JP2007264692A - Memory management method, device and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent insufficient memory or reduce the load of system resources in processing for performing memory management by use of a bit map. <P>SOLUTION: A maximum continuous free space length management part 13 inspects whether a continuous space for a necessary bit map number is present or not by comparing a necessary bit map area size with a maximum continuous free space length in a bit map area 101. When a necessary space is present in the bit map, a space bit map retrieval part 14 performs retrieval of the bit map area by use of a bit unit bit map retrieval part 15. When a necessary space bit map is found, a memory ensuring part 11 notifies its continuous space area length and location to an ensuring candidate location area management part 16, and when a plurality of continuous space areas necessary for memory ensuring is found, the part 11 compares the continuous space area length of the already found location with the continuous space area length of the second and following ones, and substitutes the content of the ensuring location area management part 16 by the smaller one. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

    The present invention relates to a method for performing memory management using a bitmap.

In Patent Document 1, when searching for a bitmap for managing a memory when free memory is secured, a bitmap area of one word or more is secured by switching word units or bit units according to the number of necessary bitmap areas. Speeds up the search process.
JP 2000-311110 A

  The above-described conventional method unconditionally secures the first free space that is found, so that a large area is inadvertently used in pieces, resulting in memory fragmentation, Although the total amount is sufficient, there is a problem that memory cannot be secured, resulting in insufficient memory.

  An object of the present invention is to provide a memory management method, an apparatus, and a program for realizing reduction of used memory by preventing fragmentation of memory.

The memory management method of the present invention includes a memory securing means, an allocated memory address calculating means, a required bitmap area number calculating means, a maximum continuous free area length managing means, a free bitmap search means, and a bitmap search position notification. A memory management apparatus having a means, a bitmap securing means, a bit-unit bitmap search means, and a securing candidate location area management means, and managing a memory having a bitmap area and an allocation area,
A step of notifying a required memory size to a required bitmap area calculating means in response to a memory securing request;
A required bitmap area number calculating means obtains a bitmap area size necessary for managing the requested memory size, and returns the value to the memory securing means;
The maximum continuous free area length management means compares the required bitmap area size notified from the memory securing means with the maximum continuous free area length in the bitmap area, and determines whether there is continuous free space for the required bitmap area size. A step of notifying the securing means;
When there is continuous free space for the required bitmap area size, a notification from the memory securing means is received, and the free bitmap search means is notified from the bitmap search position notification means using the bit unit bitmap search means. When the bitmap area is searched from the search position and the necessary continuous free bitmap is found, the step of notifying the memory securing means of the size and location of the continuous free area and the memory securing means complete the bitmap area search. If the number of consecutive free bitmaps required for reservation is one in the bitmap area, the size of the continuous free area and its location are used. Notifying the location area management means;
A step of notifying the bitmap securing means of a location stored by the securing candidate location area managing means;
The bitmap securing means secures the notified location of the bitmap area, and notifies the allocated memory address calculating means of the position of the newly secured bitmap area;
An allocated memory address calculating means calculates an allocated memory address from the position of the notified bitmap area, and returns the allocated address to the memory requester;
Have
If there is no free space continuously for the required bitmap area size, the processing is repeated from the step performed by the maximum continuous free space length management means for other memories.

  The present invention, in the process of managing the memory using a bitmap, secures the smallest of the continuous free areas necessary for securing, leaving as much of the continuous free area of a large size as possible. That is, the load of system resources is reduced.

  According to the present invention, by using the smallest continuous free area necessary for securing and leaving a continuous free area of a large size as much as possible, memory shortage due to memory fragmentation is eliminated, and system resource load is reduced. Mitigation can be achieved.

Next, embodiments of the present invention will be described in detail with reference to the drawings.

  Referring to FIG. 1, the memory management apparatus of the present invention manages a memory 100 having a bitmap area 101 and an allocation area 102, and includes a memory management section 11, a required bitmap area number calculation section 12, and a maximum continuous free area. The length management unit 13, the free bitmap search unit 14, the bit unit bitmap search unit 15, the allocation candidate location area management unit 16, the bitmap allocation unit 17, the bitmap search position notification unit 18, and the allocated memory address calculation unit 19 Have.

