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Details of the Real Time Linux Foundation Working Group Project

OSADL Project: Real Time Linux Workshops

Real Time Linux Foundation Workshops since 1999

Real Time Linux Workshops

1999 - 2000 - 2001 - 2002 - 2003 - 2004 - 2005 - 2006 - 2007 - 2008 - 2009 - 2010

Eighth Real-Time Linux Workshop on October 12 to 15, 2006, in Lanzhou, Gansu, P.R.China

Worst Case Behavior of CPU Caches

Tobias John and Robert Baumgartl
Chemnitz University of Technology
09107 Chemnitz, Germany
tobias.johnªcs.tu-chemnitz.de
robert.baumgartlªcs.tu-chemnitz.de

CPU caches reduce main memory access times and thereby speed up execution timing and significantly improve performance. Various cache architectures with different strategies and mechanisms have been developed. However, caches have a negative impact on execution timing predictability which is crucial in real-time systems. A precise understanding of available cache architectures is therefore essential. Although IA32 processors share a common instruction set, their CPU cache architectures differ significantly. Therefore, we describe in this paper a methodology for the construction of realistic worst cases for CPU caching. We compare and evaluate several IA32 processors with respect to efficiency and predictability of execution timing. Our methodology incorporates RTAI and the usage of Performance Monitoring Registers and generates very precise results in comparison to indirectly measuring execution times by counting clock cycles. Nonetheless our micro benchmarks are easily extendable and adaptable.

 

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