KR101134464B1 - Method and apparatus for providing network asynchronous input/output processing - Google Patents

Abstract

The present invention proposes a method for processing network asynchronous I / O at the user level. In particular, it provides an asynchronous I / O processing method that performs asynchronous send and receive functions at the user level by utilizing the event notification subsystem provided at the kernel level. According to the embodiment of the present invention, the network asynchronous I / O processing at the user level enables efficient network communication without compromising the stability of the operating system.

Asynchronous I / O Send, Asynchronous I / O Receive

Description

METHOD AND APPARATUS FOR PROVIDING NETWORK ASYNCHRONOUS INPUT / OUTPUT PROCESSING}

The present invention relates to a network asynchronous input and output processing technology, in particular network asynchronous suitable for performing asynchronous transmission and reception at the user level by utilizing the event notification subsystem provided at the kernel level (kernel level) An input / output method and apparatus are provided.

The present invention is derived from a study conducted as part of the IT source technology development project of the Ministry of Knowledge Economy and the Ministry of Information and Communication Research and Development.

The input / output method in a computer system can be divided into synchronous and asynchronous input / output methods according to a method of processing a user process when an input / output operation cannot be completed immediately. Can be.

The synchronous I / O method waits for the process and waits until the I / O operation is completed when the I / O operation cannot be completed immediately when performing data I / O in the user process. That is, the process waits without performing any remaining work until the I / O operation is completed.

On the other hand, in the asynchronous I / O method, even if the I / O operation cannot be completed, the remaining work of the corresponding process is performed, and the result is notified to the corresponding process when the I / O operation is completed.

Asynchronous I / O is mainly adopted to effectively handle a large number of I / O operations executed simultaneously in various operating systems. Especially, as the Internet spreads, asynchronous I / O is gaining more attention in the network environment. Network asynchronous I / O can significantly improve system performance because the program does not have to wait for I / O to complete.

However, the current network asynchronous I / O method is not properly supported in the Linux operating system. For example, there are two technologies for supporting network asynchronous I / O on Linux: the Portable Operating System Interface (POSIX) application program interface (API) method designed to be performed at the user level, and several methods designed to be executed at the kernel level. Since a thread is created and processed whenever there is an asynchronous I / O request, it is not suitable for an environment requiring high-performance network I / O, and technologies designed to execute at the kernel level have difficulty in verifying the stability of the operating system.

The conventional network asynchronous I / O technology is not reflected in the Linux operating system because it is difficult to verify the stability of the Linux operating system. Therefore, when users develop server applications using the network asynchronous I / O method, the GNU (Gnu is Not Unix) C library is used. It should be developed using POSIX API provided by. The POSIX API provided by the GNU C library is rarely used due to performance problems.

Accordingly, the present invention provides a network asynchronous I / O technology that can improve the performance of a server application program without impairing the stability of the Linux operating system by providing a network asynchronous I / O method at the user level.

According to an embodiment of the present invention, a process of generating a network asynchronous I / O library layer, and when asynchronous I / O from a user thread is requested to the network asynchronous I / O library layer, input of the network asynchronous I / O library layer Allocating a request structure and an output request structure, respectively, and registering the request structure and the output request structure in the input request queue structure and the output request queue structure, and when an input / output enabled event for a specific file is generated from the kernel-level kernel event notification subsystem layer. Searching whether there is an I / O request for a specific file in the queue structure and the output request queue structure, and if the I / O request exists, perform an I / O operation for a read or a write request and then display the completion result of the operation. Can provide asynchronous IO network comprises the process of registration.

According to another exemplary embodiment of the present invention, an asynchronous I / O read function / asynchronous I / O write function is called for a network asynchronous I / O request of a user, and a user application program for a user level network asynchronous I / O function is executed. A user application execution unit and the user application execution unit may use a user-level network asynchronous I / O function, and a plurality of I / O request structures and I / O completion structures according to the asynchronous I / O read / write function of the user application execution unit. Network asynchronous I / O library processing unit that manages and implements and operates a user level network asynchronous I / O function at kernel level, and generates arbitrary events and provides them to the network asynchronous I / O library processing unit. It may provide an asynchronous network input-output device including a kernel-level event processing.

