A delay composition theorem for real-time pipelines

Praveen Jayachandran, Tarek Abdelzaher

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Uniprocessor schedulability theory made great strides, in part, due to the simplicity of composing the delay of a job from the execution times of higher-priority jobs that preempt it. In this paper, we bound the end-to-end delay of a job in a multistage pipeline as a function of higher-priority job execution times on different stages. We show that the end-toend delay is bounded by that of a single virtual "bottleneck" stage plus a small additive component. This contribution effectively transforms the pipeline into a single stage system. The wealth of schedulability analysis techniques derived for uniprocessors can then be applied to decide the schedulability of the pipeline. The transformation does not require imposing artitifical per-stage deadlines, but rather models the pipeline as a whole and uses the end-to-end deadlines directly in the single-stage analysis. It also does not make assumptions on job arrival patterns or periodicity and thus can be applied to periodic and aperiodic tasks alike. We show through simulations that this approach outperforms previous pipeline schedulability tests except for very short pipelines or when deadlines are sufficiently large. The reason lies in the way we account for execution overlap among stages. We discuss how previous approaches account for overlap and point out interesting differences that lead to different performance advantages in different cases. We hope that the pipeline delay composition rule, derived in this paper, may be a step towards a general schedulability analysis foundation for large distributed systems.

Original languageEnglish (US)
Title of host publicationProceedings - 19th Euromicro Conference on Real-Time Systems, ECRTS 2007
Number of pages10
StatePublished - Oct 23 2007
Event19th Euromicro Conference on Real-Time Systems, ECRTS 2007 - Pisa, Italy
Duration: Jul 4 2007Jul 6 2007

Publication series

NameProceedings - Euromicro Conference on Real-Time Systems
ISSN (Print)1068-3070


Other19th Euromicro Conference on Real-Time Systems, ECRTS 2007

ASJC Scopus subject areas

  • Software
  • Hardware and Architecture


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