JPH0693232B2 - Cache memory - Google Patents

Description

The present invention relates to a cache memory, and more particularly to exclusive control of a directory memory suitable for updating the directory memory when rewriting the contents of the cache memory.

[Conventional technology]

The directory operation includes a search operation that requires several tens of microseconds and a read / write operation that ends in several microseconds. In the conventional cache memory, there is only one kind of directory exclusive instruction signal, the exclusive priority is fixed, two exclusive control devices have an exclusive instruction by a search operation, and a low priority control device. From the read / write operation, read / write
One hundred and several tens of microseconds are required to complete the write operation, and there is a drawback that proper directory update cannot be performed.

[Object of the Invention]

An object of the present invention is to provide a cache memory system,
It is to provide a cache memory system that enables an appropriate update of a directory.

[Outline of Invention]

In a cache memory system composed of a plurality of control devices and one cache memory, a directory exclusive instruction signal is divided into two types, an exclusive instruction signal for performing a search operation and an exclusive instruction signal for updating a directory by a read / write operation. Separately, by allocating the exclusive instruction signal for updating the directory by the read / write operation to the higher priority order of directory exclusive use than the exclusive instruction signal for always performing the search operation, the directory exclusive operation by the search operation is performed twice or more. It is possible to prevent the continuation and at the worst, update the directory by read / write operation in a few tens of microseconds.

[One Embodiment of the Invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2 in the case of a disk cache. The cache memory 5 is accessible by the four disk control devices 1 to 4, and the cache memory 5 stores information on the disk drive devices under the control of the four disk control devices 1 to 4. The management information of the cache memory 5 is stored in the directory of the cache memory 5 and is exclusively used by the four disk control devices 1 to 4 by exclusive control. Since the four disk control devices 1 to 4 exclusively use the directory, a short exclusive instruction signal 7 to 10 used for the read / write operation that ends the directory in several microseconds and several tens of microseconds are required for the directory, respectively. Long dedicated instruction signal 11 to 14 used in search operation
Is output to the directory exclusive control unit 6 of the cache memory 5. Further, the directory exclusive control unit 6 of the cache memory 5 reports the results of the short exclusive instruction signals 7 to 10 and the long exclusive instruction signals 11 to 14 to the respective disk controllers 1 to 4 by the exclusive signals 15 to 18. The directory exclusive control unit 6 gives priority to the short exclusive instruction signals 7 to 10 over the long exclusive instruction signals 11 to 14, and sees that the short exclusive instruction signals 7 to 10 are not present. Instruction signal
The same applies when the monopolization by any one of the long monopolization instruction signals 11 to 14 that is going to see 11 to 14 is canceled.

The disk controller 1 outputs a short exclusive instruction signal 7, the directory exclusive controller 6 reports the exclusive signal 15, and the central processing unit READs the disk controllers 2, 4 while the directory is being used for read / write operations. R when the order comes
In order to determine whether the EAD information is stored in the cache memory 5, the disk controller 2, 4 outputs a long exclusive instruction signal 12, 14 which is used for the directory search operation, and the exclusive signal 16, 18 is reported. Wait for you. Further, at this time, if the disk control device 3 is executing sequential loading from the disk drive device to the cache memory 5, after loading one track, the contents of the directory must be updated in the gap of the track switch, and the exclusive instruction signal is transmitted. In the case of the first type, the directory is exclusively used by the disk control devices 2 and 4 which issued the exclusive control signal first, and the disk control device 3 becomes able to monopolize the directory after a few tens of microseconds. Must issue a control signal to the disk drive for the next one-track load, which misses the timing of directory update. In order to eliminate such a problem, the disk control device 3 outputs a short exclusive instruction signal 9 having a high priority and occupies the directory after the disk control device 1 occupies the directory.

Thus, by having two kinds of directory exclusive use instruction signals, the directory can be updated properly, and the track just loaded in the cache memory 5 can be used as a search reference track for the next search operation.
There is an advantage that the hit rate of the cache memory 5 also increases.

〔The invention's effect〕

According to the present invention, since the directory can be updated without waiting time, for example, in the case of a disk cache, even in sequential loading from the disk drive to the cache memory, the directories are sequentially loaded in the gap of the track switch after loading one track. Can be updated,
The control of the disk drive becomes easy. Further, since the track loaded in the cache memory now becomes the search reference track for the next search operation, the hit rate becomes high.

[Brief description of drawings]

FIG. 1 is a functional block diagram of the directory exclusive control unit of a cache memory system according to an embodiment of the present invention.
Similarly, the figure is a time chart of the exclusive instruction signal and the exclusive signal of the directory exclusive control unit. 1-4 ... Disk control device, 5 ... Cache memory, 6 ... Directory exclusive control unit, 7-10 ... Short exclusive instruction signal, 11-14 ... Long exclusive instruction signal, 15-18 ... Exclusive signal .

Claims (1)

[Claims] 1. A cache memory accessed from a plurality of control devices, and management information of the cache memory are stored,
In the cache memory system configured by a directory exclusively used by the plurality of control devices, the plurality of control devices output two types of exclusive instruction signals according to the length of time for monopolizing the directory, and further, The directory detects two types of exclusive instruction signals from each of the plurality of control devices, determines the priority order of the exclusive control device according to which of the exclusive instruction signals is output, and permits the exclusive use of the directory. A cache memory for reporting the result of whether or not a directory is occupied to the plurality of control devices.