KR101881038B1 - Method for atomic update of memory mapped files stored in non-volatile memory and control apparatus thereof - Google Patents

Abstract

The present disclosure extends to a file update method and apparatus that provides a more secure and efficient memory mapped file I / O (I / O) in an in-memory file system of non-volatile memory. The file update method according to the present invention is characterized in that, when an update occurs in an original file, the updated contents are stored in a different place from the original file, and are updated at the same time when an update command is executed.

Description

TECHNICAL FIELD [0001] The present invention relates to an atomic update method and apparatus for a memory mapping file stored in a nonvolatile memory,

The present invention relates to a method and apparatus for updating a memory mapping file, and more particularly, to an atomic updating method and apparatus capable of ensuring consistency and reliability of a memory mapping file stored in a nonvolatile main memory .

Recently, nonvolatile memory devices have similar performance to dynamic random access memory (DRAM), and are expected to be the main memory of the future. As non-volatile dual in-line memory modules (NVDIMMs) have been developed, nonvolatile memories are increasingly used as main memory of computers. With nonvolatile main memory, files can be stored continuously in main memory, enabling fast file I / O without secondary storage latency. In particular, since the memory mapped file I / O technique maps a file located in main memory to a process address space, the process accesses the file directly using the load / store command without the help of the operating system . This technique is attracting attention as an important file input / output technique because it can minimize the software overhead which is the biggest overhead in the system where the secondary storage delay time is lost.

However, even a system using non-volatile memory has a volatile cache and a buffer in the processor, so that when a system crash occurs, some data is lost. The processor also uses out-of-order execution techniques to improve performance and uses cache management techniques to take advantage of data locality, so it is difficult to know when updated data is reflected in memory . Therefore, if a system error occurs while the processor is updating the file, some of the files will be updated and some will not be updated. In particular, memory mapping file I / O has a problem that the operating system can not guarantee the consistency and reliability of the file because the process directly accesses the actual memory.

The memory synchronization system function (call) provided by the operating system can be used to perform synchronization of the memory mapping file. However, there is still the problem that the consistency of the file can not be guaranteed because the updated contents can not be atomically performed on the original.

Korean Patent Publication No. 10-2015-0082010

The present specification is intended to provide an atomic update method and apparatus for a memory mapping file that can ensure consistency and reliability.

The solutions described herein are not limited to those mentioned above, and other solutions not mentioned may be clearly understood by those skilled in the art from the following description.

A memory mapping file update method for solving the above-mentioned problems is a computer system including a processor for processing a file update and a nonvolatile memory having a process address space, a page table, and a file system area, A method for updating a file mapped to an address space (hereinafter, referred to as an 'original file'), the method comprising the steps of: (a) when an update occurs on a page of the original file, Area and copying the updated content to the update page; (b) changing a mapping address of a page of the original file stored in the page table to a mapping address of the update page; (c) storing contents (hereinafter referred to as " connection information ") describing a connection relationship between the page where the update occurred and the update page among the pages of the original file; (d) locking the original file by a memory synchronization request; (e) referring to the connection information, copying an update page to a page of the original file on which the update occurred; And (f) changing a mapping address of the page table to a page where the update occurred in the page of the original file, and releasing the lock setting of the original file.

According to an embodiment of the present invention, the step (c) may be a step of storing the connection information in the process address space. In this case, the step (d) may further include, after the processor sets the original file lock, storing the connection information in the process address space into the file system area. The step (f) may include deleting the connection information stored in the process address space and the file system area, and deleting the update page stored in the file system area.

The memory mapping file updating method according to the present invention may further include: (d-1) storing data stored in the cache of the processor in the file system area.

The non-volatile memory according to the present specification can be used as main memory in a computer system.

According to an aspect of the present invention, there is provided a memory mapping file update apparatus including: a nonvolatile memory having a process address space, a page table, and a file system area; And a processor for updating the file, wherein the processor is configured to update the memory mapping file when an update occurs on a page of a file stored in the file system area and mapped to the process address space , A new page (hereinafter referred to as an 'update page') is allocated to a file system area, the updated content is stored in the update page, and a mapping address of a page in the original file stored in the page table, (Hereinafter, referred to as " connection information ") describing a connection relationship between the page where the update occurred and the update page among the pages of the original file, Locks the connection information, refers to the connection information The update page is copied to the page where the update occurred, the mapping address of the page table is changed to the page where the update occurred in the page of the original file, and the lock setting of the original file is canceled can do.

According to the file update method and control apparatus of the present disclosure, a secure memory-mapped file I / O (I / O) is possible in an in-memory file system. In addition, memory-mapped file I / O (I / O) in an in-memory file system can make full use of the characteristics of a high-performance memory storage device.

The effects described in the present specification are not limited to those mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the following description.

1 is a block diagram of an architecture of a computer system.
FIGS. 2 to 6 are reference views showing page storage and movement of a file according to a time flow to explain a file update method according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Wherever possible, the same or similar parts are denoted using the same reference numerals in the drawings.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular forms as used herein include plural forms as long as the phrases do not expressly express the opposite meaning thereto.

