One of the products we use quite frequently is the FDPR-pro product available from IBM . It's one of those "magic" products which allow you to easily optimize a program after it has been compiled and linked.
The program, Feedback Directed Program Restructuring, is available for Linux on Power programs from IBM's alphaWorks web site. Last week the Haifa development team updated the download'able version with a new version - Version 5.4.0.17 - which is what caught my eye.
The official name is Post-Link Optimization for Linux on POWER, which makes for an acronym that has never really caught on - PLOLOP - and various other strange permutations. I seem to recall that the FDPR-pro name had a name conflict somewhere in the world, but that's the name I've been familiar with for years.
The post-link optimization has been used with database engine products, big ISV products, CPU intensive benchmarks and customer workloads. Borrowing shamelessly from the alphaWorks web site, this product is a performance tuning utility which can improve the execution time of user-level application programs. It does this with a multi-step process of running the program in a commonly used mode, where FDPR gathers run-time profiles and uses those profiles to modify/optimize the executable image.
The clever part is that FDPR can be made aware of cache line sizes and specific system characteristics and optimize (if desired) for execution on a particular set of systems. The daunting aspect of FDPR is the number of possible optimizations. As happens with compilers, there are lots of optimizations and areas to focus on.
Using FDPR can become a natural part of the build process of an application. Build, link, then run the extra steps needed by FDPR. FDPR is a supported product and re-structured executables can be supported in normal business commercial environments. Sometimes the performance gains are minimal, and in many cases we'll see performance gains in the 10% to 12% range. More is possible, but it really depends on the application. In rare cases the changes will cause an executable to core-dump, but we've found the team in Haifa extremely helpful and they usually are able to fix problems quickly.
A product to help with the daunting number of FDPR options is another alphaWorks product called ESTO - Expert System for Tuning Optimizations. ESTO automates the process of identifying options and tuning with FDPR for Linux on Power. As explained on the ESTO project page, the approach leverages "iterative compilation" and uses an "adaptive genetic algorithm with exponential population reduction". I have a feeling that the team that built the product description had fun listing the technologies and the approaches used.
In the near future, we're going to get some examples posted up here and on some LoP wikis.
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