JP2718679B2 - Data transfer control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a data transfer control technique, and more particularly to data transfer control between a central processing unit and an external storage device such as a magnetic disk device in a general-purpose computer system. It relates to technology that is effective when applied. [Prior Art] Generally, in general-purpose computer systems and the like, in order to improve the efficiency of data transfer between a central processing unit that operates at high speed and a magnetic disk device that operates relatively slowly,
A cache memory, such as a semiconductor memory, which operates faster than a magnetic disk device, is interposed between them, and data output multiple times from the central processing unit is temporarily written to the cache memory so that the central processing unit waits. A so-called write-after system has been known in which the time stored in the cache memory is shortened and the data stored in the cache memory is collectively written to the magnetic disk device at any time independently of the operation of the central processing unit. On the other hand, as one method of storing data of indefinite length in a magnetic disk device or the like, a record that is a recording unit is stored in an original data portion, a key portion serving as a clue for searching, and the like in a storage medium of the record. There is a so-called count key data system (hereinafter referred to as CKD system) composed of a storage portion, a data portion, and a count portion in which management information such as the length of a key portion is recorded. When the write-out method is applied, the cache memory is generally provided with an area for storing an equal number of count units, key units, and data units corresponding to the number of records. A technique for updating data in a magnetic disk device is disclosed in, for example, Japanese Patent Application Laid-Open No. 60-25047. [Problems to be Solved by the Invention] However, as described above, in the method of providing an equal number of areas for storing the count part, the key part, and the data part in the cache memory, the central processing unit sends the data to the magnetic disk device side. In the data write operation, even when only the key portion and the data portion are updated, in order to obtain information of the count portion in which the write position and the data length in the magnetic disk device are recorded, the magnetic disk device having a slow operation speed is required. Therefore, there is a problem that the data transfer speed per unit time between the central processing unit and the magnetic disk device is reduced. An object of the present invention is to reduce the frequency of direct access to the external storage unit of the central processing unit, and to improve the data transfer rate per unit time between the central processing unit and the external storage unit. An object of the present invention is to provide transfer control technology. [Means for Solving the Problems] The present invention provides a central processing unit, an external storage unit that stores a plurality of records each including a combination of an actual data unit and management information for the actual data, A central storage unit interposed between the external storage unit and the central processing unit; and controlling the transfer of the record between the external storage unit and the central processing unit directly or via the intermediate storage unit. A data transfer control device comprising: a control unit that controls an operation of a storage unit, wherein the intermediate storage unit stores the management information of some records of the plurality of records. And a second storage area for storing the actual data of some of the plurality of records, wherein the control unit replaces the record with the oldest access time with a new record. And the control is performed such that the number of the management information stored in the first storage area is larger than the number of the actual data stored in the second area. [Operation] According to the above-described means, the probability that the management information of the record operated in the central processing unit exists in the cache memory increases, so that the frequency of direct access to the external storage unit of the central processing unit is reduced. It is possible to improve the data transfer speed per unit time between the central processing unit and the external storage unit. Embodiment FIGS. 1A to 1C and FIGS. 2A to 2C are explanatory diagrams for explaining the operation of a data transfer control system according to an embodiment of the present invention. FIG. 1 is a block diagram showing a main part of an information processing system to which the data transfer control method is applied. The information processing system to which the data transfer control method of the present embodiment is applied includes, for example, a central processing unit 1 composed of a general-purpose computer, an external storage unit 2 composed of a plurality of magnetic disk devices, and the like. An external storage control unit 3 is provided between the control unit 1 and the processing unit 1. A channel interface 4 is provided between the central processing unit 1 and the external storage control unit 3, and commands and data transmitted from the central processing unit 1 are transmitted to the channel interface control unit 5 provided in the external storage control unit 3. , And then transmitted to the microprocessor 7 via the signal path 6. Further, the microprocessor 7 includes a signal path 8, a device interface control unit 9, a device interface 1
0, the external storage unit 2 is connected via the device control adapter 11. The operation of the microprocessor 7 is controlled in accordance with the microprogram stored in the control / store register 7a provided therein, so that the microprocessor 7 responds to commands from the central processing unit 1, controls the external storage unit 2, and the like. To accomplish. In the external storage control unit 3, a data transfer control unit 14 is provided between the channel interface control unit 5 and the device interface control unit 9 via a signal path 12 and a signal path 13. 14 and the signal path 12 on the channel interface control unit 5 side
Is connected to an intermediate storage unit 17 such as a semiconductor memory via a signal path 15 and a signal path 16. The data transfer control unit 14 and the intermediate storage unit 15 are connected to the microprocessor 7 by signal paths 18 and 19, respectively.
