| // Copyright 2015 the V8 project authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "src/profiler/sampling-heap-profiler.h" |
| |
| #include <stdint.h> |
| #include <memory> |
| #include "src/api.h" |
| #include "src/base/utils/random-number-generator.h" |
| #include "src/frames-inl.h" |
| #include "src/heap/heap.h" |
| #include "src/isolate.h" |
| #include "src/profiler/strings-storage.h" |
| |
| namespace v8 { |
| namespace internal { |
| |
| // We sample with a Poisson process, with constant average sampling interval. |
| // This follows the exponential probability distribution with parameter |
| // λ = 1/rate where rate is the average number of bytes between samples. |
| // |
| // Let u be a uniformly distributed random number between 0 and 1, then |
| // next_sample = (- ln u) / λ |
| intptr_t SamplingAllocationObserver::GetNextSampleInterval(uint64_t rate) { |
| if (FLAG_sampling_heap_profiler_suppress_randomness) { |
| return static_cast<intptr_t>(rate); |
| } |
| double u = random_->NextDouble(); |
| double next = (-std::log(u)) * rate; |
| return next < kPointerSize |
| ? kPointerSize |
| : (next > INT_MAX ? INT_MAX : static_cast<intptr_t>(next)); |
| } |
| |
| // Samples were collected according to a poisson process. Since we have not |
| // recorded all allocations, we must approximate the shape of the underlying |
| // space of allocations based on the samples we have collected. Given that |
| // we sample at rate R, the probability that an allocation of size S will be |
| // sampled is 1-exp(-S/R). This function uses the above probability to |
| // approximate the true number of allocations with size *size* given that |
| // *count* samples were observed. |
| v8::AllocationProfile::Allocation SamplingHeapProfiler::ScaleSample( |
| size_t size, unsigned int count) { |
| double scale = 1.0 / (1.0 - std::exp(-static_cast<double>(size) / rate_)); |
| // Round count instead of truncating. |
| return {size, static_cast<unsigned int>(count * scale + 0.5)}; |
| } |
| |
| SamplingHeapProfiler::SamplingHeapProfiler(Heap* heap, StringsStorage* names, |
| uint64_t rate, int stack_depth) |
| : isolate_(heap->isolate()), |
| heap_(heap), |
| new_space_observer_(new SamplingAllocationObserver( |
| heap_, static_cast<intptr_t>(rate), rate, this, |
| heap->isolate()->random_number_generator())), |
| other_spaces_observer_(new SamplingAllocationObserver( |
| heap_, static_cast<intptr_t>(rate), rate, this, |
| heap->isolate()->random_number_generator())), |
| names_(names), |
| profile_root_("(root)", v8::UnboundScript::kNoScriptId, 0), |
| samples_(), |
| stack_depth_(stack_depth), |
| rate_(rate) { |
| CHECK_GT(rate_, 0); |
| heap->new_space()->AddAllocationObserver(new_space_observer_.get()); |
| AllSpaces spaces(heap); |
| for (Space* space = spaces.next(); space != NULL; space = spaces.next()) { |
| if (space != heap->new_space()) { |
| space->AddAllocationObserver(other_spaces_observer_.get()); |
| } |
| } |
| } |
| |
| |
| SamplingHeapProfiler::~SamplingHeapProfiler() { |
| heap_->new_space()->RemoveAllocationObserver(new_space_observer_.get()); |
| AllSpaces spaces(heap_); |
| for (Space* space = spaces.next(); space != NULL; space = spaces.next()) { |
| if (space != heap_->new_space()) { |
| space->RemoveAllocationObserver(other_spaces_observer_.get()); |
| } |
| } |
| |
| for (auto sample : samples_) { |
| delete sample; |
| } |
| std::set<Sample*> empty; |
| samples_.swap(empty); |
| } |
| |
| |
| void SamplingHeapProfiler::SampleObject(Address soon_object, size_t size) { |
| DisallowHeapAllocation no_allocation; |
| |
| HandleScope scope(isolate_); |
| HeapObject* heap_object = HeapObject::FromAddress(soon_object); |
| Handle<Object> obj(heap_object, isolate_); |
| |
| // Mark the new block as FreeSpace to make sure the heap is iterable while we |
| // are taking the sample. |
| heap()->CreateFillerObjectAt(soon_object, static_cast<int>(size), |
| ClearRecordedSlots::kNo); |
| |
| Local<v8::Value> loc = v8::Utils::ToLocal(obj); |
| |
| AllocationNode* node = AddStack(); |
| node->allocations_[size]++; |
| Sample* sample = new Sample(size, node, loc, this); |
| samples_.insert(sample); |
| sample->global.SetWeak(sample, OnWeakCallback, WeakCallbackType::kParameter); |
| } |
| |
| void SamplingHeapProfiler::OnWeakCallback( |
| const WeakCallbackInfo<Sample>& data) { |
| Sample* sample = data.GetParameter(); |
| AllocationNode* node = sample->owner; |
| DCHECK(node->allocations_[sample->size] > 0); |
| node->allocations_[sample->size]--; |
| sample->profiler->samples_.erase(sample); |
| delete sample; |
| } |
| |
| SamplingHeapProfiler::AllocationNode* SamplingHeapProfiler::FindOrAddChildNode( |
| AllocationNode* parent, const char* name, int script_id, |
| int start_position) { |
| for (AllocationNode* child : parent->children_) { |
