JPH066387A - Method and device for data transfer control - Google Patents

Abstract

PURPOSE:To obtain data transfer control technique which can easily increase the size of a buffer according to changes in operation environment such as an increase in the data transfer distance between devices and an increase in the speed of the data transfer. CONSTITUTION:The 2nd control circuit 14 of a storage device 3 monitors the amount of data in a 2nd data buffer 13 and informs the 1st control circuit 8, which controls a 1st data buffer 7 provided to a storage controller 2, of whether or not the amount of the data is larger than a prescribed value. The 1st control circuit 8 switches decision conditions of whether or not a data transfer request to a channel 1 is generated according to the information from the 2nd control circuit 14 to prevent the 1st buffer 7 and 2nd data buffer 13 from overflowing, thereby making the 1st data buffer 7 and 2nd data buffer 13 operate equivalently to one buffer for transfer control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transfer control technique, and more particularly to a technique effectively applied to data transfer control between a central processing unit and a peripheral device in an information processing system.

[0002]

2. Description of the Related Art For example, for data transfer in a central processing unit, an external storage unit or the like which constitutes an information processing system, generally, one device issues a data transfer request,
On the other hand, the other device returns a response to the request and then starts data transfer. In such a data transfer, considering the case where one device requests data transfer, the other device returns a response to this request, and the data transfer is executed in synchronization with the response, When the delay time of signal transmission cannot be ignored with respect to the above distance, time due to transmission delay is consumed from the data transfer request to the response. If there is a large amount of data to be transferred and the above transfer request and response are repeated in order to transfer each, until the transfer of all data is completed, (transmission delay time from request to response) × (Data volume) time is required, which is not efficient. Therefore, as a method of reducing the above required time, there is a method of collectively requesting a plurality of data at the time of requesting data transfer and collectively sending the requested amount of data at the time of responding thereto. Using this method, the time to transfer all data is (transmission delay time from request to response) x (data amount) /
(The amount of data transferred in one data request) becomes, and the larger the amount of data requested in one data request is, the shorter the transfer is completed. Further, if the method of issuing the next request after waiting for the response after requesting the data transfer is used, the required transfer time can be further shortened.

However, in the case of collectively requesting a plurality of data in this way, for example, Japanese Patent Laid-Open No.
As described in Japanese Patent Laid-Open No. 233646, a buffer is required to reliably receive already requested data and prevent its disappearance. The size of this buffer depends on how much data needs to be requested collectively, and depends on the required data transfer rate and the transmission delay time from request to response, that is, the length of the transmission path between devices. .

[0004]

Therefore, when designing a device for controlling data transfer as described above, the buffer size used therein is always sufficient to meet the maximum transmission distance and the maximum data transfer rate. It is necessary to prepare the size in advance.

On the other hand, recently, due to networking of information processing and further specification change in a short period of time due to improvement in performance of peripheral devices, host devices such as central processing units and channels, and external devices connected to the host devices are connected. It is relatively difficult to accurately predict the physical distance between peripheral devices such as storage devices and the data transfer performance, and the size of a single buffer in the data transfer control device must be accurately determined at design time. Is not easy.

An object of the present invention is to provide a data transfer control technique capable of easily expanding the buffer size in response to changes in the operating environment such as an increase in the data transfer distance between devices and an increase in the speed of data transfer. Especially.

Another object of the present invention is to provide a data transfer control technique capable of accurately realizing a required buffer size by connecting a plurality of buffers having a size smaller than the required buffer size with a simple interface. To provide.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0009]

Among the inventions disclosed in the present application, a brief description will be given to the outline of typical ones.
It is as follows.

According to the data transfer control method of the present invention, the first and second data transfer paths are serially interposed in the data transfer path between the first and second devices, and bidirectional data transfer is performed by inputting other outputs. In a data transfer control circuit including a second data buffer, the operation of issuing a data transfer request between the first data buffer and the first device is controlled based on the capacity of the second data buffer and the size of the data amount. To do.

