CN1851651A - Method for realizing process priority scheduling for embedded SRAM operating system - Google Patents

Abstract

The present invention relates to embedded system process scheduling field for providing an embedded type SRAM operation system process priority scheduling implementation method. Said method includes recording state of a process, dividing process priority, progress select, processor distribution and retrieve processor. Said method easy realizes, is in favor of respectively processing to different progress, at the same time said method has high response speed process scheduling to SRAM when progress has higher cpu use rate.

Description

The implementation method of process priority scheduling for embedded SRAM operating system

Technical field

The present invention relates to embedded system process scheduling field, particularly relate to a kind of implementation method of process priority scheduling for embedded SRAM operating system.

Background technology

In computer system, may there be hundreds of batch processing jobs to leave in the job queue of disk simultaneously, perhaps there are hundreds of terminals to be connected with main frame.How from these operations, to select operation and enter main memory operation, how distribution processor time, a major issue in the operating-system resources management beyond doubt between process.This relates to the problem that processor distributes, and is referred to as processor scheduling.

We often run into the situation that two or more processes logically all can be moved.When a plurality of processes were ready, which operating system must determine to move earlier.The part of making this decision in the operating system is called scheduler program (Scheduler).

In early days very simple as the dispatching algorithm in the batch processing system epoch of input: as to move the next operation on the tape successively with the card image on the tape.For time-sharing system, though then dispatching algorithm want more complicated on PC, also have the process competition CPU that some users start, let alone background job in addition, for example the network or the smart process of sending and receiving e-mail.

A good processor scheduling should be considered a lot of aspects, wherein has:

Fair: as to guarantee that each process obtains rational CPU share.

Effectively: make CPU absolutely busy.

Response time: make the response time of interactive user short as far as possible.

Turnaround time: make the batch processing user wait for that the time of output is short as far as possible.

Handling capacity: make the operation number of per hour handling maximum.

These targets are thought deeply a little just can find wherein contradictory part.Can prove that any one dispatching algorithm of being partial to some type of operation will damage other operations.Available after all CPU time is limited.

Another trouble that scheduler program must be faced is that each process is all different, and unpredictable.The expensive time waiting I/O of some process, and other processes will use CPU to reach several hrs under the condition that allows continuously.In order to guarantee not allow process move too for a long time, all built-in electronic timer of nearly all computing machine or clock, it will send interruption termly.On many computing machines, operating system can be arranged to arbitrary value with clock frequency as required.Clock of every generation interrupts, and operating system all will be moved, and determines whether current process should continue operation, or it has taken sufficiently long CPU time, should suspend to allow other processes move.

The strategy of the process temporary suspension that permission will can move in logic is called can deprive scheduling (PreemptiveScheduling).Operation is called the non-scheduling (NonpreemptiveScheduling) of depriving up to the scheduling mode that finishes.Process can not added warning ground at any time to be hung up, so that allow another process operation.This has caused race condition and has prevented the semaphore of race condition, tube side, message or other complicated methods.On the other hand, allow a desirable time of process bootup window to mean that a process of calculating circular constant radix point back billibit will make other processes can not get service forever.

Although so realization is dispatched simply and be easy to non-depriving, it is unsuitable for having a plurality of competition users' general-purpose system usually.On the other hand, for dedicated system, as a database server, host process starts a subprocess and allows it move up to finishing or blocking when receiving request then be quite reasonable.

Therefore usually for different task process, can adopt different dispatching methods.As embedded SRAM operating system, be characterized in that operating system is arranged in SRAM, therefore also need to adopt the dispatching method that is based upon the SRAM basis.

The common performance parameter of more various medium memory obtains various Memeory contrast properties as showing:

Memory	Idle (mA)	Active (mA)	Read (16bit)	Write (16bit)	Erase (16bit)
						Mobile?SDRAM	0.5	75	90ns	90ns	N/A
Low?Power?SRAM	0.005	3	55ns	55ns	N/A
						Fash?SRAM	5	65	10ns	10ns	N/A
NOR	0.03	32	200ns	210.5us	1.2sec
						NAND	0.01	10	10.1us	200.5us	2ms

Analytically show data, the SDRAM power consumption is used the unique main memory of the very big SDRAM of power consumption as embedded system more than the power consumption height of SRAM and flash so conventional embedded OS is actually.We find if can allow kernel code at SRAM or the flash that supports XIP as the instruction internal memory, will improve the speed of system greatly so, reduce the power consumption of system.

