Web services solutions are being increasingly adopted in enterprise systems. However, ensuring the quality of service of Web services applications remains a costly and complicated performance engineering task. Some of the new challenges include limited controls over consumers of a service, unforeseeable operational scenarios and vastly different XML payloads. These challenges make existing manual performance analysis and benchmarking methods difficult to use effectively. This paper describes an approach for generating customized benchmark suites for Web services applications from a software architecture description following a Model Driven Architecture (MDA) approach. We have provided a performance-tailored version of the UML 2.0 Testing Profile so architects can model a flexible and reusable load testing architecture, including test data, in a standards compatible way. We extended our MDABench [27] tool to provide a Web service performance testing "cartridge" associated with the tailored testing profile. A load testing suite and automatic performance measurement infrastructure are generated using the new cartridge. Best practices in Web service testing are embodied in the cartridge and inherited by the generated code. This greatly reduces the effort needed for Web service performance benchmarking while being fully MDA compatible. We illustrate the approach using a case study on the Apache Axis platform.