presto-main/src/main/java/io/prestosql/execution/scheduler/SqlQueryScheduler.java/SqlQueryScheduler/getTotalMemoryReservation
class SqlQueryScheduler:    public long getTotalMemoryReservation()
    {
        return stages.values().stream()
                .mapToLong(SqlStageExecution::getTotalMemoryReservation)
                .sum();
    }