Compare under the situation based at present common desktop computer hardware configuration and ordinary desktop operating system, embedded SRAM operating system is based on a kind of special application (the specific performance contrast sees also table) of the embedded SRAM storer of mobile terminal device, the embedded SRAM storer mainly shows the restriction of operation operation or its singularity: under the situation of SRAM, its response time will be more than fast under the SDRAM situation, operation by the operation of the SRAM of hardware supported and SDRAM is also also inconsistent, like this, the scheduling mode of embedded SRAM operating system must adopt the implementation method different with common system owing to face different conditions.

Because at present in non-embedded field, its CPU arithmetic speed is enough to satisfy the demand, but embedded system often requires higher response speed.Therefore, only there is the CPU of embedded system to have the exercisable characteristic of SRAM, and can in mobile terminal device, have obtained application.The present invention is based on the needs of embedded mobile device and is that embedded SRAM operating system has been realized its process scheduling method.

Summary of the invention

The object of the present invention is to provide a kind of implementation method of process priority scheduling for embedded SRAM operating system.

The technical scheme that the present invention solves its technical matters employing is as follows:

The invention provides a kind of implementation method of process priority scheduling for embedded SRAM operating system, comprise

1) state of record the process

To be added in the process control block (PCB) of this process of progress information typing of ready queue, and be loaded among the SRAM, because the capacity of SRAM is less, if the off-capacity of SRAM is then added the information of process status for hanging up that the SRAM off-capacity causes in process control block (PCB);

(2) process priority is divided

Each process is carried out priority level divide, the process of identical priority number is divided into same preferential group;

(3) process selection

Read the process that writes down in the process process control block (PCB) and arrive the order clauses and subclauses, processor distribution is given have high priority in the ready queue and be present in process among the SRAM; For the process in same preferential group, will carry out first process earlier;

(4) processor distribution

Relevant on-the-spot information, the especially information of SRAM capacity in the SPCB that chooses process, send in the processor relevant register, make it take the processor operation;

(5) regain processor

When course allocation to timeslice when using up, interrupt, the relevant content of registers of processor is sent into the corresponding units in the SPCB of this process, thereby is made this process abdicate processor.

As a kind of improvement of the present invention, the progress information in the described typing process control block (PCB) comprises:

Identification information is used for identifying uniquely a process;

Field data, be used for the reservation process operation the time leave in the processor scene various information and

Control information is used for management and dispatches a process.

Useful effect of the present invention is: this method realizes easily, and for the higher process of priority, its time that takies CPU is also longer, help handling respectively for different processes, this method is effectively utilized when process is arranged in SRAM simultaneously, when process was higher for the utilization rate of CPU, SRAM was for the fast characteristics of process scheduling response speed.

Description of drawings

Fig. 1 is the synoptic diagram of process of the present invention;

Fig. 2 is the synoptic diagram of process control block (PCB);

Fig. 3 is the synoptic diagram of process status formation.

Embodiment

The present invention is further illustrated below in conjunction with accompanying drawing.

A kind of implementation method of process priority scheduling for embedded SRAM operating system, accompanying drawing 1 are the overall schematic of the invention process process, and its specific implementation method is as follows:

1) remembers state of a process

Be created in process and enter ready attitude, perhaps enter into ready state from other states, they can be added into a ready queue, for each, remember state of a process, and this information general record is in the process control block (PCB) of a process;

Each process all has one also to have only a SRAM process control block (PCB) Process ControlBlock, be called for short SPCB, be that embedded SRAM operating system is used to write down and delineate process status and data structure for information about, it also is unique data structure that operating system is grasped process, it has comprised the situation when process is carried out, and process is abdicated information such as residing state behind the processor, breakpoint.In general, SPCB comprises three category informations:

Identification information, be used for identifying uniquely a process, the internal indicator that usually divides the foreign identifiers used by the user and used by system number, process all is endowed a process number unique, the inner numeric type that uses in nearly all operating system, and other control tables of operating system can come the control table of cross reference process by process number.Identification information commonly used comprises the identifier, consumer process name of Process identifier, parent process etc.;

Field data, be used for keeping a process leaves the processor scene in when operation various information, any one process must be saved in the processor field data of this moment in the process control block (PCB) when abdicating processor, and when resuming operation again, this process also answer restore processor scene, field data commonly used to comprise content, user stack pointer, system stack pointer of the content of general-purpose register, control register (as the PSW register) etc.;

Control information is used for management and dispatches a process.Control information commonly used comprises: the scheduling relevant information of process, guide unit etc. as state, waiting event or wait reason, priority, the process scheduling algorithm of employing, formation; The interprocess communication relevant information is as message queue pointer, semaphore; The address of process in second-level storage; Taking and use information of resource takies the executed temporal summation of time, process of CPU as process; Process privilege information is as in the privilege aspect internal storage access and the processor state; Resource inventory comprises the required whole resources of process, the resource of having got; In addition, for at SRAM capacity features of smaller, the process that is arranged in SRAM can not be too much, therefore, need in the SPCB of process, note the capacity of current SRAM, hang up reason, especially because some process that the SRAM off-capacity causes is suspended or the SRAM that swaps out enters SDRAM;

