Appendix A. Getting to Know Your Hardware: A Bit of Background

     

In Chapter 1, we introduced some basic concepts relating to server hardware, concepts such as processor type, multi-processor architecture, and virtual memory to name but a few. There are lots of buzzwords and acronyms that we get bombarded with in this industry. As IT advocates, we need to see past all that and get to the core issues ”ask the key questions and get to the heart of the matter. I am sure that some of you are fluent in the ways of computer architecture, while others of you may need a little refresher course on some key elements of architectural design. When it comes to high performance computing, there is much to be gained by knowing and understanding the building blocks our systems are built on, even down to the conceptual design of the CPU cache. As we see, this can have a significant bearing on performance. Then some people ask the question, "Even if the design isn't the best , what can I do about it?" This is a salient point and needs to be addressed. The short answer in most cases is there is nothing we can do about it. It is up to the application developers to understand the data model they used to design the application and how that will be affected by the size and mapping function used to access cache lines. It is not uncommon that subsequent data records, e.g., employee records, happen to be mapped to the same cache line simply by virtue of the size of each record. This can lead to the cache being unloaded and reloaded for each data structure where a simple redesign of the data model could have meant that the data structures loaded to successive cache lines. This could save on average 200-300 CPU clock cycles every time a data structure is referenced.

This appendix is not designed to go into every facet of computer architecture but to give an overview of some key concepts starting with basic processor design and continuing through to aspects of multi-processor architecture such as non-local memory.



HP-UX CSE(c) Official Study Guide and Desk Reference
HP-UX CSE(c) Official Study Guide and Desk Reference
ISBN: N/A
EAN: N/A
Year: 2006
Pages: 434

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