在Amazon EC2实例上，PHP 7比PHP5占用更多内存

I recently upgrade PHP to version 7.1 and quickly notice that the free memory left on the EC2 instance is alway 200MB less than before (using PHP version 5.4).

I run the same web application on the instance with the database bigger than before a little bit.

Did anyone encounter the same issue? And have a way to fix it?

Many thanks!