Query performance is an important part of the performance of reporting services. The majority of slow performance problems when working with reporting are slow-performing queries.

If you are querying large amounts of data, run your query through Database Engine Tuning Advisor with SQL Management Studio to see whether any improvements can be made. This is highly recommended if you are executing your own queries against the database. It will ensure the health of the database is maintained and the response times are as accurate as possible.