JPH0520264A - Method for controlling buffer - Google Patents

Abstract

PURPOSE:To shorten the useless time of unused buffer segments by reducing the number of executions of processing to be queued until an idle area is formed in a buffer segment in using, improving buffer writing performance, and even when the number of loads is small, connecting unused buffer segments and using them. CONSTITUTION:This buffer controlling system has a data buffer 1 divided into plural buffer segments 10 to 12 and a connection status table indicating the correction order of the buffer segments in the data buffer 1. The system includes a function for searching an unused buffer segment, registering the searched segment in the table to increase the capacity of usable buffer when all data can not be completely written because of the lacking of idle areas in the buffer 1 in the case of writing data in the buffer 1 and a function for queuing processing until a buffer segment is released and turned to a usable state when there is no unused buffer segment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a buffer control method, and more particularly to a buffer control method for writing data to a buffer segment of a data buffer divided into a plurality of segments.

[0002]

2. Description of the Related Art In a conventional buffer control system, when writing data into a buffer, if there is little free space in the buffer and all the data cannot be written into the buffer, there is sufficient free space in the buffer currently in use. I was waiting until.

[0003]

The conventional buffer control system described above always waits for a sufficient free space to be created in the buffer when the free space in the buffer is too small to write all the data in the buffer. The writing performance to was not good.

Further, when the load on the buffer is small, there is a drawback that many buffer segments are in an unused state and the time for idlely playing the buffer segments becomes long.

[0005]

A buffer control method according to the present invention determines a data buffer divided into a plurality of buffer segments and in what order the buffer segments of the data buffer are connected. A connection status table shown and a buffer control device having a buffer control function that enables access to the data buffer in the order of the buffer segments registered in the connection status table, when writing data to the buffer, an empty area in the buffer When not all the data can be written, there is a function of searching the unused buffer segment and registering it in the connection status table to increase the capacity of the available buffer.
As a result of searching the unused buffer segment, if there is no unused buffer segment, it has a function of waiting until the buffer segment is released and becomes available.

[0006]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a schematic diagram of a data buffer showing an embodiment of the buffer control method of the present invention. Data buffer 1 is segment 0:10, segment 1:11,
, Segment N-1: 12 is divided into N segments. A buffer control method of an input / output control device connecting two input / output devices will be described as an embodiment of the present invention. The input / output control device performs input / output operations with respect to the two input / output devices while storing the input / output data in the segment of the built-in data buffer 1.

FIG. 2 is a schematic diagram of a connection status table showing the connection order of the buffer segment being registered and the buffer segment. Data buffer 1 in connection status table 2
There are N tables 0:20, tables 1:21, ..., And tables N-1: 22, which are equivalent to the number of segments. Since the connection status table 2 needs to be provided for each input / output device, two identical connection status tables 2 exist. As shown in the bit structure 3 of the table, one table is composed of 1 byte in total including 1 effective bit and 7 segment number. The connection status table 2 is capable of registering N buffer segment numbers as many as the number of buffer segments so that all buffer segments can be used as one segment. The connection status table 2 simultaneously stores the number of the buffer segment currently connected and a valid bit indicating that the buffer segment number is valid. Since the first access process to the data buffer starts from the table 0 of the connection status table 2, if the valid bit of the table 0 is 0, it means that the input / output device has no usable buffer segment. When the valid bit of the table 0 is 1, the input / output device has a buffer segment in at least one segment, and the buffer segment shown in the table is accessed. If an overflow occurs in the access to the buffer segment indicated by table 0, the next access processing automatically moves to the buffer segment indicated by the next table 1.
At this time, access moves to the buffer segment of table 1 only when the valid bit of table 1 is 1, and when the valid bit is 0, access to the first address of the buffer segment of table 0 is performed. Done. The above-mentioned process of automatically moving the segment to be accessed is performed up to the maximum table N-1, and when the access process to the buffer segment of the table N-1 overflows, the buffer segment of the table 0 is automatically changed. Access processing moves. The contents of the connection status table 2 are cleared when the input / output operation to the input / output device corresponding to the connection status table 2 is completed, and the buffer segment used is released.

