JPH0460843A - Task scheduling system for multiprocessor system - Google Patents

Abstract

PURPOSE:To enable flexible system configuration by preparing plural task schedulers having respectively various algorithms as task schedulers and allocating each processor of a multiprocessor to any one of the plural task schedulers. CONSTITUTION:On a main storage device 1, plural executable task groups 101 is present. Task schedulers 2 select the tasks to be executed by respective processors 3a-3c of the multiprocessor and for the respective processors 3a-3c, respectively intrinsic task schedulers 2a-2c are allocated. The respective processors 3a-3c process the tasks selected by the task schedulers 2a-2c allocated to the respective processors. Thus, while preventing overhead from being increased, the efficient multiprocessor system can be realized and th system can be operated flexibly corresponding to work forms.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a task scheduling method for a multiprocessor system, and particularly to a task scheduling method suitable for reducing task scheduling overhead in a multiprocessor.

[Conventional technology]

FIG. 7 shows a conceptual diagram of a task scheduling method in a conventional tightly coupled multiprocessor system. 1 is a main storage device 1 in which a plurality of executable task groups 101 exist. 2 is a task scheduler 3a that selects tasks on the main storage device 1;

3b and 3c are processors that execute tasks selected by the task scheduler 2. Actually, the task scheduler 2 is also prepared on the main storage device 1, and is used exclusively among the plurality of processors 3a, 3b, and 3a. Respective processors 3a, 3b.

When a task switch factor occurs in the task assigned to task 3c, control is passed to the task scheduler 2, which selects the next executable task on the processor. FIG. 8 shows an example of the configuration of the algorithm for task schedule 2.

The task scheduler of conventional multiprocessor systems performs tasks such as priority selection, detection of tasks that have not been selected for a long time, and detection of tasks that are using resources unreasonably, using a system-specific program shared among processors. What was the method to achieve this?

In addition, if the dedicated instructions such as vector operations that can be executed or the input/output instructions that can be used are different for each processor, at the time of task scheduling, the task that is being selected on the processor currently running the task scheduler may be Scheduling was performed by determining whether a task was executable or not based on information set in a task control block or the like.

Note that examples related to this type of tightly coupled multiprocessor task control include, for example, Japanese Patent Publication No. 63-61699.

[Problem to be solved by the invention]

In the above conventional technology, the program that performs task scheduling is shared among multiple processors, so in order to build a general-purpose operating system, priority scheduling, detection of tasks that have not been selected for a long time,
It was necessary to simultaneously detect tasks that were occupying resources unfairly.

Furthermore, in cases where usable vector calculation processors and input/output devices differ from processor to processor, it is necessary to determine whether the task can be executed at the time of scheduling. Due to these factors, there is a problem in that the task scheduling process becomes complicated, leading to an increase in overhead. Particularly in multiprocessor systems, since task scheduling processing is executed exclusively, the increase in overhead has been an important problem.

An object of the present invention is to provide a task scheduling method that solves the above problems and realizes an efficient multiprocessor system.

Another object of the present invention is to provide a task scheduling method that enables flexible system configuration by easily changing the assignment of task schedulers to each processor.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a plurality of task schedulers each having a different algorithm as a task scheduler that selects a task to be executed by each processor in a multiprocessor system. , so that it can be assigned to one of multiple task schedulers.

(Function) Each processor in the multiprocessor sequentially processes the ready queue of executable tasks on the main memory using the task scheduler assigned to each processor.Each task scheduler uses a different algorithm. Therefore, by providing each task scheduler with an algorithm that complements each other, the overhead of each task scheduler can be kept small, while the multiprocessor as a whole can have a general-purpose task scheduling function. can be realized.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a conceptual diagram of the task scheduling method of the present invention. A plurality of executable task groups 10 are stored on the main memory 1.
1 exists. The task scheduler 2 selects a task to be executed by each processor 3a, 3b, 3c of the multiprocessor.
Each has its own task scheduler 2a, 2b.
, 2c are assigned. In addition, task scheduler 2
Although a, 2b, and 2c are actually prepared on the main storage device 1, they are extracted from the main storage device 1 and shown here for ease of understanding.

Each processor 3a, 3b, 3c has a task scheduler 2a, 2b, 2 assigned to each processor.
Process the task selected by c.

