JPH077357B2 - Buffer control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is applicable to an information processing apparatus having a main storage device, a plurality of central processing units, and buffer storage devices respectively connected to these central processing units. The present invention relates to a buffer control method for managing a copy of the data in the main storage device loaded in the buffer storage device.

[Prior Art] FIG. 3 is a block diagram showing a configuration of an information processing apparatus of this type. In the figure, 4 is a main storage device for storing data, 1 is a plurality of central processing units that share the main storage device 4 to perform arithmetic and control necessary for data processing, and 2 is corresponding to a plurality of central processing units 1. A plurality of buffer storage devices for storing copies of part of the data in the main storage device 4. A buffer storage control circuit 8, a data section 9, and a block management table 10 are provided in the buffer storage device 2. The block management table 10 is for managing the state of a block stored in the buffer storage device 2 for each of a plurality of sub-blocks included in the block. 5 is a central processing unit 1
Data / control lines connecting the buffer storage device 2 with the buffer storage device 3,
Is a bus connecting the buffer storage device 2 and the main storage device 4.

FIG. 4 shows one entry of the block management table 10 in the case of performing write-through type control using the block management table 10 of the buffer storage device 2 in the conventional buffer control method. In the figure, 11 is the block address. , And 12 is a status bit indicating whether or not the corresponding block is valid.

FIG. 5 shows one entry of the block management table 10 in the case of performing copy-back type control using the block management table 10 of the buffer storage device 2 in the conventional buffer control system. In the figure, 11 is the block address. Key to indicate, 13 ~
Reference numeral 14 indicates whether or not the corresponding block is valid, and if it is valid, whether or not the corresponding block is exclusively used by its own central processing unit 1 and whether or not the corresponding block needs to be written back to the main storage device 4, etc. Is a plurality of status bits J1 to J2.

FIG. 6 shows one entry of the block management table 10 when the block management table 10 of the buffer storage device 2 is expanded to perform write-through type control in units of four sub-blocks in the conventional buffer control method. In the figure, 11 is a key indicating a block address, and 15 to 18 are status bits indicating whether or not each corresponding sub-block is valid.
U1 to U4.

FIG. 7 shows one entry of the block management table 10 when the block management table 10 of the buffer storage device 2 is expanded to perform copyback type control in units of four sub-blocks in the conventional buffer control method. In the figure, 11 is a key indicating the address of a block, 19 to 26 are valid / invalid of each corresponding subblock, and if valid, whether or not the corresponding block is exclusively occupied by its own central processing unit 1. , And a plurality of status bits (S11, S1) indicating whether or not the corresponding block needs to be written back to the main memory 4.
2) to (S41, S42).

Next, the operation will be described. When performing write-through type control using the block management table 10 of the buffer storage device 2, one entry of the block management table 10 is a key 11 indicating a block address and a status bit 12 indicating whether or not the block is valid. When the central processing unit 1 refers to the main storage device 4 and a block including the corresponding address exists in the data section 9 of the buffer storage device 2, the corresponding entry of the block management table 10 The address of the block in key 11 and status bit 12 indicating whether the block is valid or not
Is set to a flag indicating validity. In the case of writing in the case of performing the write-through control, the status bit 12 may be 1 bit because the corresponding data in the main memory 4 is always updated.

On the other hand, one entry of the block management table 10 in the case of performing the copy-back type control is the key 11 indicating the block address.
And whether or not the corresponding block is valid, and if it is valid, whether or not the corresponding block needs to be written back to the main storage device 4, and a copy of the corresponding block is made in order to improve efficiency at the time of writing. It is composed of a plurality of status bits J1 (13) to J2 (14) indicating whether or not it is exclusively occupied by the CPU, and when the central processing unit 1 refers to the main memory 4, the corresponding entry of the block management table 10 The key 11 stores the address of the block, and if the reference is a write, it indicates that the block must be written back to the main memory 4 in addition to the state indicating that the block is valid. The status bits J1 (13) to J2 (14) are set so as to indicate a state indicating that the block is occupied by only the central processing unit 1 in order to improve efficiency in writing. .

Compared with the method of performing write-through control, the method of performing copy-back control can generally delay the write-back timing of the corresponding block to the main storage device 4, and as a result, the usage rate of the bus 3 can be reduced. Therefore, there is an advantage that more sets of the central processing unit 1 and the buffer storage device 2 can be connected to one bus 3.

As a method for managing more blocks while minimizing the increase in the capacity of the block management table 10 of the buffer storage device 2, a key 11 having a large number of bits is provided for each block.
There is a method of managing a state with a small number of bits for each of a plurality of sub-blocks in a block. For example, in the management method using the sub-block in the write-through type control, in one entry of the block management table 10, the number of bits is larger than the status bit 11 Manage U1 (15) to U4 (18).

