Optimize TransitEventBuffer expansion

include/quill/backend/TransitEvent.h

@@ -31,7 +31,7 @@ class LoggerBase;
 struct TransitEvent
 {
  /***/
- TransitEvent() { formatted_msg.reserve(32); }
+ TransitEvent() = default;
 
  /***/
  ~TransitEvent() = default;
@@ -81,6 +81,9 @@ struct TransitEvent
  return (macro_metadata->log_level() != LogLevel::Dynamic) ? macro_metadata->log_level() : dynamic_log_level;
  }
 
+ /***/
+ void reserve_formatted_msg(size_t capacity) { formatted_msg.reserve(capacity); }
+
  uint64_t timestamp{0};
  MacroMetadata const* macro_metadata{nullptr};
  detail::LoggerBase* logger_base{nullptr};

include/quill/backend/TransitEventBuffer.h

@@ -28,6 +28,10 @@ class TransitEventBuffer
  _storage(std::make_unique<TransitEvent[]>(_capacity)),
  _mask(_capacity - 1u)
  {
+ for (size_t i = 0; i < _capacity; ++i)
+ {
+ _storage.get()[i].reserve_formatted_msg(32);
+ }
  }
 
  TransitEventBuffer(TransitEventBuffer const&) = delete;
@@ -108,13 +112,22 @@ class TransitEventBuffer
 
  auto new_storage = std::make_unique<TransitEvent[]>(new_capacity);
 
- // Copy existing elements to the new storage
+ // Move existing elements from the old storage to the new storage.
+ // Since the buffer is full, this moves all the previous TransitEvents, preserving their order.
+ // The reader position and mask are used to handle the circular buffer's wraparound.
  size_t const current_size = size();
  for (size_t i = 0; i < current_size; ++i)
  {
  new_storage[i] = std::move(_storage[(_reader_pos + i) & _mask]);
  }
 
+ // For the new elements in the expanded buffer, reserve memory for formatted messages.
+ // This mirrors the pre-allocation done in the constructor
+ for (size_t i = current_size; i < new_capacity; ++i)
+ {
+ new_storage.get()[i].reserve_formatted_msg(32);
+ }
+
  _storage = std::move(new_storage);
  _capacity = new_capacity;
  _mask = _capacity - 1;