The data transfer control method of the present invention is the data transfer control method according to claim 1, wherein at least one of a data transfer rate and a distance between the first device and the first data buffer, or 2nd device and 2nd
The capacity of the second data buffer is optimally set according to at least one of the data transfer rate and the distance from the data buffer.

Further, the data transfer device of the present invention is a first data transfer device that intervenes in series in the data transfer path between the first and second devices and performs bidirectional data transfer by inputting other outputs to each other. And a second data buffer, a first control circuit for controlling a data transfer request between the first data buffer and the first device, and a second control circuit for controlling the second data buffer. In a data transfer control device including: first means for presetting the capacity of the second data buffer for the first control circuit; and second data for the second control circuit for the first control circuit. A second means for notifying the amount of data in the buffer is provided, and the control condition in the first control circuit is switched based on the capacity and the amount of data in the second data buffer.

The data transfer device of the present invention is the data transfer control device according to claim 3, wherein the first and second data transfer devices are provided.
Device comprises a storage device having a storage medium for storing data exchanged with the channel and the channel, respectively, and the first data buffer and the first control circuit are provided between the channel and the storage device. The second data buffer and the second control circuit are arranged in a storage control device that controls data transfer between them via the interposition, and the second data buffer and the second control circuit are arranged in the storage device.

[0014]

The buffer size for preventing transfer data loss, that is, the maximum value of the storable data amount is S1,
The integrated value of the number of requests from the start of the data transfer is DR, the integrated value of the data amount input to the data buffer is received as DI1, and the integrated value of the data use output from the data buffer to the device side is as DO1. To do. Here, the data buffer has a function of temporarily storing the received data, and outputs the stored data to the device side immediately as long as the device side can receive the data. The condition for preventing data loss in this case is DR-DO1 ≤ S1, so DR and DO1 are counted, and the difference between them is S.
It is necessary to control the transmission of the data transfer request so that it does not become larger than 1.

In the above-described data transfer technique of the present invention, for example, the size of the first data buffer provided in the storage control device is not changed, but the second data buffer is provided on the storage device side, and the second data buffer is provided, for example. By changing the control of the first data buffer according to the state of the data buffer,
First, without changing the size of the data buffer of
And the size S1 of the apparent single data buffer consisting of the second data buffer is freely expanded.

That is, the size of the second data buffer is S2, the integrated value of the amount of data that is output from the first data buffer and is directly input to the second data buffer is DI2, and the integrated value is output from the second data buffer. , Where the integrated value of the amount of data sent to the second device is DO2, the condition for preventing data loss is DR-DO2 ≤ S1 + S2. When this is modified, it becomes DR-DO1 + DI2-DO2 <= S1 + S2. The second control circuit of the second data buffer is D
Only I2-DO2 and S2 are compared, and only the magnitude of the result is notified to the first control circuit of the first data buffer. In the first control circuit of the first data buffer,
The value of S2 is set by a predetermined method, and based on this and the comparison result obtained from the second control circuit, the first control circuit controls the data transfer request as follows.

1) When the comparison result indicates DI2-DO2≤S2, it is considered that DI2-DO2 = 0, and the data transfer request is controlled so as to satisfy DR-DO1≤S1 + S2.

2) When the comparison result indicates DI2-DO2> S2, it is considered that DI2-DO2 = S2, and the data transfer request is controlled so that DR-DO1≤S1 is satisfied.

However, even when DI2-DO2 = S2, it is considered that DI2-DO2 = 0.
2 × S2 capacity is required as the data buffer of.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A data transfer control method and apparatus according to an embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing a case where the data transfer control method and apparatus of the present invention is applied to data transfer between a central processing unit and an external storage unit in an information processing system.

The information processing system according to the present embodiment includes a channel 1 for controlling input / output of data with the outside under the control of a central processing unit (not shown), and a storage device connected to the channel 1 via a storage control device 2. Equipped with 3. Channel 1
A channel interface 4 between the storage controller 2 and
The storage control device 2 and the storage device 3 are connected by an inter-device interface 10.

