JPH07234764A - Scheduler - Google Patents

Abstract

PURPOSE:To correctly control the execution order of plural commands irrespectively of priority by controlling the execution order of the plural commands necessary for processing in an execution device to be a desired order based on a state flag, first and second lists. CONSTITUTION:The state flag F shows the processing state of plural commands 111 to 11n. The first list (master list) Lp stores the list of all the commands necessitating processing in advance of some command and the second list (slave list) Lc stores all the list of the commands waiting for the completion of the execution of some command. Then, based on the state flag F, the first and second lists Lp and Lc, this scheduler controls the execution order of the plural commands 111 to 11n to be the desired order. Thereby, the scheduler can lock the execution of some command until the execution of the other commands is completed so as to strictly control the execution order of the plural commands 111 to 11n without any influence on the side of the execution device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system called a scheduler for managing the order and system of commands (instructions) supplied to a system called an execution unit such as an optical disk auto changer (ODAC). In particular, due to the nature of the hardware of the execution unit that executes the command, some commands need to be forced to execute only when the execution of another command is complete. The present invention relates to a sequence control type scheduler having a function of processing various commands.

[0002]

2. Description of the Prior Art The essential concept of a scheduler currently used to operate a system is a ladder structure of priorities, as shown in FIG. 12, in which each level of this priority is run within that level. -It has a chain structure of commands executed by the Robin method.

When a command is given, the priority of the command is determined by the elements described below.

(A) Hardware Execution Speed: Some hardware units are relatively slow as far as execution time is concerned, but commands sent to such hardware are usually given low priority. To be This allows
Commands that need to be processed faster are executed first, which prevents the system from unnecessarily slowing down.

(B) Reliability: In addition, some commands include
Some of them involve the processing and storage of important data, depending on their nature. These commands should be executed as soon as possible to minimize the risk of data loss. Therefore, such important commands are assigned high priority.

(C) Urgency: Since an emergency has been reached, sometimes a command must be executed immediately. In this case, such commands are typically given the highest priority available at that time (often referred to as the "emergency level").

The order of command execution is as follows. Commands for each priority are run
Handled in the Robin system. That is, the commands are executed one after another without any special handling. However, the command that comes first is treated first.

For example, in the priority ladder structure shown in FIG. 12, the commands start with command 1 and start with command 9.
The command numbers are executed in ascending order, ending with.

Further, the simultaneity of command execution is as follows. Depending on the structure of the execution unit and the nature of the hardware attached to it, several commands can be executed simultaneously. Therefore, for example, assuming that a maximum of four commands can be executed at the same time, the scheduler can immediately send the first four commands one after another without waiting for the response of completion of execution in the middle of them.

[0010]

By the way, it is often the case that commands related to a certain sequence must be executed in a very strict order. That is, one command must not start executing until the other commands have completed execution. However, since the above-mentioned conventional scheduler does not have a function of ensuring such a strictly limited sequence, the only way to obtain such a sequence is to execute it on the program of the execution device.

This inconvenience will be described in more detail with specific examples. Now, as hardware, multiple optical disks
It shall consist of an auto changer (ODAC). Each of the optical disc auto changers has a number of shelves for storing optical discs (OD), one or two disc drives for reading / writing data from / to the optical discs, and optical discs from the shelves to the disc drives or On the contrary, it is provided with a mechanical disc operating mechanism (referred to as robotics) for carrying. It is assumed that the operation here is to copy a file from the currently used optical disk (disk 1) to a new, unformatted optical disk (disk 2).

In this case, the commands of the three superordinate concepts are executed. That is,

[Outer 1] When the commands of these three superordinate concepts are expanded a little more finely, the flow chart shown in FIG. 13 is obtained.

As can be seen from this flow chart,
The steps of the commands A, B, and C that define "reading a file from the disk 1" must be sequentially executed. Similarly, the commands D, E, and F that define the "format of the disk 2" must be processed in order. However, the group of commands A, B and C is
They can be executed simultaneously while the E and F groups are being executed. Commands G, H, I must also be executed sequentially, but the entire group of commands G, H, I is executed by both command groups "A, B, C" and "D, E, F". Execution can be started only after completion.

