In this paper we present the design of SvPablo, a language independent performance analysis and visualization system that can be easily extended to new contexts with minimal changes to the software infrastructure. At present, SvPablo supports analysis of applications written in C, Fortran 77, Fortran 90, and HPF on a variety of sequential and parallel systems. In addition to capturing application data via software instrumentation, SvPablo also exploits hardware performance counters to capture the interaction of software and hardware. Both hardware and software performance data are summarized during program execution, enabling measurement of programs that execute for hours or days on hundreds of processors. This performance data is stored in a format designed to be language transparent and portable. We demonstrate the usefulness of SvPablo for tuning application programs with a case study running on an SGI Origin 2000.