I am experimenting Admission control to handle memory spikes in clusters. I have created a pool with query memory limit. Had come to know that Admission control doesn't take queries current usage into account while admitting any new query. Because of this, though some queries doesn't require more memory also has been set with pool level query memory limit. Hence, though memory is available in cluster, still admission control is not allowing any new queries because it does calculation based on no. of queries * query mem limit pool level <= pool limit.
Whereas, If I don't set query mem limit for the pool, it allows more no. of simple queries as their estimated memory usage is less.