JPH06243040A - Disk cache control system - Google Patents

Abstract

PURPOSE:To permit even a magnetic disk which does not have a cache function to inexpensively obtain the cache function without providing a private hardware by comparing the contents of a starting parameter with a cache control table when the number of starts is less than a prescribed value. CONSTITUTION:When the number of starts is larger than a prescribed value, regular data transfer is executed, namely, data only for the number of starts are read out of the magnetic disk 4 and they are transferred to the user area of a main storage device 2. When the number of starts is less than the prescribed value, a system shifts to a cache control processing. When data for the number of starts are previously stored in a cache area in a hardware-only area from a start address, data stored in the cache area is transferred and stored in the user area. When it is not stored in the cache area, data for the number of starts are transferred and stored in the user area from the start address, and data only for the number of succeeding starts are transferred and stored in the cache area in the hardware-only area as look-ahead data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk cache control system in a system having a magnetic disk storage device, and more particularly to a disk cache control system capable of realizing a cache function without providing dedicated hardware for cache.

[0002]

2. Description of the Related Art In the prior art, cache dedicated hardware such as a cache controller and a cache memory is added. Further, the pre-read data stored in the cache memory is also a method of transferring and holding all the data of all tracks during the disk rotation waiting time to the cache memory. Japanese Patent Laid-Open No. 3-116221 and the like are known as this type of system.

[0003]

The above-mentioned prior art basically has a control unit and a memory dedicated to the cache as hardware, and is expensive in cost. In the SCSI I / F, which has become the standard interface for magnetic disks in recent years, there is a problem that the performance of the magnetic disk device itself cannot be brought out because the data transfer speed of the SCSI bus is low. There was a performance problem in the processing of handling data in record units such as sort processing. An object of the present invention is to provide a cache function at a low cost without having dedicated hardware even for a magnetic disk that does not have a cache function, and to improve processing performance for processing data in record units such as COBOL language. Especially.

[0004]

To achieve the above object, a plurality of cache areas are provided in a dedicated hardware area of a main storage device, and a cache control table corresponding to the cache areas is provided in a control unit of a magnetic disk control device. Set up. Then, the control unit receives an input / output activation command from the central processing unit, and when reading is activated, if the number of activations of the activation parameter is larger than a predetermined value, the controller reads data from the magnetic disk device and writes the data to the user area of the main storage device. Transfer to and store. If the number of activations is less than or equal to a predetermined value, the activation parameters and the contents of the cache control table are compared, and if they match, the data in the cache area corresponding to the matched cache control table is transferred and stored in the user area. If they do not match, the cache control table with the lowest update order is updated with a start parameter in which the start address of the start parameters is an address obtained by adding the number of starts to the start address. Data is read, the first half data is transferred and stored in the user area, and the second half data is transferred and stored as prefetch data in the cache area corresponding to the updated cache control table.

[0005]

By taking the above means, when the number of activations of the activation parameter is larger than the predetermined number, the data read from the magnetic disk device is transferred and stored as it is in the user area of the main storage device. Is less than a predetermined number, if the start-up parameters and the contents of the cache control table match, the prefetch data stored in the cache area corresponding to the table is transferred and stored in the user area. The contents of the cache control table with the lower rank are updated, and the address is obtained by adding the disk device number and the number of start-up parameters, and the start-up address to the start-up address, and the data twice the start-up number is read from the magnetic disk device. , The first half of the data is transferred and stored in the user area as the originally designated read data, and the data of the second half is stored. Since the data is transferred and stored as prefetch data in the cache area corresponding to the updated cache control table, even if the cache dedicated hardware is not provided, by slightly modifying the magnetic disk control device, The cache function can be easily realized at low cost with a small memory capacity.

