JP2009059190A - Cache system, data recording apparatus, program, and control method of cache system - Google Patents

Abstract

Provided is a cache system capable of efficiently accelerating processing when recording data on a storage medium.
A cache system 90 is mounted on a data recording apparatus 1 that records data on a storage medium 60 via a file system 30 and includes a plurality of entries that hold data in units of sectors. 10 and a cache control unit 20 that determines a cache hit / miss for the cache memory based on an access request from the file system and accesses at least one of the cache memory and the storage medium according to the determination result. . The cache control unit receives an access command relating to an access request from the file system, determines whether the data size to be accessed satisfies a predetermined condition based on the access command, and determines whether the cache memory is Control through access.
[Selection] Figure 1

Description

  The present invention relates to a cache system, a data recording apparatus, a program, and a control method for the cache system.

A drive recorder incorporating a data recording device that receives input data from a camera module or audio module, temporarily stores it in an SDRAM, etc., and then saves it in a nonvolatile storage medium (for example, a CF / SD card) when a predetermined event occurs And surveillance camera systems are known.
JP 2002-209173 A

  In such a data recording apparatus, a large number of image data files are often written to a nonvolatile storage medium using a general-purpose file system. However, when the file system writes data, a read operation for searching for a writable area is also performed for each file, so that the number of accesses to a nonvolatile storage medium (for example, a CF / SD card) increases. The processing speed is also slowed down.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a cache system capable of efficiently accelerating processing when recording data on a storage medium. .

(1) The present invention
A cache system mounted on a data recording apparatus that records data on a storage medium via a file system,
A cache memory including a plurality of entries that hold data in units of sectors;
A cache control unit that determines a cache hit / miss for the cache memory based on an access request from a file system and accesses at least one of the cache memory and the storage medium according to a determination result;
The cache control unit
Control that receives an access command related to an access request from the file system, determines whether the data size to be accessed satisfies a predetermined condition based on the access command, and passes through access to the cache memory based on the determination result It is characterized by performing.

  A sector is a minimum recording unit of a storage medium. Therefore, for example, when one sector is x bytes, the minimum recording unit is x bytes, so writing is performed in units of x bytes.

  For example, when a plurality of other caches are used, a configuration for accessing the information storage medium or another cache memory is also within the scope of the present invention.

  In the present invention, whether to perform cache processing or to bypass cache processing is controlled according to the data size to be accessed. For example, when the data size to be accessed is n sectors or less, the cache memory is accessed, and when it is larger than n sectors, the access to the cache memory may be passed through.

  According to the present invention, it is possible to construct a cache memory targeting a specific operation (for example, searching for a free area or writing header data) that can be specified by the data size to be accessed. Moreover, since the data size to be accessed in the cache memory is limited, the cache hit rate can be improved by reducing the data size. Therefore, it is possible to provide a cache system capable of efficiently increasing the processing speed when performing data recording on a storage medium.

(2) The cache system of the present invention
The cache control unit
As the predetermined condition, it is determined whether or not the data size to be accessed is a single sector size. If the data size is not a single sector size, control to pass through access to the cache memory is performed.

  When the file system writes data, read operations for searching writable areas frequently occur, so the number of accesses to the storage medium increases and the processing speed also decreases. Since the read operation for searching for such a writable area often involves determining whether or not it is a writable area (empty area) by referring to a header area provided near the head of each sector area. It is a great thing to be done as a lead.

  Also, writing of header information is often performed as a single sector write.

  According to the present invention, since the cache access is performed only at the time of single sector access, the cache hit rate is increased. In addition, a single sector read for searching for a writable area and a single sector write for writing header information frequently occur during data recording, so that a cache capable of efficiently increasing the processing speed when recording data on a storage medium. A system can be provided.

(3) The present invention
A cache system mounted on a data recording apparatus for recording data on a storage medium,
A cache memory including a plurality of entries that hold data in units of sectors;
A cache controller that performs a cache hit / miss determination on the cache memory when accessing the storage medium, and accesses at least one of the cache memory and the storage medium according to a determination result;
The cache memory is
Including multiple entries containing a data area smaller than the sector size,
The cache control unit
When the access is not a read access for searching a writable area of the storage medium, control is performed to pass through access to the cache memory.

  When data is written, read operations for searching writable areas frequently occur, so that the number of accesses to the storage medium increases and the processing speed also decreases. Since the read operation for searching for such a writable area often involves determining whether or not it is a writable area (empty area) by referring to a header area provided near the head of each sector area. It is a great thing to be done as a lead.