According to the embodiment of the present invention, by providing the network asynchronous I / O function at the user level, it is possible to utilize the network asynchronous I / O function of higher performance without compromising the stability of the Linux operating system when developing server applications.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms, and only the embodiments make the disclosure of the present invention complete, and the general knowledge in the art to which the present invention belongs. It is provided to fully inform the person having the scope of the invention, which is defined only by the scope of the claims. Like numbers refer to like elements throughout.

In describing the embodiments of the present invention, if it is determined that a detailed description of a known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, terms to be described below are terms defined in consideration of functions in the embodiments of the present invention, which may vary according to intentions or customs of users and operators. Therefore, the definition should be based on the contents throughout this specification.

Each block of the accompanying block diagrams and combinations of steps of the flowchart may be performed by computer program instructions. These computer program instructions may be mounted on a processor of a general purpose computer, special purpose computer, or other programmable data processing equipment such that instructions executed through the processor of the computer or other programmable data processing equipment may not be included in each block or flowchart of the block diagram. It will create means for performing the functions described in each step. These computer program instructions may be stored in a computer usable or computer readable memory that can be directed to a computer or other programmable data processing equipment to implement functionality in a particular manner, and thus the computer usable or computer readable memory. It is also possible for the instructions stored in to produce an article of manufacture containing instruction means for performing the functions described in each block or flowchart of each step of the block diagram. Computer program instructions may also be mounted on a computer or other programmable data processing equipment, such that a series of operating steps may be performed on the computer or other programmable data processing equipment to create a computer-implemented process to create a computer or other programmable data. Instructions that perform processing equipment may also provide steps for performing the functions described in each block of the block diagram and in each step of the flowchart.

In addition, each block or step may represent a portion of a module, segment or code that includes one or more executable instructions for executing a specified logical function (s). It should also be noted that in some alternative embodiments, the functions noted in the blocks or steps may occur out of order. For example, the two blocks or steps shown in succession may in fact be executed substantially concurrently or the blocks or steps may sometimes be performed in the reverse order, depending on the functionality involved.

1 is a diagram illustrating a hierarchical structure of a system operating system for performing a network asynchronous input and output method at a user level according to the present embodiment.

As illustrated in FIG. 1, the hierarchical structure of the system operating system for performing the network asynchronous I / O method according to the present embodiment includes a network asynchronous I / O library layer 10 and a user application program 12 and a kernel at a user level. Kernel event notification subsystem layer 14 at the kernel level.

Through the network asynchronous I / O library layer 10 according to the present embodiment, a user level network asynchronous I / O function is provided to the user application 12, and the user level network asynchronous I / O function is provided at a kernel level kernel. It can be implemented and operated on an event notification subsystem layer 14, such as an event poll subsystem. That is, at the time of program development, the asynchronous I / O function according to the present embodiment can be used in the corresponding program.

Therefore, the network asynchronous I / O device according to the present embodiment operating at the user level does not affect the stability of the Linux operating system.

FIG. 2 is a diagram illustrating in more detail a hierarchical structure of a system operating system for performing a network asynchronous input / output method at a user level according to an embodiment of the present invention. Level of user thread (1), network asynchronous I / O library layer (100).

As illustrated in FIG. 2, the network asynchronous I / O library layer 100 according to the present embodiment is a form of the network asynchronous I / O library layer 10 that operates at a user level, and includes an input / output information structure 102 and a plurality of inputs. An input request queue structure 104 having request structures 104a through 104e, an output request queue structure 106 having a plurality of output request structures 106a through 106e, and a plurality of input / output completion structures 108a through 108e. It may include an input / output completion queue structure 108, the event notification waiting thread (110).

