JPH0827778B2 - Peripheral device control method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control method for peripheral devices, and is particularly effective when the load is high or when the input / output requests are biased toward specific peripheral devices. The present invention relates to a peripheral device control system.

[Conventional technology]

Conventionally, this type of peripheral device control method is to control the peripheral device when the input / output from the host device is small and the processing is interrupted, or when a constant time or a constant number of input / output requests are continuously processed. A control method has been used in which the processing is ended and the pointers pointing to the peripheral devices to be processed are changed to sequentially execute the processes to other peripheral devices.

[Problems to be Solved by the Invention]

In the above-mentioned conventional peripheral device control method, since the processes for the connected peripheral devices are executed in sequence, when a large number of peripheral devices are connected, a peripheral device preferentially processes an instruction to be processed. Even when the instruction is received from the higher-level device, the process of another peripheral device is performed before the instruction can be executed, so that it may be kept waiting during that time.

For example, a magnetic tape control device that controls the operation of a streamer type magnetic tape device has a large-capacity buffer to reduce the number of times the magnetic tape is started and stopped and to improve the throughput. If the commands are issued to some extent in succession,
Control is performed so that reading or writing can be continuously performed without stopping the magnetic tape.

This operation is forcibly stopped by the magnetic tape control device if it takes too long, but it is generally performed continuously for several seconds.
During this time, since data transfer is performed between the magnetic tape control device and the magnetic tape device to maintain the logical connection, the command from the higher-level device to another magnetic tape device cannot be executed, and the magnetic tape device enters a waiting state. .

On the other hand, in response to a rewind instruction, an unload instruction, etc., the operation time in the magnetic tape device extends from several seconds to several tens of seconds, but the operation itself is performed by the magnetic tape device alone, and the operation between the magnetic tape control device and the magnetic tape device is performed. The logical connection requires an extremely short time as compared with the read and write operations.

Now, read and write operations are performed continuously,
When a magnetic tape controller keeps a logical connection to a specific magnetic tape device for a long time, or when many magnetic tape devices are connected to one magnetic tape controller, that is, a high load. In this state, even if a short-time logical connection such as a rewind instruction or an unload instruction is sufficient, it takes several seconds to several tens of seconds to wait.

As described above, the start of the operation may be delayed regardless of the instruction that can be executed by the magnetic tape device alone. However, in the case of the magnetic tape device, the delay of the operation start is due to the delay of the exchange trigger of the magnetic tape medium. Connect The delay in the start of processing means that the response to the host device is also delayed accordingly.

Further, depending on the operating system, there is a case where a command that does not need to perform any operation is issued to the peripheral control device at regular intervals to monitor the state of the peripheral device. Is delayed,
An instruction that does not require any operation causes the host device to wait for a long time, resulting in a decrease in the throughput of the entire system.

[Object of the Invention]

The present invention is intended to solve such a problem of the related art, and is because a read instruction or a write instruction is continuously issued to a specific peripheral device or a high load is applied. In addition, when an instruction for other peripheral devices is waiting to be executed and the instruction to be prioritized is accepted, the processing such as the continuously executed read instruction and write instruction is interrupted. A peripheral device control method that executes the received instruction to be preferentially processed first, thereby improving the throughput of the entire system without incurring an extreme decrease in the processing capacity of the peripheral device. The purpose is to do.

[Means for solving the problem]

In order to solve such a problem of the prior art, the peripheral device control method of the present invention has a buffer, and asynchronously with the peripheral device via the buffer in response to a read / write command from the host device. And a priority command acceptance flag indicating that the peripheral device accepts a predetermined executable command that can be independently executed and that the command is in a processing waiting state, And a peripheral control device having a pointer pointing to the peripheral device to be processed. When a command to be preferentially processed is given from the host device to the peripheral device and the peripheral control device is in the process of data transfer with another peripheral device and cannot execute the command, priority command acceptance A flag is set, the pointer is changed to the peripheral device to be processed, data transfer between another peripheral device and the peripheral control device is interrupted, and then the preferential processing is performed in the peripheral device supported by the pointer. It is characterized in that it executes the instruction that should be executed.

Example of Invention

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a block diagram showing a structural example of a magnetic tape control device for controlling a streamer type magnetic tape device to which the present invention is applied. In FIG. 1, reference numeral 1 is a magnetic tape control device, and reference numeral 2 is a magnetic tape device. Of these, the magnetic tape control device 1 is equipped with a large capacity buffer 15. The micro program control unit 16 has a micro program and controls the entire operation of the magnetic tape control device 1. The input / output control unit 17 controls input / output between a host device (not shown) and the magnetic tape control device 1. Read (READ) / Write (WRIT
E) The circuit 18 is provided between the buffer 15 and the magnetic tape device 2,
Read and write processing is performed via the interface (I / F) circuit 19.