[0006]

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

FIG. 1 is a block diagram showing a system configuration according to the present invention. Reference numeral 1 is a central processing unit (CPU) having a DMAC (DMA controller) 6 for analyzing and executing a program to transfer data. 2 is a main storage device provided with a user area and a dedicated hardware area, 3
Is a magnetic disk controller (DKC) for controlling the magnetic disk device. Reference numeral 7 is a microprocessor (MP) that controls the DKC, and 4 is a magnetic disk device (DK
U). Normally, when starting up to a magnetic disk, an I / O start-up command is issued from the CPU 1 and D is sent through the data bus 5.
Transferred to KC3. In the DKC 3, the microprocessor 7 analyzes the input / output activation parameters of the input / output activation instruction, activates the DKU 4, and activates the data bus 5 and the DMAC 6
The data is transferred to the user area of the main storage device through. Here, the input / output start-up parameter is shown as 60 in FIG. 3 and is composed of the disk device NO, command, start-up address, start-up number, and chaining table address. In the present embodiment, as will be described later in detail, when the read / start is performed by analyzing the input / output start parameters, if the number of starts (for example, the number of sectors) is larger than a predetermined value, the above-mentioned normal data transfer, that is, Data corresponding to the number of boots is read from the magnetic disk and transferred to the user area of the main storage device. If the number of activations is less than or equal to the predetermined value, the process proceeds to cache control processing. In other words, if the data for the number of activations from the activation address has already been stored in the cache area of the dedicated hardware area, the data stored in this cache area will be transferred to the user area. If not stored, the data for the number of activations from the activation address is transferred and stored in the user area, and the data for the number of subsequent activations is transferred and stored as the prefetch data in the cache area of the dedicated hardware area. Then, these controls are performed using various tables described later.

FIG. 2 shows a cache area 1 used in this embodiment in a dedicated hardware area of the main storage device 2.
It is the figure which showed the mode that 0, 11 and the chaining table 12 were allocated. FIG. 3 shows control information used and created in this embodiment and its table. The cache control table describes parameters related to the data stored in the cache area of the dedicated hardware area.
Two tables are prepared corresponding to 2, and these tables are prepared in the internal memory of the microprocessor 7. The cache control flag is a flag for designating the last updated table, and is prepared in the microprocessor 7. The magnetic disk input / output start parameter is sent to the microprocessor 7 when the magnetic disk is started,
The chaining table 70 is prepared in a register in the DKC 3, and the chaining table 80 is the chaining table 12 provided in the dedicated hardware area.

FIG. 4 shows a schematic flow of processing in this embodiment. When the CPU 1 issues an input / output activation instruction to the DKC 3, the DKC 3 accepts the input / output activation instruction by the MP 7 and performs processing, and when reading is activated, the processing proceeds to processing 100. In process 100, the number of activations to DKU4 is checked. In this embodiment, it is determined whether the number of activations is 4 sectors (record) or less. Here, the number of startup is
When the number of sectors is 4 or less, the cache control process of the present invention is started. If it is larger than 4 sectors, normal processing is performed, and the data of sectors corresponding to the number of activations from the activation address is transferred and stored in the user area. That is, the number of data transfers (the number of bytes) corresponding to the number of activations (one sector is 256B) is transferred to the data transfer address in the user area indicated by the chaining table 70. Data transfer address of the chaining table 70,
The number of data transfers is set when the I / O activation parameter is issued. It should be noted that the number of activations that is the criterion for the above determination, that is, the number of activations that shifts to the cache control processing is not limited to 4 sectors, and can be arbitrarily specified, but if an excessively large number of activations is specified, the hardware Data cannot be stored in the dedicated area, and the time required to read the data from the magnetic disk becomes long, which hinders the execution of the next instruction.

In the process 101, the input / output activation parameter and the parameters in the cache control table 40 or 50, the disk device NO, the activation address, and the number of activations, are compared to see if they are the same value. If the comparison results show the same value and match, it is considered that a cashish hit has occurred and the process 110
Move to. In this embodiment, the cache control tables 40 and 50 are set on two sides, but this table can be arbitrarily increased. In the process 110, the data stored in the cache area of the dedicated hardware area corresponding to the cache hit table is set to the data transfer address in the user area shown in the chaining table 70 and set to the number of activations. Transfer only the corresponding data transfer count (byte count). I / O startup parameters,
As a result of comparison with the parameters of the cache control table,
If no match is found with either of the cache control tables 40 and 50, the process proceeds to step 102.

In process 102, cache control flag 3
Check 0. The cache control flag is a flag indicating which side of the cache control tables 40, 50 is the last updated table, that is, the table with the highest update order, and is stored in the microprocessor 7. The flag indicates that the first side (cache control table 40) is being updated when it is on ('1'), and the second side (cache control table 5) when it is off ('0').
0) is updated. The flag is updated as will be described later with the update of the cache control table. If the flag is on, proceed to step 103, and if it is off, proceed to step 10.
Go to 4.