Means that a particular feature, region, integer, step, operation, element and / or component is specified and that other specific features, regions, integers, steps, operations, elements, components, and / It does not exclude the existence or addition of a group.

All terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Predefined terms are further interpreted as having a meaning consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or very formal meanings unless defined otherwise.

Hereinafter, a file updating method and a control apparatus thereof according to the present specification will be described with reference to the drawings.

1 is a block diagram of an architecture of a computer system.

Referring to FIG. 1, a computer system 100 including a processor 120 and a non-volatile memory 140 may be identified.

The non-volatile memory 140 may have a process address space 142, a page table 144, and a file system area 146. The process address space 142, the page table 144, and the file system area 146 are well-known to those skilled in the art, and detailed description of each configuration will be omitted .

The processor 120 may update a file (hereinafter referred to as a 'source file') stored in the file system area and mapped to a process address space. To that end, the processor 120 may include a core 121 and a cache 122. Since the core 121 and the cache 122 are well known to those skilled in the art, a detailed description of each configuration will be omitted.

The non-volatile memory 140 and the processor 120 may be connected through a memory bus (I / O bus) 160. The memory bus 160 is also a well-known term to those skilled in the art, so that a detailed description of the configuration will be omitted.

FIGS. 2 to 6 are reference views showing page storage and movement of a file according to a time flow to explain a file update method according to an embodiment of the present invention.

Referring to FIG. 2, it can be seen that a file in the non-volatile memory is stored. The file system area is a physical area where files are actually stored. The file stored in the file system area may be an 'original file', and the file may be composed of a plurality of pages (A to F). The process address space is a virtual area in which a process recognizes that a file is stored. The process address space is a virtual area used by a process, and is an independent area for each process. The process can directly access the original file by mapping the original file to the process address space.

The page table is a place where information for mapping the process address space, which is a virtual area, and the file system area, which is an actual area, is stored. Accordingly, when the processor accesses a specific file (or a specific page, memory), the processor accesses the process address space, identifies a mapping address stored in the page table, and stores the address in the physical file (or page) Approach.

In the example shown in FIG. 2, it can be confirmed through the page table that virtual addresses '1 to 6' corresponding to pages 'A to F' stored in the file system area are stored in the processor address space.

As an example, the file system area may be an Ext4-DAX system.

The method of updating a memory mapping file according to the present invention can be handled by a processor that processes an instruction to update a file. Therefore, in describing the present specification, a subject which copies, moves, and stores a file can be considered as a processor. Also, in this specification, what is referred to as a processor is a name that refers to a device that performs a process, and it is apparent that a single processor can mount two or more processes. Therefore, when it is necessary to distinguish two or more processes, it will be referred to as a 'first process' and a 'second process', respectively.

Referring to FIG. 3, it can be confirmed that the update occurs in the page 'E' of the page corresponding to the virtual address '5'. The processor may allocate a new page (hereinafter referred to as an 'update page') to the file system area and store the updated content in the update page when an update occurs on a page of the original file.

According to an embodiment of the present invention, when an update occurs on a page of the original file, the processor copies some pages of the original file in which an update has occurred to the update page and updates the updated page to the update page Can be stored.

The processor may change a mapping address of a page of the original file stored in the page table to a mapping address of the update page. Referring to FIG. 3, it can be seen that the physical address of the virtual address '5' of the page table is changed from 'E' to 'G'.

The processor may store contents (hereinafter referred to as " connection information ") describing a connection relationship between the page where the update occurred and the update page among pages of the original file.

According to one embodiment of the present disclosure, the processor may store the connection information in a process address space. Referring to FIG. 3, connection information described as 'E-G' can be confirmed in the processor address space. The process address space in which the connection information is stored is not a space to which the file system area is mapped.

The above process can be repeated every time a plurality of updates occur until a synchronization request of a memory mapping file occurs. Referring to FIG. 4, an update occurs in a page stored in physical addresses 'B' and 'D', and updates contents are stored as 'H' and 'I' after allocation of an update page, Connection information is added.

5 is a situation where a synchronization request of a memory mapping file is executed.

The system calls that cause the memory mapping file to be synchronized correspond to 'msync' on Linux OS or Unix-like OS and 'FlushFileBuffers' on Windows OS. However, the above example is merely an example according to the operating system, and it should be considered as a system call corresponding to the present specification depending on whether or not the memory mapping file is synchronized regardless of the operating system.

First, the processor can lock the original file by a memory synchronization request. The locking of the original file means that the reading / writing is prohibited. The read / write prohibition can prevent the first process and the second process from accessing the original file that has not been updated before the update is completed.