[Problems to be Solved by the Invention]

Since the conventional buffer control method performs the above-mentioned processing, for example, if a management method in units of sub-blocks is introduced in the copy-back type control, as shown in FIG. 6, a plurality of status bits ( S11 (19), S12 (20))
~ S41 (25), S42 (26)) is required, and there is a problem that the total capacity of the block management table 10 increases considerably.

The present invention has been made to solve the above problems, and suppresses an increase in the number of status bits when a sub-block unit management method is used for copy-back type control of a buffer storage device. It is an object of the present invention to provide a buffer control method capable of performing the above.

[Means for Solving the Problems]

According to the buffer control method of the present invention, the status bits 26 to 26 of each entry in the block management table 10 for managing the status of a block stored in the buffer storage device 2 for each of a plurality of sub-blocks included in the block. 31
When managing the copy of the data of the main memory 4 which is taken into the buffer memory 2 by dividing into a part common to the whole block and a unique part for each sub-block, A bit S1 (26) that indicates whether the entire block needs to be written back to main memory with a status bit for the common part
And a bit S2 (27) indicating whether or not the entire block is exclusively occupied by one central processing unit, and when transferring the entire block or sub-blocks to the buffer device, each of the status bits Based on the above, it is controlled whether to perform from the main storage device or from another buffer device.

[Action]

The status bits 26 to 31 of each entry of the block management table 10 are
It is divided into a part common to all blocks stored in the buffer storage device 2 and a unique part for each sub-block. Therefore, the copy of the data in the main memory 4 which is stored in the buffer memory 2 is managed by the above-mentioned separated status bits.

Example of Invention

FIG. 1 is a diagram showing one entry of a block management table of a buffer storage device according to a buffer control system according to an embodiment of the present invention. The configuration of the information processing apparatus according to this embodiment is the same as that shown in FIG. In FIG. 1, 11 is a key indicating the address of a block stored in the buffer storage device 2 (see FIG. 3), 26 to 27 are a plurality of status bits S1 to S2 common to the block, and 28 to 31 are Unique 1-bit status bits V1 to V4 are shown for each sub-block included in the block.

FIG. 2 is a flow chart showing a swap-in algorithm for reading data into the own buffer storage device 2 in this embodiment. In step S1, it is determined whether the corresponding subblock is invalid but the corresponding block exists. In step S2, it is determined whether or not another valid buffer storage device of the corresponding sub-block exists in the case of “yes” in step S1. In step S3, it is determined whether or not there is another valid buffer storage device of the corresponding subblock in the case of "no" in step S1. In step S4, in the case of “yes” in step S2, only the relevant subblock is transferred from another buffer storage device. In step S5, "No" in step S2
In this case, only the relevant sub block is transferred from the main storage device 4. In step S6, in the case of “yes” in step S3, the entire corresponding block is transferred from another buffer storage device. In step S7, if the answer in step S3 is “No”, the entire corresponding block is transferred from the main storage device 4.

Next, the overall operation of this embodiment will be described. One entry of the block management table 10 of the management method using the sub-block in the copy-back type control is to write the key 11 indicating the address of the block and the corresponding block in a common state to the main storage device 4. Status bits S1 (26) to S indicating a status indicating whether or not it needs to be returned, and a status indicating whether or not the corresponding block is exclusively occupied by its own central processing unit 1 in order to improve efficiency during writing. (27) and status bits V1 (28) to V4 (31) indicating whether or not each sub-block is valid.

When the central processing unit 1 refers to the data, the buffer control circuit 8 of the buffer storage device 2 performs the following control.

(A) When the reference is read and the corresponding sub-block exists in the own buffer storage device 2, the data is read from the data section 9. In this case the block status bit S1
(26) to S2 (27), and subblock status bit V1
The values of (28) to V4 (31) do not change.

(B) When the reference is read and the corresponding sub-block does not exist in the own buffer storage device 2, the data is read into the own buffer storage device 2 by the algorithm shown in FIG.
There is an entry for the block containing the corresponding subblock, but the status bits V1 (28) to V4 (3
If 1) is in the invalid state, only the relevant subblock is read, and if there is no entry for the block containing the relevant subblock, the entire relevant block is read. In either case, the valid subblock is read. All status bits V1 (28) to V4 (31) are set. If there is another buffer storage device 2 having the corresponding block, the status bit S1 (26) to
Set to S2 (27).