The input / output information structure 102 serves to manage various pieces of information necessary for the execution of a user program that wants to utilize a network asynchronous input / output function.

The input request queue structure 104 and the output request queue structure 106 serve to manage a plurality of input request structures 104a-104e and a plurality of output request structures 106a-106e.

The input / output completion queue structure 108 serves to manage a plurality of input / output completion structures 108a to 108e.

The event notification wait thread 110 calls the kernel event notification subsystem layer 14 at the kernel level, for example, through the kernel event notification subsystem layer 14 by calling the event poll wait function (epoll_wait ()) of the event poll subsystem. It waits for an event to occur.

Looking at the input and output processing in the network asynchronous I / O library layer 100 as follows.

First, when asynchronous I / O is requested through the asynchronous I / O read function (aio_read ()) / asynchronous I / O write function (aio_write ()) call from the user thread 1, the network asynchronous I / O library layer 100 receives a plurality of input request structures. And a plurality of output request structures 106a to 106e, respectively, and register them in the input request queue structure 104 and the output request queue structure 106, respectively.

Thereafter, when an input / output capable event for a specific file is provided from the kernel-level kernel event notification subsystem layer 14 through the event notification waiting thread 110, the network asynchronous I / O library layer 100 receives an input request queue structure 104. ) And the output request queue structure 106 to check whether there is an I / O request for a specific file, and if there is an I / O request, the request operation is performed.

The result of performing the request operation is allocated to the input / output completion queue structure 108 by allocating a plurality of input / output completion structures 108a to 108e.

In addition, the user thread 1 calls the asynchronous I / O completion acquisition function (aio_get_completion ()) to the network asynchronous I / O library layer 100 to output a result of a read or write request requested by the user through the I / O completion queue structure 108. You can check it.

Hereinafter, with reference to the configuration described above, with reference to the flowchart of Figure 3 attached to the network asynchronous input and output method according to an embodiment of the present invention will be described by way of example.

As illustrated in FIG. 3, the network asynchronous I / O library layer 100 registers the use of the kernel event notification subsystem layer 14 (S300), creates an event notification waiting thread 110 (S302), and input / output The information structure 102, the input request queue structure 104, the output request queue structure 106, and the input / output completion queue structure 108 are allocated and initialized (S304).

The allocation and initialization of the input / output information structure 102, the input request queue structure 104, the output request queue structure 106, and the input / output completion queue structure 108 are performed through a call to the asynchronous input / output layer creation function aio_create (). This may mean that a network asynchronous I / O library layer is created.

Thereafter, when asynchronous I / O is requested from the user thread 1 through an asynchronous I / O read function (aio_read ()) / asynchronous I / O write function (aio_write ()) call, the network asynchronous I / O library layer 100 receives a plurality of input request structures. Each of the 104a through 104e and the plurality of output request structures 106a through 106e is allocated and registered in the input request queue structure 104 and the output request queue structure 106, respectively (S306). In this case, a file descriptor may be registered in the kernel event notification subsystem layer 14 of the kernel level through a call of the event poll control function epoll_ctl ().

Thereafter, when an I / O (eg, read or write) capable event for a specific file is provided from the kernel-level kernel event notification subsystem layer 14 through the event notification waiting thread 110, the network asynchronous I / O library layer ( 100) detects whether there is an I / O request (read or write request) for a particular file in the input request queue structure 104 and the output request queue structure 106, and if there is an I / O request, the request operation, that is, the read or write request. Perform input / output operations on. When the work is completed, the result may be registered in the input / output completion queue structure 108 (S308).

Checking the I / O completion queue for the completed I / O request may be performed through a call to the asynchronous I / O completion acquisition function (aio_get_completion ()) (S310), and the user may check the operation result for the read or write request requested by the user. Can be. This process is repeated until the user no longer needs the input / output request (S312).

If the user's I / O request does not exist and the network asynchronous I / O library layer is no longer needed, the network asynchronous I / O library layer 100 can call the asynchronous I / O layer release function (aio_destroy ()) to call a kernel-level kernel event. The use of the notification subsystem layer 14 is released (S314), and the event notification waiting thread 110 is terminated (S316).

