JP2011165093A - Memory access examination device, memory access examination method and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To rapidly examine a state of an access to a memory from a program with low load. <P>SOLUTION: The memory access examination device having an operating system compatible with a virtual storage system and a memory to be managed in units of a predetermined blocks by the operating system includes: a memory information storage means which stores table information that stores flag information showing whether the memory is accessed by a target program to be executed for each block; and a memory access examination means which acquires information showing the access state to the memory by referring to the flag information in the table information for each predetermined block, and stores the information in the storage means. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a technique for investigating a state of access to a memory from a program executed in a computer.

  In recent computers, a virtual storage system is generally employed as a memory management system. In the virtual storage system, the virtual address space is virtually expanded by assigning a virtual address space to the program.

In general, a memory (a physical memory such as a main memory) is divided into a plurality of pages and managed in units of pages. In the virtual storage system, page data that is not often used is saved in the auxiliary storage device, and when the page is accessed, if there is no page data in the memory, the page data is read from the auxiliary storage device and stored in the memory. Control such as loading is performed.
Here, if the amount of memory included in the virtual storage system computer as described above is too large, resources are wasted and cost increases, and if it is too small, access to the auxiliary storage device increases and processing load increases. Increases, and the program cannot be executed properly. Therefore, it is required to grasp an appropriate amount of memory corresponding to a program executed by the computer, that is, a necessary minimum amount of memory.

  In recent years, server virtualization technology that includes multiple virtual machines in a computer has been introduced. Virtual memory as a program has been introduced to improve the memory density, which is indispensable for improving the density of virtual machines. There is also a need to know the minimum amount of memory required to run a machine.

Zhao, Weiming et al .: Dynamic memory balancing for virtual machines, VEE '09, pp.21-30 (2009) Zhou, Pin et al .: Dynamic tracking of page miss ratio curve for memory management, ASPLOS-XI, pp. 177-188 (2004)

  In order to grasp the minimum amount of memory required for a program executed by a virtual storage system computer, it is necessary to investigate and grasp how often the program executed by the computer accesses which page. is required.

  Here, Non-Patent Document 1 describes a technique in which a memory accessed on a virtual machine is examined and used for adjusting the memory amount of the virtual machine. Non-Patent Document 2 describes a technique for examining memory accessed on a computer (physical machine) and adjusting the amount of memory for a program running on the computer.

  In each of the above prior arts, by using a mechanism called page fault, an interrupt is generated when memory is accessed, and access to the memory is detected.

  With reference to FIG. 1, an outline of a method for investigating access from a program (referred to as a target program) to a memory using a page fault will be described. FIG. 1 shows a situation where the memory is divided into pages. The access investigation mechanism shown in FIG. 1 corresponds to an investigation program (referred to as an investigation program) executed on a computer. Upon receiving a page fault notification, the corresponding page has been accessed from the program. Is a functional unit that records information indicating that in the storage means as access information.

As shown in FIG. 1, in the method using page faults, every time the target program accesses the memory (step 110), a page fault is generated (step 120), and the access investigation notified by the page fault is received. The mechanism updates the access information (step 130), and resumes execution of processing from the location where the memory is accessed for the target program (step 140).
In the conventional method described above, since the survey is performed every time the program is accessed, the accuracy of the survey is high. However, since the memory is accessed many times during execution of the target program, this method has a problem that the processing load increases.

  That is, in this method, the operation of the target program that was trying to access the memory is stopped every time access is performed, and the investigation program (access investigation mechanism) is executed, so the investigation program is executed numerous times and the load increases. .

  In addition, the process of stopping the operation of the target program that was trying to access the memory and restarting it after running the investigation program requires saving and restoring the execution state of the current target program. High load is applied.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a technique for investigating a memory access state by a program at a high speed with a small load.

  In order to solve the above problems, the present invention is a memory access investigation device having an operating system corresponding to a virtual storage system and a memory that is divided and managed in units of predetermined blocks by the operating system, Flag information indicating whether or not the memory has been accessed from a target program executed in the memory access investigation device, memory information storage means for storing table information for each block, and flag information in the table information. By referring to each predetermined block, it is possible to configure as a memory access investigation device comprising: memory access investigation means for acquiring information indicating an access status to the memory and storing the information in the storage means .

  The operating system has a memory recovery function, a predetermined list acquired by the memory recovery function is stored in the memory information storage means, and the memory access checking means sets a flag for each block included in the predetermined list. Information can be referenced.

  Further, as the predetermined list, an activity list acquired by the memory collection function can be used.

  The block may be a page, the table information may be a page table, and the flag information may be an access bit in a page table entry in the page table.

