JP2004280333A - Buffer memory device and free space management method for same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manage the free space of a buffer memory through a small memory space and easily determine an overflow of the buffer memory, in a chain system buffer memory device and a free space management method therefor. <P>SOLUTION: In a free space chain memory 1-1 for managing the free space of the buffer memory, when a new free space of an address #X is generated to a free space chain with an address #N stored as the head of a free space, the address #X of the new free space is added before the head #N of the free space chain. The management where the new free space is added to the head of the free space chain keeps a tail pointer of the free space chain continuously at an initial value. At an overflow of the buffer memory, the value of a free space head pointer memory 1-2 becomes "the last free space address #Z+1" to enable easy detection of the overflow. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a buffer memory device and an empty area management method thereof, and more particularly, to a buffer memory device of a chain system used when data frames such as IP (Internet Protocol) packets are temporarily stored in a buffer memory and transfer control is performed, and a buffer memory device using the same. It relates to a free space management method.
[0002]
2. Description of the Related Art In recent years, the amount of transfer data flowing through the Internet network has been increasing more and more, and especially, variable-length data frames such as streaming data and moving image data provided from an Internet service provider to a user are rapidly and abundantly distributed. If these data frames are not efficiently stored in the buffer memory for the service, the buffer memory becomes full immediately. The present invention relates to a chain type buffer memory device for accumulating such transfer data in a buffer memory, and a method of managing a free area thereof.
[0003]
[Prior art]
When performing transfer control of data frames such as IP packets, since transfer data is input in bursts from an Internet service provider or a user, the transfer data is stored in a buffer memory and data transfer control is performed in frame units. Then, a method of storing transfer data in a buffer memory and managing the storage area by connecting an address pointer of the storage area with a chain is effective.
[0004]
Therefore, separately from the buffer memory for storing transfer data, a memory area for storing a chain connecting pointers of data storage areas in the buffer memory and a pointer for a free area of the buffer memory for storing transfer data are managed. Memory area, and based on the information on the data storage area and free area of the buffer memory stored in those memory areas, read and write of the buffer memory are managed, and data is efficiently stored in the buffer memory. Is going.
[0005]
The management of the free area of the buffer memory for storing data is performed by storing a head pointer indicating the head pointer of the free area and a tail pointer indicating the tail pointer of the free area, and linking the free area pointers by a chain. Each time an area is generated, a pointer to a new empty area is added after the tail pointer to form an empty area chain.
[0006]
As a prior art related to the present invention, there is “a memory, a memory management method and a memory management circuit” described in Patent Document 1 below. The memory described in Patent Literature 1 includes a management area and a data area. In the management area, as management information of the entire memory, the number of recorded phrases in the data area, the number of remaining blocks in the free area of the data area, the free area The overall management area for storing the start address and the free area end address, respectively, and the recording time of the phrase, the data start address, and the data end address are stored as individual management information for each phrase stored in the data area. Each block of the data area stores an address of a block to be accessed next to the block as a chain address.
[0007]
[Patent Document 1]
JP-A-8-320822
[Problems to be solved by the invention]
In order to use the buffer memory for storing the transfer data efficiently, the reading and writing of the buffer memory are managed by a chain method. For this purpose, separately from the buffer memory for storing the transfer data, the management for the data storage area is performed. A memory area for the pointer chain and a memory area for managing the free area of the buffer memory (for storing the head / tail pointer of the free area) must be separately provided, and the memory capacity increases.
[0009]
Further, in order to manage the overflow of the buffer memory for storing the transfer data, it is necessary to provide an overflow monitoring circuit, and there is a problem that the circuit scale increases. SUMMARY OF THE INVENTION It is an object of the present invention to provide a buffer memory device capable of managing a free area of a buffer memory in a small memory area and easily managing an overflow of the buffer memory, and a method of managing the free area. .
[0010]
[Means for Solving the Problems]
The buffer memory device according to the present invention comprises: (1) a buffer memory for storing variable-length data in a free area, a means for generating a free area chain connecting addresses of free areas in the buffer memory, and A free area chain memory for storing the free area chain pointer; and a free area head pointer memory for storing a head address of the free area chain, and when storing data in the buffer memory, the free area stored in the free area head pointer memory. A vacant area corresponding to the data length is extracted from the head address of the chain for data storage, and when a vacant area is generated by reading data from the buffer memory, the vacant area is located at the front of the head of the vacant area chain. Means for additionally generating a free space chain.
