JPH04329446A - Storage device - Google Patents

Abstract

PURPOSE:To precisely execute transfer control for the unit of a word, to shorten time for transfer and to reduce the cost of a hardware by executing the transfer control corresponding to the state of a history to write data in a storing means. CONSTITUTION:A data writing means 10 writes data in both storing means A21 and B22 or any one of them, and the presence/absence of write to these storing means 21 and 22 is held in write histories A31 and B32. A transfer means 40 to transfer data between the storing means A and B is controlled by a transfer control means 50 corresponding to the states of the write histories A31 and B32. Namely, the write of data from the data writing means 10 is stored in the storing means A21 or B22 and at a certain time point, the contents of the both storing means A21 and B22 are made equal. Then, two write modes are alternately repeated, the storing means A21 and B22 alternately holds the states at the time point and therefore, they can be recovered to the held states.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a storage device that maintains a memory state at a certain point in time so that the memory state can be restored.

0002

2. Description of the Related Art In a conventional storage device for retaining a memory state at a certain point in time and restoring the memory state, a plurality of storage means are arranged to maintain the memory state at each point in time to cope with this problem. (e.g., W. Hwu and Y. Pat
t: “Checkpoint Repair for
r High-Performance Out-
of-Order Execution Mach
ines”, IEEE Transactions
on Computers, Vol. C-36,N
o. 12, pp. 1496-1514, Dec. 198
7). In this storage device, the storage state can be restored by transferring the entire storage state at a certain point in time as shown in FIG.

0003

However, in the above-mentioned storage device, as the amount of storage per storage state increases, the time cost and hardware cost required for transfer increase. As described above, conventional storage devices have problems to be solved regarding transfer time and hardware costs.

[0004] An object of the present invention is to provide a highly efficient storage device by solving these problems and avoiding redundant data transfer.

[0005]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the first invention of the present application is to write data in a storage device that makes it possible to restore the storage state by retaining the storage state at a certain point in time. a first means for performing the above, two second means that are storage means to which data is written by the first means, and a history of data writing by the first means to the two second means, respectively. two third means for holding data, a fourth means for transferring data between the two second means, and a transfer control for the fourth means depending on the state of the write history of the third means. redundant data transfer between the third means is avoided by further managing the second means for each plurality of words and transferring data between the third means. It is characterized by

[0006] Also, the second invention of the present application is; by providing a sixth means for changing the writing history to the second means in addition to the first invention, redundant data between the third means can be eliminated. Characterized by avoiding transfer.

[0007]

[Operation] By taking such a measure, it is possible to transfer only the necessary portion when returning to the state at a certain point in time. This avoids redundant data transfer and provides an efficient storage device.

FIG. 1 is a block diagram showing an apparatus according to an embodiment of the present invention. In the figure, numeral 10 denotes data writing means for writing data into the storage means. 21 and 22 are storage means A and storage means B, respectively, and data is written into both or one of 21 and 22 by the data writing means 10. 31 and 32 are storage means A21, respectively;
Maintaining the presence or absence of writing to the storage means B22;
They are writing history A and writing history B. 40 is storage means A
This is a transfer means for transferring data between the storage means B and the storage means B. 50 is a transfer control means that controls the transfer means 40 based on the states of the write history A31 and the write history B32.

FIG. 2 shows the format of write history A31 or write history B32. Here, storage means A2
Both 1 and B22 are composed of N words, and 0
Addresses of ~(N-1) are attached. This address is also used in the write history A31 and the write history B32, and is an address x (x=0 to (N-1) of the storage means A21.
)) is managed by the address x of the write history A31, and an address y (y=0 to (N-1)) in the storage means A22 is managed by the address y of the write history A32.

The operation of the storage device configured as above will be explained. Data written from the data writing means 10 is stored in the storage means A21 or the storage means B22. If the contents of both the storage means A21 and the storage means B22 are made equal at a certain point, the following two write modes are alternately repeated to write the contents of the storage means A21 and the storage means B22.
By alternately holding the state at a certain point in time, it becomes possible to return to the held state. However, the initial contents of the write history A31 and the write history B32 are all zero.

In the first mode, in order to retain the state at the time of entering this mode in the storage means A21, writing to the storage means A21 is temporarily stopped and writing is performed only to the storage means B22. . In this first mode, writing is performed only in the storage means B22, so for example, when writing is performed in the Xth word of the storage means B22, the writing history B22 is written.
The content of the Xth word of No. 32 is set to 1, and the history of this writing is saved. Also, in this first mode, the write history A
If the content of the Y-th word of No. 31 is 1, the data of the Y-th word of storage means A21 is transferred to the Y-th word of storage means B22. If this transfer is successful, the content of the Y-th word in the write history A31 is set to 0. At this time, if the content of the Y-th word in the write history 32 is 1, the transfer is not performed and the content of the Y-th word in the write history A31 is set to 0. This transfer is the write history A31
This continues until the content of all words in becomes 0, and the mode does not switch to the other mode until this ends.

