IBM Updates Performance Guide For Latest Power10 Iron
May 1, 2023 Timothy Prickett Morgan
No matter what system you are talking about, no matter what kind of applications you are running, there are always ways to squeeze more performance out of the system. The IBM i platform running atop Power10 and earlier processors is no exception, and to that end, for several years now Big Blue has provided some guidance on pushing performance with each new CPU family and as new features are added to the OS/400 and IBM i software stack.
The latest such update, according to Steve Will, chief architect of the IBM i platform, has just been published, and you can get your copy of this at this link right here. There are some knobs and dials for system performance tuning that you may not be aware of, and in fact, I learned about a few of them in this latest update, IBM Power10 Performance Optimization for IBM i, which was put together by the development team and performance team for the IBM i platform as well as people who work for IBM’s Technology Expert Labs, which we did not know even existed. We are not certain how this relates to the Lab Services organization that has existed in many different forms and names within what used to be Server Group and then Systems group over the decades. (We will try to sort it out.)
The most interesting ones, and we did not know this, is that there is a feature called Licensed Internal Code Options (LICOPTs) that bypass the homogeneity principle of the Technology Independent Machine Interface, an intermediate hardware abstraction that is one of the hallmarks of the AS/400 architecture, that allows for code to be tuned specifically for a particular processor in the Power Systems product line. The idea is that compatibility and portability are maintained, but specific information about clock speeds, cache sizes, and other factors relevant to a particular CPU model used in a specific machine are maximized such that the performance of applications are pushed to their limits. Moreover, there are a superset of performance features called Adaptive Code Generation, that can help push performance.
There are other optimizations that programmers pushing the performance envelope need to consider as they opt to use Single-Level Storage, which is another of the architectural hallmarks of the AS/400 design, or the more modern Teraspaces storage model, which creates large temporary spaces outside of Single-Level Storage that a particular application can use by which do not persist as objects do across memory, disk, and flash configured as Single-Level Storage. (See this link for more on the two different kinds of storage available in the modern IBM i architecture.)
The document also outlined how to optimize applications running in the PASE AIX runtime environment that has been embedded inside of OS/400 and IBM i since V4R5 launched in June 2000, and also provides some tips about how to make use of the vector and matrix math engines available in the Power10 chip. There are also pointers to resources to help companies tune the performance of the Db2 for i database and the SQL queries that are used to access information stored within it. We found it interesting that Db2 Symmetric Multiprocessing, which speeds up SQL queries by running them across many processors and threads, as well as Db2 Multisystem, which allows the database to scale across multi-node Power System machines running IBM i, still exist as options with IBM i 7.5. No one talks much about these features, but they were ground-breaking when they were announced decades ago and they are still useful in extreme cases. (It is probably time to talk to Scott Forstie and get an update on these features, in fact.)
If you are one of the lucky IBM i customers who has far more oomph in your system than you can use, then you don’t have to worry about any of the tips and tricks included in the IBM Power10 Performance Optimization for IBM i document. Hooray for you! And if you are having issues, this performance guide won’t solve all of your problems, but will help you to shape how you can attack performance problems as they crop up. It is a valuable starting point if things are going wrong or you need to wring every clock of performance out of your machine.
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