JPH05134810A - Command reordering method for disk device - Google Patents

Abstract

PURPOSE:To prevent a command whose priority order is lowered by command reordering from becoming to time-out. CONSTITUTION:In a disk device 2 equipped with a command queuing function 3 and a command reordering function 4, a first counting means 5 is provided to be incremented every time one command is received, and a second counting means 6 is provided to be incremented every time one command is executed. Then, a table 7 for storing the waiting matrix of commands additionally stores values counted by the first counting means 5 in the order of receiving the respective commands and when executing command reordering after the commands are executed at prescribed number of times, the value counted by the second counting means 6 is compared with the counted value of the first counting means 5 stored in the table 7 and added to the unexecuted command. When the value counted by the second counting means 6 is larger than a prescribed value, the priority order of the processing of the unexecuted command is changed into the highest priority order.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk device for prefetching a plurality of input / output instructions and processing them by command queuing (creating a queue of instructions), and particularly command reordering (where the head is positioned). When a command that accesses the closest cylinder to the current cylinder is executed by changing the priority of the queue so that it can be executed first), the command with lower priority will not time out. The present invention relates to a command reordering method for a disk device.

In computer systems of recent years, miniaturization, high speed, and large capacity have become a major trend. For this reason, disk devices are also required to have high speed and high reliability. Therefore, there is provided a disk device that realizes a high-speed processing by prefetching a plurality of commands issued from the host, queuing the commands, and further reordering the commands.

By the way, when command reordering is performed, a command for accessing a cylinder near the cylinder in which the head is positioned is processed with priority.
Execution of commands directing access to cylinders far away from the cylinder where the head is located is slowed down.

A command whose processing has been delayed will time out after a lapse of a predetermined time, but it is necessary to prevent such a situation.

[0005]

2. Description of the Related Art A disk device having a conventional command queuing function and performing command reordering is an S
A command queue (command queue) that is connected to the CSI interface and stores information (address, data length, etc.) for executing a plurality of commands issued from the initiator host based on this interface standard. ), The command information is reordered according to this command information, and the command that can access the cylinder closest to the cylinder where the head is positioned is selected and prioritized for priority processing. Have decided.

Therefore, a command for accessing a cylinder near the cylinder in which the head is positioned is preferentially processed, and data writing / reading is executed. Therefore, the processing priority of the command for accessing the cylinder away from the cylinder where the head is positioned becomes low, and the data writing / writing by this command is low.
Reading was slow.

[0007]

As described above, the conventional command reordering lowers the priority of processing of a command requesting access to a cylinder away from the cylinder in which the head is located, so that the host does not process the head. If the command for accessing a cylinder near the cylinder positioned by is continuously sent, the command processing requesting the access of the cylinder away from the cylinder where the head is positioned is executed each time command reordering is performed. The priority is lowered each time. Therefore, the execution of this command will be postponed.

For this reason, there has been a problem that the processing of a command issued from the host to access a cylinder far from the cylinder in which the head is positioned is delayed and timed out.

In view of the above problems, the present invention provides a method in which the processing of a command for accessing a cylinder distant from the cylinder in which the head is positioned is delayed, and the delay is greater than a predetermined command execution count. , The purpose is to prevent a command whose processing is delayed from timing out by increasing the priority when performing command reordering.

[0010]

FIG. 1 is a block diagram for explaining the principle of the present invention. The disk device 2 exchanges the processing order of the command queuing function 3 that creates a command queue by prefetching a plurality of commands from the higher-level device 1 and the processing order of the queue created by this command queuing function 3, Is provided with a command reordering function 4 that gives the highest priority to the processing order of the command that accesses the cylinder closest to the cylinder in which is located.

A first counting means 5 is provided for incrementing each time one command issued from the host device 1 is received, and a second counting means 6 is provided for incrementing each command executed. There is.

Then, the command queuing function 3
Table 7 that stores the queue of commands created by
At the time of performing command reordering after executing the command a predetermined number of times, the values counted by the first counting means 5 are sequentially added to each command and stored in the order in which they are received,
The second counting means 6 compares the value counted by the second counting means 6 with the count value of the first counting means 5 stored in the table 7 and added to the unexecuted command. If the determined value is larger than the predetermined value, the priority of processing of the unexecuted command is set to the highest.

[0013]

With the above configuration, the command reordering function 4 executes the command a predetermined number of times even if the priority of the processing of the command for accessing the cylinder away from the cylinder where the head is positioned is lowered. Each time it is executed, it is checked whether the processing of the command has been executed.

If the command has not been executed, the priority of the process becomes the highest, and therefore the process of the unexecuted command is executed before the time-out.

[0015]

2 is a block diagram of a circuit showing an embodiment of the present invention, and FIG. 3 is a diagram for explaining the operation of FIG.

The processor 11 of the disk device 2 is a ROM
When the command issued by the host 10 enters the SCSI control circuit 16 of the disk device 2 via the SCSI bus by reading the program stored in the storage device 12, the command is being executed via the read / write control circuit 19. Check if there is.

If the command is being executed and the sense has not been changed, the command cannot be executed immediately, so it is determined that the command cannot be executed immediately and command queuing is performed.

That is, a plurality of commands entered into the SCSI control circuit 16 are stored in the table 7 provided in the RAM 15 as shown in FIG.
As shown in, the queue is created by sequentially storing. At this time, the processor 11 operates the counter 13 by the software provided in the ROM 12, increments each time one command is stored in the table 7, adds the count value of the counter 13 to the command information, and stores it.

