Standard monitoring tools and web application middleware offer very limited support for detailed performance analysis of HTTP request-based, multi-tier web applications. They measure resource usage system-wide or per command name, but are unable to isolate usage per action specific to the target application. This inablity has several causes: first, many HTTP requests are executed by one application or script concurrently, making it hard to isolate them, and second, different types of actions are often handled by one application or script, hindering type-based distinction. Moreover, SQL queries, a common cause of web applications performance problems, cannot be backtracked to the HTTP request that triggered them. As a result, debugging performance problems of web applications is hard and requires time and effort of highly-skilled people. This paper describes mBrace, a work-in-progress effort that takes advantage of the hardware performance monitoring unit and uses minimal system and framework instrumentation in order to provide efficient and request-based performance analysis of multi-tier web applications.