  In the present invention, a cache memory is provided that is used when the access is a read access for searching for a writable area of the storage medium. When the access is not a read access for searching for a writable area, the cache memory is accessed. To pass through. Since the data for determining the writable area does not need even one sector, the cache memory includes a plurality of entries including a data area smaller than the sector size.

  According to the present invention, it is possible to provide a cache system having a high hit rate with respect to a single sector read for searching a writable area at the time of data recording with a small capacity cache memory.

(4) The present invention
A data recording apparatus including the cache system described above and recording data on a storage medium.

(5) The data recording apparatus of the present invention
A data recording area control unit that receives a plurality of data files of different data types, determines a directory of a write area according to the data type of each data file, and makes a write request to the determined directory of the storage medium,
The data recording area control unit
A writing order is determined so that writing of data files of the same data type is continuously performed for a plurality of data files to be written, and a writing request is made according to the determined order.

  According to the present invention, since the frequency of changing the directory to be accessed can be lowered, it is possible to provide a high-speed data recording apparatus with a high cache hit rate.

(6) The present invention
A program for controlling a cache system mounted on a data recording apparatus that records data on a storage medium via a file system,
A cache memory including a plurality of entries that hold data in units of sectors;
Based on an access request from a file system, a cache hit / miss is determined for the cache memory, and the computer is caused to function as a cache control unit that accesses at least one of the cache memory and the storage medium according to the determination result,
The cache control unit
Control that receives an access command related to an access request from the file system, determines whether the data size to be accessed satisfies a predetermined condition based on the access command, and passes through access to the cache memory based on the determination result It is characterized by performing.

(7) The present invention
A control method for a cache system mounted on a data recording apparatus for recording data on a storage medium via a file system,
Based on an access request from the file system, a cache hit / miss is determined for a cache memory including a plurality of entries that hold data in units of sectors, and at least one of the cache memory and the storage medium is accessed according to the determination result. When doing
Control that receives an access command related to an access request from the file system, determines whether the data size to be accessed satisfies a predetermined condition based on the access command, and passes through access to the cache memory based on the determination result It is characterized by performing.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below do not unduly limit the contents of the present invention described in the claims. Moreover, not all of the configurations described below are essential constituent requirements of the present invention.

  FIG. 1 is a diagram for explaining a cache system and a data recording apparatus according to the present embodiment.

  The cache system 90 of the present embodiment is a cache system that is mounted on the data recording apparatus 1 that records data on a storage medium (CF / SD card) 60 via the file system 30.

  The application 40 is software that performs various processes related to data recording of the data recording apparatus 1. The file system 30 is general-purpose software for accessing data in a file format. In the data recording apparatus 1 of the present embodiment, the data recording processing application 40 performs processing for storing data in a CF / SD (storage medium) 60 that is a medium for recording data via the file system 30. .

  The CF / SD driver 50 is driver software for reading / writing data from / to the CF / SD 60, and access to the CF / SD (storage medium) 60 is performed via the CF / SD driver 50.

  The cache system 90 includes a cache memory 10 including a plurality of entries that hold data in units of sectors. The cache memory may be configured using a built-in SDRAM, for example.

  Based on the access request from the file system 30, the cache system 90 determines cache hit / miss for the cache memory 10 and accesses at least one of the cache memory 10 and the storage medium (CF / SD card) 60 according to the determination result. And a cache control unit 20 for performing The cache control unit 20 receives an access command related to an access request from the file system, and determines whether or not the data size to be accessed satisfies a predetermined condition based on the access command (for example, a single sector, the data size is predetermined). Based on the determination result, control is performed to pass through access to the cache memory.

  As the predetermined condition, the cache control unit 20 determines whether or not the data size to be accessed is a single sector size. If the data size is not a single sector size, the cache control unit 20 performs control to pass through the access to the cache memory 10. You may do it.

  The application 40, the file system 30, the cache control unit 20, and the CF / SD driver 50 can be realized, for example, by executing a program for realizing various processes by the CPU of the data recording apparatus.

  FIG. 2 shows a configuration example of the cache memory 10 according to the present embodiment. As an entry of the cache memory 10, a tag portion 12 storing a sector number (sector address of a storage portion) and a data portion 14 corresponding to the sector number (sector address) (a plurality of data areas capable of storing data for one sector) ) May be included.

