JPH1031616A - Inter-process communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inter-process communication system by which the time for transmission/reception can be shortened in the case of making communication by using the transmission/reception queue of a mail box system. SOLUTION: Between a transmission side process 51 and a reception side process 53, a commonly accessable shared memory 58 is arranged. The transmission side process 51 constructs data 59 to be a communication object in this shared memory 58, copies its start address and the amount of data from a memory area 52 to a transmission/reception queue 57 as information 56 and copies this information into a memory area 54. Thus, a flag 61 is changed into '1' and the reception side process 53 can read data from the relevant area of the shared memory 58. Since the shared memory 58 is constructed for commonly accessing the main section of data, the time required for copy can be remarkably economized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inter-process communication system using a shared memory, and more particularly to an inter-process communication system for performing data communication by a mailbox system using a transmission / reception queue.

[0002]

2. Description of the Related Art Some interprocess communication systems that perform communication between processes use a send / receive queue to perform data communication by a mailbox method. In this mailbox-type system, each of the transmitting process and the receiving process can independently allocate a memory area at the time of initialization. The sender process constructs the send data in the memory area assigned to this sender. The constructed data is copied to the send / receive queue and then posted to the mailbox. The mailbox notifies the receiving process to which the posted send / receive queue should be delivered that the data has been sent.
This notification is performed using a flag. Upon receiving the notification by this flag, the receiving process copies all the data stored in the transmission / reception queue to the memory area allocated at initialization.

FIG. 2 shows an outline of the configuration of such a conventional inter-process communication system. In this system, the first memory area 12 allocated at the time of initialization is arranged on the side of the transmitting process 11, and the second memory area 14 similarly allocated at the time of initialization is arranged at the side of the receiving process 13. It is arranged. A transmission / reception queue 17 for temporarily storing the data 16 to be transmitted / received is arranged between these processes 11 and 13. The receiving process 13 includes a flag 18 indicating whether or not the transmission / reception queue 17 is transmitted.

In such an interprocess communication system, the transmitting side process 11 constructs the data 21 to be transmitted in the first memory area 12. When transmitting, the constructed data 21 is all copied to the transmission / reception queue 17 as data 16 and posted to the mailbox. When the transmission / reception queue 17 holding data in the mailbox system is transmitted from the transmission side process 11, the reception side process 1
3 is notified of this fact by a flag. Then, the reception side process 13 copies the data 16 held in the transmission / reception queue 17 to the second memory area. By such an operation, the receiving side process 13 becomes the transmitting side process 11
The data 21 constructed by can be copied to the second memory area 14 and read as the data 19.

[0005]

In the inter-process communication system shown in FIG. 2, the data 21 in the first memory area 12 is copied to the transmission / reception queue 17 by the first copy operation 31, and then this copied data is copied. The copied data 16 is copied to the second memory area 14 by a second copy operation 32. Here, when the size of the data 21 constructed in the first memory area 12 is large, it takes a certain amount of time to copy to the transmission / reception queue 17 in the first copy operation 31. Then, the mail is posted to the mailbox. Receiving process 13
Also, when reading the data 19, it is necessary to copy the data 16 in the transmission / reception queue 17 to the second memory area 14, and when the size of the data 16 is large, the copying requires a relatively long time. It will be.

[0006] The amount of data required for real-time communication such as voice and moving images is increasing. When transmitting such data by inter-process communication, it is important that the communication is immediate or speedy. However, in inter-process communication, the first and second memory areas 12 and 14 allocated at the initialization of the system are completely independent in each process 11 and 13. Therefore, the first memory area 12
Is copied once to the transmission / reception queue 17 and posted to the mailbox. However, with this, the first and second two copying operations 3
Nos. 1 and 32 reduce the immediacy of data communication, and particularly when the size of the data to be copied is large, there is a problem in that the performance of transmission / reception time of inter-process communication is reduced and real-time communication becomes difficult.

In Japanese Patent Application Laid-Open No. 60-237566, an area corresponding to each processor is allocated, and an interrupt notification is sent to the other processor via the area to confirm that data exists in that area. In addition to the notification, the processor receiving the data writes the specified pattern in the area assigned to its own processor to notify the processor on the transmitting side that the data has been received.

FIG. 3 shows the proposed inter-process communication system. In this figure, the first processor 4
The first and second processors 42 have a shared memory area 43. The shared memory area 43 is a first area 44 transmitted by the first processor 41 and received by the second processor 42.
Received by the first processor 41 and received by the second processor 4
2 has a second area 45 to transmit. Therefore, when transmitting data from the first processor 41 to the second processor 42, the data to be transmitted is stored in the first area 44 of the shared memory area 43. afterwards,
The first processor 41 is connected to the second processor 42 by I / O.
Send commands, etc. The second processor 42 uses this I / O
Immediately returns a response signal to end the command. Then, after that, the first area 44 is accessed to read the data. The second processor 42 on the receiving side clears the received area and writes a response pattern in that area.

