1、操作系統(tǒng)操作系統(tǒng)Chapter10-OSChapter10-OS多處理器調(diào)多處理器調(diào)度和實(shí)時(shí)調(diào)度度和實(shí)時(shí)調(diào)度210.1 Multiprocessor Scheduling -Classifications of Multiprocessor SystemsMultiprocessor systems : 包含兩個(gè)或更多處理器的計(jì)算機(jī)系統(tǒng)Loosely coupled or distributed multiprocessor, or cluster (集群系統(tǒng))l Each processor has its own memory and I/O channelsFunctionally sp

2、ecialized processors (Master Slave)l Such as I/O processorl Controlled by a master processorTightly coupled multiprocessing(緊密耦合)l Processors share main memory l Controlled by operating system1. 執(zhí)行機(jī) 310.1 Multiprocessor Scheduling -10.1.1 ParallelismIndependent ParallelismCoarse and Very Coarse-Grai

3、ned ParallelismMedium-Grained ParallelismFine-Grained Parallelism4Independent Parallelism Separate application or job No synchronization among processes Example is time-sharing system5Coarse and Very Coarse-Grained Parallelism Synchronization among processes at a very gross level Good for concurrent

4、 processes running on a multiprogrammed uniprocessor Can by supported on a multiprocessor with little change6Medium-Grained Parallelism Single application is a collection of threads Threads usually interact frequently7Fine-Grained Parallelism Highly parallel applications Specialized and fragmented a

5、rea810.1 Multiprocessor Scheduling -10.1.2 Scheduling Assignment of processes to processors Use of multiprogramming on individual processors Actual dispatching of a process9 Assignment of Processes to Processors Treat processors as a pooled resource and assign process to processors on demand Permane

6、ntly assign process to a processor Dedicate short-term queue for each processor Processor could be idle while another processor has a backlog10 Assignment of Processes to Processors Global queue Schedule to any available processor Master/slave architecture Key kernel functions always run on a partic

7、ular processor Master is responsible for scheduling Slave sends service request to the master Disadvantages Failure of master brings down whole system Master can become a performance bottleneck Peer architecture Each processor does self-scheduling Complicates the operating system Make sure two proce

8、ssors do not choose the same process11 Use of multiprogramming on individual processors 粗粒度或無約束同步粒度(傳統(tǒng)多處理器)，能進(jìn)行進(jìn)程間切換。 中等粒度 平均性能更重要1210.1.3 Process Scheduling 雙CPU系統(tǒng)中，進(jìn)程采用各種調(diào)度算法比較，系統(tǒng)吞吐量的變換很小。 對(duì)于多CPU系統(tǒng)，調(diào)度算法的選擇不像在單處理器中那種重要。 1310.1.4 Thread Scheduling Executes separate from the rest of the process An ap

9、plication can be a set of threads that cooperate and execute concurrently in the same address space Threads running on separate processors yields a dramatic gain in performance14Multiprocessor Thread Scheduling Load sharing Processes are not assigned to a particular processor Gang scheduling A set o

10、f related threads is scheduled to run on a set of processors at the same time Dedicated processor assignment Threads are assigned to a specific processor Dynamic scheduling Number of threads can be altered during course of execution15 Load Sharing Load is distributed evenly across the processors No

11、centralized scheduler required Use global queues16Disadvantages of Load Sharing Central queue needs mutual exclusion May be a bottleneck when more than one processor looks for work at the same time Preemptive threads are unlikely resume execution on the same processor Cache use is less efficient If

12、all threads are in the global queue, all threads of a program will not gain access to the processors at the same time17 Gang Scheduling Simultaneous scheduling of threads that make up a single process Useful for applications where performance severely degrades when any part of the application is not

13、 running Threads often need to synchronize with each other18Scheduling Groups19 Dedicated Processor Assignment When application is scheduled, its threads are assigned to a processor Some processors may be idle No multiprogramming of processors20 Dynamic Scheduling Number of threads in a process are

14、altered dynamically by the application Operating system adjust the load to improve utilization Assign idle processors New arrivals may be assigned to a processor that is used by a job currently using more than one processor Hold request until processor is available Assign processor a jog in the list

15、 that currently has no processors (i.e., to all waiting new arrivals)2110.2 Real-Time Systems Tasks or processes attempt to control or react to events that take place in the outside world These events occur in “real time” and tasks must be able to keep up with them Correctness of the system depends

16、not only on the logical result of the computation but also on the time at which the results are produced2210.2 Real-Time Systems Control of laboratory experiments Process control in industrial plants Robotics Air Traffic control ESP (Electronic Stablity Program ) Telecommunications Military command

17、and control systems23Characteristics of Real-Time Operating Systems Deterministic Operations are performed at fixed, predetermined times or within predetermined time intervals Concerned with how long the operating system delays before acknowledging an interrupt and there is sufficient capacity to ha

18、ndle all the requests within the required time24Characteristics of Real-Time Operating Systems Responsiveness How long, after acknowledgment, it takes the operating system to service the interrupt Includes amount of time to begin execution of the interrupt Includes the amount of time to perform the interrupt Effect of interrupt nesting25Characteristics of Real-Time Operating Systems User control User specifies priority Specif