JPH0488539A - Disk cache control system - Google Patents

Abstract

PURPOSE:To immediately obtain an effect of disk cache when ordinary processing is restarted by holding data with high access frequency accumulated in cache memory in previous processing as it is. CONSTITUTION:When a data write request is issued from a host computer 11 to a magnetic disk 12, the cache write flag of a flag register 18 is set, and data is written on the magnetic disk 12. Simultaneously, it is written on the cache memory 17. Also, when a data readout request is issued, the flag of the flag register 18 is set similarly in a write operation. When the readout request exists in the cache memory 17, the readout of the data is performed, and it is transmitted to a host computer 11. In the ordinary processing in which the designation of cache is received, the update processing of the cache memory 17 is performed, and the data with high access frequency can be accumulated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a disk cache control method for controlling a cache memory in response to a disk access request from a host computer.

(Prior Art) For example, a computer system equipped with a magnetic disk device as a data memory is provided with a disk cache device. This disk cache device is an R
A cache memory composed of AM or the like is provided as an auxiliary storage area.In other words, by storing some of the data stored in the magnetic disk device that is frequently accessed in the cache memory, Efforts are being made to speed up data access.

In other words, when there is a data write request from the host computer and the requested data does not exist in the cache memory (cache miss), the data is written to both the magnetic disk device and the cache memory. If the write request data exists in the cache memory (cache hit), the data is written only to the magnetic disk device.

Furthermore, when there is a request to read data from the host computer, if the requested data does not exist in the cache memory (cache miss), the corresponding data is read from the magnetic disk device and is stored in the cache memory. The read data is written to.

On the other hand, if the read request data exists in the cache memory (cache hit), it is not read from the magnetic disk device but only directly read from the cache memory.

In other words, with the disk cache method described above,
Since data writing processing is always performed also on the magnetic disk device, only when reading data in the case of a cache hit, data access is made faster than when reading data from the magnetic disk device.

In this case, when reading and writing data to the cache memory, the storage order level in the cache memory of the data to be accessed is replaced with the highest level.
Frequently accessed data will always be held in the upper levels of cache memory. Note that when new data is written to the highest level of the cache memory, the previously existing data is shifted downward one block at a time, and the lowest level cache data is evicted.

(Problem to be Solved by the Invention) However, if the above disk cache control processing is performed for all disk accesses,
For example, if a long file load/write process is performed between frequently executed processes, all of the data previously stored in the cache memory will be updated in accordance with the frequently executed processes. The data will be updated. In this case, even if you return to normal processing,
When accessing the disk, no cache hits are seen for a while, and the disk cache becomes ineffective.

The present invention has been made in view of the above-mentioned problems. For example, when executing a process that is rarely executed between frequently executed processes, the contents of the cache memory are not changed, and the cache memory is not changed during the execution of the normal process. The purpose of this invention is to provide a disk cache control method that makes it possible to improve cache efficiency.

[Configuration of the Invention (Means for Solving the Problems) In other words, the disk cache control method according to the present invention writes and updates data to the cache memory when a host computer accesses a magnetic disk device. It controls the processing, and includes a cache instruction means for instructing cache writing at the time of disk access according to the content of the processing to be executed in the host computer, and a cache instruction means for instructing cache writing when the cache instruction is specified by the cache instruction means. a cache flag operating means for setting a flag indicating writing of access data to a cache memory; and a flag indicating cache writing is set by the cache flag operating means when the host computer accesses the magnetic disk device. In some cases, the cache data update means writes and updates access data to the highest level of the cache memory.

(Function) In other words, if the cache instruction means does not issue a cache write instruction, the data that has been accumulated in the cache memory in the previous process and is frequently accessed will be retained as is, and the normal process will be restarted. You can benefit from disk caching immediately.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a computer system that implements the disk cache control method of the present invention. In this computer system, a magnetic disk device 12 is provided for a host computer 11, and the magnetic disk device 12 is equipped with a magnetic disk device 12 for a host computer 11. It is connected to the host computer 11 through a disk interface 13.

The disk interface 13 includes a CPU (central processing unit) 14. When a disk access request is received from the host computer 11 via the host interface 15, the CPU 14 controls data access processing with the magnetic disk device 12 through the disk controller 16, and controls data access to the cache memory 17. It also controls processing, and in this case, data write update processing for the cache memory 17 is executed depending on whether a cache write designation flag managed by the cache flag register 18 is set.

In other words, when the cache flag register 18 holds a flag indicating cache write designation, the data must be updated in the cache memory 17 when accessing data to the magnetic disk device 2. Further, if the cache flag register 18 does not hold a flag indicating cache write designation and is "0", no data is updated in the cache memory 17 at all.

Here, the flag operation for the cache flag register 18 is controlled by the CPU 14 in response to a cache designation command given together with a disk access request from the host computer 11, and the presence or absence of cache designation in the host computer 11 will be determined in the future, for example. Is the process to be executed frequently during normal times?
Alternatively, the settings may be arbitrarily set by the operator in advance depending on whether the process is rarely executed.

Next, a description will be given of the disk access processing of the computer system that implements the disk cache control method with the above configuration.

First, an operator instructs the host computer 11 to designate a cache in order to perform processing that is frequently executed during normal times. Then, the host computer 11
A cache specification command will always be added to disk access requests from .