The microprocessor 7 controls the data transfer control unit 14 and the intermediate storage unit 17 so that the transfer of data between the central processing unit 1 and the external storage unit 2 is controlled by the data transfer control unit 14. Via the intermediate storage unit 17 directly. In the present embodiment, the storage of data in the external storage unit 2 is performed by the above-described CKD method, and the intermediate storage unit 17 that stores the data of the CKD method includes a count unit 20 (management information) that forms a record. First storage area 17a to be stored
A second storage area 17b in which a key section 21 (actual data) and a data section 22 (actual data) are stored;
Directory entry which is the management information of
And a directory area 17c in which 23 is stored. Here, the counting unit 20 and the key unit 2 in the intermediate storage unit 17
1, a plurality of data sections 22 are collectively managed for each track unit of the magnetic disk constituting the external storage section 2, for example.
(Hereinafter, a unit managed collectively is referred to as a slot.) A directory entry 23 as management information is secured for each of the slots. That is, as shown in FIG. 1A, a plurality of counting units 20 stored in the first storage area 17a and indicated by C _XZ
, The subscript X represents the number of the directory entry 23 to which the count unit 20 belongs, the count unit 20 having the same subscript X belongs to the same slot, and the subscript Z represents the record number in the same slot (within the track). Is represented. Similarly, as shown in FIG. 1 (b), the subscripts X of arbitrary K _XZ and D _XZ of the plurality of key portions 21 and data portion 22 stored in the second storage area 17b are The number of the directory entry 23 to which the data section 22 belongs is shown, and the suffix Z represents the record number in the same slot (in the track). Also, as shown in FIG. 3C, the fields of the individual counting units 20 include a cylinder number C and a head number H, a record number R, and a corresponding record number in which the record identified by the counting unit 20 is stored. Are composed of the length KL of the key part 21 and the length DL of the data part 22, and a write record flag WR indicating that the record has been updated in the intermediate storage unit 17. In this case, as shown in FIGS. 1 (a) and 1 (b), the number of slots of the counting section 20 in the first storage area 17a of the intermediate storage section 17 is the same as that of the key section in the second storage area 17b. The number of slots is controlled to be greater than the number of slots of the data section 21 and the data section 22. That is, the first storage area 17a and the second storage area 1
The slot 7b is shared by 1 to n, and the slot of the second storage area 17b corresponding to the slot of n + 1 to m of the first storage area 17a is opened as a replaceable area. In the present embodiment, the first storage area 17 is stored in a register (not shown) provided inside the microprocessor 7.
By storing a parameter indicating the relationship between the number of slots in a and the number of slots in the second storage area 17b, the first storage area 17a can be changed simply by changing the parameter.