  The necessary bitmap area number calculation unit 12 obtains a bitmap area size necessary for managing the requested memory size. The maximum continuous free area length management unit 13 compares the required bitmap area size with the maximum continuous free area length in the bitmap area 101 and notifies the memory management unit 11 of the presence or absence of continuous free space for the required bitmap area size. When the empty bitmap search unit 14 receives the notification from the memory securing unit 11 and there is a continuous free space corresponding to the required bitmap area size, the bitmap search unit 15 uses the bit-unit bitmap search unit 15 to send the bitmap search position notification unit 18. When the bitmap area 101 is searched from the notified bitmap search position and a necessary continuous free bitmap is found, the memory management section 11 is notified of the continuous free area size and location. Upon receipt of the memory allocation request, the memory management unit 11 notifies the required bitmap area number calculation unit 12 of the required memory size, and the required bitmap area size calculated by the necessary bitmap area number calculation unit 12 is the maximum continuous free area. When the length management unit 13 is notified, the notification from the free bitmap search unit 14 is received, and the search of the bitmap area 101 is completed, the continuous free bitmap necessary for securing is one in the bitmap area 101 In the case where there are a plurality of continuous free area sizes and their locations, the minimum candidate free space length and its location are notified to the secured candidate location area management means 16. The bitmap securing unit 17 secures the location of the bitmap area 101 notified from the memory securing unit 11 and notifies the allocation memory address calculating unit 19 of the position of the newly secured bitmap. The allocated memory address calculation unit 19 calculates an allocated memory address from the position of the bitmap notified from the bitmap securing unit 17, and returns the allocated address to the memory requester.

  Next, the operation of the memory management device of this embodiment will be described with reference to FIG.

  In response to the memory reservation request, the memory reservation unit 11 notifies the required memory size calculation unit 12 of the required memory size (step 201). The necessary bitmap area number calculation unit 12 obtains the bitmap area size necessary for managing the requested memory size by dividing the requested memory size by the memory size per bit of the bitmap area 101, and calculates the value. It returns to the memory securing unit 11 (step 202). The maximum continuous free area length management unit 13 compares the required bitmap area size notified from the memory securing unit 11 with the maximum continuous free area length in the bitmap area 101, and determines whether or not there is a continuous free space corresponding to the required number of bitmaps. The reservation unit 11 is notified (step 203). If there is no necessary space in the bitmap area 101, the memory reservation unit 11 searches for another memory area (step 204). If there is a space, the free bitmap search unit 14 starts from the memory reservation unit 11. In response to this notification, the bitmap area 101 is searched from the search position notified from the bitmap search position notification section 18 using the bit unit bitmap search section 15 (step 205).

  When the memory securing unit 11 finds the necessary continuous free bitmap, it notifies the secured candidate location region length management unit 16 of the continuous free region length and its location, and the free bitmap search unit 14 determines whether there are other candidates. The bitmap area 101 is further searched (steps 206 to 209). When a plurality of continuous free areas necessary for memory reservation are found, the memory securing unit 11 secures the smaller one by comparing the continuous free area length of the already found place with the continuous free area length found after the second one. Replaced with the contents of the location area management unit 16 (steps 210 and 211).

  As a result of searching the entire bitmap area 101, the memory securing unit 11 notifies the bitmap securing unit 17 of the position of the bitmap area 101 stored in the secured location area length management unit 16, and the bitmap securing unit 17 Secures the bitmap of the notified position and notifies the allocated memory address calculation unit 18 of the position of the newly secured bitmap area 101 (steps 212 and 213). The allocated memory address calculation unit 19 calculates the allocated memory address from the notified position of the bitmap area 101 by multiplying the number of bits indicated by the position by the number of bits per bit (step 214). The assigned address is returned to the requester (step 215).

  Next, a specific example of this embodiment will be described in detail with reference to FIG.

  As shown in FIG. 3, the memory 100 includes a bitmap area 101 and an allocation area 102, and the empty areas of the bitmap area 101 are bitmaps A1, A2, A3, B, and C. Assume that a memory request requiring 6 bytes of bitmap is made.

