Real-time I/O management system with COTS peripherals

Emiliano Betti, Stanley Bak, Rodolfo Pellizzoni, Marco Caccamo, Lui Sha

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


Real-time embedded systems are increasingly being built using commercial-off-the-shelf (COTS) components such as mass-produced peripherals and buses to reduce costs, time-to-market, and increase performance. Unfortunately, COTS-interconnect systems do not usually guarantee timeliness, and might experience severe timing degradation in the presence of high-bandwidth I/O peripherals. Moreover, peripherals do not implement any internal priority-based scheduling mechanism, hence, sharing a device can result in data of high priority tasks being delayed by data of low priority tasks. To address these problems, we designed a real-time I/O management system comprised of 1) real-time bridges with I/O virtualization capabilities, and 2) a peripheral scheduler. The proposed framework is used to transparently put the I/O subsystem of a COTS-based embedded system under the discipline of real-time scheduling, minimizing the timing unpredictability due to the peripherals sharing the bus. We also discuss computing the maximum delay due to buffered I/O data transactions as well as determining the buffer size needed to avoid data loss. Finally, we demonstrate experimentally that our prototype real-time I/O management system successfully exports multiple virtual devices for a single physical device and prioritizes I/O traffic, guaranteeing its timeliness.

Original languageEnglish
Article number6051430
Pages (from-to)45-58
Number of pages14
JournalIEEE Transactions on Computers
Issue number1
StatePublished - 2013
Externally publishedYes


  • COTS
  • Linux
  • Real-time
  • bus
  • input/output
  • peripheral
  • scheduling


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