In processes 103 and 104, the disk device number, the boot address, and the boot number of the corresponding cache control table are updated and set. Here, the disk device NO sets the disk device NO in the magnetic disk input / output activation parameter 60. The start address is the same as the start address in the magnetic disk input / output start parameter 60.
The value obtained by adding the number of activations within 0 is set as the activation address. As the number of activations, the number of activations itself in the parameter 60 is set. After setting each data in this way, the process 10
Go to 5. The address of the corresponding cache area is set as the address of the dedicated hardware area. In process 105, the cache control flag 30 is updated. In the process 106, the parameter for actually starting the DKU4 is updated. That is, in order to read the cache read-ahead data, the number of activations in the magnetic disk input / output activation parameter 60 is reset to double.

In step 107, a chaining table is created. That is, the chaining table 8
0 (chaining table 12 in the dedicated hardware area)
The hardware dedicated area address and the data transfer number (starting number) are set for the same) and the next chaining table address is set for the chaining table 70. The address of the cache area 1 or 2 is set as the dedicated hardware area address, and the chaining table 70 is set as the data transfer number.
The same value is set, and the address of the chaining table 12 is set as the next chaining table address. After the setting is completed, the process proceeds to step 108. Process 108
Then, actual input / output activation is applied to DKU4. DK
The C3 indicates in the chaining table 70 the normal read data, that is, the data corresponding to the number of data transfers of the chaining table 70 starting from the start address, by the magnetic disk input / output start-up parameter 60 updated in the process 106. The data is transferred from the DKU 4 to the data transfer address in the user area of the main memory 2 via the DMAC 6. Next, the chaining table 12 of the dedicated hardware area is referred to by the “next chaining table address” of the chaining table 70, and the dedicated hardware area address (address of the cache area) is set to the number of data transfers, The data (preread data) read subsequently to the normal read data is transferred from the DKU 4 to the DMAC 6. CPU1
When a magnetic disk input / output command is issued from, and reading is started, the above-described processing is repeated.

As can be seen from the above-mentioned embodiments, in the system without the disk cache, the disk D
By modifying the microprocessor 7 in the KC3, the cache function can be easily realized by utilizing the dedicated hardware area of the storage device without adding hardware.

[0015]

According to the present invention, in a system having no disk cache, the cache function can be realized at a low cost with a small memory capacity without preparing hardware dedicated to the cache. The cache function can be incorporated without changing the disk storage device and the upper program (OS level). The unit of disk access handled in a high-level language such as COBOL language is a record (sector) unit, and the processing performance can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a system configuration in the present invention.

FIG. 2 is a diagram illustrating each area in a main storage device.

FIG. 3 is a diagram showing control information used and created in the embodiment and its table.

FIG. 4 is a diagram showing a schematic flow of a process in an example.

[Explanation of symbols]

 1 central processing unit 2 main memory unit 3 magnetic disk control unit 4 magnetic disk unit 5 data bus 6 DMAC 7 microprocessor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuichi Yuichi 1 Ikegami, Haruoka-cho, Owariasahi-shi, Aichi Incorporated Hitachi Office Systems Division

Claims (1)

[Claims] 1. A central processing unit, a magnetic disk unit,
A disk cache control method in a computer system comprising a magnetic disk control device having a control unit and a main storage device having a user area and a hardware dedicated area inaccessible from a normal program. A plurality of cache areas are provided in a dedicated area, and a cache control table corresponding to the cache area is provided in the control unit of the magnetic disk control device. The control unit receives an input / output start instruction from the central processing unit and starts reading. If the number of startup parameters is greater than the specified value, the data is read from the magnetic disk device and transferred to the user area and stored. If the number of startup parameters is less than the specified value, the contents of the startup parameter and cache control table Compare and if matched, match cache The data in the cache area corresponding to the control table is transferred and stored in the user area, and when they do not match, the cache control table with the lowest update order is used, and the activation address in the activation parameters is used as the activation number. The data is updated by the start parameter that is the added address, the data twice as many as the start number is read from the magnetic disk device, the first half data is transferred and stored in the user area, and the second half data is stored in the updated cache control table. A disk cache control method characterized in that it is transferred and stored as preread data in the corresponding cache area.