  According to the present invention, the flag information in the table information stored in the memory information storage means is referred to for each predetermined block, so that the information indicating the access status to the memory is acquired. It becomes possible to investigate the access situation at high speed.

It is a figure for demonstrating the conventional memory access investigation method. It is a functional block diagram of the memory access investigation apparatus 1 which concerns on embodiment of this invention. It is a figure for demonstrating the memory access processing method based on a virtual memory system. It is a figure which shows an example of a page table entry. 6 is a diagram for explaining processing of a page collection function unit 132. FIG. It is a figure for demonstrating the outline | summary of operation | movement of the memory access investigation apparatus 1. FIG. 10 is a flowchart showing a specific processing example of the operation of the memory access examining unit 11.

  Embodiments of the present invention will be described below with reference to the drawings. Note that although an example in which the memory is divided into pages is shown in this embodiment, the unit into which the memory is divided is not limited to pages. What is necessary is just to divide | segment by the unit of a predetermined block.

(Device configuration)
FIG. 2 shows a functional configuration diagram of the memory access investigation device 1 according to the embodiment of the present invention. As shown in FIG. 2, the memory access investigation device 1 according to the present embodiment includes a memory access investigation unit 11, a program function unit 12, an OS unit 13, and a memory 14 to be subjected to access investigation.

  The memory access investigation unit 11 is a functional unit that performs a memory access investigation according to the present invention, performs a memory access investigation, and stores the investigation result in the memory access information storage unit 111 provided in the memory access investigation unit 11. Details of the memory access investigation will be described later.

  The program function unit 12 is a function unit corresponding to an investigation target program, and is a function unit that executes predetermined processing defined in the program while accessing the memory 14 via the OS unit 13. This program is, for example, an application program, a virtual machine program, or the like.

  The OS unit 13 is a functional unit corresponding to a commonly used OS (operating system) such as UNIX (registered trademark) or Linux (registered trademark). The OS unit 13 has various functions included in a general OS. In this embodiment, the memory management function unit 131 is particularly shown. The memory management function unit 131 includes functions necessary for realizing the virtual storage method, and a page collection function unit 132 is shown as one of the functions. In addition, the memory management function unit 131 includes a memory information storage unit 133 that stores information about pages.

  The memory access investigation device 1 has a general computer configuration including a storage means such as a memory and a hard disk, and a CPU as hardware. Each functional unit is realized by executing a program on a computer.

  Each functional unit shown in FIG. 2 shows functional elements realized by the cooperation of a program and hardware such as a CPU in a computer. The target “memory 14” is shown as physical memory (hardware). For convenience, the program function unit 12 may be referred to as a “program”, and the OS unit 13 may be referred to as an “OS (operating system).” A “program” corresponding to the program function unit 12 may be referred to as a process.

  Further, if the program corresponding to the memory access investigation unit 11 is installed in a computer having a general OS having a memory recovery function, the memory access investigation device 1 can be realized. The program can be installed in a computer from a recording medium such as a portable memory, or can be downloaded from a server on the network and installed.

  Here, a memory access processing method based on the virtual storage method executed by the memory management function unit 131 will be described with reference to FIG.

  In the present embodiment, the memory information storage unit 133 managed by the memory management function unit 131 stores a page directory table 31 and a page table 32 as shown in FIG. In this example, conversion from a virtual address (also referred to as a logical address) to a physical address of a memory (also referred to as a real address) is performed in two stages of the page directory table 31 and the page table 32.

  In the example shown in FIG. 3, when the program function unit 12 accesses the memory 14, the logical address shown in FIG. 3 is passed to the memory management function unit 131. The memory management function unit 131 first refers to the page directory table 31 and acquires a page table address from the page directory entry indicated by the page directory table index.

  Subsequently, the memory management function unit 131 refers to the page table 32 corresponding to the page directory address, and in the page table 32, the page base entry (page start address of the page on the memory) from the page table entry indicated by the page table index. ) To get. Then, the memory management function unit 131 performs memory access using a value obtained by adding an offset to the base address as a physical address.

  An example of the page table entry in the present embodiment is shown in FIG. As shown in FIG. 4, the page table entry has a page base address and an access bit that is information indicating whether or not the page has been accessed. The access bit is set to “1” by the memory management function unit 131 (that is, the CPU executing the OS program) when the corresponding page is accessed. In addition, the memory management function unit 131 performs a process of periodically setting the access bit set to “1” to “0” in each page table entry.

  The basic mechanism of conversion from a logical address to a physical address, management of information corresponding to access bits, and the like described here are common to computers equipped with an OS adopting a virtual storage system.

  Next, the page collection function unit 132 included in the memory management function unit 131 will be described.

