from the page-processing-patch-provides-performance-plus-power-perks dept.
Mark D. Hill and his peers at the University of Wisconsin-Madison have been analyzing computing systems, trying to look for delays in the architecture and the interfaces between them.
Through careful analysis, Hill uncovers inefficiencies, sometimes major ones, in the workflows by which computers operate. Recently, he investigated inefficiencies in the way that computers implement virtual memory and determined that these operations can waste up to 50 percent of a computer's execution cycles.
The inefficiencies he found were due to the way computers had evolved over time. Memory had grown a million times bigger since the 1980s, but the way it was used had barely changed at all. A legacy method called paging, that was created when memory was far smaller, was preventing processors from achieving their peak potential.
Hill designed a solution(pdf) that uses paging selectively, adopting a simpler address translation method for key parts of important applications. This reduced the problem, bringing cache misses down to less than 1 percent. In the age of the nanosecond, fixing such inefficiencies pays dividends. For instance, with such a fix in place, Facebook could buy far fewer computers to do the same workload, saving millions.