When the above-mentioned nine commands are processed by the conventional scheduler under such conditions, it is difficult to execute them in the order described above. This is because the Runoud-Robin method used in the conventional scheduler does not limit the detailed execution order even after the completion of commands C and F. This is because it is impossible to instruct the scheduler to start executing the command G.

Even if the above three groups of commands have three
Even if the system is operated by assigning three different priorities, it is impossible to guarantee such a proper execution order, considering that the execution unit can execute a large number of commands at the same time.

The present invention has been made in view of the above-described problems of the prior art. When the execution of another command can be locked until the execution of the other command is completed, and when the execution of the other command is completed, To provide a sequence control type scheduler with a function that can automatically unlock the required command from the commands that have been waiting,
To aim.

[0017]

In order to achieve the above object, a scheduler according to the present invention manages the execution order of a plurality of commands required for processing in an execution device, and the plurality of commands are individually managed. In each of the command blocks to be stored, a status flag indicating the processing status of the command, a first list that stores a list of all commands that need to be processed prior to the command, and wait for the completion of execution of the command. And a second list storing all command lists stored therein, and a sequence control for controlling the execution order of the plurality of commands to a desired order based on the status flag, the first list, and the second list. Means were provided.

In particular, the scheduler according to the second aspect of the present invention allocates to the state flag the processing states of "standby", "ready", "in execution", and "execution completed", and The order control means keeps its status flag "waiting" unless the first list is empty, and the status control means when the first list is empty Second flag control means for changing the flag from "standby" to "ready" and third flag control for changing the status flag from "ready" to "running" when the command is executed Means, and when the execution of the above command is completed, set the status flag to "running"
And a fourth flag control means for changing from "execution completed" to "execution completed", and the command can be executed only when the contents of the status flag of each command are evaluated and "ready". When the flag search means and the processing of the command currently being executed are completed, each waiting command in the second list of completed commands is scanned and the first list of each command is scanned. And a command deleting means for deleting the completed command.

[0019]

According to the present invention, the order control means controls the command execution order in the target device to a predetermined desired order. For example, unless the first list of a command is empty, its status flag is kept "waiting" (first flag control means), and when the first list is empty, the status flag is The status is changed from "standby" to "ready" (second flag control means). The content of the status flag of each command is evaluated by the flag search means,
Only when it is "ready" will the command be moved to a ready state. When the command is executed, the status flag is changed from "ready" to "running" (third flag control means), and when the execution is completed, the status flag is changed from "running" to "running completed". (Fourth flag control means). When the processing of the command being executed is completed, each waiting command in the second list of completed commands is scanned, and the completed command is deleted from the first list of each command by the command deleting means. To be done.

As described above, the command is not executed while the first list is not empty, and waits in the locked state. The command names of the first list of commands in this locked state are deleted one by one for the commands specified in the second list of the previously completed commands,
When the first list is empty, it is in the unlocked state (state flag = "ready", and execution is possible. Despite the command deletion, if the first list is not empty, it is still in the locked state. (Status flag = "waiting") Therefore, in the first list of each command, the command name to be executed prior to the command is listed, and similarly, in the second list of each command, If the command names waiting for the completion of execution of the current command are listed, the execution order of a plurality of commands can be controlled appropriately.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

As shown in FIG. 1, a sequence control type scheduler 1 according to the present invention includes an application unit 3 which an operator accesses through a console 2,
It is inserted between the optical disk auto changer (ODAC) 4 as an execution device,
It is activated in response to a request from the unit 3. The execution device is an optical disc auto changer (ODAC) 4
However, the device is not limited to the above, and may be any device as long as it has a program for processing at least a plurality of commands in a desired order.