Inside the storage control device 2, a channel interface control 5 for performing interface control with the channel 1, a first data buffer 7 for temporarily storing data exchanged with the channel 1, and the first data buffer 7 A data buffer interface 6 that connects the data buffer 7 and the channel interface control 5 is provided, a first control circuit 8 that controls the operation of the first data buffer 7, and a microprocessor 9 that collectively controls these units. There is.

The storage device 3 temporarily stores data exchanged with the storage control device 2 via the data storage part 17 composed of a desired durable storage medium and the inter-device interface 10 to temporarily store the data. Second to interact with
A data buffer 13, a second control circuit 14 that controls the operation of the second data buffer 13, and a microprocessor 15 that controls the entire storage device 3 are provided.

Further, the first control circuit 8 of the storage control device 2 and the second control circuit 14 of the storage device 3 are connected by a control line 11, and similarly, the microprocessor 9 and the microprocessor 15 are connected to each other by the communication interface 12. Are connected to each other via.

The operation of the data transfer control method and apparatus of this embodiment will be described below for the case of performing a write operation, that is, the case of transferring data from channel 1 to storage device 3.

The channel interface control 5 performs protocol control in the channel interface 4. This protocol is predetermined, and various interfaces such as one using a metal cable as an interface line and one using an optical fiber can be used.

Data transfer is mainly performed by the first control circuit 8
And is controlled by the second control circuit 14.

The first control circuit 8 is a microprocessor 9
The preset size of the second data buffer 13, the storage state of the data in the second data buffer 13 notified from the second control circuit 14 via the control line 11, and the data in the first data buffer 7. Whether or not to request the data transfer to the channel 1 is determined according to the storage state of the data, and the data transfer request 16 is controlled.

The channel interface control 5 converts the data transfer request sent via the data transfer request 16 into a format suitable for the protocol on the channel interface 4 and sends it to the channel 1. Receiving this, the channel 1 sequentially sends out the requested amount of data to the channel interface 4 according to the protocol on the channel interface 4. Upon receiving this data, the channel interface control 5 extracts only that data from the protocol and sends it to the first data buffer 7 via the data buffer interface 6.

The first control circuit 8 for controlling the first data buffer 7 stores the data temporarily stored in the first data buffer 7 as long as the data stored in the second data buffer 13 is not full. The data is sent to the second data buffer 13 via the inter-interface 10.

The second control circuit 14 for controlling the second data buffer 13 synchronizes the data temporarily stored in the second data buffer 13 with the data storage unit 17 in synchronization with the operating speed of the data storage unit 17. Send to 17.

The operation of the first control circuit 8 and the second control circuit 14 in such a data transfer process will be described in more detail.

The second control circuit 14 monitors the amount of input data to the second data buffer 13 and the amount of output data to know the amount of data stored in the second data buffer 13. Two kinds of binary information indicating whether or not this data amount is larger than 1/2 of the total data storage amount of the second data buffer 13 and whether or not it is equal to the total data storage amount are set as 2 bits, and the control line 11 The first control circuit 8 is notified via.

Similarly, the first control circuit 8 also monitors the input data amount and the output data amount of the first data buffer 7 to know the stored data amount. Further, the first control circuit 8 includes a second data buffer 13 from the microprocessor 9.
The total data storage amount (storable capacity) therein is preset. This setting is performed, for example, by the microprocessor 9 receiving information about the capacity from the microprocessor 15 via the communication interface 12 when the power of the device is turned on.

The first control circuit 8 determines the following from the set value and the information notified via the control line 11, the data amount already requested for the channel 1 and the output data amount from the first data buffer 7. The method determines whether to request data transfer to channel 1.

(1). When the amount of data in the second data buffer 13 notified via the control line 11 is less than 1/2 of the total storage amount, the past number of data transfer requests and the first data buffer 7 If the difference in the amount of output data is less than the total amount of data stored in the first data buffer 7 and the total amount of data stored in the second data buffer 13, the data transfer is requested. Do not request.

