operating systems for reconfigurable embedded platforms: online scheduling of real-time tasks...
TRANSCRIPT
Operating Systems for Reconfigurable Embedded Platforms: Online Scheduling of
Real-Time Tasks
-Ramkumar Shankar
Reference
2
C.Steiger, H.Walder and M.Platzner, “Operating Systems for Reconfigurable Embedded Platforms:Online Scheduling of Real-Time Tasks” ,IEEE Transactions on computers vol 53, No.11, pp. 1393-1407 Nov. 2004
Web link: http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=1336761
Outline
3
Models and Limitations Practical OS
Target Architecture OS Modules
Scheduling Real-Time Tasks Techniques for 1D and 2D model
Results, Conclusion and Future Scope
Preliminaries
4
Hardware task Digital circuit that has been preplaced and prerouted.
Functional characteristics transparent to the OS.
Structural characteristics visible to the OS. Area and timing requirements
Limitations of the area model
6
Internal Fragmentation External Fragmentation Assumes Homogeneity of the RC Device.
OS takes up some of the special resources Tasks not relocatable
Operating System Modules on CPU
10
Task Scheduler Resource Manager Task Preparation Unit Raw Task Repository COMM Driver C/R Driver
Operating System Modules on RC Device
11
Task Controller Memory Management Unit(MMU) Device Drivers OS Bridge
Scheduling Real-Time Tasks
12
Factors affecting the scheduling: arrival time, execution time, deadline Width, height
Constraints for the scheduler Scheduled tasks must not overlap in space and
time The tasks must meet the deadline
1D Horizon Technique
13
Execution list (E) Maintains tasks (Ti), Finish time(fi) and
placement(xi) Reservation List (R)
Stores all tasks scheduled but not executing Horizon List(H)
Stores the position and time step at which the units become available.
Placement Algorithms and related issues
16
Free space management Merging free spaces in Horizon Technique. Mimic future tasks for Stuffing Technique.
Strip Packing Scheduling tasks for 2D mesh – very costly
Conclusion and Further Work
19
Design issues for RC Hardware operating system.
Scheduling techniques for 1D and 2D area models
Scheduling tasks for non-real time systems Tasks with unknown execution times Tasks without deadlines Periodic tasks