However, in this proposed technique, the shared memory area 43 is allocated for each pair of transmission and reception of each processor, so that it is necessary to secure each area when the number of pairs of processors increases. . Therefore, if an attempt is made to secure an area for storing data of a relatively large size, the entire size of the shared memory area becomes extremely large, causing a problem of increasing the cost of the inter-process communication system.

An object of the present invention is to provide an inter-process communication system capable of shortening the transmission / reception time when performing communication using a mailbox type transmission / reception queue.

Another object of the present invention is to provide an interprocess communication system capable of saving the entire memory capacity when performing communication using a mailbox type send / receive queue.

[0012]

According to the first aspect of the present invention, (a) a transmitting process as a data transmitting device;
(B) A receiving side process as a data receiving side,
(C) a shared memory capable of at least writing data from the transmitting process and reading data from the receiving process; and (d) transmitting data between the transmitting process and the receiving process. A send / receive queue that stores the information indicating the location of the communication target data written by the process in the shared memory and is sent from the sending process to the receiving process, and (e) this sending / receiving queue is sent to the receiving process. When the reception completion notifying means for notifying this and (f) the reception side process is arranged, and when the reception completion notifying means notifies the completion of transmission of the transmission / reception queue, the location of the data to be communicated from the transmission / reception queue And a data reading means for reading the corresponding data from the shared memory based on the extracted information. Interprocess is provided to the communication system.

That is, according to the first aspect of the present invention, a shared memory is provided between a transmitting process and a receiving process so that data to be communicated by the transmitting process can be directly written in the shared memory. In order to effectively use the memory, the area is used without being allocated in advance. Information indicating in which area of the shared memory the data has been written is sent to the receiving process by the transmission / reception queue, and the reception completion notifying means notifies the receiving process. As a result, the receiving process reads the data in the corresponding area of the shared memory. As a result, it is possible to prevent a delay in processing time due to copying of data, and to allow a shared memory to be shared, thereby suppressing an increase in the memory size and reducing the cost of the system.

According to the second aspect of the invention, (a) a transmission side process as a data transmission side, (b) a reception side process as a data reception side, and (c) a transmission side process at the time of system initialization. (D) a shared memory area in which data can be written from the sender process and data can be read from the receiver process, and (e) a sender process and a receiver process. A transmission / reception queue, which is copied from the transmission-side memory area and transmitted from the transmission-side process to the reception-side process, in which information indicating the location of data to be communicated written by the transmission-side process to the shared memory is transmitted by the transmission-side process when performing data communication between the , (F) reception completion notifying means for notifying this when the transmission / reception queue is transmitted to the receiving side process,
(G) When the reception completion notifying means arranged on the receiving side process side notifies that the transmission / reception queue has been transmitted, information indicating the location of the data to be communicated is extracted from the transmission / reception queue and the extracted information is used as a basis. And a data reading means for reading corresponding data from the shared memory.

That is, according to the second aspect of the present invention, a shared memory is provided between the transmitting process and the receiving process so that the data transmitted by the transmitting process can be directly written in the shared memory. In order to effectively use the memory, the area is used without being allocated in advance. Information indicating in which area of the shared memory data has been written is copied from the transmission-side memory area to the transmission / reception queue and sent to the reception-side process. The reception completion notifying means notifies the reception side process of the completion of the transmission. As a result, the receiving process reads the data in the corresponding area of the shared memory. As a result, it is possible to prevent a delay in processing time due to copying of data, and to share the shared memory so as to suppress an increase in the memory size and reduce the system cost.

In the third aspect of the invention, the data written in the shared memory from the transmitting side process has a variable length,
The information indicating the location of the data to be communicated is characterized by including an address indicating one end of the data stored in the shared memory and the data amount. That is, in claim 3, communication of variable-length data is handled, and in order to specify data stored in the shared memory, an address indicating the leading end or the trailing end of the data and the amount of data are used. .

According to the fourth aspect of the present invention, the data written from the transmitting process to the shared memory has a fixed length.
The information indicating the location of data to be communicated is characterized by comprising an address indicating one end of the data stored in the shared memory. That is, the invention according to claim 4 deals with communication of fixed-length data. Since the amount of data is fixed and fixed, the address indicating the leading end or the trailing end of the data may be present to specify the data stored in the shared memory.

According to a fifth aspect of the present invention, in the inter-process communication system according to the first to third aspects, the reception completion notifying means is a flag indicating transmission completion in one of two states. There is. For example, when the raster is "1", it indicates that the data has been transmitted.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION

[0020]

EXAMPLES The present invention will be described in detail below with reference to examples.

FIG. 1 shows the configuration of an inter-process communication system according to an embodiment of the present invention. In this system, a first memory area 52 allocated at the time of initialization is arranged on the transmitting process 51 side, and a second memory area 54 also allocated at the time of initialization is allocated on the receiving process 53 side. Are located. Between these processes 51 and 53, a transmission / reception queue 57 for storing a pointer indicating the position of data to be transmitted and received and information 56 for indicating the data size, and a shared memory 58 accessible by both processes 51 and 53 are provided. It is arranged. The shared memory 58 stores data 59 to be communicated. Further, a flag 61 for displaying the presence / absence of transmission in the transmission / reception queue 57 is arranged on the reception side process 53 side. The flag 61 indicates "0" when the transmission / reception queue 57 is not transmitted.

