src/mongo/util contains a number of files owned by different teams. Some of them could reasonably be split into different subdirectories to clean up the code ownership situation. blake.oler@mongodb.com suggested these two options, but it could be split in a variety of ways:

util/
util/query/
util/query/execution
util/query/optimization
util/workload_scheduling/
util/security/

util_query/
util_query/execution
util_query/optimization
util_workload_scheduling
util_security