The number of slots in the second storage area 17b can be set to a desired value. As shown in FIG. 2A, each directory entry 23 includes a device address DA for specifying one of the plurality of external storage units 2, a cylinder number C in one selected external storage unit 2, Number H, storage address CA in first storage area 17a, valid flag V indicating that data at storage address CA1 is valid, storage address CA2 in second storage area 17b, and storage address C
Valid flag V indicating that the data in A2 is valid
2, a write flag W indicating that a part of the plurality of records managed by the directory entry 23 has been updated by a command from the central processing unit 1 after being loaded from the external storage unit 2, and a plurality of records in the intermediate storage unit 17 Pointer for connecting the directory entries 23 of each other in a list structure
It is composed of LRUU, pointer LRUL, etc. That is, in the present embodiment, as a method of controlling the access order and replacement of a plurality of slots in the intermediate storage unit 17, slots are arranged in the order of the latest access time, and the directory entry 23 for managing each slot is By storing the address of the immediately preceding directory entry 23 in the pointer LRUU and storing the address of the immediately following directory entry 23 in the pointer LRUL, the plurality of directory entries 23 form a list structure. Then, by storing the addresses of the first directory entry 23 and the last directory entry 23 in the order in the upper register 24 and the lower register 25, respectively, the last slot (the oldest accessed time) is stored in the external storage unit. So-called LRU method (lease and
(Listening used system). FIGS. 2B and 2C show an update process when a new directory entry 23 is added according to the LRU method. That is, when a new directory entry 23 is added to the list as an LRUk, since the directory entry 23 is the latest access, it is replaced with the highest LRU0, and the LRUk becomes the highest register.
24, and the directory entries 23 in the order of LRU0 or lower are shifted down by one order, and the last LR
The directory entry 23 indicated by Um is deleted. Although LRUm is seen to be deleted in FIGS. 2B and 2C, the LRUk to be added is actually
In addition, the pointer LRUU and the pointer LRUL are updated in the directory entries 23 of LRU0 to LRU (m-1), whereby the process of adding the LRUk is performed. When a directory entry 23 other than the highest LRU0 is accessed, the pointers LRUU and LRUL of the directory entry 23 corresponding to each of LRU0 to LRUm are accessed.
Is updated, and the accessed directory entry 23 is positioned at the top. Hereinafter, the operation of the present embodiment will be described. First, when a write command is issued from the central processing unit 1 to the intermediate storage unit 17, the microprocessor 7 sets the device address D of the directory entry 23 shown in FIG.
The directory area 17c is searched based on A, cylinder number C, and head number H. At this time, the directory entry 23 corresponding to the search condition
Is present between LRU0 and LRUn, the counting unit 20, the key unit 21, and the key unit 21 corresponding to the record in the first storage area 17a and the second storage area 17b based on the instruction from the central processing unit 1. The data section 22 is updated, and the write update flag of the field of the count section 20 shown in FIG. 1 (c) is set to "1". Further, the pointer LRUU and the pointer LRUL are updated so that the directory entry 23 of the slot to which the updated record belongs is positioned at the top of the list structure as the most recently accessed, and the write flag W is set. It is set to “1”, and the uppermost register 24 is updated to indicate the directory entry 23. The microprocessor 7 has a directory area 17 at any time.
When a directory entry 23 in which the write flag W is set to “1” is found with reference to c, the record belonging to the slot indicated by the directory entry 23 is stored in the external storage from the intermediate storage 17 independently of the central processing unit 1. A write-after operation is performed to transfer the data to the unit 2 and write the data. At this time, the write record flag WR of the count section 20 of each record shown in FIG. 1C is referred to, and only the record for which the write record flag WR is set to "1" is sent to the external storage section 2. Write is executed,
A decrease in write efficiency caused by writing unnecessary records is avoided. Then, after a predetermined write operation to the external storage unit 2 is completed, the write flag W of the directory entry 23 and the write record flag WR of the count unit are updated to “0”. On the other hand, when the record for which the write is instructed by the central processing unit 1 exists in the range of LRUn + 1 to LRUm of the directory entry 23, the microprocessor 7 stores the key unit 21 and the data unit 22 in the second storage area 17b. And the address of the slot in the second storage area 17b is stored in the CA2 field of the directory entry 23, and the flag V2 indicating that the slot is valid is set to "1". At the same time, the list structure is updated by the LRU method, and the directory entry 23 is registered in the highest-order register 24 as the most recently accessed one. The records thus stored in the intermediate storage unit 17 are independent of the operation of the central processing unit 1 as in the above case.