Further, the microprogram control unit 16 sets the priority command acceptance flag indicating that the instruction to be preferentially processed has been accepted.
11, a processing pointer 12 for pointing the magnetic tape device 2 to be processed, a buffer management table 13 for holding information for managing the buffer 15, information for managing control of each peripheral device including the magnetic tape device 2. It has a device control table 14 for holding.

The magnetic tape control device 1 uses a buffer to reduce the number of starts and stops in the magnetic tape device 2.
Has 15 During the writing operation, writing to the magnetic tape device 2 is not started until the buffer 15 is filled to some extent with the data sent from the host device. Further, during a read operation, once a read command is received from the host device, subsequent blocks are read and the buffer 15 is read without stopping the magnetic tape device 2 until the buffer 15 is full even if the next read command is not sent. When a read command is given from the host device, the magnetic tape device 2 is not operated as long as the prefetched data is stored in the buffer 15
The data in 15 is sent to the host device.

The host device side of the buffer 15 and the magnetic tape device side can transfer different data at the same time, and in this case, the data transfer rates of both are the same. Therefore, when a read command or a write command from the host device is issued to one magnetic tape device 2 at a sufficiently short time interval,
The magnetic tape device 2 can perform a read or write operation without stopping.

2 (1), (2) and (3) are flow charts for explaining the operation of the magnetic tape controller 1 in the embodiment of FIG. In addition, here, in order to simplify the explanation, the magnetic tape control device 1 reads (REA
D), write (WRITE), and only the instructions to be preferentially processed, such as rewind and unload.

The operation of the magnetic tape controller using the peripheral device control method of the present invention will be described below with reference to the flowcharts shown in FIGS. 2 (1) (2) (3).

The magnetic tape controller 1 inputs / outputs (I /
O) Monitor the presence or absence of a request (reference number 300), receive the command if there is an input / output request from the host device, and check whether the command is a read (READ) command or a write (WRITE) command. Judge (reference number 302). If it is a read command or a write command, the contents of the buffer management table 13 are checked (reference numeral 303). That is, if it is a read command, it is checked whether or not the data to be sent to the next higher-level device is stored in advance in the buffer 15 by prefetching. If it is a write command, it is checked whether or not there is room to store the data block sent from the next higher-level device in the buffer 15.

Then, it is determined from these check results whether or not data transfer is possible with the host device (reference number 304),
If data transfer is possible, data transfer is executed between the host device and the magnetic tape device (reference numeral 305), and then the command received from the host device is terminated (reference numeral 30).
6).

On the other hand, if it is impossible to transfer data to the higher-level device as determined by the reference numeral 304, that is, if the data to be sent to the higher-level device is not prepared in the buffer 15 if it is a read command, or if it is a write command. If so, if the buffer 15 is already full of data and the next data cannot be received unless the data is written to the magnetic tape device 2, is it possible to transfer the data to the magnetic tape device 2? It is determined whether or not (reference numeral 308). That is, specifically, it is determined whether the magnetic tape control device 1 is not performing data transfer with another magnetic tape device 2.

If data transfer is not being performed with another magnetic tape device 2, the magnetic tape control device 1 reads or writes data with the magnetic tape device 2 that is the target of the process that has received an instruction from the host device. When the writing process is started (reference number 309), the buffer contents are checked thereafter (reference number 303), and when data transfer is possible with the host device (reference number 304), the host device and the magnetic tape Data is transferred to and from the control unit 1 (reference number 30
5) Terminate the instruction from the host device (reference number 30)
6).

If the data cannot be transferred to and from the magnetic tape device 2 according to the reference numeral 308, the processing wait flag 141 for the corresponding device in the device control table 14 is set (reference numeral 310) and the processing wait state is set. And

When a read command and a write command are issued to a plurality of magnetic tape devices 2 from the host device, the magnetic tape control device 1 can execute data with only one magnetic tape device 2 at the same time. I / O instructions are referenced 310
After all the processing, the processing waits.

These input / output commands from the host device in the process wait state are set by the process wait flag 141 corresponding to the magnetic tape device 2 pointed to by the process pointer 12 in the device control table 14, It is restarted sequentially (reference number 301).

When the command received from the host device is not a read command or a write command (reference numeral 302), that is, when it is a command to be preferentially processed, the magnetic tape control device 1
It is checked whether or not data is being transferred between the magnetic tape device 2 and the magnetic tape device 2 (reference numeral 311). If data transfer is not performed and an instruction can be issued immediately, processing of the instruction from the higher-level device is executed, end processing is performed (reference number 312), and the priority command reception flag 11 is reset (reference number 31).
3).

In the judgment of reference numeral 311, the magnetic tape controller 1
If the command cannot be executed immediately because data is being transferred between the device and the magnetic tape device 2, the priority command acceptance flag 11
(Reference number 314) and set the device control table 14
The process wait flag 141 relating to the corresponding magnetic tape device 2 in (1) is set (reference number 315), the processing pointer is changed to the magnetic tape device to be processed by the instruction to be preferentially processed (reference number 316), and the instruction is not executed. It will be in a waiting state until it becomes possible.

