/**
 * Logs a message with the given type and category.
 * If [[traceLevel]] is greater than 0, additional call stack information about
 * the application code will be logged as well.
 * @param string|array $message the message to be logged. This can be a simple string or a more
 * complex data structure that will be handled by a [[Target|log target]].
 * @param integer $level the level of the message. This must be one of the following:
 * `Logger::LEVEL_ERROR`, `Logger::LEVEL_WARNING`, `Logger::LEVEL_INFO`, `Logger::LEVEL_TRACE`,
 * `Logger::LEVEL_PROFILE_BEGIN`, `Logger::LEVEL_PROFILE_END`.
 * @param string $category the category of the message.
 */
public function log($message, $level, $category = 'application')
{
 $time = microtime(true);
 $traces = [];
 if ($this->traceLevel > 0) {
  $count = 0;
  $ts = debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS);
  array_pop($ts); // remove the last trace since it would be the entry script, not very useful
  foreach ($ts as $trace) {
   if (isset($trace['file'], $trace['line']) && strpos($trace['file'], YII2_PATH) !== 0) {
    unset($trace['object'], $trace['args']);
    $traces[] = $trace;
    if (++$count >= $this->traceLevel) {
     break;
    }
   }
  }
 }
 
 // 这里是造成内存的罪魁祸首
 $this->messages[] = [$message, $level, $category, $time, $traces];
 if ($this->flushInterval > 0 && count($this->messages) >= $this->flushInterval) {
  $this->flush();
 }
}

\Yii::getLogger()->flushInterval = 100; // 设置成一个较小的值

\Yii::getLogger()->flush(true); // 参数传 true 表示每次都会将 message 清理到磁盘中