(C) If the reference is writing and the corresponding sub-block exists in the own buffer storage device 2, prior to the writing of data, if a copy of the corresponding sub-block exists in another buffer storage device, those sub-blocks are also written. All the corresponding status bits V1 (28) to V4 (31) are reset to invalidate, and only the statuses V1 (28) to V4 (31) of the corresponding sub-block of the self buffer storage device 2 are set. Status bit S1 (26) of the corresponding block of own buffer storage device 2
S2 (27) is set to a state that needs to be written back to the main storage device 4.

(D) If the reference is writing and the corresponding sub-block does not exist in the own buffer storage device 2, prior to writing,
At the same time that the fetch-on-write processing for performing the same write processing as in (b) above is performed, and if a copy of the corresponding sub-block exists also in another buffer storage device, the corresponding state V1 of these sub-blocks (28) -V4 (31) are reset to invalidate all, and only the status bits V1 (28) to V4 (31) of the corresponding sub-block of the own buffer storage device 2 are set. The status bits S1 (26) to S2 (27) of the corresponding block of the own buffer storage device 2 indicate sharing if there is another buffer storage device 2 having a copy of the corresponding block, or the own buffer if not present. It is set together with the fact that only the storage device 2 occupies it, and in any case, it is necessary to write back to the main storage device 4.

According to the above-described embodiment, the status bit in the case of performing the copy-back type control in the buffer storage device and the sub-block management method is used for the part common to the block and the sub-blocks included in the block. In addition, since the status bit necessary for each sub-block is divided into a unique part and the necessary status bit is set to the minimum required one bit, the size of the block management table of the buffer storage device can be reduced, and the device can be inexpensive.

Although the number of sub-blocks in the block is four in the above embodiment, the same effect can be obtained even if the number of sub-blocks in the block is not four.

〔The invention's effect〕

As described above, according to the present invention, by dividing the status bit of each entry of the block management table of the buffer storage device into a part common to the whole block and a unique part for each sub-block, Since the copy of the data in the main memory that has been fetched is managed, the total number of status bits can be reduced compared to the case where all status bits are provided for each sub-block. When a sub-block management method is used for type control, an increase in the number of status bits is suppressed, so the total capacity of the block management table can be reduced, and the cost of the information processing device can be reduced. can get.

In addition, a status bit for the part common to the entire block, indicating whether the entire block needs to be written back to main memory, and whether the entire block is occupied by only one central processing unit. And a bit indicating whether or not to control whether to perform from the main memory device or from another buffer device based on each status bit when transferring the whole block or sub-block to the buffer device. Further, since the determination for invalidation is performed by referring to the corresponding status bit of the sub-block, the invalidation determination and transfer processing of the entire block can be performed reliably and quickly with a simple hardware configuration. .

[Brief description of drawings]

FIG. 1 is a diagram showing one entry of a block management table of a buffer storage device according to a buffer control system according to an embodiment of the present invention, and FIG. 2 is a swap-in process for reading data into its own buffer storage device in this embodiment. FIG. 3 is a flowchart showing the algorithm of FIG. 3, FIG. 3 is a block diagram showing the configuration of an information processing apparatus according to this embodiment and a conventional example, and FIG.
FIG. 5 is a diagram showing one entry of the block management table when performing write-through type control using the block management table of the buffer storage device in the conventional buffer control system, and FIG. 5 is a buffer storage device in the conventional buffer control system. FIG. 6 is a diagram showing one entry of the block management table when performing copy-back type control using the block management table of FIG. 6, and FIG. 6 is a write-through type control using the block management table of the buffer storage device in the conventional buffer control method. FIG. 7 is a diagram showing one entry of a block management table when it is expanded so that it can be performed in units of four sub-blocks. FIG. 7 shows a copy-back type control using the block management table of the buffer storage device in the conventional buffer control method. Diagram showing one entry in the block management table when expanded so that it can be performed in units of four sub-blocks A. 1 ... Central processing unit, 2 ... Buffer storage device, 4 ...
Main memory, 10 ... block management table, 26-27 ... block status bits, 28-31 ... sub-block status bits.

Claims (1)

[Claims] 1. A main storage device for storing data, a plurality of central processing units that share the main storage unit to perform arithmetic and control necessary for data processing, and the main processing units respectively corresponding to the central processing units. A plurality of buffer memories having a block management table for storing a copy of a part of the data of the storage device and managing the state of the block storing this copy for each of a plurality of sub-blocks included in the block. In an information processing device including a device, as a status bit of each entry in the block management table of each buffer storage device, a first status bit common to the entire block and a unique second status bit for each sub-block.
And a bit indicating whether or not the entire block needs to be written back to the main memory, and whether or not the entire block is occupied by only one central processing unit. Or a bit indicating whether or not to transfer the entire block or sub-block to the buffer device, based on the first and second status bits, from the main memory device or from another buffer device. A buffer control method characterized in that it is controlled whether to perform.