Accordingly, the input / output information structure 102, the input request queue structure 104, the output request queue structure 106, and the input / output completion queue structure 108 may be released (S318).

4 is an exemplary configuration diagram of an input request queue structure and an output request queue structure for quickly finding an input / output request in the network asynchronous I / O process according to the present embodiment.

As illustrated in FIG. 4, an input request queue structure 40 managing an input request and an output request queue structure 42 managing an output request may be included to manage input and output requests.

An input request structure 40a and an output request structure 42a may be registered and managed in each of the input request queue structure 40 and the output request queue structure 42, respectively. When the kernel-level kernel event notification subsystem layer 14 notifies an event, the input request queue structure 40 and the output request queue structure 42 are file descriptors in order to detect the existence of the corresponding input and output requests more quickly. The hash entry may be determined based on a hash table based on the value of. Since there may be different file descriptors with the same hash value, and multiple input or output requests may occur in one file descriptor, multiple input or output request structures may be assigned to one hash value.

5 is a flowchart illustrating a process of registering, searching, and deleting an input request queue structure and an output request queue structure.

As illustrated in FIG. 5, when the asynchronous I / O read function (aio_read ()) and the asynchronous I / O write function (aio_write ()) for performing network asynchronous I / O are called by the user to the network asynchronous I / O device 100 (S500). In operation S502, an input request structure or an output request structure corresponding to the request is allocated.

In operation S504, a hash value is calculated based on a function value of a file descriptor desired for input / output, and the corresponding hash entry is searched for (S504).

The input request structure or the output request structure allocated to the found hash entry is registered (S506).

Thereafter, it is determined whether an event occurs in the kernel event notification subsystem layer 14 at the kernel level through the event notification waiting thread 110 (S508).

If an event occurs, it is determined whether the corresponding event is read (input) or write (output), and whether the request has been found in the input request queue structure 104 or the output request queue structure 106 (S510). This process is similar to registering the input request structures 104a to 104e or the output request structures 106a to 106e, and calculates a hash value based on the value of the file descriptor where the event occurs, and finds the corresponding hash entry. The input request structures 104a through 104e or the output request structures 106a through 106e assigned to the hash entry may be sequentially searched to check whether there is a read or write request.

When a read result or a read or write request is found in the request result of the input request queue structure 104 or the output request queue structure 106 (S512), an input / output operation on the corresponding file descriptor is performed (S514).

When the execution of such an input / output operation is completed (S516), the input / output completion structures 108a to 108e are allocated, the execution result is stored, and the corresponding input / output completion structures 108a to 108e are registered to the input / output completion queue structure 108. The user can check the result (S518).

In this way, by providing the network asynchronous I / O function in the Linux operating system, it is possible to improve the performance of a high performance server requiring a large number of network I / O, and to develop a server program more easily. It also extends the reach of the Linux operating system.

6 is a block diagram illustrating a network asynchronous I / O device according to the present embodiment, and includes a user application program executing unit 602, a network asynchronous I / O library processing unit 604, and a kernel level event processing unit 606. .

As illustrated in FIG. 6, the user application execution unit 602 calls an asynchronous I / O read function / asynchronous I / O write function for a network asynchronous I / O request of a user, and a user level network asynchronous I / O according to the present embodiment. Run the user application for the function.

The network asynchronous I / O library processing unit 604 enables a user level network asynchronous I / O function in the user application execution unit 602, and according to the asynchronous I / O read / write functions of the user application execution unit 602, It manages the I / O request structure and the I / O completion structure, and calls the event poll wait function (epoll_wait ()) of the kernel level event processing unit 606, which will be described later, to wait for an event occurring through the kernel level event processing unit 606. do.