[0011]
In the method of managing the free area of a buffer memory according to the present invention, (2) a step of generating a free area chain connecting addresses indicating free areas of the buffer memory for storing variable-length data in the free area; Storing the head address of the chain in a free area head pointer memory; and storing the data in the free area head pointer memory from the free area chain head address stored in the free area head pointer memory according to the data length. Extracting an area for data storage, and, when an empty area is generated by reading data from the buffer memory, adding the empty area to the front of the beginning of the empty area chain to generate an empty area chain; .
[0012]
(3) In the initial step of generating the free area chain, storing a value obtained by adding a predetermined value to the own address in a data area of each address of the free area chain memory that stores the area chain. In the process of storing data in the free area of the buffer memory, the overflow area of the buffer memory is detected by detecting that a value exceeding the last address value of the free area is stored in the free area head pointer memory. Is determined.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows an initial configuration of a chain for free space management according to the present invention. A free area chain memory 1-1 for storing and holding a free area chain for managing a free area of the buffer memory is provided separately from the buffer memory, and each address (# 1, # 2) of the free area chain memory 1-1 is provided. ,..., #Z), an initial free area chain is generated by writing the next free area address (own address + 1) of the own address as data at the time of initialization, as shown in FIG.
[0014]
Here, it is assumed that the free area address next to the own address is “own address + 1”, but the free area address next to the own address is not limited to this, and a predetermined value is added to the own address. It may be a value.
[0015]
FIG. 1 shows an example in which there are Z free areas, in which the next second address # 2 is stored in the data area of the first address # 1, and the next second address # 2 is stored in the data area of the second address # 2. The address # 3 is written as data, and thereafter, similarly, the next address of the own address is similarly written as data, and (# Z + 1) is added to the data area of the Z-th address #Z, that is, 1 is added to the total number Z of free areas. The added value is written, and a free area chain for managing the free area of the buffer memory is generated. Also, the initial value # 1 of the head pointer of the free area chain is stored in the free area head pointer memory 1-2.
[0016]
When writing variable-length transfer data to the buffer memory, a free area corresponding to the data length of the transfer data is extracted from the beginning of the free area chain, and the transfer data is stored in the free area. The next address of the area is stored in the head pointer memory 1-2 of the empty area as the head address of the empty area chain.
[0017]
When an empty area is generated in the buffer memory by reading the transfer data from the buffer memory, a pointer of the newly generated empty area is assigned to this empty area chain memory 1-1 as shown in FIG. Add to the front of the head pointer in the current free space chain.
[0018]
In the example of FIG. 2, as shown in FIG. 2A, the N-th address #N is the head of the free area, and #N is stored in the head pointer memory 1-2 of the free area. I have. Then, when a free area of the address #X is newly generated, the address #X is stored as a free area head pointer in the free area head pointer memory 1-2 as shown in FIG. The address #N of the next free area is written in the data area of the start address #X.
[0019]
As described above, when writing the transfer data to the buffer memory, the free area is taken out from the head of the free area chain and written, and the address of the newly generated free area in the buffer memory by reading the transfer data from the buffer memory is written. The tail pointer of the free space chain always remains at the initial value #Z because the tail pointer of the free space chain is always added to the front of the head pointer of the free space chain, instead of being added to the tail of the tail pointer of the free space chain. The value of “last address # Z + 1 of free area” is stored in the data area.
[0020]
Next, monitoring of buffer memory overflow will be described. When the transfer data is sequentially stored in the buffer memory, the free area gradually decreases, and when the remaining free area becomes one, as shown in FIG. Stores the address #Z.
[0021]
Then, data is stored in the buffer memory of the last one free area #Z, and when the last free area #Z is in use, as shown in FIG. A value indicating “the last address # Z + 1 of the empty area” is written in 2, and at this time, the buffer memory is in an overflow state, and writing to the buffer memory cannot be performed.
[0022]
Therefore, when writing to the buffer memory, if the contents of the head pointer memory 1-2 of the empty area are "last address # Z + 1 of the empty area", the buffer memory can be regarded as being in the overflow state. Thus, it is possible to easily monitor the overflow.
[0023]
FIG. 4 shows an embodiment of the buffer memory management according to the present invention. In the embodiment shown in the figure, it is assumed that a buffer memory 4-1 capable of storing 256 Mbytes of data is used, and one byte of the buffer memory 4-1 stores 8 bytes (64 bits) of data. 4-1 has an address of 32 × 1024 × 1024.