According to an embodiment of the present invention, the processor may store the connection information in the file system area in the process address space after setting the original file lock. A journaling effect can be obtained by simply storing the connection information in the file system area. If the connection information is stored in the process address space, a memory synchronization request has not yet occurred. In this case, when a system error occurs and the system is rebooted, the connection information disappears, and the updated contents are not reflected in the original file. When the connection information is stored in the file system area, a memory synchronization request is generated. Even if a system error occurs during the memory synchronization, the connection information, the update page and the original page remain in the file system area. Therefore, the memory synchronization operation can be completed through the connection information remaining in the file system area. In addition, since the size of the connection information is small, the burden on the processor can be reduced as compared with general journaling.

According to one embodiment of the present disclosure, the processor may store data stored in the cache of the processor in the file system area. The update may not be immediately stored in the file system area and may remain in the processor's cache. Thus, the update is nonvolatile, which is a continuously storable area, so that the memory can be reliably stored in the remaining file system area without being initialized even after a reboot.

Next, the processor can refer to the connection information and copy the update page to the page where the update occurred among the pages of the original file.

After the copying of the update file is completed, as shown in FIG. 6, the processor changes the mapping address of the page table to the page of the original file that the update occurred, and the process address space and the file system area Lt; / RTI > The processor may also delete the update page stored in the file system area. The processor can then unlock the original file.

According to the apparatus and method for updating a memory mapping file according to the present specification, when the memory synchronization operation is started, the processor stores the connection information in the file system area, and when the processor completes the memory synchronization, Atomic updates are possible even if system errors occur during memory synchronization. This is because, after rebooting, the connection information remaining in the file system area is referred to, and the memory synchronization operation that can not be completed due to a system error can be re-executed. If there is no remaining connection information, the current file system can be determined to be in a state of maintaining consistency.

As another embodiment of the present invention, the computer program may be a computer program written in a computer-readable recording medium so as to perform each step of the memory mapping file updating method described above. That is, the apparatus according to the embodiment of the present invention can be implemented as a computer-readable code on a computer-readable recording medium. The computer-readable recording medium may include various types of recording apparatuses in which data that can be read by the computer system shown in FIG. 1 is stored. Examples of the recording medium include ROM, RAM, optical disk, magnetic tape, floppy disk, hard disk, nonvolatile memory and the like. The computer-readable recording medium may also be distributed over a networked computer system so that computer readable code can be stored and executed in a distributed manner.

The embodiments and the accompanying drawings described in the present specification are merely illustrative of some of the technical ideas included in the present invention. Accordingly, the embodiments disclosed herein are for the purpose of describing rather than limiting the technical spirit of the present invention, and it is apparent that the scope of the technical idea of the present invention is not limited by these embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

100: Computer system
120: Processor
121: Core
122: Cache
140: Nonvolatile memory
142: Process address space
144: Page table
146: File system area

Claims (13)

A method for updating a source file stored in the file system area and mapped to the process address space in a computer system including a nonvolatile memory having a process address space, a page table, and a file system area, The processor
(a) allocating a new update page to the file system area when an update occurs on a page of the original file, and copying the contents of the page where the update of the original file occurred to the update page;
(b) changing a mapping address of a page where the update of the original file stored in the page table occurs to a mapping address of the update page;
(c) storing, in the process address space, connection information indicating a connection relationship between the page where the update of the original file occurred and the update page, and storing the update content in the update page;
(d) locking the original file by a memory synchronization request;
(e) referring to the connection information, copying the update page to a page where the update of the original file occurred; And
(f) changing a mapping address of the page table to a page where the update of the original file occurs, and releasing the lock setting of the original file,
The step (d) further comprises: after the processor locks the original file, storing the connection information in the process address space into the file system area;
The step (f) includes deleting the connection address information stored in the process address space and the file system area, and deleting the update page stored in the file system area;
(d-1) storing data stored in the cache of the processor in the file system area, and
Wherein the non-volatile memory is used as main memory in the computer system. delete delete delete delete delete A non-volatile memory having a process address space, a page table, and a file system area; And
And a processor for updating an original file stored in the file system area and mapped to the process address space,
The processor comprising:
Allocating a new update page to the file system area when an update occurs on a part of the page of the original file, copying the contents of the page where the update of the original file occurred to the update page,
A mapping address of a page in which the update of the original file stored in the page table is generated is changed to a mapping address of the update page,
Storing connection information describing a connection relationship between the page where the update of the original file occurred and the update page in the process address space, storing update information in the update page,
Lock the original file by a memory synchronization request,
Referring to the connection information, copying the update page to a page where the update of the original file occurred,
Changing a mapping address of the page table to a page where the update of the original file occurred,
The lock setting of the original file is canceled,
Wherein the processor stores the connection information in the file system area in the process address space after the processor locks the original file and deletes the connection information stored in the process address space and the file system area, Deleting the update page stored in the file system area, further storing data stored in the cache of the processor in the file system area,
Wherein the non-volatile memory is used as main memory in a computer system including the non-volatile memory and the processor. delete delete delete delete delete A computer program recorded on a computer-readable recording medium, the computer program being written in the computer to perform the steps of the memory mapping file update method according to claim 1.

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