Dr. Dobb's Journal - September 2008 - (Page 53)

d09levent_p3db 7/14/08 10:07 AM Page 53 own timer. In the best mix run, a total of 23 percent improvement on aggregate elapsed time was achieved. But if again: TLn.>…> TL(i-1) > TLi >…>TL1 then starting Ln first gives the worst aggregate elapsed time response. The explanation to this is that Ln will take all the available cores and yet still finish last, so that other benchmarks will start with a low number of threads and will complete without having a chance to increase their thread count. This is the only condition where a traditional (oversubscription) framework will out-perform the proposed framework. It was also noted that the more loaded the system or the longer the applications ran (higher iteration count), the better the aggregate performance. The dynamic nature of the framework can be analyzed by the Intel Thread Profiler. The load governor uses a basic metric—processor idle time—to compute system utilization Figure 5 shows the Thread Profiler analysis of one of the benchmarks during the test run. One can easily see that OpenMP worker threads were increased every time more processors became available. Conclusion Many applications are becoming demanding in how they use processor resources to take advantage of parallelism. However, these applications are not aware of the other applications running alongside them on the same system. Clearly, the lack of systemwide knowledge hinders not only the applications’ performance but also the overall system performance. This framework showed that with a very basic metric and feedback mechanism, overall performance of the applications can be significantly improved. While the described lightweight framework is easy to implement and to take advantage of, it has some aspects that need improvement. Therefore, further study is needed on how to eliminate the dependency on the execution order of the applications. This can be solved by letting the load governor keep some state information about the thread usage of applications and their timing. In this manner, rather than merely increasing their thread count, applications can also decrease the number of threads they use. DDJ Get data right AddressObject API Prevent errors before they occur to ensure the integrity of your database. Use AddressObject API to verify, cleanse and format customer data at the point of entry or in batch. Address Object easily integrates with Perl, PHP Java and .NET. , - offering a better way to build-in data validation. right from the start Get a FREE demo at: MelissaData.com/dobbs 1.800.MELISSA 53 September 2008 l www.ddj.com l Dr. Dobb’s Journal http://www.abxsoft.com http://www.abxsoft.com http://MelissaData.com/dobbs http://MelissaData.com/dobbs http://www.ddj.com

Table of Contents Feed for the Digital Edition of Dr. Dobb's Journal - September 2008

Dr. Dobb's Journal - September 2008 Contents Friday Night Fish Fry Alia Vox Developer Diaries Developer’s Notebook A Conversation With Erik Demaine Application Lifecycle Management Meets Model-Driven Development Building a Robust Development Environment Real Users Really Matter Matching Wildcards: An Algorithm The Android Mobile Phone Platform Managing Application Thread Use Signalling Integer Overflows in Java .NET Development & the IBM WebSphere Portal Server The Agile Edge Effective Concurrency Swaine’s Flames

Dr. Dobb's Journal - September 2008

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