(2). When the amount of data in the second data buffer 13 notified via the control line 11 is larger than 1/2 of the total storage amount, the past number of data transfer requests and the first data buffer 7 If the difference in the output data amount is less than the total data storage amount of the first data buffer 7, the data transfer is requested, and if the difference is equal to or more than the total data storage amount, the data transfer is not requested.

By the above control, data transfer during the write operation is performed without causing a concern such as overflow of the first data buffer 7 and the second data buffer 13 and loss of data.

As described above, according to the data transfer control method and apparatus of this embodiment, the following effects can be obtained.

(1). The first data buffer 7 is enlarged by providing the second data buffer 13 on the storage device 3 side without increasing the size of the first data buffer 7 on the storage control device 2 side. This makes it possible to perform control equivalent to that of the case.

(2). First control circuit 8 for independently controlling each of the first data buffer 7 and the second data buffer 13.
Since the control information exchanged between the second control circuit 14 and the second control circuit 14 is simple, the required bit width of the control line 11 for exchanging the information is reduced, and the interface between the storage control device 2 and the storage device 3 is reduced. Will be easier.

(3). When the storage device 3 connected to the storage control device 2 is switched to another type, the required data buffer size can be changed by changing the data transfer rate or transmission distance for the channel 1. Even if it occurs, it is not necessary to change the size of the first data buffer 7 of the storage control device 2 only by changing the size of the second data buffer 13 on the storage device 3 side, and the storage control device 2 can be used for various storage devices. 3 and transmission distance can be used in common.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say.

[0045]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows.
It is as follows.

That is, according to the data transfer control method and device of the present invention, the buffer size can be easily expanded in response to changes in the operating environment such as an increase in the data transfer distance between devices and an increase in the speed of data transfer. The effect of being able to be obtained is obtained.

Further, according to the data transfer control method and apparatus of the present invention, a plurality of buffers having a size smaller than the required buffer size can be connected to achieve the required buffer size with a simple interface. The effect of being able to do is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a case where a data transfer control method and device according to an embodiment of the present invention are applied to data transfer between a central processing unit and an external storage device in an information processing system.

[Explanation of symbols]

 1 channel (first device) 2 storage controller 3 storage device (second device) 4 channel interface 5 channel interface control 6 data buffer interface 7 first data buffer (first data buffer) 8 first control circuit ( First control circuit) 9 Microprocessor 10 Inter-device interface 11 Control line (second means) 12 Communication interface (first means) 13 Second data buffer (second data buffer) 14 Second control circuit ( Second control circuit) 15 Microprocessor 16 Data transfer request 17 Data storage unit

Claims (4)

[Claims] 1. A first data buffer and a second data buffer which serially intervene in a data transfer path between a first device and a second device and perform bidirectional data transfer by inputting other outputs to each other. In the data transfer control circuit, the second
The data transfer control method, wherein the data transfer request issuing operation between the first data buffer and the first device is controlled based on the size of the data buffer and the amount of data. 2. A data transfer rate and / or a distance between the first device and the first data buffer, or a data transfer rate between the second device and the second data buffer. The data transfer control method according to claim 1, wherein the capacity of the second data buffer is optimally set according to at least one of the distance and the distance. 3. A first data buffer and a second data buffer which serially intervene in a data transfer path between the first and second devices and perform bidirectional data transfer by inputting mutually different outputs. A data transfer control device including a first control circuit that controls a data transfer request between the first data buffer and the first device, and a second control circuit that controls the second data buffer. And the first
Means for presetting the capacity of the second data buffer for said control circuit, and the amount of data in said second data buffer for said first control circuit from said second control circuit And a second means for notifying that the control condition in the first control circuit is switched based on the capacity and the data amount of the second data buffer. 4. The first and second devices are storage devices each including a channel and a storage medium for storing data exchanged with the channel, and the first and second devices are provided.
Data buffer and the first control circuit are provided in the storage control device that intervenes between the channel and the storage device to control data transfer between them, and the second data buffer and the second control circuit are provided. The data transfer control device according to claim 3, wherein a circuit is provided in the storage device.