  The page collection function unit 132 saves page data that is not often accessed to an auxiliary storage device when the memory capacity managed by the memory management function unit 131 is insufficient, and provides a free area in the memory. It is. Note that the “less frequently accessed page” is, for example, the oldest page or the like when it is last accessed (timing) within a predetermined period.

  The page collection function unit 132 performs memory management using two lists, an active list and an inactive list, in order to efficiently save data in a memory area that is not accessed very often. These lists are stored in the memory information storage unit 133. In the active list and the inactive list, identification information (such as a pointer for accessing the page) indicating the page is recorded.

  The active list contains identification information of frequently accessed pages, and the inactive list contains identification information of pages that are not frequently accessed. Actually, the active list and the inactive list are represented by structures, and each member in the structure is represented by a page structure of a page to be managed.

  With reference to FIG. 5, an outline of processing of the page collection function unit 132 will be described. The page collection function unit 132 adds a page newly assigned to the program (corresponding to the program function unit 12) to the active list (indicated by “a” in FIG. 5). Then, the page collection function unit 132 periodically checks the pages in the active list and the inactive list, and deletes the pages in the active list from the active list even though they are not accessed so much. Add to list (b). Also, pages of the inactive list that are frequently accessed are deleted from the inactive list and added to the active list (c).

  The page collection function unit 132 checks the inactive list when the memory is insufficient, and makes the page usable by saving the data of the page determined to have not been accessed to the auxiliary storage device at this time. .

  Note that the method of performing page collection management using two lists, an active list and an inactive list, is a general method for an OS that is often used in recent years, and is not a method that depends on a specific OS.

(Processing details of memory access investigation)
Next, the operation of the memory access investigation device 1 related to the memory access investigation will be described. First, an outline of the operation will be described with reference to FIG.

  When the memory 14 is accessed from the program function unit 12 via the OS unit 13 (step 210), the access bit in the page table entry corresponding to the accessed page is set (set to 1) (step 220). ). Note that the access bit is not set before being accessed and is 0. Further, immediately after the access bit 1 is recorded, the processing of the program function unit 12 is resumed (step 230).

  On the other hand, apart from the processing in steps 210 to 230, the memory access checking unit 11 checks the page table entry in the page table stored in the memory information storage unit 133 (step 250). However, in this embodiment, before examining the page table entry, the active list managed by the page collection function unit 132 described above is referred to (step 240), and the identification information of the page included in the active list The page table entry investigation in step 250 is performed with only the pages included in the activity list as the target of the page table entry investigation, and the information of the page with the access bit set is obtained. Then, the result is stored in the memory access information storage unit 111 as a memory access investigation result (step 260). In step 260, the access bit of “1” is set to “0”.

  The processing from step 240 to step 260 is performed periodically, and the access status to the memory can be grasped from the investigation result obtained as a result.

  The memory access investigation unit 11 reads out the memory access investigation result from the memory access information storage unit 111 based on an instruction from the user, for example, and transmits it to another device via the communication network or displays it on a display. It can be performed.

  As described above, in the present embodiment, the memory access check is periodically performed separately from the processing in the program function unit 12, so that the load on the program execution in the program function unit 12 is reduced. In the present embodiment, the range of pages to be investigated (that is, the number of page table entries to be investigated) can be limited by using the information (activity list) created by the page collection function unit 132. And high-speed surveys are possible. That is, by using the activity list, only the page table entry corresponding to the page that is likely to be accessed can be investigated, and the time and load required for the investigation can be greatly reduced.

  In the present embodiment, it is not always essential to limit the investigation range using the activity list. Even if the search range is not limited using the activity list, the search can be performed with a low load compared to the conventional technique using the page fault.

(Specific example of memory access investigation processing)
Hereinafter, a processing example in the memory access examining unit 11 will be described in more detail with reference to a flowchart shown in FIG.

  In this example, the memory access examining unit 11 performs processing using the variables List, m, e, addr, and access_bmp [addr]. access_bmp [addr] is an array, and in this example, information indicating the access amount for each page address is recorded in access_bmp [addr]. By referring to the information recorded here, it is possible to grasp the tendency of which memory page has been accessed. Note that each variable is a predetermined area in the storage means used by the memory access examining unit 11. Here, for convenience, processing using the above variable will be described.

  As shown in FIG. 7, first, the memory access examining unit 11 acquires an activation list from the memory information storage unit 133 and substitutes it into the List (step 310). This limits the scope of the survey to the range of pages indicated by the activity list.

  The memory access checking unit 11 checks whether the List is empty (step 320), and if it is empty, ends the process. If the list is not empty in step 320, the memory access examining unit 11 substitutes page identification information, which is the first element of the list, in m (step 330), and deletes the substituted page identification information from the list (step 330). 340).