The data is transferred to the external storage unit 2 as needed. Further, when the record instructed to be written by the central processing unit 1 does not exist in the intermediate storage unit 17, after the microprocessor 7 searches the intermediate storage unit 17, the central processing unit specifies the storage position of the external storage unit 2. Although the external storage unit 2 is directly accessed from the unit 1, the external storage unit 2 composed of a magnetic disk device or the like involves a mechanical operation such as head movement, so that the access time is relatively long. . Here, in the present embodiment, the number of slots for storing the count section 20 in the first storage area 17a in the intermediate storage section 17 is the number of slots for storing the key section 21 and the data section 22 in the second storage area 17b. Is controlled so as to be mn more than the number of records, so that when a write of a record is instructed from the central processing unit 1, the probability that the count unit 20 of the record exists in the intermediate storage unit 17 increases. . For this reason, the frequency at which the central processing unit 1 is constituted by a magnetic disk device or the like and directly accesses the external storage unit 2 having a relatively low operation speed to search for the target counting unit 20 is reduced. The data transfer rate per unit time between the processing unit 1 and the external storage unit 2 can be improved. In the above description, the record management unit in the intermediate storage unit 17 is a track unit in the external storage unit 2 such as a magnetic disk device. However, the present invention is not limited to this. May be managed as one block in block units. [Effects of the Invention] As described above, according to the present invention, a central processing unit, an external storage unit that stores a plurality of records including a combination of management information and actual data, an external storage unit, and the central processing unit A data transfer control system comprising an intermediate storage unit interposed between the external storage unit and the central processing unit, wherein the transfer of records between the external storage unit and the central processing unit is performed directly or via the intermediate storage unit. The storage unit has a first storage area for storing management information of a record and a second storage area for storing actual data corresponding to the management information. Since the number is controlled so as to be larger than the number of actual data stored in the second storage area,
The probability that the management information of the record operated in the central processing unit exists in the cache memory increases, and the frequency of direct access to the external storage unit whose operation speed of the central processing unit is relatively low can be reduced. It is possible to improve the data transfer rate per unit time between the processing unit and the external storage unit.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 (a) to 1 (c) are explanatory diagrams for explaining the operation of a data transfer control system according to an embodiment of the present invention, and FIGS. 2 (a) to 2 (c) are the same. FIG. 3 is an explanatory diagram for explaining the operation of a data transfer control system according to one embodiment of the present invention; FIG. It is. 1 Central processing unit 2, External storage unit 3, External storage control unit 4, Channel interface 5, Channel interface control unit 6, Signal path 7, Microprocessor 7a … Control store cash register,
8 signal path, 9 device interface control unit, 10 device interface, 11 device control adapter, 12, 13 signal path, 14 data transfer control unit, 15, 16 signal path , 17... Intermediate storage section, 17a... First storage area, 17b... Second storage area, 17c... Directory area, 18, 19... Signal path, 20. 21 key part (actual data), 22 data part (actual data), 23 directory entry, 24 top register, 25 bottom register, C cylinder number, H head Number, R …… Record number, KL ……
The length of the key portion, DL ... the length of the data portion, WR ... the write record flag, DA ... the device address, CA1 ... the storage address in the first storage area 17a, V1 ... the data in the storage address CA1 , A valid flag indicating that the data at the storage address CA2 is valid, a valid flag indicating that the data at the storage address CA2 is valid, a write flag, LRU
U, LRUL ... pointer.

Claims (1)

(57) [Claims] A central processing unit, an external storage unit that stores a plurality of records each including a combination of real data and management information for the real data, an intermediate storage unit that is provided between the external storage unit and the central processing unit, A data transfer comprising: a control unit that controls transfer of the record between the external storage unit and the central processing unit directly or via the intermediate storage unit and that controls an operation of the intermediate storage unit. The control device, wherein the intermediate storage unit is a first storage area that stores the management information of some of the plurality of records,
A second storage area for storing the actual data of some of the plurality of records, wherein the control unit controls the record having the oldest access time to be replaced with a new record. A data transfer control device for controlling the number of the management information stored in the first storage area to be larger than the number of the actual data stored in the second area. 2. 2. The method according to claim 1, wherein the external storage unit and the intermediate storage unit are a magnetic disk device and a cache memory, respectively, and the management information is a count unit of a count key data recording method in the magnetic disk device. 2. The data transfer control device according to claim 1, wherein: