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// Copyright 2016 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/libplatform/tracing/trace-buffer.h"
namespace v8 {
namespace platform {
namespace tracing {
TraceBufferRingBuffer::TraceBufferRingBuffer(size_t max_chunks,
TraceWriter* trace_writer)
: max_chunks_(max_chunks) {
trace_writer_.reset(trace_writer);
chunks_.resize(max_chunks);
}
TraceBufferRingBuffer::~TraceBufferRingBuffer() {}
TraceObject* TraceBufferRingBuffer::AddTraceEvent(uint64_t* handle) {
base::LockGuard<base::Mutex> guard(&mutex_);
if (is_empty_ || chunks_[chunk_index_]->IsFull()) {
chunk_index_ = is_empty_ ? 0 : NextChunkIndex(chunk_index_);
is_empty_ = false;
auto& chunk = chunks_[chunk_index_];
if (chunk) {
chunk->Reset(current_chunk_seq_++);
} else {
chunk.reset(new TraceBufferChunk(current_chunk_seq_++));
}
}
auto& chunk = chunks_[chunk_index_];
size_t event_index;
TraceObject* trace_object = chunk->AddTraceEvent(&event_index);
*handle = MakeHandle(chunk_index_, chunk->seq(), event_index);
return trace_object;
}
TraceObject* TraceBufferRingBuffer::GetEventByHandle(uint64_t handle) {
base::LockGuard<base::Mutex> guard(&mutex_);
size_t chunk_index, event_index;
uint32_t chunk_seq;
ExtractHandle(handle, &chunk_index, &chunk_seq, &event_index);
if (chunk_index >= chunks_.size()) return nullptr;
auto& chunk = chunks_[chunk_index];
if (!chunk || chunk->seq() != chunk_seq) return nullptr;
return chunk->GetEventAt(event_index);
}
bool TraceBufferRingBuffer::Flush() {
base::LockGuard<base::Mutex> guard(&mutex_);
// This flushes all the traces stored in the buffer.
if (!is_empty_) {
for (size_t i = NextChunkIndex(chunk_index_);; i = NextChunkIndex(i)) {
if (auto& chunk = chunks_[i]) {
for (size_t j = 0; j < chunk->size(); ++j) {
trace_writer_->AppendTraceEvent(chunk->GetEventAt(j));
}
}
if (i == chunk_index_) break;
}
}
trace_writer_->Flush();
// This resets the trace buffer.
is_empty_ = true;
return true;
}
uint64_t TraceBufferRingBuffer::MakeHandle(size_t chunk_index,
uint32_t chunk_seq,
size_t event_index) const {
return static_cast<uint64_t>(chunk_seq) * Capacity() +
chunk_index * TraceBufferChunk::kChunkSize + event_index;
}
void TraceBufferRingBuffer::ExtractHandle(uint64_t handle, size_t* chunk_index,
uint32_t* chunk_seq,
size_t* event_index) const {
*chunk_seq = static_cast<uint32_t>(handle / Capacity());
size_t indices = handle % Capacity();
*chunk_index = indices / TraceBufferChunk::kChunkSize;
*event_index = indices % TraceBufferChunk::kChunkSize;
}
size_t TraceBufferRingBuffer::NextChunkIndex(size_t index) const {
if (++index >= max_chunks_) index = 0;
return index;
}
TraceBufferChunk::TraceBufferChunk(uint32_t seq) : seq_(seq) {}
void TraceBufferChunk::Reset(uint32_t new_seq) {
next_free_ = 0;
seq_ = new_seq;
}
TraceObject* TraceBufferChunk::AddTraceEvent(size_t* event_index) {
*event_index = next_free_++;
return &chunk_[*event_index];
}
TraceBuffer* TraceBuffer::CreateTraceBufferRingBuffer(
size_t max_chunks, TraceWriter* trace_writer) {
return new TraceBufferRingBuffer(max_chunks, trace_writer);
}
} // namespace tracing
} // namespace platform
} // namespace v8
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