JPH06195265A - Operation of cache memory - Google Patents

Abstract

PURPOSE:To eliminate structural overhead and to transfer data to a host computer at high speed by counting the number of times for accessing data which is slightly larger than a reference value and registering it in a cache memory when access is executed for more than the previously decided number of times. CONSTITUTION:A read command for reading data on a disk 2 is transmitted from the host computer 7, a microcomputer 6 executes a command processing for deciding the transfer start sector and the length of data to be read. The number of the decided sectors is compared with the reference value for judging whether data that is read from the disk 2 is unconditionally stored in the cache memory 5 or not, size with eight sectors, for example. When it is less than eight sectors, data is possibly stored in the cache memory 5. Thus, a cache memory collation processing is executed. When data does not exist in the cache memory 5, data is read from the disk 2 and it is fetched into the cache memory 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of operating a cache memory provided in a disk device for speeding up access.

[0002]

2. Description of the Related Art In a disk device such as a magneto-optical disk device and a hard disk device, when performing access such as data read / write, a seek operation for moving a head to a predetermined track and a rotation waiting operation for finding a predetermined sector are performed. , Is hindering fast access. In order to reduce this mechanical overhead, it is common practice to provide a cache using a semiconductor memory such as RAM in the disk device and store the accessed data to reduce the number of times the disk is accessed. There is.

FIG. 2 is a block diagram showing a disk device having a cache. In FIG. 2, 1 is a disk device, and 7 is a host computer that uses the disk device 1 as an external storage device. Reference numeral 2 is a disk, 3 is a disk drive device for executing processing such as read / write and verify on the disk 2, 4 is a disk control circuit for controlling the drive of the disk drive device, 5 Reference numeral 6 is a cache memory for temporarily storing a part of the data read / written and verified by the disk drive device 3, and reference numeral 6 is a drive of the disk control circuit 4, data read / write to the cache memory 5, and a host computer. 7 is a microcomputer that controls communication with the computer 7, and includes a disk controller and peripheral devices for interface.

The operation method of the cache memory of the disk device configured as described above will be described below. FIG. 3 shows a flowchart of a read process of the cache memory. In the figure, when a read command is sent from the host computer 7, the microcomputer 6
Is a command process S that determines the transfer start sector of the block of data to be read and its length from the read command.
Do 1. In the processing of S2, the microcomputer 6 compares the number of sectors of the data determined in the command processing S1 with a predetermined reference value for storing the data on the disk 2 in the cache memory 5, for example, 8 sectors. Compare.

If the data to be read is larger than 8 sectors, the disk control circuit 4 and the disk drive device 3 are operated to access the disk 2, read the written read data and transfer it to the host computer 7. Perform S7.

If the data to be read is 8 sectors or less, it is possible that the data to be read is stored in the cache memory 5.
Do 4. If there is no data to be read in the cache memory 5, the disk control circuit 4 and the disk drive device 3 are operated to access the disk 2, and processing S6 for fetching the data in the cache memory 5 is performed. Then, the process S5 of transferring the read data to the host computer 7 is performed.

In the cache memory collation processing S4,
When it is confirmed that the data to be read already exists in the cache memory 5, the process S of transferring the data stored in the cache memory 5 to the host computer 7.
5 is performed, and the read process ends.

[0008]

However, in the above-mentioned conventional method, the number of sectors serving as a reference for storing the data on the disk in the cache memory, in the above-mentioned conventional example, the data which is slightly longer than 8 sectors is stored in the cache memory. It is never stored. Therefore, when a command for reading data in the same sector, which is slightly longer than the reference value of 8 sectors, is frequently sent from the host computer, the head seek operation is performed on a track having a desired sector to find the sector. For this reason, mechanical operations such as the rotation waiting operation are frequently performed, so that there is a problem that the speeding up of the read operation of the disk device is hindered.

The present invention solves the above-mentioned problems, and even when data that slightly exceeds the number of sectors that is the standard for direct transfer or use of cache memory is used, as long as it is a sector that is frequently accessed. It is an object of the present invention to provide a cache memory operating method for accelerating a read operation of a disk device by storing it in a cache memory.

[0010]

In order to achieve this object, a method of operating a cache memory according to the present invention is such that, when data smaller than a certain reference value among data on a disk is read, it is always stored in the cache memory. In addition to storing the data to be read, if the data that is larger than the reference value and smaller than a predetermined upper limit value is read, the number of times of reading is counted and the same data is read a predetermined number of times or more. Is stored in the cache memory when it is read.

[0011]

According to the above method, even if the data larger than the reference value that is always stored in the cache memory is frequently read, if the data smaller than the upper limit value is stored in the cache memory, the mechanism is mechanical. Overhead can be reduced, and data can be transferred at high speed.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a flowchart of a read process in the cache memory operating method of this embodiment. The hardware configuration of the disk device to which this embodiment is applied is almost the same as the block diagram of FIG. 2, and the function of the microcomputer 6 different from the conventional example will be described in the following process flow.

