Performance counters are very useful in performance profiling because the limitation of software profiling. Therefore they are available in most of modern high-end processors. As the performance requirement of embedded systems growing up, it's necessary to design performance counters for embedded processors.
This is performance counter for Xilinx microblaze processor. It's connected to processor via FSL bus. A driver library is available for easy use. It's also integrated into Soft Multiprocessor on FPGA project http://opencores.orgproject,mpdma,overview so that it can be automatically inserted in designing.
2007/09/06 v0.1 Support wall-clock counting for Microblaze processor