  When the memory securing unit 11 receives a memory securing request, the memory securing unit 11 uses the necessary bitmap area number calculating unit 12 in order to obtain the number of bitmap areas necessary for managing the memory of the requested size. In this case, it is assumed that the necessary number of bitmap areas is 6.5 bytes (52 bits). The memory securing unit 11 compares the maximum continuous free area length with the previously obtained 6.5 bytes. In this case, since the maximum continuous free area length is larger, it is determined that memory can be secured in the bitmap area 101, and the processing is continued. The memory securing unit 11 that has determined that the memory can be secured by the bitmap 101 searches the free bitmap area 101 through the free bitmap search unit 14. The empty bitmap search unit 14 first notifies the bit unit bitmap search unit 15 of the number of necessary bitmap areas. The bit unit bitmap search unit 15 finds an area starting from A1, determines that an area necessary for securing is found, further checks the free area length behind it, and stores the location of A1 in the allocation candidate place area management unit 16 And the continuous free area length (12 bytes) of A1, A2, and A3 is stored. Thereafter, the subsequent bitmap area 101 that has not been searched is further searched to find the area B, the same processing as described above is performed, and it is determined that the area can be secured. At this time, since the currently found area is shorter (8 bytes) than the continuous empty area length of the previously found candidate place, B is stored in the reserved candidate place area management unit 16. As a result, the shaded portion shown in the figure is determined to be a continuous 6.5-byte space, and is notified to the bitmap securing unit 17. The bitmap securing unit 17 changes the previously found 6.5-byte empty space to be in use (0000000000000 → 11111111111111). The allocated memory address calculating unit 19 that has received the bitmap position from the bitmap securing unit 17 calculates the actual memory address to be allocated from the bitmap position, and returns the requested address to the memory securing requester.

  In this way, by using small areas instead of inadvertently using large sized free areas (A1, A2, A3), memory shortage due to memory fragmentation can be prevented and system resource load can be reduced. It is possible to realize.

  Referring to FIG. 5, a memory management apparatus according to another embodiment of the present invention includes a word management bitmap search unit 20 that searches a bitmap area in units of words and a bitmap in units of bytes. A byte unit bitmap search unit 21 for searching an area is added.

  In the present embodiment, when there is a necessary space in the bitmap area 101, the space bitmap search unit 14 selects the word unit bitmap search unit 20, the byte unit bitmap search unit 21, according to the number of necessary bitmap regions, The difference from the first embodiment is that a bitmap area is searched using the bit unit bitmap search means 15.

  Here, if necessary, if the required bitmap area size exceeds 1 word, empty space is searched for by the number of words of the required area size, and the remainder is 1 word or less. Searching for vacancy in byte units, and searching for vacancy in bit units for the last remaining (this means less than 8 bits).

  The function of the memory management device is to record a program for realizing the function on a computer-readable recording medium, and cause the computer to read and execute the program recorded on the recording medium. Also good. The computer-readable recording medium refers to a recording medium such as a flexible disk, a magneto-optical disk, and a CD-ROM, and a storage device such as a hard disk device built in a computer system. Further, the computer-readable recording medium is a medium that dynamically holds the program for a short time (transmission medium or transmission wave) as in the case of transmitting the program via the Internet, and in the computer serving as a server in that case Such as a volatile memory that holds a program for a certain period of time.

1 is a block diagram of a memory management device according to an embodiment of the present invention. FIG. 3 is a flowchart showing an operation of the memory management device of FIG. 1. It is a figure which shows the example of the bitmap which shows operation | movement of the memory management apparatus of FIG. FIG. 5 is a block diagram of a memory management device according to another embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Memory reservation part 12 Necessary bitmap area number calculation part 13 Maximum continuous free area length management part 14 Empty bitmap search part 15 Bit unit bitmap search part 16 Reserve candidate place area management part 17 Bitmap reservation part 18 Bitmap search position Notification unit 19 Allocation memory address calculation unit 20 Word unit bitmap search unit 21 Bit unit bitmap search unit 100, 100A Memory 101 Bit map region 102 Allocation region 201-205 Steps

Claims (5)

