任务执行时间 AET Deadline d (Actual Execution Time) slack Computation time Period (2) 1) Task Task ■■■■■■■■■■■■ 0 Deadline=Period BCET (Best Case Execution TimeWCET (Worst Case Execution Time) ·BCET Static analysis Measurements gives safe timing values! ·WCET might miss the longest time! possible program execution times time
任务执行时间 • BCET • WCET
Types of Jitter:原因？ Finishing-time Jitter Ti f Start-time Jitter Completion-time Jitter (1/O Jitter) 三6I 571 05 05 constant const也nt constant service unit execution tme constant service unlt execution time constant servioe untt Interrupt interrupt servlced serviced Task 2 OS Task 3 os Task 1 nterrup时c珠◆nct c intemupt clk ck c靠 cK Intemupt gate ungate gate ungate gate ungate gate ungate
Types of Jitter：原因？
precedence graph,task graphs Independent Periodic jobs (0,7J (2J (4,11 (6,13) (8,15] P=2,D=7 0 0 0 0 0 Feasible (5,8 (8,11] Periodic jobs,dependent intervals (2,5] (11,14] (14,17] Q 0 o on immediate predecessor 9p=2,p=3,D=3 (0,5] (4,8 (5,20] Conditional block 0---0 branch (0,6] Jobs with AND complex dependencies (2,10] 2/30R 1/2 Producer-Consumer 三类：chains、intree(AND/OR)、outtree(branch) 顺序依赖边（偏序）、数据依赖边、时间依赖边
precedence graph，task graphs • 三类：chains、intree(AND/OR)、outtree(branch) • 顺序依赖边（偏序）、数据依赖边、时间依赖边
maintained by RTOS 专每年人 Task Control Block relative deadline D; task identifier task address a 4 task type absolute deadline criticalness response time Ri (d=a:+R) prionty ∩Deadline d state computation time period Computation time Period relative deadline absolute deadline BLOCKED utilization factor signal wait context pointer dispatching precedence pointer activation termination READY RUNNING resource pointer preemption pointer to the next TCB ACTIVE
maintained by RTOS
Task scheduling e》 0 逐一调度并发任务执行，满足约束条件 一功能：排序、定时、分配（单处理器、多处理器、 多核) activation dispatching termination Execution scheduling preemption Thread ID Starting Address Task Parameters Thread Context Task Type rejection Priority queues Phase Acceptance Scheduling Period Sporadic Information Jobs Test Relative Deadline Synchronization Number of Instances Information Periodic Time Usage Event List Jobs Processor Information Timer Information TCB Aperiodic Other Information Jobs
Task scheduling • 逐一调度并发任务执行，满足约束条件 – 功能：排序、定时、分配（单处理器、多处理器、多核） TCB Priority queues