Multi-IMA Partition Scheduling for Global I/O Synchronization
- 1. MULTI-IMA PARTITION SCHEDULING FOR GLOBAL I/O SYNCHRONIZATION Jung Eun Kim, Man Ki Yoon, and Lui Sha University of Illinois at Urbana-Champaign
- 2. Background • Zero-partition has been used as a special-purpose ‘I/O partition’. • In IMA, all I/O is consolidated in one zero-partition. Easy to manage. • Synchronizing challenge among zero-partitions arise, when migrating multiple single-core IMAs to a multi-core system. • Ex. Shared device and shared I/O channel • Supporting multiple rate groups is required. • Partitions may not be harmonic in general.
- 3. Background • Zero-partition has been used as a special-purpose ‘I/O partition’. • In IMA, all I/O is consolidated in one zero-partition. Easy to manage. • Synchronizing challenge among zero-partitions arise, when migrating multiple single-core IMAs to a multi-core system. • Ex. Shared device and shared I/O channel • Supporting multiple rate groups is required. • Partitions may not be harmonic in general.
- 4. Background • Zero-partition has been used as a special-purpose ‘I/O partition’. • In IMA, all I/O is consolidated in one zero-partition. Easy to manage. • Synchronizing challenge among zero-partitions arise, when migrating multiple single-core IMAs to a multi-core system. • Ex. Shared device and shared I/O channel • Supporting multiple rate groups is required. • Partitions may not be harmonic in general.
- 5. A Solution – Serialized I/O Partitions • Generate a Multi-IMA Schedule in which only one I/O partitions runs at a time. • Dedicated core (I/O core) for serializing I/O partitions • As I/O partition running, other normal partitions can run concurrently. • No application logic modification • No additional certification cost
- 6. Physical I/O vs. Device I/O • Physical I/O (P_I/O): – Physical I/O for raw data between physical environment and I/O device. – Periodically operated at each I/O device. • Device I/O (D_I/O): – Device I/O. Buffered I/O. Between I/O device and DRAM. – Scheduled as IMA partitions. (e.g., device: camera, radar, sensor….; raw data: temperature, pressure, radar signal…) • We are using zero-partition for device I/O.
- 8. Requirements on Partition Scheduling • Precedence requirements: P_I -> D_I -> processing partition -> D_O -> P_O • Only one device I/O partition can (exclusively) run at a time.* • Processing partitions on the same core must not be overlapped.
- 9. Assumptions • A partition has its own device I/O partitions. – Device I/O partitions are not shared. • Processing partition and physical I/O: strictly periodic. • Device I/O partitions: semi-periodic. – Each invocation’s offset can vary at each minor frame • Periods don’t need to be harmonic.
- 10. Partitions Schedule Generation by Constraint Programming
- 11. Problem Description • Input – Lengths of physical I/O, device I/O, and processing partitions. – Periods of those partitions. • Assume physical I/O periods are same with processing. – Relative Deadline of device output. • from the start of physical input • Output – Offsets of physical I/O, device I/O and processing partitions. • The whole multi-IMA schedule. (like a time table)
- 12. Example of Scheduled Partitions Overview
- 13. Example of Scheduled Partitions Overview
- 14. Example of Scheduled Partitions Overview
- 15. Example of Scheduled Partitions Overview
- 16. Example of Scheduled Partitions Overview
- 17. Practical Example • IMA workload example – Selectively made up from Generic Avionics Software Specification (SEI, 1990)
- 18. Practical Example • IMA workload example – Selectively made up from Generic Avionics Software Specification (SEI, 1990)
- 19. Result of Practical Example • 1 I/O Core + 2 Processing cores; Periods (core_1: 40,200,100,100,100,40; core_2: 60, 40, 100); LCM=600 (magnified) I/O core (core 0) core 1 core 2
- 20. Result of Practical Example (magnified) I/O core (core 0) core 1 core 2 • 1 I/O Core + 2 Processing cores; Periods (core_1: 40,200,100,100,100,40; core_2: 60, 40, 100); LCM=600
- 21. Extension • Can be extended to add any “non-overlapping” constraints – Ex: No simultaneous execution of • specific or all Level-A partitions, specific or all high-bandwidth partitions I/O core (core 0) core 1 core 2 Enforcement of non-overlapping between Partition 5 and Partition 8 I/O core (core 0) core 1 core 2
- 22. Summary • IMA partition scheduling for synchronized I/O partitions – Serializing on a dedicated core • Can support multiple rate groups • No application logic modification -> no additional certification cost • More issues – Multiple I/O devices • Multiple I/O partitions can be on different cores if allowed to run simultaneously. • Can achieve a higher degree of parallelism. – Inter-Partition communication • Producer-Consumer. Some partitions may not need I/O partitions. – Reassigning and relocating partitions • The minimum number of required cores. – Approximation algorithm • CP can be slow with big inputs. Needs to develop a fast heuristic algorithm.