Memory securing means, allocated memory address calculating means, required bitmap area number calculating means, maximum continuous free area length managing means, free bitmap search means, bitmap search position notifying means, bitmap securing means, A method of managing a memory having a bitmap area and an allocation area using a memory management device having a bit-unit bitmap search means and a reservation candidate location area management means,
The memory securing means receiving a memory securing request and notifying the required bitmap area number computing means of the requested memory size;
The necessary bitmap area number calculating means obtains a bitmap area size necessary for managing the requested memory size, and returns the value to the memory securing means;
The maximum continuous free area length management means compares the required bitmap area size notified from the memory securing means with the maximum continuous free area length in the bitmap area, and the continuous free area length corresponding to the required bitmap area size. Notifying the memory securing means of presence or absence;
When there is continuous free space for the required bitmap area size, upon receiving notification from the memory securing means, the free bitmap search means uses the bit-unit bitmap search means for the bitmap search position notification means. The bitmap area is searched from the search position notified from, and when the necessary continuous free bitmap is found, the step of notifying the memory securing means of the continuous free area size and location; and the memory securing means, At the point where the search of the bitmap area is completed, if there is one continuous free bitmap necessary for securing in the bitmap area, the size and location of the continuous free area are the same. Notifying the reservation candidate location area management means of the length and its location;
The memory securing means notifying the bitmap securing means of the location stored in the securing candidate location area managing means;
The bitmap securing means secures the notified location of the bitmap area, and notifies the allocated memory address calculation means of the position of the newly secured bitmap area;
The allocated memory address calculating means calculates an allocated memory address from the position of the notified bitmap area, and returns the allocated address to the memory requester;
Have
If there is no free space continuously for the required bitmap area size, repeat the process from the step performed by the maximum continuous free space length management means for other memory,
Memory management method.   When the required bitmap area size exceeds one word when the empty bitmap search means searches the bitmap area, the word unit bitmap search means uses the word area bitmap search means for the number of words. If there is a remaining space or less than one word, the space is searched in byte units using the byte unit bitmap search means, and the last bit space is searched using the bit unit bitmap search means. The memory management method according to claim 1, wherein a vacancy is searched in bit units. An apparatus for managing a memory having a bitmap area and an allocation area,
A necessary bitmap area number calculating means for obtaining a bitmap area size necessary for managing the required memory size;
Comparing the required bitmap area size with the maximum continuous free area length in the bitmap area, maximum continuous free area length management means for notifying whether there is a continuous free space for the required bitmap area size;
Bitmap search position notifying means for notifying the search position of the bitmap area;
When there is a continuous space for the required bitmap area size, the bitmap region is searched from the search position notified from the bitmap search position notification unit using the bit-unit bitmap search unit, and the necessary continuous space is obtained. When the bitmap is found, the free bitmap search means for notifying the continuous free area size and location, the reserved candidate place area management means,
In response to a memory allocation request, the required memory size is notified to the required bitmap area number calculating means, the required bitmap area size is notified to the maximum continuous free area length managing means, and the empty bitmap search means is notified. When the bitmap area search is completed and there is one continuous free bitmap in the same bitmap area, the size of the continuous free area and its location are the minimum continuous in the case of multiple. Memory securing means for notifying the securing candidate location area managing means of the free space length and its location;
Bitmap securing means for notifying the location of the newly secured bitmap area while securing the bitmap of the notified location from the memory securing means,
An allocated memory address calculating unit that calculates an allocated memory address from the position of the bitmap area notified from the bitmap securing unit, and returns the allocated address to the memory requester;
A memory management device.   Further comprising a word unit bitmap search unit and a byte unit bitmap search unit, wherein the free bitmap search unit performs the search of the bitmap region, and if the required bitmap region size exceeds one word, A word unit bitmap search means is used to search for free space in word units by the number of words of the required area size. If there is a surplus or less than one word, the byte unit bitmap search means uses the byte unit bitmap search means to free space. The memory management device according to claim 3, wherein a search is made for a vacancy in bit units using the bit unit bitmap search means for the last remaining portion.   A memory management program for causing a computer to execute as the memory management device according to claim 3.

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