  The page identification information here is a structure for page management, and includes address information necessary for accessing the data of the page table entry.

  Subsequently, the memory access examining unit 11 acquires the page table entry data in the page table stored in the memory information storage unit 133 using the page identification information substituted for m, and substitutes it for e. (Step 350).

  The data structure of the page table entry assigned to e is as shown in FIG. 4, and the memory access examining unit 11 determines whether the access bit is set in the data of the page table entry (whether it is 1). (Step 360).

  If the access bit is not set, the process returns to step 320. In step 360, when the access bit is set, the memory access examining unit 11 substitutes the page address (start address of the page) included in the page table entry into addr (step 370), and adds it to addr in the array access_bmp. The corresponding value is increased by 1 (step 380). Further, in this example, in step 380, the access bit of “1” in the page table entry to be investigated is set to “0”.

  The above processing is performed until List becomes empty, that is, the number of elements in the active list. Further, the process shown in FIG. 7 is executed at predetermined time intervals. Thereby, for example, an element of an array corresponding to a page whose access bit is almost always 1 is a large number, and an element of an array corresponding to a page whose access bit is only 1 is a small number. As a result, by referring to the value of access_bmp [addr], it is possible to grasp how often and how often the page has been accessed, and to predict the minimum amount of memory required by the program.

  Note that access_bmp [addr] obtained as described above is merely an example of information representing the access status acquired by referring to the access bit. For example, information representing the access status may be calculated based on LRU (Least Recently Used) widely used as a page replacement algorithm.

(Effect of embodiment)
The memory access checking unit 12 described in the present embodiment checks the memory access by referring to the page table entry, so that the currently executing program is stopped as in the conventional technique for checking using the page fault. This makes it possible to investigate the access status of the memory without reducing the processing load compared to the prior art.

  In addition, since the page table entries to be investigated are limited by using the information of the memory collection mechanism of the OS, the processing load and the time required for the investigation are reduced as compared with the case of searching all page table entries. It becomes possible.

  The present invention is not limited to the above-described embodiments, and various modifications and applications are possible within the scope of the claims.

DESCRIPTION OF SYMBOLS 1 Memory access investigation apparatus 11 Memory access investigation part 111 Memory access information storage part 12 Program function part 13 OS part 131 Memory management function part 132 Page collection | recovery function part 133 Memory information storage part 14 Memory 31 Page directory table 32 Page table

Claims (9)

A memory access investigation device having an operating system corresponding to a virtual storage system and a memory managed by being divided into predetermined blocks by the operating system,
Memory information storage means for storing table information for holding, for each block, flag information indicating whether or not the memory has been accessed from a target program executed in the memory access investigation device;
Memory information investigation means for obtaining information indicating an access status to the memory by referring to flag information in the table information for each predetermined block, and storing the information in a storage means, Memory access investigation device. The operating system has a memory recovery function, and a predetermined list acquired by the memory recovery function is stored in the memory information storage means,
The memory access investigation device according to claim 1, wherein the memory access investigation unit refers to flag information for each block included in the predetermined list.   3. The memory access investigation device according to claim 2, wherein the predetermined list is an activity list acquired by the memory collection function. The block according to any one of claims 1 to 3, wherein the block is a page, the table information is a page table, and the flag information is an access bit in a page table entry in the page table. The memory access investigation device described.   5. The memory access investigation device according to claim 1, wherein a computer having an operating system compatible with a virtual storage system and a memory that is divided and managed in units of predetermined blocks by the operating system. Program for functioning as a memory access investigation means. A memory access investigation method executed by a memory access investigation device having an operating system corresponding to a virtual storage system and a memory that is divided and managed by a predetermined block unit by the operating system,
The memory access investigation device comprises memory information storage means for storing table information for holding for each block flag information indicating whether or not the memory has been accessed from a target program executed in the memory access investigation device, The memory access investigation method is:
A flag information recording step of changing flag information corresponding to the block to a value indicating access when the block of the memory is accessed from the target program;
A memory access investigation step of obtaining information indicating an access status to the memory by referring to the flag information in the table information for each predetermined block, and storing the information in a storage unit. To check memory access. The operating system has a memory recovery function, and a predetermined list acquired by the memory recovery function is stored in the memory information storage means,
The memory access investigation method according to claim 6, wherein, in the memory access investigation step, the memory access investigation device refers to flag information for each block included in the predetermined list.   The memory access investigation method according to claim 7, wherein the predetermined list is an activity list acquired by the memory collection function. The block according to any one of claims 6 to 8, wherein the block is a page, the table information is a page table, and the flag information is an access bit in a page table entry in the page table. The memory access investigation method described.

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