JPH06161897A - Control method for disk cache device - Google Patents

Abstract

PURPOSE:To effectively utilize a cache memory. CONSTITUTION:A main storage device 2 is provided with a soft cache area 8 for making data for control residual. When a read request is received from the main storage device 2 to a disk device 7, a disk control channel device 3 judges whether the data of an access object are the data for control or not by using a data judging means 4. When they are the data for control, data in the disk device 7 are not stored in a cache memory 6 but transferred to the soft cache area 8 by a data transfer means 5. On the other hand, when they are not the data for control, the data are stored in the cache memory 6 and transferred to the relevant area of the main storage device 2 by the data transfer means 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention effectively uses a cache memory in order to improve the cache hit rate of a disk cache device having a cache memory in order to speed up access to a magnetic disk device. The present invention relates to a method of controlling a disk cache device.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing a configuration example of an electronic computer system in which a conventional disk cache device is mounted. The illustrated system includes a central processing unit 11 and
It is composed of a main memory 12 and a magnetic disk control channel 13. The central processing unit (CPU) 11 transfers the data stored in the magnetic disk device 15 to the main memory device (MEM) 12 via the magnetic disk control channel 13, and reads the sequential instructions and data from the main memory device 12. Data processing. The main memory 12 is a random
It comprises an access memory and the like, and temporarily stores the data stored in the magnetic disk device 15.

The magnetic disk control channel 13 is a magnetic disk control device having a cache memory 14 built-in. The magnetic disk device 15 stores various programs and data. FIG. 3 is an explanatory diagram of a data flow at the time of reading from the disk cache device. When a read request is issued to the disk cache device, if there is no read target data in the cache memory 14 in the disk cache device, the magnetic disk device 1
5 is accessed. Then, the data is transferred to the main storage device 12 (T1). At the same time, the data is also transferred to the cache memory 14 in the disk cache device (T2). When the read target data exists in the cache memory 14 in the disk cache device, the data is transferred from the cache memory 14 to the main memory device 12 without executing the access to the magnetic disk device 15 (T
3).

[0004]

However, the above-mentioned conventional technique has the following problems. That is, the magnetic disk control channel 13 stores all requested read target data in the cache memory 14. on the other hand,
In addition to the cache memory 14 in the magnetic disk control channel 13, the operating system (OS) secures a soft cache area in the main storage device in order to reduce actual access to the magnetic disk device 15. Then, cache control is performed for this soft cache area. That is, in the conventional disk cache device control method, the data to be cache-controlled by the operating system is also stored in the cache memory 14 in the disk cache device.
However, such data is read into the soft cache area of the main storage device 12 by the operating system and cache-controlled. Therefore, data that is unlikely to be issued with a read request occupies the cache memory 14 in the disk cache device.

As described above, the conventional method of controlling the disk cache device has a problem in that the cache memory stores data that is unlikely to be a read request target, resulting in a decrease in cache efficiency. The present invention has been made paying attention to the above points. By storing data that is a cache control target by the operating system and is unlikely to issue a read request in the cache memory of the disk cache device,
It is an object of the present invention to provide a control method of a disk cache device that solves the problem of cache efficiency deterioration and improves cache efficiency.

[0006]

A method for controlling a disk cache device according to the present invention is a method for controlling a disk cache device when reading data into an main memory device from an input / output channel containing a cache memory. The target data to be read on is used by the control program that controls the system, determines whether or not the data is stored in the soft cache area on the main storage device, and if it is the data to be stored in the soft cache area, Read directly to the soft cache area without storing it in the cache memory in the disk cache device,
If the data is not stored in the soft cache area, it is stored in the cache memory in the disk cache device and read in the corresponding area in the main storage device.