[0024]
A storage data head pointer memory 4-2 and a storage data tail pointer memory 4-3 for storing a head pointer and a tail pointer of storage data for managing writing and reading of data to and from the buffer memory 4-1 are provided. .
[0025]
The storage data head pointer memory 4-2 and the storage data tail pointer memory 4-3 are provided for each port, and manage writing and reading of transfer data for each port. FIG. 4 illustrates an example of managing writing and reading of transfer data of two ports (port0, port1).
[0026]
The buffer memory 4-1 is provided with a free area chain memory 1-1 for managing the free area, and the free area chain memory 1-1 has the same number of 32 × 1024 × 1024 addresses as the buffer memory 4-1. The value of “own address + 1” is written as an initial value in each data area of the free area chain memory 1-1.
[0027]
The data area of the free area chain memory 1-1 has at least the number of bits capable of storing the value of "last address + 1". If the address has 32 × 1024 × 1024 addresses, the data area uses a memory having at least 25 bits.
[0028]
When writing data to the buffer memory 4-1, the free area is sequentially used from the start address 0, which is a free area, and the area which becomes empty by reading data from the buffer memory 4-1 is used as the free area. The free area is managed by adding it to the head of the chain.
[0029]
The value of the free area head pointer memory 1-2 at the time when all the free areas are used indicates 32 × 1024 × 1024, and since this value is a fixed value, the value of the free area head pointer memory 1-2 is equal to this value. Is reached, it is determined that the buffer memory has overflowed and that writing to the buffer memory 4-1 is impossible.
[0030]
【The invention's effect】
As described above, according to the present invention, when data is stored in the buffer memory, a vacant area is taken out from the head address of the vacant area chain for data storage, and a vacant area generated by reading data from the buffer memory is obtained. By adding an area to the beginning of the free area chain to generate a free area chain, the tail pointer of the free area chain remains at the fixed value set as the initial value, so There is no need to secure a memory area for storing the tail pointer, and the memory capacity can be reduced accordingly.
[0031]
Also, by detecting that a value exceeding the last address value of the free area is stored in the free area head pointer memory and determining the overflow state of the buffer memory, the overflow state of the buffer memory can be determined by a simple circuit. Thus, the size of the overflow monitoring circuit can be reduced, and the size of the package can be reduced.
[0032]
Furthermore, when the free area chain memory is initialized, a value obtained by adding a predetermined value to its own address is stored in the data area of each address, and a free area chain is generated, so that the size of the free area is considered. A free area chain can be generated without any restriction, and free area management with a high degree of freedom can be performed without being restricted by the size of the free area.
[Brief description of the drawings]
FIG. 1 is a diagram showing an initial configuration of a free space management chain according to the present invention.
FIG. 2 is a diagram showing an example of adding a new free area to a free area chain memory according to the present invention.
FIG. 3 is a diagram showing an overflow state of a buffer memory according to the present invention.
FIG. 4 is a diagram showing an embodiment of buffer memory management according to the present invention.
[Explanation of symbols]
1-1 Free area chain memory 1-2 Free area head pointer memory 4-1 Buffer memory 4-2 Storage data head pointer memory 4-3 Storage data tail pointer memory

Claims (3)

A buffer memory for storing variable-length data in a free area;
Means for generating a free area chain connecting addresses of free areas of the buffer memory;
A free area chain memory for storing the free area chain;
A free area head pointer memory for storing a head address of the free area chain,
When storing data in the buffer memory, a free area corresponding to the data length is taken out from the head address of the free area chain stored in the free area head pointer memory for data storage, and data is read from the buffer memory. Means for generating a free space chain by adding the free space to the front of the head of the free space chain when a free space is generated by
A buffer memory device comprising: Generating a free area chain linking addresses indicating free areas of the buffer memory for storing variable-length data in the free area;
Storing the head address of the free space chain in a free space head pointer memory;
When storing data in the buffer memory, a free area corresponding to the data length is taken out from the head address of the free area chain stored in the free area head pointer memory for data storage, and data is read from the buffer memory. Generating an empty area chain by adding the empty area to the front of the beginning of the empty area chain when an empty area is generated,
A method for managing a free area in a buffer memory, comprising: In the initial step of generating the free area chain, a step of storing a value obtained by adding a predetermined value to its own address in the data area of each address of the free area chain memory that stores and holds the area chain,
Determining the overflow state of the buffer memory by detecting that a value exceeding the last address value of the free area is stored in the free area head pointer memory in the process of storing data in the free area of the buffer memory; 3. The method according to claim 2, further comprising the steps of:

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