Here, when a data write request is received from the host computer 11 to the disk interface 13,
Based on the cache designation command input in conjunction with the data write request, the CPU 14 sets a cache write designation flag 1'' in the cache flag register 18, and writes the cache to a prespecified address position in the magnetic disk device 12 through the disk controller 16. In this case, write data to the above-mentioned
Since the cache write designation flag 1 is set in the flag register 18, the data written to the magnetic disk device 12 is also written to the highest level of the cache memory 17.

That is, when a cache designation command is received along with a data write request from the host computer 11, data write update processing is also executed for the cache memory 17 at the same time as data is written to the magnetic disk device 12.

Also, when a data read request is received from the host computer 11 to the disk interface 13, the C
PtJ14 is based on the Kya Sosh specified command input in response to the data read request in the same way as when writing above.
Set the cache write designation flag 1" in the cache flag register 18, and
If there is cache data corresponding to the read request (cache hit), the host computer 1 only reads this cache data.
Send to 1. Furthermore, if there is no cache data corresponding to the read request in the cache memory 17 (cache miss), the data is transferred from a pre-specified address position of the magnetic disk device 12 to the disk controller 16. and transmitted to the host computer 11.

In this case, the cache flag register 18 has the following information:
Since the cache write designation flag 1'' is set, regardless of the cache hit or cache miss, the write update process of the corresponding data to the highest level of the cache memory 17 is executed.

In other words, when a cache specification command is received together with a data read request from the host computer 11, the data write update process is performed on the cache memory 17 at the same time as the data is read from the cache memory 17 or the magnetic disk device 12. is executed.

That is, during the execution of normal processing for which cache has been designated in advance in the host computer 11, in both data writing processing and data reading processing,
The cache memory 17 is updated, and frequently accessed data is stored.

FIG. 2 is a flowchart showing the cache control processing at the time of the cache miss.

On the other hand, when performing a process of reading all stored data in the magnetic disk device 12, which is not normally executed, for example, the operator does not instruct the host computer 11 to designate a cache. In this case, a cache specification command will not be attached to a disk access request from the host computer 11.

Here, when a data read request is received from the host computer 11 to the disk interface 13,
Based on the fact that the cache designation command is not input manually in response to the data read request, the CPU 14 lowers the cache write designation flag 1' set in the cache flag register 18 to "0" and writes the data corresponding to the read request to the magnetic field. The information is sequentially read from a pre-specified address position of the disk device 12 through the disk controller 16 and transmitted to the host computer 11.

In this case, the cache flag register 18 has the following information:
Since the cache write designation flag 1'' is not set, the write update process of the corresponding data to the highest level in the cache memory 17 accompanying the data read process from the magnetic disk device 12 cannot be executed at all. do not have.

That is, if a cache designation command is not received along with a data read request from the host computer 11, even if data is read from the magnetic disk device 12, data write update processing for the cache memory 17 is not executed.

That is, during the execution of normally rare processing in which the cache is not specified in advance in the host computer 11, the update processing of the cache memory 17 is not executed during either the data write processing or the data read processing, and the normal processing is performed. At the time of execution, frequently accessed data stored in advance is retained as is.

Therefore, according to a computer system that implements the disk cache control method with the above configuration, the host computer
The cache flag register 18 is specified by the cache flag register 18 when executing normal processing.
The data contents of the cache memory 17 are always updated by setting a cache write designation flag for the cache memory 17, and when executing rare processing, a cache write designation flag is set for the cache flag register 18. Since data update processing in the cache memory 17 is not performed at all without performing any processing, when executing the normally rare processing, the cache data at the time of executing the normal processing is retained as is, so that the data in the cache memory 17 is not updated. You can immediately take advantage of the disk cache upon restart.

[Effects of the Invention] As described above, according to the present invention, when a host computer performs disk access to a magnetic disk device, the data writing update process to the cache memory is controlled, and a cache instruction means for instructing cache writing at the time of disk access according to the content of the processing to be performed; and a flag indicating writing of accessed data to the cache memory when cache writing is specified by the cache instruction means. and a cache flag operating means that sets a cache flag to the highest level of the cache memory when a flag indicating cache writing is set by the cache flag operating means when the host computer accesses the magnetic disk device. cache data update means for writing and updating accessed data, and when the cache instruction means does not issue a cache write instruction, the cache data is updated in advance from frequently accessed data accumulated in the cache memory in previous processing. For example, when executing a process that is rarely executed between frequently executed processes, the contents of the cache memory will not be changed, and the cache efficiency during normal process execution will be improved. It becomes possible to improve.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a computer system according to an embodiment of the disk cache control method of the present invention, and FIG. 2 is a flowchart showing cache control processing in the case of a cache miss in the computer system. 11...Host computer, 12.Magnetic disk device, 13.Disk interface, 14...CP
U (central processing unit), 15... host interface, 16... disk controller, 17... cache memory, 18... cache flag register. Applicant's agent Patent attorney Takehiko Suzue No. 15il Figure 2

Claims (1)

[Scope of Claims] In a disk cache control method for controlling data writing update processing to a cache memory when a host computer performs disk access to a magnetic disk device, the contents of the processing executed in the host computer include: and a cache flag that sets a flag indicating that the accessed data should be written to the cache memory when cache writing is specified by the cache instruction means. an operating means; and when a flag indicating cache writing is set by the cache flag operating means when the host computer accesses the magnetic disk device, writing and updating access data to the highest level of the cache memory; 1. A disk cache control method comprising cache data update means for performing.