上海交通大学：《操作系统 Operating System》课程教学资源（课件讲稿）OS-cpuscheduling_Lec10

OPERATING SYSTEMS 1 龚玲 lgong@sjtu.edu.cn

OPERATING SYSTEMS 龚玲 lgong@sjtu.edu.cn 1

REVIEW o Thread issues ohttp://wenku.baidu.com/course/study/77f1dcccda38376ba flfae94#665ea0c7aa00b52acfc7ca94

REVIEW  Thread issues  http://wenku.baidu.com/course/study/77f1dcccda38376ba f1fae94#665ea0c7aa00b52acfc7ca94

Chapter 5:CPU Scheduling o Basic Concepts o Scheduling Criteria o Scheduling Algorithms o Real-Time Scheduling o Thread Scheduling o Operating Systems Examples o Java Thread Scheduling o Algorithm Evaluation

Chapter 5: CPU Scheduling  Basic Concepts  Scheduling Criteria  Scheduling Algorithms  Real-Time Scheduling  Thread Scheduling  Operating Systems Examples  Java Thread Scheduling  Algorithm Evaluation

Goals for today o Basic Concepts o Scheduling Criteria o Scheduling Algorithms

Goals for today  Basic Concepts  Scheduling Criteria  Scheduling Algorithms

Diagram of Process State new admitted interrupt exit terminated ready running 1/O or event completion scheduler dispatch 1/O or event wait waiting

Diagram of Process State

Created Terminated Main Memory Running Ready Blocked Swapped out and waiting Swapped out and blocked Page file/swap space The various process states,displayed in a state diagram,with arrows indicating possible transitions between states-as can be seen,some processes are stored in main memory,and some are stored in secondary (virtual)memory. Reference from http://en.wikipedia.org/wiki/Process_states

The various process states, displayed in a state diagram, with arrows indicating possible transitions between states - as can be seen, some processes are stored in main memory, and some are stored in secondary (virtual) memory. Ready Reference from http://en.wikipedia.org/wiki/Process_states

Process and Thread Scheduling o Process scheduling Long term scheduling Move process to Ready List (RL")after creation (When and in which order?)Decision-making policies to determine the order in which active processes should compete for the use of the CPU(s). o Dispatching o Short term scheduling Select process from Ready List to run The actual binding of a selected process to a CPU,removal from the ready queue,change of status,and loading the processor state

Process and Thread Scheduling  Process scheduling  Long term scheduling  Move process to Ready List (“RL”) after creation (When and in which order?) Decision-making policies to determine the order in which active processes should compete for the use of the CPU(s).  Dispatching  Short term scheduling  Select process from Ready List to run The actual binding of a selected process to a CPU, removal from the ready queue, change of status , and loading the processor state. 7

Basic Concepts o Maximum CPU utilization obtained with multiprogramming o CPU-I/O Burst Cycle-Process execution consists of a cycle of CPU execution and I/O wait o CPU burst distribution

Basic Concepts  Maximum CPU utilization obtained with multiprogramming  CPU–I/O Burst Cycle – Process execution consists of a cycle of CPU execution and I/O wait  CPU burst distribution

Alternating Sequence of CPU And I/O Bursts load store add store CPU burst read from file wait for l/O 1/O burst store increment index CPU burst write to file wait for l/O 1/O burst load store add store CPU burst read from file wait for l/O 1/O burst ●

Alternating Sequence of CPU And I/O Bursts

Histogram of CPU-burst Times 160 140 120 100 030 40 20 0 8 16 24 32 40 burst duration(milliseconds)

Histogram of CPU-burst Times