The scheduler 1 has a CPU (central processing unit) 10 and a memory 11 built therein, and a plurality of command blocks 11 ₁ ... 11 _n are formed in a storage area of the memory 11. Each of the command blocks 11 ₁ ... 11 _n includes a command name, a status flag F, a parent list Lp, and a child list Lc. The status flag F indicates the processing status of each command, and is "waiting for execut
Ion) ”,“ ready for execution ”,“ executing ”, and“ completed (: done) ”. On the other hand, the parent list Lp corresponds to the first list of the present invention, and when one command is focused, it stores all command lists that need to be processed prior to the command. The child list Lc corresponds to the second list of the present invention, and when one command is focused on, it stores all command lists waiting for the completion of execution of the command.

The CPU 10 executes the command execution order in the ODAC 4 in the same manner as in the prior art by using the priority ladder structure and the round robin method in each ladder structure, and the plurality of command blocks 11 ₁ ... 11 Manage based on _n stored data. For this management, a sub program shown in FIGS. 3 to 5 and a main program (not shown) that manages the sub program are built in, and during execution of the main program, for example, by timer interrupt processing at regular time intervals. It is designed to process the above subprogram.

Of the above subprograms, the one shown in FIG. 3 relates to checking the parent list of waiting commands.
Specifically, the state flag F = “standby”,
Refer to the parent list Lp of a command (step 2
0), it is determined whether the parent list Lp is empty (that is, the command name data is zero) (step 21). If this determination is NO, that is, if the parent list Lp is not empty,
The status flag F = “standby” of the command is maintained (step 22), and it is determined whether reference of the parent list has been completed for all the commands waiting (step 23).
Here, if the determination is NO, that is, if all of the processing is not finished yet, the process proceeds to the next command (step 24),
Return to step 20 above. YE in the judgment of step 21
When S, that is, when the parent list Lp is empty, the status flag F of the command is updated from "standby" to "ready" (step 25), and the determination of step 23 is started. In this way, the parent list is referred to for all commands that are waiting.

The process described in FIG. 4 relates to the command status flag reference. Status flag F = for a command
It is determined whether "preparation is complete" (step 30), and if NO (not "preparation is complete"), it is determined whether flag reference has been completed for all commands (step 31).
If the determination is NO (that is, there is a command that has not been referred to yet), the process proceeds to the next command (step 32) and the process returns to step 30. When the determination in step 30 is YES, that is, when the status flag F = "ready", the flag F is changed from "ready" to "running" (step 33), and the command can be executed. After that (step 34), the above determination is similarly performed in step 31. Therefore, the status flag of the command that has been "ready" by the process of FIG. 3 is "execution".
If there is a predetermined execution instruction in ODAC4,
The command contents are moved to execution.

Further, the processing of FIG. 5 relates to updating the status flag and referring to the child list at the end of command execution.
When the current command execution ends with ODAC4, OD
Since there is an execution end response from the AC4, the CPU 10 uses this response signal to determine whether or not the command execution has ended (step 40). If NO in this determination, the process returns to the main program and waits for the next timer interrupt timing. YE
When S, execution of the command has ended, so
The status flag F of the command is changed from "currently executing" to "completed" (step 41). Next, the child list Lc of the command that has been executed is referenced (step 42), and it is determined whether the command name data of the child list Lc is empty (step 43). If the result of this determination is YES, that is, if the child list Lc is empty, there are no commands waiting, so management of the command execution order is no longer necessary, and the process returns to the main program. If the determination in step 43 is NO, the command name data of the completed child list Lc is checked, and the command name data that has been executed is deleted from the parent list Lp of the command (standby command) (step 44). After this, return to the main program. Thus, the parent list L of waiting commands
Of the p command name data, the command names that have been executed are sequentially deleted.

In the above-mentioned configuration and processing, the processing of step 22 of FIG. 3 constitutes the main part of the first flag control means,
The process of step 25 in the figure constitutes the essential part of the second flag control means, the process of step 33 in FIG. 4 constitutes the essential part of the third flag control means, and the process of step 41 in FIG. Form an essential part of the fourth flag control means. Also, in FIG.
The flag search means is formed by the processing of 0 and 34, and the command deleting means is formed by the processing of steps 40, 42 and 44 of FIG.

The operation of this embodiment will be described below with reference to FIGS. 3 to 5 and 6 to 8.

