I'm using wp_insert_post in a loop to insert 500 posts in a new WP install. It works quickly, and memory usage is from 25M to 28M. The next run of a second batch of 500 posts, takes the memory from 25M to 178M. So the memory usage seems to be based on how many posts are already in the table. A third run of 500 posts exhausts the available memory. What is being stored to increase the memory that I can cleanup?