In FIG. 1, when a read command for reading data on the disk 2 is sent from the host computer 7, the microcomputer 6 executes a command processing S8 for determining the transfer start sector and the length of the data read by the read command. To do. In the processing of S9, the microcomputer 6 sets the number of sectors of the data to be read determined in the processing of S8 and a reference value for unconditionally storing the data read from the disk 2 in the cache memory 5, for example, 8 sectors. Compare big and small.

If the data to be read is equal to or less than the reference value of 8 sectors, the process proceeds to step S10. If it is 8 sectors or less, the data to be read may be stored in the cache memory 5, so the microcomputer 6 performs the cache memory collation processing S10 on the cache memory 5.

In S11, when the data already exists in the cache memory 5, a process S12 of transferring from the cache memory 5 to the host computer 7 is performed, and the read process is ended. When there is no data in the cache memory 5 in S11, the microcomputer 6 operates the disk control circuit 4 and the disk drive device 3 to access the disk 2 and read the data from the disk 2. Then, the process S13 of fetching the read data into the cache memory 5 is performed, and the process S12 of transferring the data to the host computer 7 is performed to complete the read process.

When the length of the data to be read in the processing S9 is larger than the reference value of 8 sectors, it is checked in the processing S14 whether or not the data is slightly larger than 8 sectors. That is, in the process S14, an upper limit value which is slightly larger than the reference value is set as the number of sectors of the data to be stored in the cache memory 5, and the length of the data to be read is compared with the upper limit value or less, for example, 16 sectors or less. Perform processing to

When the length of the data is less than the upper limit of 16 sectors, the process proceeds to step S15, and the microcomputer 6 refers to the cache memory 5 to see if the data to be read is stored in the cache memory 5. S1
If the data already exists in the cache memory 5 in 6, the process branches to the process A, and in the process S12,
Data in the cache memory 5 is transferred to the host computer 7
Then, the read process is completed.

If there is no data to be read in the cache memory 5 in S16, the process branches to step S17, and the head sector of the block to be read, the length, and the number of times of access are stored in a table provided in the RAM in the microcomputer 6. set. The table provided in the microcomputer 6 has a certain number of past times (for example, 100 times) performed on data larger than the reference value of 8 sectors and smaller than the upper limit of 16 sectors.
The above information is registered according to the read command, and when the same data is read by a new read command, the data in the table is updated.

In step S18, a table registered in the RAM of the microcomputer 6 is referred to check whether the number of times the disk 2 has been accessed has reached a predetermined number or more, and a predetermined value (for example, 20 times) or more. If it reaches, it is determined that the block is frequently accessed,
In the process S13, the information of the table registered in the microcomputer 6 is deleted, and in the process S13, the data whose access count exceeds a certain value in the empty part of the cache memory 5 or the memory region where the read process is small. After executing the process of taking in the data, the process S12 of transferring to the host computer 7 is performed, and the read process ends. Process S1
If the number of accesses in 8 is not more than the predetermined number of times,
The process S19 of transferring to the host computer 7 is executed, and the read process ends.

Further, in the process S14, for data whose sector number of the data to be read is larger than the upper limit of 16 sectors, the process S20 of accessing the disk 2 and transferring the data to the host computer 7 is performed and the read process is terminated. .

[0021]

As described above, the cache memory operating method of the present invention is an improvement over the conventional cache memory operating method in which only data having a size smaller than a certain reference value is stored in the cache memory. The number of times that data slightly larger than the reference value is accessed is counted, and if the data is accessed a predetermined number of times or more, it is registered in the cache memory. Therefore, when frequently reading data that exceeds the reference value but is not so large, mechanical overhead can be eliminated and data can be transferred to the host computer at high speed.

[Brief description of drawings]

FIG. 1 is a flowchart of a read process in an embodiment of a cache memory operating method according to the present invention.

FIG. 2 is a block diagram illustrating the principle of a disk device.

FIG. 3 is a flowchart of read processing in a conventional cache memory operating method.

[Explanation of symbols]

 1 disk device 2 disk 3 disk drive device 4 disk control circuit 5 cache memory 6 microcomputer 7 host computer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takeshi Yokokawa, 2-10, Shoucho, Takamatsu City, Kagawa Prefecture Matsushita Electronics Co., Ltd. (72) Hiromi Kuwahara, 2nd, Shoucho, Takamatsu City, Kagawa Prefecture No. 10 Matsushita Hisashi Electronic Industry Co., Ltd.

Claims (1)

[Claims] 1. When data smaller than a certain reference value among data on the disk is read, the read data is stored in a cache memory without fail, and the upper limit larger than the reference value and a predetermined upper limit is stored. When data smaller than the value is read, the number of read times is counted, and when the same data is read a predetermined number of times or more, the cache memory is stored in the cache memory. Method.