First, as shown in FIG. 6, four commands # 001 to # 004 are targets of the execution order of the scheduler 1, and the status flags F of the commands # 001 to # 004,
It is assumed that the parent list Lp and the child list Lc are set as illustrated. That is, the command # 00 currently being executed
1 is the status flag F = “running”, the parent list Lp = empty,
The child list Lc = 003,004, and the command # 002 for completion of execution preparation has a status flag F = “ready”,
While the parent list Lp = empty and the child list Lc = 004, # 003 of the two waiting commands is the status flag F = “waiting”, the parent list Lp = 001, the child list Lc = empty, # 004. Is the state flag F = “waiting”, the parent list Lp = 001,002, and the child list Lc = empty. In this state, since the parent lists Lp of the commands # 003 and # 004 are not “empty”, they are on standby and are not scheduled to be executed, and the execution is locked (locked state). There is.

In this state, the processing shown in FIGS.
It is implemented in PU10. When the completion of execution of the command # 001 which is being executed now is notified from the ODAC 4, the status flag F = of the command # 001 by the process of FIG.
“Completed”, and the child list Lc is checked. Now, since the child list Lc = 003,004, the CPU 10 respectively refers to the parent lists Lp of the waiting commands # 003,004 as shown in FIG. Then, the parent list Lp of those commands # 003 and 004
As shown in FIG. 7, the command name data of the execution completion command # 001 is deleted from among the above. As a result, the parent list Lp of command # 003 = empty, command # 003
The parent list of 004 is Lp = 002.

Further, by the processing of FIG. 3, command # 00
The status flag F of 4 is not empty, so that the status is still "waiting", that is, the lock status is maintained, but the command # 0
03 state flag F = empty, so the state flag F
= Updated to "ready" (see FIGS. 7 and 8). As a result, the lock state of the command # 003 is released, and the command # 003 shifts to the unlock state in which it can be executed.

Further, by the processing of FIG. 4, the status flag F of the command # 004 which has been prepared is updated to “execution in progress” (see FIGS. 7 and 8).

Furthermore, the command # 0 which is being executed this time
When the execution of 02 is completed, the state flag F of the command # 002 becomes “completed” by the next processing described in FIG. 5, and the child list Lc = 004 is referred to. By this reference, the command name “002” in the parent list Lp = 002 of the designated waiting command # 004 is deleted. As a result, the command # 002 that has been waiting in the locked state until then is unlocked, becomes executable by the processing of FIG. 3, and is scheduled to be executed through the processing of FIG.

As described above, as long as the command name data remains in the parent list of each command, the command remains in the locked state, and when all command names in the parent list are deleted and become empty, the locked state is released. Becomes feasible. As a result, the status flag, the parent list, and the child list are set in each command block as described above, and the CPU executes the above-described processing to automatically execute another command after the execution of the specific command is completed. Therefore, the execution order among a plurality of commands can be surely set to a desired one. Therefore, it is possible to reliably guarantee the desired execution order even when the execution device executes a large number of commands at the same time without assigning different priorities to the commands and operating the execution device.

In order to make the above advantages clearer, the specific operation of the scheduler of this embodiment will be described in comparison with that of the conventional one. First, the same situation as in FIG. 13 described above is introduced again. In other words, optical disc auto changer (OD
AC) is a situation where files are being copied from the currently used optical disk (disk 1) to a new, unformatted optical disk (disk 2),

[Outside 2] There are three command groups (the contents of commands A to I are the same as in FIG. 13).

Normally, the format-related commands (D, E, F) are read-related commands (A, B,
It is realistic that the priority is set lower than that of C) and the command (G, H, I) related to writing. As a result, the conventional scheduler sets the command group in the ladder structure shown in FIG. However, in this case, the disk 2 is written before the disk 2 is formatted, and an accurate execution order cannot be obtained.