The kernel level event processing unit 606 implements and operates a user level network asynchronous I / O function at the kernel level. The kernel level event processing unit 606 generates an arbitrary event, for example, an I / O capable event for a specific file and provides it to the network asynchronous I / O library processing unit 604. Play a role.

As described above, according to the present embodiment, by providing the network asynchronous I / O function at the user level, it is possible to implement the network asynchronous I / O function of higher performance without compromising the stability of the Linux operating system when developing server applications. will be.

1 is a diagram illustrating a hierarchical structure of a system operating system for performing a network asynchronous input / output method at a user level according to the present embodiment;

2 is a detailed illustration of the hierarchical structure of the system operating system of FIG. 1;

3 is a flowchart illustrating a network asynchronous input and output method according to the present embodiment;

4 is an exemplary configuration diagram of an input request queue structure and an output request queue structure in the network asynchronous I / O method according to the present embodiment;

5 is a flowchart illustrating a process of registering, searching, and deleting an input request queue structure and an output request queue structure according to the present embodiment;

6 is a block diagram illustrating a network asynchronous I / O device according to the present embodiment.

<Explanation of symbols for the main parts of the drawings>

1: user thread 14: kernel event notification subsystem

102: input / output information structure 104: input request queue structure

106: output request queue structure 108: I / O completion queue structure

110: event notification waiting thread

602 user application execution unit

604: network asynchronous I / O library processing unit

606 kernel level event processing unit

Claims (12)

delete Creating a network asynchronous I / O library layer, When asynchronous I / O from a user thread is requested to the network asynchronous I / O library layer, allocating an input request structure and an output request structure of the network asynchronous I / O library layer and registering them in an input request queue structure and an output request queue structure, respectively; , Searching for an input / output request for a specific file in the input request queue structure and the output request queue structure when an input / output event for a specific file is generated from a kernel-level kernel event notification subsystem layer; If there is an I / O request, after performing an I / O operation for a read or write request, registering the completion result of the operation in the I / O completion queue structure, The network asynchronous I / O library layer generation process, Registering a file descriptor in the kernel-level kernel event notification subsystem layer; Creating a user level event notification waiting thread in response to registration of the file descriptor; Allocating and initializing an input / output information structure, an input request queue structure, an output request queue structure, and an input / output completion queue structure in the network asynchronous I / O library layer. Network asynchronous I / O method. The method of claim 2, And the file descriptor is registered through a call of an event poll control function. The method of claim 2, And allocating and initializing the input / output information structure, the input request queue structure, the output request queue structure, and the input / output completion queue structure through a call to an asynchronous input / output layer generation function. The method of claim 2, The asynchronous I / O is requested through the asynchronous I / O read function and the asynchronous I / O write function call. The method of claim 2, The input / output enabled event is delivered via the user level event notification waiting thread. The method of claim 2, The method, Checking the I / O completion queue for the completed I / O request by calling the asynchronous I / O completion acquisition function, If the user input / output request does not exist, the process of releasing the kernel-level kernel event notification subsystem layer by invoking the asynchronous I / O layer release function and terminating the user-level event notification waiting thread. Network asynchronous I / O method further comprising. delete delete A user application execution unit that calls an asynchronous I / O read function / asynchronous I / O write function for a user's network asynchronous I / O request, and performs a user application for a user level network asynchronous I / O function; A network asynchronous I / O library for enabling a user level network asynchronous I / O function in the user application execution unit and managing a plurality of I / O request structures and I / O completion structures according to the asynchronous I / O read / write function of the user application execution unit. Processing unit, It implements and operates a user-level network asynchronous I / O function at the kernel level, and includes a kernel level event processing unit that generates an arbitrary event and provides the network asynchronous I / O library processing unit. The network asynchronous I / O library processor may call an event poll wait function of the kernel level event processor to wait for an arbitrary event generated through the kernel level event processor. Network Asynchronous I / O Device. 11. The method of claim 10, The random event, the network asynchronous input and output device including an input and output event for a particular file. 11. The method of claim 10, The kernel level event processing unit includes an event polling subsystem.

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