I recently had to delete and recreate an NFS directory to shrink its size after it had previously bloated. In the process, I found a fairly efficient way to do this using rsync and hard links. This method avoids copying the actual files, while still accomplishing the goal of recreating the directory with the same contents.
Since we needed to take downtime to do this operation during our maintenance window, making the rebuilt directory available as soon as possible was important for us. If simplicity is more important to you, change the first move command to an 'rm -rf' on the source directory, and skip the other 'rm -rf' command.
I extracted these commands from a larger process, and abstracted the directory names, so apologies if I've made a mistake in that translation.
rsync -ai --delete --link-dest=/path/to/source_dir/ /path/to/source_dir/ /tmp/holding_dir/
mv /path/to/source_dir/ /tmp/deleteme/
mv /tmp/holding_dir/ /path/to/source_dir/
Then later, we remove the directory. Depending on size, you may need to use a more sophisticated technique to do this. For example, using rsync with the --delete flag to sync an empty directory into this directory may be more efficient.
rm -rf /tmp/deleteme/