The first thing to do is to make sure you have the latest version of the module, as I'm constantly improving it to reduce memory consumption, both on the database side and on the hard disk.
The second thing is to run a purge periodically (every 2 or 3 days). A purge removes the cache of pages that no longer exist or whose context no longer exists. This does not affect cache performance. You can perform a purge manually via a button under the cache statistics table, or by scheduling a CRON task with the URL displayed in the "API (CRON URLs)" menu of the module configuration.
Finally, if there are directories in /var/cache/pagecache ending in "please_delete_me", you can delete them. These are old caches that PHP was unable to delete completely (too long).