAllSpaces(other_spaces_observer_.get(),
77 59 : new_space_observer_.get());
78 59 : }
79 :
80 104783 : void SamplingHeapProfiler::SampleObject(Address soon_object, size_t size) {
81 : DisallowHeapAllocation no_allocation;
82 :
83 104783 : HandleScope scope(isolate_);
84 : HeapObject heap_object = HeapObject::FromAddress(soon_object);
85 104783 : Handle<Object> obj(heap_object, isolate_);
86 :
87 : // Mark the new block as FreeSpace to make sure the heap is iterable while we
88 : // are taking the sample.
89 : heap_->CreateFillerObjectAt(soon_object, static_cast<int>(size),
90 104783 : ClearRecordedSlots::kNo);
91 :
92 104783 : Local<v8::Value> loc = v8::Utils::ToLocal(obj);
93 :
94 104783 : AllocationNode* node = AddStack();
95 104783 : node->allocations_[size]++;
96 : auto sample =
97 104783 : base::make_unique<Sample>(size, node, loc, this, next_sample_id());
98 : sample->global.SetWeak(sample.get(), OnWeakCallback,
99 : WeakCallbackType::kParameter);
100 : #if __clang__
101 : #pragma clang diagnostic push
102 : #pragma clang diagnostic ignored "-Wdeprecated"
103 : #endif
104 : // MarkIndependent is marked deprecated but we still rely on it here
105 : // temporarily.
106 : sample->global.MarkIndependent();
107 : #if __clang__
108 : #pragma clang diagnostic pop
109 : #endif
110 209566 : samples_.emplace(sample.get(), std::move(sample));
111 104783 : }
112 :
113 17880 : void SamplingHeapProfiler::OnWeakCallback(
114 17880 : const WeakCallbackInfo<Sample>& data) {
115 17880 : Sample* sample = data.GetParameter();
116 17880 : AllocationNode* node = sample->owner;
117 : DCHECK_GT(node->allocations_[sample->size], 0);
118 17880 : node->allocations_[sample->size]--;
119 17880 : if (node->allocations_[sample->size] == 0) {
120 68 : node->allocations_.erase(sample->size);
121 77 : while (node->allocations_.empty() && node->children_.empty() &&
122 76 : node->parent_ && !node->parent_->pinned_) {
123 4 : AllocationNode* parent = node->parent_;
124 : AllocationNode::FunctionId id = AllocationNode::function_id(
125 8 : node->script_id_, node->script_position_, node->name_);
126 : parent->children_.erase(id);
127 : node = parent;
128 : }
129 : }
130 17880 : sample->profiler->samples_.erase(sample);
131 : // sample is deleted because its unique ptr was erased from samples_.
132 17880 : }
133 :
134 156239 : SamplingHeapProfiler::AllocationNode* SamplingHeapProfiler::FindOrAddChildNode(
135 : AllocationNode* parent, const char* name, int script_id,
136 : int start_position) {
137 : AllocationNode::FunctionId id =
138 156239 : AllocationNode::function_id(script_id, start_position, name);
139 156239 : AllocationNode* child = parent->FindChildNode(id);
140 156239 : if (child) {
141 : DCHECK_EQ(strcmp(child->name_, name), 0);
142 : return child;
143 : }
144 : auto new_child = base::make_unique<AllocationNode>(
145 283 : parent, name, script_id, start_position, next_node_id());
146 566 : return parent->AddChildNode(id, std::move(new_child));
147 : }
148 :
149 226884 : SamplingHeapProfiler::AllocationNode* SamplingHeapProfiler::AddStack() {
150 104783 : AllocationNode* node = &profile_root_;
151 :
152 : std::vector<SharedFunctionInfo> stack;
153 138918 : JavaScriptFrameIterator it(isolate_);
154 : int frames_captured = 0;
155 : bool found_arguments_marker_frames = false;
156 331670 : while (!it.done() && frames_captured < stack_depth_) {
157 : JavaScriptFrame* frame = it.frame();
158 : // If we are materializing objects during deoptimization, inlined
159 : // closures may not yet be materialized, and this includes the
160 : // closure on the stack. Skip over any such frames (they'll be
161 : // in the top frames of the stack). The allocations made in this
162 : // sensitive moment belong to the formerly optimized frame anyway.
163 244208 : if (frame->unchecked_function()->IsJSFunction()) {
164 122101 : SharedFunctionInfo shared = frame->function()->shared();
165 122101 : stack.push_back(shared);
166 122101 : frames_captured++;
167 : } else {
168 : found_arguments_marker_frames = true;
169 : }
170 122104 : it.Advance();
171 : }
172 :
173 104783 : if (frames_captured == 0) {
174 : const char* name = nullptr;
175 68270 : switch (isolate_->current_vm_state()) {
176 : case GC:
177 : name = "(GC)";
178 0 : break;
179 : case PARSER:
180 : name = "(PARSER)";
181 0 : break;
182 : case COMPILER:
183 : name = "(COMPILER)";
184 5037 : break;
185 : case BYTECODE_COMPILER:
186 : name = "(BYTECODE_COMPILER)";
187 277 : break;
188 : case OTHER:
189 : name = "(V8 API)";
190 15020 : break;
191 : case EXTERNAL:
192 : name = "(EXTERNAL)";
193 13801 : break;
194 : case IDLE:
195 : name = "(IDLE)";
196 0 : break;
197 : case JS:
198 : name = "(JS)";
199 0 : break;
200 : }
201 34135 : return FindOrAddChildNode(node, name, v8::UnboundScript::kNoScriptId, 0);
202 : }
203 :
204 : // We need to process the stack in reverse order as the top of the stack is
205 : // the first element in the list.