On the other hand, when the sequence control type scheduler according to the present invention is used, the command ladder structure shown in FIG. 10 is obtained, and even if the "format of disk 2" has a low priority, the "format of disk 2" is used. "And" read from disk 1 "are both completed until" disk 2
"Write to" execution is locked. FIG. 11 shows a specific command block for implementing the ladder structure (the process of controlling the list of each command block is the same as that in FIGS. 3 to 5). According to FIG. 11, since two command names C and F are set in the parent list Lp of the command G, the command G will be locked until both the commands C and F are executed. That is, this lock function is equivalently expressed by the block of the "AND" symbol in FIG.

Therefore, cross-cutting with priority neglected,
Moreover, the strict execution order can be managed accurately. On the other hand, since no restrictions are imposed on "read from disk 1" and "format of disk 2", the execution unit (for example, ODAC) can execute these command groups in parallel.

In the above embodiment, the case where there are two command groups to be processed prior to a certain command group has been described, but the present invention is not necessarily limited to this, and, for example, three or more command groups may be processed. It may be applied to a locking mechanism which is processed in advance.

The parent list and the child list may each have a command block structure in which two or more types are prepared as needed.

[0042]

As described above, according to the scheduler of the present invention, the first flag which stores the status flag indicating the processing status of a command and the list of all commands that need to be processed prior to a certain command is stored. And a second command that stores a list of all commands that are waiting for the execution of a certain command
, And the execution order of a plurality of commands is controlled to a desired order based on the status flag, the first list, and the second list, so that the execution of other commands is completed. Command execution can be locked, and the execution order of a plurality of commands can be strictly managed without affecting the execution device side.

[Brief description of drawings]

FIG. 1 is a block diagram of a scheduler according to an embodiment of the present invention.

FIG. 2 is a block diagram schematically showing a command block.

FIG. 3 is a schematic flowchart showing a process of checking a parent list of a command on standby.

FIG. 4 is a schematic flowchart showing a search process of a command status flag.

FIG. 5 is a schematic flowchart showing updating of a status flag and reference of a child list at the end of command execution.

FIG. 6 is a state schematic diagram of four command blocks for explaining the outline of the operation of the embodiment.

FIG. 7 is a state schematic diagram of four command blocks for explaining the outline of the operation of the embodiment.

FIG. 8 is a state schematic diagram of four command blocks for explaining the outline of the operation of the embodiment.

FIG. 9 is an explanatory diagram for explaining a concrete ladder structure of commands by a conventional scheduler.

FIG. 10 is an explanatory diagram illustrating a specific command ladder structure by the scheduler according to the embodiment.

11 is a schematic diagram illustrating command blocks of each command corresponding to the ladder structure of FIG.

FIG. 12 is a schematic diagram showing a priority and a ladder structure of a command of the Runudo-Robin method according to the prior art.

FIG. 13 is a schematic flowchart illustrating a command execution order according to a conventional specific example.

[Explanation of symbols]

1 scheduler 10 CPU 11 memory 11 ₁ ... 11 _n command block F status flag Lp parent flag Lc child list

Claims (2)

[Claims] 1. A scheduler that manages the execution order of a plurality of commands required for processing in an execution device, in each of command blocks that individually store the plurality of commands, a status flag indicating the processing status of the command,
A first list storing a list of all commands that need to be processed prior to the command and a second list storing a list of all commands waiting for the completion of execution of the command are added, and the above-mentioned state is added. A scheduler comprising an order control means for controlling the execution order of the plurality of commands to a desired order based on the flag, the first list, and the second list. 2. The status flag is assigned to each of the processing statuses of "standby", "ready", "running", and "execution completed", while the order control means sets the first list. Unless the flag is empty, the first flag control means for maintaining the status flag in "standby", and when the first list is empty, the status flag is changed from "waiting" to "ready". To the second flag control means for changing the status flag from "ready" to "in execution" when executing the command, and when the execution of the command is completed. A fourth flag control means for changing the status flag from "in execution" to "execution completed" is provided, and only when the contents of the status flag of each of the above commands are evaluated to be "ready" , That command can be executed When the processing of the command currently being executed is completed, the flag search means for performing scanning is performed to scan each waiting command in the second list of the completed commands, and the first command of each command is scanned. The scheduler according to claim 1, further comprising command deleting means for deleting a completed command from the list.