In the second mode, in order to retain the state at the time of entering this mode in the storage means B22, writing to the storage means B22 is temporarily stopped and writing is performed only to the storage means A21. . In this second mode, writing is performed only in the storage means A21, so for example, when writing is performed in the Xth word of the storage means A21, the writing history A21 is written.
The content of the Xth word of 31 is set to 1, and the history of this writing is saved. Also, in this second mode, write history B
If the content of the Y-th word of No. 32 is 1, the data of the Y-th word of storage means B22 is transferred to the Y-th word of storage means A21. If this transfer is successful, the content of the Y-th word in the write history B32 is set to 0. At this time, if the content of the Y-th word in the write history A31 is 1, the transfer is not performed and the content of the Y-th word in the write history B32 is set to 0. This transfer is the write history B3
This continues until the contents of all words in 2 become 0, and the mode does not switch to the other mode until this is completed.

In the above two operating modes, the storage means A2
By using either 1 or the storage means B22 to hold the state at a certain point in the past, it becomes possible to return to that past state. That is, in the first mode, the state at the time of entering this mode is held in the storage means A21, and the storage means B22 can be returned to this state by the next procedure. First, write history B
If the content of the Y-th word of No. 32 is 1, the data of the Y-th word of storage means A21 is transferred to the Y-th word of storage means B22. If this transfer is successful, the content of the Y-th word in the write history B32 is set to 0. This transfer is continued until the contents of all words in the write history B32 become 0. And writing history A
If the content of the Y-th word of No. 31 is 1, the data of the Y-th word of storage means A21 is transferred to the Y-th word of storage means B22. If this transfer is successful, the content of the Y-th word in the write history A31 is set to 0. This transfer is continued until the contents of all words in the write history A31 become 0. Through this procedure, both the storage means A21 and the storage means B22 can return to the state at the time of entering this mode.

Furthermore, in the second mode, the state at the time of entering this mode is held in the storage means B22, and the storage means A21 can be returned to this state by the following procedure. First, if the content of the Y-th word of the write history A31 is 1, the data of the Y-th word of the storage means B22 is transferred to the storage means A
Transfer to the 21st Y word. If this transfer is successful, the content of the Y-th word in the write history A31 is set to 0. This transfer is continued until the contents of all words in the write history A31 become 0. If the content of the Y-th word of the write history B32 is 1, the data of the Y-th word of the storage means B22 is transferred to the storage means A.
Transfer to the 21st Y word. If this transfer is successful, the content of the Y-th word in the write history B32 is set to 0. This transfer is continued until the contents of all words in the write history B32 become 0. By this procedure, storage means A21 and storage means B2
2 can both return to the state they were in when entering this mode.

Next, another embodiment of the present invention will be explained with reference to FIG. FIG. 3 is an embodiment of a storage device according to the present invention. In the figure, write history A31 and write history B3
2, except that redundant transfer avoidance means 60 is provided between
It has the same configuration as the embodiment shown in FIG. 1 described above. In this configuration, the redundant transfer avoidance means 60 operates the write history A31 or the write history B32 depending on the states of the write history A31 and the write history B32, thereby avoiding redundant data transfer. That is, in the first mode described above, when the contents of the Xth word of the writing history A31 and the Xth word of the writing history B32 both become 1, the contents of the Xth word of the writing history A31 are set to 0. In the second mode, when the contents of the Xth word of the writing history A31 and the Xth word of the writing history B32 both become 1, the contents of the Xth word of the writing history B32 are set to 0. This makes it possible to avoid redundant data transfer in the storage device described above.

[0016]

[Effects of the Invention] As is clear from the above explanation, according to the present invention, compared to the conventional storage device which transfers the entire storage means, by performing fine control on a word-by-word basis,
It is possible to provide a lean and efficient storage device with low transfer time costs and low hardware costs.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an apparatus according to an embodiment of the first invention of the present application.

FIG. 2 is a diagram showing the configuration of write history A or write history B in FIG. 1;

FIG. 3 is a configuration diagram showing an embodiment of the second invention of the present application.

FIG. 4 is a configuration diagram showing a conventional storage device.

[Explanation of symbols]

10 Data writing means 21, 22 Memory means 31, 32 Write history 40 Transfer means 41 All transfer means 50 Transfer control means 60　　　　　　　　　　　Redundant transfer avoidance means”

Claims (2)

[Claims] Claim 1: A storage device that enables restoration of a storage state by retaining a storage state at a certain point in time, comprising a first means for writing data, and a memory to which data is written by the first means. two second means which are means, and two third means each holding a history of data writing by the first means to the two second means;
a fourth means for transferring data between two second means;
and a fifth means for controlling the transfer to the fourth means according to the state of the write history of the third means, and further includes a fifth means for controlling the transfer for each of the plurality of words and transferring the information between the third means and the third means. A storage device characterized in that redundant data transfer between the third means is avoided by performing the data transfer. 2. Redundant data transfer between the third means is avoided by comprising a sixth means for changing the write history to the second means.
The storage device described in .