It's been reported that eZ Platform consumes a lot of memory on Redis which can't be freed when using RedisTagAwareAdapter.

Valid workaround is to use another adapter, primarily:

• RedisAdapter
• MemcachedAdapter (Memcached is known to use less memory and better handle heavy load compared to plain RedisAdapter)

However as we in general recommend using RedisTagAwareAdapter for performance (less backend lookups), there needs to be some improvements to tag usage with it, as they seem to consume a lot of memory (up to 1Gb for 100k content objects just for tags).