Changing the stack size and memtable space

Some Solr users have reported that increasing the stack size improves performance under Apache Tomcat®. To increase the stack size, uncomment and modify the default -Xss256k setting in the cassandra-env.sh file. Also, decreasing the memtable space to make room for Solr caches might improve performance. Modify the memtable space using the memtable_heap_space_in_mb and memtable_offheap_space_in_mb properties in the cassandra.yaml file.