FIG. 3 shows a procedure performed by the microprogram for instructing writing of data in the data buffer. When a data write request is issued to the buffer, the microprogram determines from the control information of the buffer whether there is sufficient free space in the buffer and writing is possible (step 30). When there is not enough space in the buffer segment and writing is not possible, and when the buffer segment is written for the first time, connection processing of the buffer segment is executed to enable writing to the buffer (step 31). This processing will be described later in detail with reference to FIG. Step 32
Then, since the data can be written in the buffer segment, the buffer controller is instructed to write the data. After writing the data, assuming that the length of the next data is the same as the length of the data written this time,
Calculates whether all data can be stored in the connected buffer segment. If the data cannot be stored, the information that the writing to the buffer is impossible is stored in the storage area, and if the information can be stored, the information that the writing is possible is stored in the storage area (steps 34 and 3).
5).

FIG. 4 shows that the buffer segment has little space and cannot write all data to the buffer.
Alternatively, when the valid bit of table 0 is 0 and there is no buffer segment, the procedure of the process of connecting an unused buffer segment to make a usable buffer segment is shown. The microprogram determines whether or not the buffer segment has an unused buffer segment, and if there is an unused buffer segment (step 4).
(Yes at 0), register in the connection status table 2 (step 44), and terminate the process. If another I / O device is using all the remaining buffer segments, there is no unused buffer segment (No in step 40), and the valid bit of table 0 of the connection status table 2 is 0 (step 41 is No), and waits until any buffer segment used by another I / O device is released (step 42). When one segment is released, it is registered in the connection status table 2 ( Step 44) ends the process. If there is no unused buffer segment (No in step 40), the valid bit of the table 0 of the connection status table 2 is 1, and at least one segment is registered in the connection status table 2 (Yes in step 41). The process waits until there is a free space in the currently connected buffer segment (step 43), and the process ends when the free space is available.

[0011]

As described above, according to the buffer control method of the present invention, when writing data into the buffer, when there is little free space in the buffer and all the data cannot be written into the buffer, an unused buffer segment number is set. By registering in the connection status table and increasing the available buffer capacity, the number of executions of the process of waiting until there is free space in the currently used buffer segment is reduced and the performance of writing to the buffer is improved. Even when the load is small, the number of unused buffer segments is reduced by the process of connecting and using the unused buffer segments, and the time for idle use of the buffer segments can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a data buffer showing an embodiment of a buffer control method of the present invention.

FIG. 2 is a schematic diagram of a connection status table showing a buffer segment being registered and a connection order of the buffer segments according to the present embodiment.

FIG. 3 is a flowchart showing a procedure in which the microprogram of the present embodiment instructs the buffer control device to write data in the buffer.

FIG. 4 is a flow chart showing a process of increasing the available buffer capacity by connecting an unused buffer segment when the buffer segment has little free space and data cannot be written to the buffer segment according to the present embodiment.

[Explanation of symbols]

1 data buffer 2 connection status table 10, 11, 12 buffer segment 0, 1, N-
1 20, 21, 22 Tables 0, 1, N-1

Claims (1)

Claim: What is claimed is: 1. A data buffer divided into a plurality of buffer segments, and a connection status table indicating in what order the buffer segments of the data buffer are connected. A buffer control device having a buffer control function capable of accessing the data buffer in the order of the buffer segments registered in the connection status table has a small empty area in the buffer when writing data to the buffer, and all the data is stored. When it is not possible to write, a function of increasing the capacity of the available buffer by searching for the unused buffer segment and registering it in the connection status table, and a result of searching the unused buffer segment, If there is no buffer segment before Buffer control method characterized by comprising a function to wait until the buffer segment is released becomes usable state.