SPCB is an of paramount importance data structure in the embedded SRAM operating system, each SPCB has comprised all required progress informations of operating system management, the set of SPCB has in fact defined the current state of an operating system, process control block (PCB) uses or the power of amendment only belongs to operating system program, comprise scheduler program, resource allocator, interrupt handling routine, performance monitoring and routine analyzer etc., the process that has had SPCB the to be arranged in SRAM execution that just can be scheduled is as Fig. 2.

2) process priority is divided

Each process provides a priority number, and the process of identical priority number is divided into same preferential group, for having high priority and being present in process among the SRAM, will at first be assigned with execution;

Do you how to determine priority number? following several consideration can be arranged, use the frequent person's priority number of peripherals big, help like this raising the efficiency; The process priority number of important arithmetic problem program is big, and this is auspicious to help the user; The process priority number that enters length computer time is big, helps like this shortening the time that operation is finished; The process priority number of oolhiu interactive user is big, helps response time of terminal user or the like like this.

In order to prevent that high priority process from ceaselessly moving down, scheduler program may reduce the priority of current process at each clock ticktack.If this action causes its priority to be lower than time high priority, then will carry out process switching.Perhaps give each process set one section it can use the timeslice of CPU continuously, in case use up the process of operation time high priority then during this period of time.Priority can be for static or dynamic.

3) process selection

Enter into the process of ready queue for each, the details of this process have all been write down among its SPCB, processor is before scheduling, read the clauses and subclauses of the process priority that writes down among the process SPCB, at first processor will judge whether this process is arranged in SRAM among the SPCB according to SPCB, and perhaps whether the capacity of SRAM can be dispatched, if satisfy condition, CPU is distributed to first process in the process that priority valve is identical in the ready queue;

In general, be in same state, for example all process control block (PCB)s of ready attitude link together, such data structure is called process queue, be called for short formation, can further segment for the process queue of waiting state, each process enters corresponding formation by the reason of waiting for;

When certain incident that takes place changes a state of a process, this process will withdraw from certain formation at place and be drained into and go in another formation; The work that process withdraws from from the formation at a place is called team, and on the contrary, process is drained into work in the formation of an appointment and is called and joins the team; The functional module of being responsible in the processor scheduling joining the team and going out team's work is called queue management module, is called for short queue management, as Fig. 3.

4) processor distribution

Relevant on-the-spot information in the SPCB that chooses process, send in the processor relevant register, thereby allow it take the processor operation;

5) regain processor

When course allocation to timeslice when using up, interrupt, the relevant content of registers of processor is sent into the corresponding units in the SPCB of this process, thereby is made this process abdicate processor.

At last, it is also to be noted that what more than enumerate only is specific embodiments of the invention.Obviously, the invention is not restricted to above examples of implementation, many distortion can also be arranged.All distortion that those of ordinary skill in the art can directly derive or associate from content disclosed by the invention all should be thought protection scope of the present invention.

Claims (2)

1, a kind of implementation method of process priority scheduling for embedded SRAM operating system comprises

(1) state of record the process

To be added in the process control block (PCB) of this process of progress information typing of ready queue, and be loaded among the SRAM, because the capacity of SRAM is less, if the off-capacity of SRAM is then added the information of process status for hanging up that the SRAM off-capacity causes in process control block (PCB);

(2) process priority is divided

Each process is carried out priority level divide, the process of identical priority number is divided into same preferential group;

(3) process selection

Read the process that writes down in the process process control block (PCB) and arrive the order clauses and subclauses, processor distribution is given have high priority in the ready queue and be present in process among the SRAM; For the process in same preferential group, will carry out first process earlier;

(4) processor distribution

Relevant on-the-spot information, the especially information of SRAM capacity in the SPCB that chooses process, send in the processor relevant register, make it take the processor operation;

(5) regain processor

When course allocation to timeslice when using up, interrupt, the relevant content of registers of processor is sent into the corresponding units in the SPCB of this process, thereby is made this process abdicate processor.

2, the implementation method of process priority scheduling for embedded SRAM operating system according to claim 1 is characterized in that, the progress information in the described typing process control block (PCB) comprises:

Identification information is used for identifying uniquely a process;

Field data, be used for the reservation process operation the time leave in the processor scene various information and

Control information is used for management and dispatches a process.

Images