JPS62282345A - Cache memory - Google Patents

Abstract

PURPOSE:To properly update a directory by providing two kinds of directory exclusive instruction signals. CONSTITUTION:The directory monopoly instruction signal is divided into exclusive instruction signals 11-14 applying search operation and exclusive instruction signals 7-10 applying the revision of directly by read/write operation in a cache memory system comprising plural controllers 1-4 and a cache memory 5. Then the exclusive instruction signals 7-10 applying the revision of directory by the read/write operation are placed to the priority with high directory exclusiveness by using the exclusive instruction signals 11-14 always applying the searching. Thus, the consecutive exclusiveness of directory by the searching for two times or over is prevented and the revision of the directory by the read/write is finished in several tens of microseconds even in the worst case.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cache memory, and particularly to exclusive control of a directory memory suitable for updating the directory memory when rewriting the contents of the cache memory.

[Conventional technology]

Directory operations include search operations that take several tens of microseconds and read/write operations that complete in several microseconds. In conventional cache memory, there is only one type of directory exclusive instruction signal, and the priority of exclusive use is fixed. Two control devices with high priority receive exclusive instructions by search operation, and one control device with low priority If an exclusive instruction is issued by read/write operations from
It takes more than 100 microseconds to complete the write operation.

There was a drawback that the directory could not be updated properly.

[Purpose of the invention]

An object of the present invention is to provide a cache memory system with:
[Summary of the Invention] In a cache memory system configured with a plurality of control devices and one cage island memory, a signal for directing exclusive use of a directory is provided. The exclusive instruction signal is divided into two types: an exclusive instruction signal that performs a search operation, and an exclusive instruction signal that updates the directory through read/write operations. By placing the instruction signal at a high priority for IJ exclusive use, it is possible to prevent the directory from being monopolized by a search operation more than once, and to prevent directory updates caused by read/write operations even if there is a mistake. It can be completed in several 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 can be accessed by the four disk control devices 1 to 4, and stores information about the disk drive devices subordinate to the four disk control devices 1 to 4. The directory of the cache memory 5 stores management information of the cache memory 5, and is exclusively used by the four disk control devices 1 to 4 under exclusive control. In order to exclusively use the IJ, the four disk controllers 1 to 4 send short proprietary instruction signals 7 to 10, which are used for read/write operations that complete the directory in microseconds, and short proprietary instruction signals 7 to 10, which are used for read/write operations that complete the directory in a few tens of microseconds. Is the long exclusive use instruction signal 11 to 14 used in a search operation that takes seconds a directory exclusive use system of the cache memory 5? It is output to the MJ section 6. The directory exclusive control unit 6 of the cache memory 5 also provides a short exclusive instruction 1.
The results of No. 8 7-10 and long exclusive use instruction signals 11-14 are reported to the respective disk controllers 1-4 using exclusive signals 15-1. The directory exclusive control unit 6 selects shorter exclusive instruction signals 7 to 1 from longer exclusive instruction signals 11 to 14.
Priority 1f for exclusive use of 0! :: After seeing that there are no short exclusive instruction signals 7 to 10, I go to see the long exclusive instruction signals 11 to 14 (and the exclusive use by any one of the long exclusive instruction signals 11 to 14 is canceled). The same applies if the

The disk controller ii1 outputs a short exclusive use instruction signal 7, the exclusive use signal 15 is reported from the directory exclusive control unit 6, and while the directory is being used for read/write operations, the central processing unit sends READ to the disk controllers 2 and 4. In order to determine whether the relevant READ information is stored in the cache memory 5 when a command arrives, the disk controllers 2 and 4 output long proprietary instruction signals 12 and 14 that use the directory in a search operation, and 16, 18
Wait for it to be reported. Also, at this time, the disk control device 3
is executing a sequential load from the disk drive device to the cache memory 5, and after one track is loaded, the contents of the directory must be updated during the track switch gap. The directory is monopolized by the disk control devices 2 and 4 that have issued the exclusive instruction signal, and the disk control device 5 is able to monopolize the directory after a hundred and several tens of microseconds, unless it issues a control signal to the disk drive and drive device. In order to avoid this, the timing of directory update will be missed and a serious problem will occur.In order to avoid this, the disk control device 3 outputs a short proprietary instruction signal 9 with a high priority to the U disk control device 1.
Exclusive the directory after exclusive use of the directory.

By having two types of directory exclusive instruction signals in 5, it is possible to update the directory appropriately, and the track just loaded into the cache memory 5 can be used as a search target track for the next search operation.
There is an advantage that the hit rate of the Φ Yash memory 5 is also increased.

〔Effect of the invention〕

According to the present invention, the directory can be updated without any waiting time. Therefore, in the case of a disk cache, for example, even in sequential loading from the disk drive device to the cache memory, the directory can be updated sequentially during the gap of the track switch after loading one track. It is now possible to update
Since the track loaded into the cache memory becomes the search reference track for the next search operation, the hit rate also increases.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram of the directory exclusive control unit of the Gachet memory system according to an embodiment of the present invention, and FIG.
The figure is also a time chart of the exclusive use instruction signal and the exclusive use signal of the dinktree exclusive use control section. 1 to 4...Disk control device, 5...Cache memory, 6...Directory exclusive system? Part a, 7 to 10...Short proprietary instruction No. f3, 11 to 14...Long proprietary instruction signal, 15 to 18... Proprietary signal.

Claims (1)

[Claims] 1. In a cache memory system configured of a cache memory accessed by a plurality of control devices and a directory that stores management information of the cache memory and is used exclusively by the plurality of control devices, the plurality of control devices Two types of exclusive instruction signals are outputted depending on the length of time for exclusive use of the directory, and the directory further detects two types of exclusive instruction signals from each of the plurality of control devices, and which exclusive instruction signal is outputted. The cache memory is characterized in that the priority order of the exclusive control device is determined depending on whether the directory is exclusive, the directory is allowed to be exclusive, and the result of whether or not the directory is exclusive is reported to the plurality of control devices.