The task schedulers 2a, 2b, and 2c each have a different algorithm, as shown in FIG. 2, and execute relatively few processing steps. Here, the respective task schedulers 2a and 2b.

By providing 2c with mutually complementary algorithms, the overhead of each task scheduler can be kept small, while a general-purpose advanced task scheduling function can be realized as a whole.

A few specific examples of the present invention will be shown below.

FIG. 3 is an example in which the present invention is applied to prefix control. In FIG. 3, processors 35 and 36 are provided with prefix registers 37 and 38, respectively.
Prefix area (area for interrupt vectors, etc.) 31 corresponding to each processor on the main storage device 30.
It points to 34. Prefix areas 31 and 34 of each processor 35 and 36 on main memory 1
The addresses of the respective task schedulers 32 and 33 are stored in , and control can be passed to them. The task schedulers 32 and 33 are implemented using different algorithms. An example of an effective algorithm is
It is conceivable to apply an absolute priority schedule to the scheduler 32 and a first-come, first-served schedule to the scheduler 33.

FIG. 4 is an example in which the present invention is applied to input/output control. Fourth
In the figure, input/output device 44 is connected to processor 43. This input/output device 44 is controlled by the main storage device 4
This is performed by the dedicated task group 41 on 0. processor 4
The task scheduler 46 corresponding to No. 3 processes the task group 41 dedicated to input/output control with the highest priority. Thereby, the usage rate of the input/output device 44 can be improved. On the other hand, the task scheduler 4-7L corresponding to the processor 45 selects a desired task from the task group 42 common to the processors on the main memory 40 using an algorithm that prioritizes the efficiency of memory resources. In addition, task scheduler 4
6.47 is actually prepared on the main storage device 40.

According to this embodiment, each processor 43.4 improves the usage efficiency of multiple resources such as input/output resources and memory resources.
This can be achieved while suppressing the overhead of the scheduler 46 and 47 relative to 5.

FIG. 5 is an example of effectively using a smaller number of task schedulers than the number of processors in a multiprocessor. Fifth
In the figure, a multiprocessor system has four processors.
Consists of a stand. The task scheduler 55
0.51 and performs an absolute priority schedule that is effective for, for example, an online system. A task scheduler 54, on the other hand, is connected to the processors 52.53 and performs first-come, first-served scheduling useful for patch jobs, for example.

In the configuration of FIG. 5, each processor 50.5
By making it possible to change the assignment of the scheduler 54.55 for the scheduler 1, 52.53 at the time of system startup or by a command or the like during operation, flexible operation according to the business content can be realized. FIG. 6 is an example of this, and shows that the entire system is given online priority by changing the processor 52 from the task scheduler 54 for first-come, first-served schedule to the task scheduler 55 for absolute priority schedule.

〔Effect of the invention〕

According to the present invention, by assigning a task scheduler using a relatively simple algorithm to each processor that makes up a multiprocessor system, the entire system can achieve advanced task scheduling functions, thereby preventing an increase in overhead and improving efficiency. A multi-processor system can be realized.

In addition, since it is easy to change the assignment of task schedulers to each processor, flexible system operation can be achieved according to business types. Furthermore, since a plurality of task schedulers are distributed to each processor, the risk of a defect in the task scheduler can be distributed, and the reliability of the system can be increased.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram of a task scheduling method according to the present invention, FIG. 2 is a conceptual diagram of a task scheduling algorithm according to the present invention, FIGS. 3 to 6 are diagrams showing specific application examples of the present invention, and FIG. 8 is a conceptual diagram of a conventional task scheduling method, and FIG. 8 is a diagram showing an example of the configuration of a conventional task scheduling algorithm. DESCRIPTION OF SYMBOLS 1... Main storage device, 101... Task ready queue 2a, 2b, 2c... Task scheduler, 3a, 3
b, 3c...processor.

Claims (1)

[Claims] (1) A multiprocessor consisting of multiple processors, a main memory shared by these processors, and a task scheduler that selects a task to be executed by each processor from among multiple tasks existing on the main memory. A task scheduling method for a multiprocessor system, wherein a plurality of task schedulers each having a different algorithm are prepared as the task schedulers, and each processor is assigned to one of the plurality of task schedulers.