In such an interprocess communication system, the transmitting process 51 writes data 59 to be transmitted on the shared memory 58. Sender process 5
1 transfers the written data 59 to the receiving process 53, the first memory area 5 as a working memory thereof.
2, a pointer A indicating the head address of the data 59 constructed in the shared memory 58 and the information 56 including the data size a are stored. The information 56 is copied to the transmission / reception queue 57 as the first copy work 71 when the data 59 is passed to the reception side process 53, and is posted to the mailbox by the copy work 72. As a result, the flag 61 changes from “0” indicating the non-transmission state to “1” indicating the transmission state.

The receiving process 53 is notified by the change of the flag 61 that the data 59 to be received is stored in the shared memory 58. Then, the pointer A and the data size a constituting the information 56 are copied and held in the second memory area 54 as a work memory allocated at the time of system initialization. The receiving side process 53 refers to the transmitted pointer A and the data size a to read the continuous data 59 of the data size a from the head address A constructed on the shared memory 58 by the transmitting side process 51. You can

In the embodiment described above, the pointer A indicating the head address of the data 59 to be communicated and the data size are stored in the transmission / reception queue 57 as the information 56, but the head and tail of the data 59 are stored. Can be specified instead of storing pointers A and B respectively indicating the range of data to be read from the shared memory 58. Further, even if the address indicating the end of the data 59 stored in the shared memory 58 and the data size thereof are stored, the data constructed by the transmitting process 51 on the shared memory 58 is similarly read on the receiving process 53 side. be able to.

This is the data 59 to be communicated.
Is assumed to have a variable length. When the data 59 to be communicated has a fixed length, it is only necessary to copy only the pointer indicating the beginning or end of the data to the transmission / reception queue to the transmission / reception queue.

[0026]

As described above, according to the first and second aspects of the present invention, the shared memory is an area that can be commonly used for data to be communicated, and the area is allocated to each process. Unlike the case, the memory can be effectively used, and the cost can be reduced. Moreover, since a small amount of data such as an address is put in the transmission / reception queue for transmission, the amount of data to be copied can be reduced, and communication performance can be improved with shortening the transmission / reception time of inter-task communication. In addition, it is possible to reduce the size of the packet for transmission and reception.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a configuration of an inter-process communication system in an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram illustrating a configuration of a conventional inter-process communication system.

FIG. 3 is a schematic configuration diagram showing a configuration of another communication system proposed conventionally.

[Explanation of symbols]

 51 sending process 52 memory area 53 receiving process 54 second memory area 56 information 57 send / receive queue 58 shared memory 59 data 61 flag

Claims (5)

[Claims] 1. A transmitting process as a data transmitting side, a receiving process as a data receiving side, and at least writing of data from the transmitting process and at least reading of data from the receiving process are possible. When performing data communication between the transmitting process and the receiving process, the shared memory stores information indicating the location of data to be communicated written in the shared memory by the transmitting process, and receives the information from the transmitting process. A transmission / reception queue to be transmitted to the receiving process; a reception completion notifying means for notifying the transmission / reception queue when the transmission / reception queue is transmitted to the receiving process; When the completion of the queue transmission is notified, the location of the data to be communicated is indicated from the transmission / reception queue. Interprocess communication system, characterized in that based on the retrieved information retrieves the information comprises a data reading means for reading the corresponding data from the shared memory. 2. A transmission-side process as a data transmission-side, a reception-side process as a data-reception-side, a transmission-side memory area allocated to the transmission-side process during system initialization and held by the transmission-side process. A shared memory in which at least data can be written from the sender process and at least data can be read from the receiver process, and when the sender process and the receiver process communicate data, A transmission / reception queue in which information indicating the location of communication target data written in the shared memory is copied from the transmission side memory area and transmitted from the transmission side process to the reception side process; and the transmission / reception queue is transmitted to the reception side process. And a reception completion notifying means for notifying this when the processing is performed, and arranged on the receiving side process side. When the reception completion notifying unit notifies that the transmission of the transmission / reception queue has been completed, information indicating the location of the data to be communicated is taken out of the transmission / reception queue and a response is made from the shared memory based on the extracted information. An inter-process communication system, comprising: data reading means for reading data. 3. The data written from the transmitting process to the shared memory has a variable length, and the information indicating the location of the data to be communicated is an address and data indicating one end of the data stored in the shared memory. 3. The inter-process communication system according to claim 1, wherein the communication system comprises an amount. 4. The data written from the transmitting process to the shared memory has a fixed length, and the information indicating the location of the data to be communicated comprises an address indicating one end of the data stored in the shared memory. The inter-process communication system according to claim 1 or 2, wherein: 5. The inter-process communication system according to claim 1, wherein said reception completion notifying means is a flag indicating transmission completion in one of two states.