That is, as shown in (1) to (7) of FIG.
Add the number (1) to the first received read command and store it with the command information cylinder 3, and then add the number (2) to the next received read command and store it with the command information cylinder 4. Let Since the same applies to the following, detailed description will be omitted.

When the command queuing process is completed, the processor 11 performs a command reordering process,
If the current position of the head is, for example, the cylinder 2, the read command (1) instructing access to the cylinder 3 closest to the cylinder 2 is given the highest priority, and the cylinder 4 closest to the cylinder 3 is given priority. The priority order of the read command (2) for which the access instruction is given is the priority order of the read command (7) for which the access instruction of the cylinder 5 closest to the cylinder 4 is.

Cylinder 6 closest to cylinder 5
The priority order of the read command (3) giving the access instruction of is, and the priority order of the read command (4) giving the access instruction of cylinder 7, which is the closest to cylinder 6,
Set the priority of the read command (6) instructing access of the cylinder 8 closest to the cylinder 7 to the cylinder 8
The priority of the write command (7) instructing access to the cylinder 30 closest to is set to.

The processor 11 controls the read / write control circuit 19 to execute the processing of the read command (1) having the priority order, and sets the head to the cylinder 3 of the disk medium 20.
The data is read from the designated sector and sent to the buffer control circuit 17.

The buffer control circuit 17 stores the data to be transferred in the buffer memory 18 and then reads it out to make the SCSI data.
The data is transferred to the host 10 via the control circuit 16. When the processing of the read command (1) is completed, the processor 11 stores the ROM
When the counter 14 by the software provided in 12 is operated to perform the increment for counting the completion of the processing of one command, the read / write control circuit 19 subsequently reads the read command ( The process of 2) is instructed, and this operation is repeated, for example, when the command process is performed 6 times, the command queuing of the command stored in the SCSI control circuit 16 is performed.

Therefore, as shown in (8) to (13) of FIG. 3B, the information of each command is recorded by the same processing as described above. When the command reordering process is executed in the same manner as described above, the write command shown in (5) has the cylinder number 30 to be accessed, so the cylinder in which the head is positioned to process the read command (6) is Since the numbers of the cylinders that are apart from the number 8 and are accessed by the commands (8) to (13) are all in the vicinity of the cylinder 8, the priorities as shown in (1) to (3) of FIG. 3B are given.

Therefore, the write command shown in (5) has the lowest priority again. Since the processor 11 has executed the predetermined number of command processing times, the processor 11 recognizes the number of unexecuted commands from the number of processing times and the number of command queues created in the table 7, and executes the command from the number indicating the priority order. Extract the command. Then, the count value 6 of the counter 14 is compared with the count value (5) of the counter 13 added to the unexecuted write command. The difference at this time is 6-5
= 1 and the predetermined value is 6, for example, the priority value is equal to or less than the predetermined value. Therefore, the priority order shown in FIG.

When the processor 11 executes the command processing six times, the command queuing and the command reordering are executed again, and as shown in (14) to (19) of FIG. 3C,
Information of each command is recorded by the same processing as described above.

By the command reordering, the write command of (5) is given the lowest priority again, but the processor 11 executes the predetermined number of times of command processing, so that the count value 12 of the counter 14 and The count value (5) of the counter 13 added to the write command for execution is compared. The difference at this time is 12-5 = 7, and if the predetermined value is, for example, 6, the difference is more than the predetermined value. Therefore, as shown in FIG. 3C, the priority order is changed and the write command ( The processing priority of 5) is the highest.

In order to position the head on the cylinder 30, the command (19) for instructing access to the cylinder closest to this cylinder 30 is given a priority order, and the priority order is given in the same manner as described above. Continue processing.

[0029]

As described above, according to the present invention, every time a command is executed a predetermined number of times, it is checked whether or not the processing of the command given the lowest priority by the command reordering has been executed.

If the command has not been executed, the priority of the process becomes the highest, so that the process of the unexecuted command can be executed before the time-out occurs.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating the principle of the present invention.

FIG. 2 is a block diagram of a circuit showing an embodiment of the present invention.

FIG. 3 is a diagram for explaining the operation of FIG.

[Explanation of symbols]

 1 host device 2 disk device 3 command queuing function 4 command reordering function 5 first counting means 6 second integer means 7 table 10 host 11 processor 12 ROM 13, 14 counter 15 RAM 16 SCSI control circuit 17 buffer control circuit 18 Buffer memory 19 Read / write control circuit 20 Disk medium

Claims (1)

[Claims] 1. A command queuing function (3) for prefetching a plurality of commands from a host device (1) and creating a command queue, and processing of a queue created by the command queuing function (3) In a disk device (2) equipped with a command reordering function (4) that changes the order and gives top priority to the processing order of commands that access the cylinder closest to the cylinder where the head is positioned, ), A first counting means (5) that increments each time it receives one command, and a second counting means (6) that increments each time one command is executed. A table (7) that stores a queue of commands created by the queuing function (3) is sequentially assigned the values counted by the first counting means (5) to each command in the order in which they are received. When the command reordering is performed after the commands have been executed a predetermined number of times, the value counted by the second counting means (6) and the unexecuted commands stored in the table (7) are stored. Comparing with the count value of the first counting means (5) added to
A command reordering method for a disk device, wherein when the value counted by the second counting means (6) is larger than a predetermined value, the priority of processing of the unexecuted command is set to the highest.