206 192749 : for (auto it = stack.rbegin(); it != stack.rend(); ++it) {
207 122101 : SharedFunctionInfo shared = *it;
208 244202 : const char* name = this->names()->GetName(shared->DebugName());
209 : int script_id = v8::UnboundScript::kNoScriptId;
210 244202 : if (shared->script()->IsScript()) {
211 107762 : Script script = Script::cast(shared->script());
212 : script_id = script->id();
213 : }
214 122101 : node = FindOrAddChildNode(node, name, script_id, shared->StartPosition());
215 : }
216 :
217 70648 : if (found_arguments_marker_frames) {
218 : node =
219 3 : FindOrAddChildNode(node, "(deopt)", v8::UnboundScript::kNoScriptId, 0);
220 : }
221 :
222 70648 : return node;
223 : }
224 :
225 316 : v8::AllocationProfile::Node* SamplingHeapProfiler::TranslateAllocationNode(
226 : AllocationProfile* profile, SamplingHeapProfiler::AllocationNode* node,
227 : const std::map<int, Handle<Script>>& scripts) {
228 : // By pinning the node we make sure its children won't get disposed if
229 : // a GC kicks in during the tree retrieval.
230 316 : node->pinned_ = true;
231 : Local<v8::String> script_name =
232 316 : ToApiHandle<v8::String>(isolate_->factory()->InternalizeUtf8String(""));
233 : int line = v8::AllocationProfile::kNoLineNumberInfo;
234 : int column = v8::AllocationProfile::kNoColumnNumberInfo;
235 : std::vector<v8::AllocationProfile::Allocation> allocations;
236 316 : allocations.reserve(node->allocations_.size());
237 465 : if (node->script_id_ != v8::UnboundScript::kNoScriptId &&
238 149 : scripts.find(node->script_id_) != scripts.end()) {
239 : // Cannot use std::map<T>::at because it is not available on android.
240 : auto non_const_scripts =
241 : const_cast<std::map<int, Handle<Script>>&>(scripts);
242 149 : Handle<Script> script = non_const_scripts[node->script_id_];
243 149 : if (!script.is_null()) {
244 298 : if (script->name()->IsName()) {
245 60 : Name name = Name::cast(script->name());
246 : script_name = ToApiHandle<v8::String>(
247 30 : isolate_->factory()->InternalizeUtf8String(names_->GetName(name)));
248 : }
249 149 : line = 1 + Script::GetLineNumber(script, node->script_position_);
250 149 : column = 1 + Script::GetColumnNumber(script, node->script_position_);
251 : }
252 : }
253 1506 : for (auto alloc : node->allocations_) {
254 1748 : allocations.push_back(ScaleSample(alloc.first, alloc.second));
255 : }
256 :
257 : profile->nodes_.push_back(v8::AllocationProfile::Node{
258 : ToApiHandle<v8::String>(
259 316 : isolate_->factory()->InternalizeUtf8String(node->name_)),
260 : script_name, node->script_id_, node->script_position_, line, column,
261 948 : node->id_, std::vector<v8::AllocationProfile::Node*>(), allocations});
262 316 : v8::AllocationProfile::Node* current = &profile->nodes_.back();
263 : // The |children_| map may have nodes inserted into it during translation
264 : // because the translation may allocate strings on the JS heap that have
265 : // the potential to be sampled. That's ok since map iterators are not
266 : // invalidated upon std::map insertion.
267 884 : for (const auto& it : node->children_) {
268 : current->children.push_back(
269 504 : TranslateAllocationNode(profile, it.second.get(), scripts));
270 : }
271 316 : node->pinned_ = false;
272 316 : return current;
273 : }
274 :
275 64 : v8::AllocationProfile* SamplingHeapProfiler::GetAllocationProfile() {
276 64 : if (flags_ & v8::HeapProfiler::kSamplingForceGC) {
277 : isolate_->heap()->CollectAllGarbage(
278 20 : Heap::kNoGCFlags, GarbageCollectionReason::kSamplingProfiler);
279 : }
280 : // To resolve positions to line/column numbers, we will need to look up
281 : // scripts. Build a map to allow fast mapping from script id to script.
282 : std::map<int, Handle<Script>> scripts;
283 : {
284 64 : Script::Iterator iterator(isolate_);
285 361 : for (Script script = iterator.Next(); !script.is_null();
286 : script = iterator.Next()) {
287 594 : scripts[script->id()] = handle(script, isolate_);
288 : }
289 : }
290 64 : auto profile = new v8::internal::AllocationProfile();
291 64 : TranslateAllocationNode(profile, &profile_root_, scripts);
292 128 : profile->samples_ = SamplingHeapProfiler::BuildSamples();
293 :
294 64 : return profile;
295 : }
296 :
297 : const std::vector<v8::AllocationProfile::Sample>
298 64 : SamplingHeapProfiler::BuildSamples() const {
299 : std::vector<v8::AllocationProfile::Sample> samples;
300 64 : samples.reserve(samples_.size());
301 43941 : for (const auto& it : samples_) {
302 : const Sample* sample = it.second.get();
303 : samples.emplace_back(v8::AllocationProfile::Sample{
304 43813 : sample->owner->id_, sample->size, ScaleSample(sample->size, 1).count,
305 87626 : sample->sample_id});
306 : }
307 64 : return samples;
308 : }
309 :
310 : } // namespace internal
311 183867 : } // namespace v8
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