[0007]

In the control method of the disk cache device of the present invention, when a read request is issued from the main storage device to the input / output channel, the requested data is stored in the soft cache area. Or not. If the result of this determination is that the data is to be stored in the soft cache area, it is not stored in the cache memory. On the other hand, if the data is not the data to be stored in the soft cache area, the corresponding block is read from the magnetic disk device to the cache memory at the time of a cache hit miss.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram of an embodiment of a disk cache device to which the control method of the present invention is applied. The illustrated system includes a central processing unit 1, a main storage unit 2,
It comprises a disk control channel device 3 and the like. A central processing unit (CPU) 1 stores data stored in a disk device 7 via a disk control channel device 3 into a main storage device (ME).
M) 2, the sequential instruction and data are read from the main storage device 2 and data processing is executed. Main memory 2
Is a random access memory or the like, and temporarily stores the data stored in the disk device 7.

The disk control channel 3 is a magnetic disk control device having a cache memory 6 built therein. The disk control channel 3 is provided with data transfer means 5 in addition to the cache memory 6. Data transfer means 5
Stores the data read from the magnetic disk device 7 in the cache memory 6 in accordance with an instruction from the control program, and at the same time transfers the data to the main storage device 2 and stores the data in the main memory device 2 without storing the data in the cache memory 6. It has two functions of transferring. The disk device 7 stores various programs and data.

FIG. 4 is a flow chart for explaining the procedure of the control method of the disk cache device of the present invention. FIG. 5 is an explanatory diagram of the data flow according to the present invention. Hereinafter, the control method of the disk cache device according to the present invention will be described with reference to FIG.
An explanation will be given based on the data flow of. When a data read request is issued to the magnetic disk device (step S
1) It is determined whether the read target data is data such as FLCB (file management information) that is subject to soft cache control by the OS, or data such as a file entity that is not subject to soft cache control by the OS (step S
2). If the data is the soft cache control target data, it is determined whether the requested data exists in the soft cache area on the main storage device (step S3).

If the requested data exists in the soft cache area, the data in the soft cache area is copied and used without issuing a read request to the disk cache device, as shown in FIG. 5A. Yes (step S4). If the requested data does not exist in the soft cache area, as shown in FIG. 5B, the disk cache device directly reads the data from the disk device and stores the data in the soft cache area on the main storage device. To do. At this time, the contents of the cache memory in the disk cache device are not updated (step S
5). If the requested data is outside the soft cache control target, a read request is issued to the disk cache device. When the requested data exists in the cache area in the disk cache device (step S6), the data in the cache memory is stored in the data storage area in the main storage device, as shown in FIG. 5C. (Step S7).

When the requested data does not exist in the cache memory of the disk cache device, the data is read from the disk device and stored in the data storage area on the main memory as shown in FIG. At this time, the contents of the cache memory in the disk cache device are also updated at the same time (step S8). In the above-mentioned embodiment, it goes without saying that the disk device is not limited to the magnetic disk device but may be an optical disk device or the like.

[0013]

As described above, according to the control method of the disk cache device of the present invention, the OS (control program) makes the soft cache control target in the main storage device, and the data is once read from the disk device. After that, data that is unlikely to be issued a data read request to the disk device is controlled as being out of the cache control target in the disk cache device, so the cache memory in the disk cache device is accessed. Only the data with high possibility can be stored, and the cache memory can be effectively used. As a result, the hit rate of the cache memory can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a control method of a disk cache device of the present invention.

FIG. 2 is a block diagram of an example of a computer system in which a conventional disk cache device is mounted.

FIG. 3 is an explanatory diagram of a data flow when reading from a disk cache device.

FIG. 4 is a flowchart illustrating a processing procedure of a control method of the present invention.

FIG. 5 is an explanatory diagram of a data flow according to the present invention.

[Explanation of symbols]

 1 Central Processing Unit 2 Main Storage Device 3 Disk Control Channel Device 4 Data Judgment Device 5 Data Transfer Device 6 Cache Memory 7 Disk Device

Claims (1)

[Claims] 1. A method of controlling a disk cache device when reading data into a main storage device from an input / output channel containing a cache memory, wherein data to be read into the main storage device is used by a control program for controlling a system. Data is stored in the soft cache area of the main storage device, and if it is the data to be stored in the soft cache area, the data is stored in the cache memory in the disk cache device without being stored. In the disk cache device, the data is directly read into the cache area, and if the data is not stored in the soft cache area, the data is stored in the cache memory in the disk cache device and read into the corresponding area in the main memory device. Control method.