The data transfer initiated at reference numeral 310 is being monitored during other processing, and if a read or write operation is in process between the magnetic tape controller 1 and the magnetic tape device 2 (reference numeral 317), the magnetic It is checked whether or not the data transfer with the tape device 2 is completed (reference number 318), and if the data transfer is completed, the contents of the buffer management table 13 are checked (reference number 319) to determine the next block. It is determined whether or not the data transfer is possible (reference numeral 320). That is, if the buffer 15 has room to read and store the next block from the magnetic tape device 2 if the read process is in progress, and if the write process is in progress, the next data to be sent to the magnetic tape device 2 is the buffer. Check if it is in 15.

When the data transfer of the next block is possible, it is checked whether or not the priority command reception flag is set (= 1) (reference number 321), and when it is not set, the magnetic tape is stopped or started. In order to prevent a decrease in throughput due to, the data transfer of the next block is immediately started (reference numeral 322).

On the other hand, in the determination of the reference number 320, when the data of the next block cannot be transferred, that is, when there is no room to store the next read data in the buffer 15 or there is no data block to be written to the magnetic tape device 2 next time. If the priority command reception flag 11 is set (reference numerals 320 and 323) or the data of the next block can be transferred, the priority command reception flag 11
If is set (reference numbers 320 and 321), the data transfer between the magnetic tape control device 1 and the magnetic tape device 2 is stopped, and the process can be executed to another magnetic tape device 2.

At this time, since the processing pointer 12 points to the magnetic tape 2 which is the processing target of the instruction to be preferentially processed, which is set by the processing of reference numeral 316 when the instruction to be preferentially processed is received, it is determined at the reference numeral 301. The instruction to be restarted first among the instructions in the waiting state is the instruction to be preferentially processed.

When the command to be preferentially processed is executed and the ending process is performed (reference numeral 312), the priority command reception flag 1 is reset (reference numeral 313).

Since the priority command acceptance flag 11 is reset except when the command to be preferentially processed is accepted and is in the waiting state, the input / output command issued from the host device at a short time interval is stored in the magnetic tape device 2. It can be executed without starting and stopping.

Further, when the operation of the magnetic tape device 2 is stopped due to the opening of the input / output command from the host device, or although not shown in the flowchart, the processing for one magnetic tape device 2 takes a long time, and If the magnetic tape control device 1 forcibly stops the data, the data transfer between the magnetic tape device 2 and the magnetic tape control device 1 will not be performed, and therefore the processing to another magnetic tape device 2 will be performed. Can be executed.

In the processing of reference numbers 307 and 309, the processing pointer
Since 12 is incremented by 1 and updated, when the operation of the magnetic tape device 2 is stopped, the instructions in the processing waiting state are sequentially processed from the magnetic tape device indicated by the processing pointer 12.

〔The invention's effect〕

As described above, according to the present invention, in the peripheral control device, a command to be preferentially processed is defined in advance, and a priority command reception flag indicating that such a command is received is provided to give priority to the command. When a command to be processed is received, the priority command reception flag is set and the pointer pointing to the peripheral device to be processed is updated, so that the peripheral device can execute the command independently or the higher-level device. It is possible to respond to commands, etc. that need to be returned as soon as possible by the request of the user side, regardless of the load status of the peripheral control device, without having to wait for the host device for a long time. It has an unprecedented excellent peripheral device control that can improve the throughput of the entire system without incurring an extreme decrease in processing capacity. It is possible to provide a method.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the peripheral device control system of the present invention, and FIGS. 2 (1), (2) and (3) are flowcharts for explaining the operation of FIG. 1, respectively. DESCRIPTION OF SYMBOLS 1 ... Magnetic tape control device as a peripheral control device, 2 ... Magnetic tape device as a peripheral device, 11 ... Priority command acceptance flag, 12 ... Processing pointer, 13 ... Buffer management table, 14 ... Device control table, 15 ... Buffer, 16 ... Micro program control section, 17 ... Input / output control section, 18 ... Read (READ) / write (WRITE) circuit, 19 ... Interface (I / F) circuit, 141 ... Processing wait flag.

Claims (1)

[Claims] 1. A buffer is provided, which asynchronously performs read / write with a peripheral device via the buffer in response to a read / write command from a host device, and the peripheral device independently executes the read / write. A priority command reception flag indicating that a predetermined predetermined priority processing command is received and the command is in a processing waiting state;
It has a peripheral control device equipped with a pointer to the peripheral device that is the target of processing, and when a command for priority processing is given to the peripheral device from a higher-level device, the peripheral control device is When the instruction cannot be executed during the data transfer between the two peripheral devices, the priority command reception flag is set, the pointer is changed to the peripheral device to be processed, and the other peripheral device and the peripheral control device are connected. A peripheral device control system characterized in that after interrupting data transfer between the peripheral devices, the peripheral device designated by the pointer executes the instruction to be preferentially processed.