| if (child->script_id_ == script_id && |
| child->script_position_ == start_position && |
| strcmp(child->name_, name) == 0) { |
| return child; |
| } |
| } |
| AllocationNode* child = new AllocationNode(name, script_id, start_position); |
| parent->children_.push_back(child); |
| return child; |
| } |
| |
| SamplingHeapProfiler::AllocationNode* SamplingHeapProfiler::AddStack() { |
| AllocationNode* node = &profile_root_; |
| |
| std::vector<SharedFunctionInfo*> stack; |
| StackTraceFrameIterator it(isolate_); |
| int frames_captured = 0; |
| while (!it.done() && frames_captured < stack_depth_) { |
| JavaScriptFrame* frame = it.frame(); |
| SharedFunctionInfo* shared = frame->function()->shared(); |
| stack.push_back(shared); |
| |
| frames_captured++; |
| it.Advance(); |
| } |
| |
| if (frames_captured == 0) { |
| const char* name = nullptr; |
| switch (isolate_->current_vm_state()) { |
| case GC: |
| name = "(GC)"; |
| break; |
| case COMPILER: |
| name = "(COMPILER)"; |
| break; |
| case OTHER: |
| name = "(V8 API)"; |
| break; |
| case EXTERNAL: |
| name = "(EXTERNAL)"; |
| break; |
| case IDLE: |
| name = "(IDLE)"; |
| break; |
| case JS: |
| name = "(JS)"; |
| break; |
| } |
| return FindOrAddChildNode(node, name, v8::UnboundScript::kNoScriptId, 0); |
| } |
| |
| // We need to process the stack in reverse order as the top of the stack is |
| // the first element in the list. |
| for (auto it = stack.rbegin(); it != stack.rend(); ++it) { |
| SharedFunctionInfo* shared = *it; |
| const char* name = this->names()->GetFunctionName(shared->DebugName()); |
| int script_id = v8::UnboundScript::kNoScriptId; |
| if (shared->script()->IsScript()) { |
| Script* script = Script::cast(shared->script()); |
| script_id = script->id(); |
| } |
| node = FindOrAddChildNode(node, name, script_id, shared->start_position()); |
| } |
| return node; |
| } |
| |
| v8::AllocationProfile::Node* SamplingHeapProfiler::TranslateAllocationNode( |
| AllocationProfile* profile, SamplingHeapProfiler::AllocationNode* node, |
| const std::map<int, Script*>& scripts) { |
| Local<v8::String> script_name = |
| ToApiHandle<v8::String>(isolate_->factory()->InternalizeUtf8String("")); |
| int line = v8::AllocationProfile::kNoLineNumberInfo; |
| int column = v8::AllocationProfile::kNoColumnNumberInfo; |
| std::vector<v8::AllocationProfile::Allocation> allocations; |
| allocations.reserve(node->allocations_.size()); |
| if (node->script_id_ != v8::UnboundScript::kNoScriptId && |
| scripts.find(node->script_id_) != scripts.end()) { |
| // Cannot use std::map<T>::at because it is not available on android. |
| auto non_const_scripts = const_cast<std::map<int, Script*>&>(scripts); |
| Script* script = non_const_scripts[node->script_id_]; |
| if (script) { |
| if (script->name()->IsName()) { |
| Name* name = Name::cast(script->name()); |
| script_name = ToApiHandle<v8::String>( |
| isolate_->factory()->InternalizeUtf8String(names_->GetName(name))); |
| } |
| Handle<Script> script_handle(script); |
| line = 1 + Script::GetLineNumber(script_handle, node->script_position_); |
| column = |
| 1 + Script::GetColumnNumber(script_handle, node->script_position_); |
| } |
| for (auto alloc : node->allocations_) { |
| allocations.push_back(ScaleSample(alloc.first, alloc.second)); |
| } |
| } |
| |
| profile->nodes().push_back(v8::AllocationProfile::Node( |
| {ToApiHandle<v8::String>( |
| isolate_->factory()->InternalizeUtf8String(node->name_)), |
| script_name, node->script_id_, node->script_position_, line, column, |
| std::vector<v8::AllocationProfile::Node*>(), allocations})); |
| v8::AllocationProfile::Node* current = &profile->nodes().back(); |
| size_t child_len = node->children_.size(); |
| // The children vector may have nodes appended to it during translation |
| // because the translation may allocate strings on the JS heap that have |
| // the potential to be sampled. We cache the length of the vector before |
| // iteration so that nodes appended to the vector during iteration are |
| // not processed. |
| for (size_t i = 0; i < child_len; i++) { |
| current->children.push_back( |
| TranslateAllocationNode(profile, node->children_[i], scripts)); |
| } |
| return current; |
| } |
| |
| v8::AllocationProfile* SamplingHeapProfiler::GetAllocationProfile() { |
| // To resolve positions to line/column numbers, we will need to look up |
| // scripts. Build a map to allow fast mapping from script id to script. |
| std::map<int, Script*> scripts; |
| { |
| Script::Iterator iterator(isolate_); |
| Script* script; |
| while ((script = iterator.Next())) { |
| scripts[script->id()] = script; |
| } |
| } |
| |
| auto profile = new v8::internal::AllocationProfile(); |
| |
| TranslateAllocationNode(profile, &profile_root_, scripts); |
| |
| return profile; |
| } |
| |
| |
| } // namespace internal |
| } // namespace v8 |