1 // Copyright 2016 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/libplatform/tracing/trace-buffer.h"
6
7 namespace v8 {
8 namespace platform {
9 namespace tracing {
10
TraceBufferRingBuffer(size_t max_chunks,TraceWriter * trace_writer)11 TraceBufferRingBuffer::TraceBufferRingBuffer(size_t max_chunks,
12 TraceWriter* trace_writer)
13 : max_chunks_(max_chunks) {
14 trace_writer_.reset(trace_writer);
15 chunks_.resize(max_chunks);
16 }
17
~TraceBufferRingBuffer()18 TraceBufferRingBuffer::~TraceBufferRingBuffer() {}
19
AddTraceEvent(uint64_t * handle)20 TraceObject* TraceBufferRingBuffer::AddTraceEvent(uint64_t* handle) {
21 base::LockGuard<base::Mutex> guard(&mutex_);
22 if (is_empty_ || chunks_[chunk_index_]->IsFull()) {
23 chunk_index_ = is_empty_ ? 0 : NextChunkIndex(chunk_index_);
24 is_empty_ = false;
25 auto& chunk = chunks_[chunk_index_];
26 if (chunk) {
27 chunk->Reset(current_chunk_seq_++);
28 } else {
29 chunk.reset(new TraceBufferChunk(current_chunk_seq_++));
30 }
31 }
32 auto& chunk = chunks_[chunk_index_];
33 size_t event_index;
34 TraceObject* trace_object = chunk->AddTraceEvent(&event_index);
35 *handle = MakeHandle(chunk_index_, chunk->seq(), event_index);
36 return trace_object;
37 }
38
GetEventByHandle(uint64_t handle)39 TraceObject* TraceBufferRingBuffer::GetEventByHandle(uint64_t handle) {
40 base::LockGuard<base::Mutex> guard(&mutex_);
41 size_t chunk_index, event_index;
42 uint32_t chunk_seq;
43 ExtractHandle(handle, &chunk_index, &chunk_seq, &event_index);
44 if (chunk_index >= chunks_.size()) return nullptr;
45 auto& chunk = chunks_[chunk_index];
46 if (!chunk || chunk->seq() != chunk_seq) return nullptr;
47 return chunk->GetEventAt(event_index);
48 }
49
Flush()50 bool TraceBufferRingBuffer::Flush() {
51 base::LockGuard<base::Mutex> guard(&mutex_);
52 // This flushes all the traces stored in the buffer.
53 if (!is_empty_) {
54 for (size_t i = NextChunkIndex(chunk_index_);; i = NextChunkIndex(i)) {
55 if (auto& chunk = chunks_[i]) {
56 for (size_t j = 0; j < chunk->size(); ++j) {
57 trace_writer_->AppendTraceEvent(chunk->GetEventAt(j));
58 }
59 }
60 if (i == chunk_index_) break;
61 }
62 }
63 trace_writer_->Flush();
64 // This resets the trace buffer.
65 is_empty_ = true;
66 return true;
67 }
68
MakeHandle(size_t chunk_index,uint32_t chunk_seq,size_t event_index) const69 uint64_t TraceBufferRingBuffer::MakeHandle(size_t chunk_index,
70 uint32_t chunk_seq,
71 size_t event_index) const {
72 return static_cast<uint64_t>(chunk_seq) * Capacity() +
73 chunk_index * TraceBufferChunk::kChunkSize + event_index;
74 }
75
ExtractHandle(uint64_t handle,size_t * chunk_index,uint32_t * chunk_seq,size_t * event_index) const76 void TraceBufferRingBuffer::ExtractHandle(uint64_t handle, size_t* chunk_index,
77 uint32_t* chunk_seq,
78 size_t* event_index) const {
79 *chunk_seq = static_cast<uint32_t>(handle / Capacity());
80 size_t indices = handle % Capacity();
81 *chunk_index = indices / TraceBufferChunk::kChunkSize;
82 *event_index = indices % TraceBufferChunk::kChunkSize;
83 }
84
NextChunkIndex(size_t index) const85 size_t TraceBufferRingBuffer::NextChunkIndex(size_t index) const {
86 if (++index >= max_chunks_) index = 0;
87 return index;
88 }
89
TraceBufferChunk(uint32_t seq)90 TraceBufferChunk::TraceBufferChunk(uint32_t seq) : seq_(seq) {}
91
Reset(uint32_t new_seq)92 void TraceBufferChunk::Reset(uint32_t new_seq) {
93 next_free_ = 0;
94 seq_ = new_seq;
95 }
96
AddTraceEvent(size_t * event_index)97 TraceObject* TraceBufferChunk::AddTraceEvent(size_t* event_index) {
98 *event_index = next_free_++;
99 return &chunk_[*event_index];
100 }
101
CreateTraceBufferRingBuffer(size_t max_chunks,TraceWriter * trace_writer)102 TraceBuffer* TraceBuffer::CreateTraceBufferRingBuffer(
103 size_t max_chunks, TraceWriter* trace_writer) {
104 return new TraceBufferRingBuffer(max_chunks, trace_writer);
105 }
106
107 } // namespace tracing
108 } // namespace platform
109 } // namespace v8
110