  The tag unit 12 can be configured with, for example, a 4-byte sector number storage area corresponding to the number of entries (for example, 256). Further, the data section 14 can be configured by a real data (storage medium data) holding area having a sector size (for example, 512 bytes) corresponding to the number of entries (for example, 256).

  Corresponding entry addresses 13 and 15 are assigned to the areas of the tag part 12 and the data part 14, respectively. Therefore, the entry address is obtained from the sector address to be accessed, and if the sector address stored in the entry address 13 of the tag unit 12 is the address to be accessed, it is determined as a cache hit and has the entry address. The data unit 14 may be accessed.

  The relationship between the sector address to be accessed and the entry address can be set as appropriate. For example, the entry address may be assigned according to the remainder obtained by dividing the sector address by the number of entries (the entry address using the lower bits of the sector number). May be assigned).

  Note that the cache memory may be configured by a write-through method or a write-back method. However, in the case of a configuration in which the cache-through is performed when the size is larger than 2 sectors (for example, 3 sectors or more), since the control becomes complicated when the write-back method is used, the write-through method may be used.

  FIG. 3 is a flowchart showing the processing flow of the cache control unit of the present embodiment.

  First, an access command to the storage medium is received from the file system (step S10). The access command includes information such as a sector address to be accessed, an access type (whether it is a read request or a write request), a data size to be accessed, and data to be written in the case of a write request.

  Based on the access command, an access type (whether it is a read request or a write request) and an access target data size are acquired (step S20).

  If the access type is a read request (step S30), read control processing is performed (step S40). The contents of the read control process will be described with reference to FIG.

  If the access type is a write request (step S30), a write control process is performed (step S50). The contents of the write control process will be described with reference to FIG.

  FIG. 4 is a flowchart showing the flow of the read control process according to this embodiment.

  If the data size to be accessed is a single sector size (step S110), the cache hit / miss determination for the cache memory is performed (step S120).

  If it is not a cache hit (step S130), or if the data size to be accessed is not a single sector size (step S110), access to the cache memory is made through and a CF / SD read driver is called (step S140). .

  If it is a cache hit (step S130), data is copied from the corresponding entry in the cache memory and returned to the file system (step S150).

  FIG. 5 is a flowchart showing the flow of the write control process according to this embodiment.

  If the data size to be accessed is a single sector size (step S210), the write data is overwritten from the corresponding entry in the cache memory, the data is copied, and the process proceeds to step S230 (step S220).

  If the data size to be accessed is a single sector size (step S210), the CF / SD read driver is called (step S230).

  According to the embodiment described above, it is possible to construct a cache memory that targets a specific operation that can be specified by the data size to be accessed (for example, searching for a free area or writing header data). Moreover, since the data size to be accessed in the cache memory is limited, the cache hit rate can be improved by reducing the data size.

  Further, since cache access is performed only during single sector access, the cache hit rate is increased. In addition, a single sector read for searching a writable area and a single sector write for writing header information frequently occur at the time of data recording, so a cache that can efficiently process at the time of data recording on a storage medium. A system can be provided.

  FIG. 6 is a hardware block diagram of the drive recorder 100 which is an example of the image data recording system of the present embodiment.

  The drive recorder 100 (including the image data recording system 1) may be configured as a system mounted on a moving body such as a car (for example, a drive recorder system mounted on an automobile).

  The drive recorder 100 according to the present embodiment includes an integrated circuit device (IC) 101 for image data recording processing, but other camera modules 170-1 and 170-2, audio modules connected to the image data recording processing IC 101. 190, various sensors 180, CF / SD card (storage unit medium) 160, and SDRAM 150 may be included.

  The data recording processing IC 101 includes a CPU 210, image processing circuits 160-1 and 160-2, camera I / Fs 172-1 and 172-2, an interrupt controller 240, a DMAC (Direct Memory Access Controller) 220, an A / D converter (sensor). I / F) 182, sound processing circuit 192, audio I / F 194, RTC 180, CF / SD interface 162, memory I / F 152, ROM 250, RAM 250, timer 230, and the like.

  The CPU 210 performs various processes for data recording processing in accordance with a control program stored in the ROM 240, and functions as the application 40, the file system 30, the cache control unit 20, and the CF / SD driver 50.

  In addition, the CPU 210 and the DMAC 220 cooperate with each other to store image data acquired by the camera modules 170-1 and 170-2, sound data acquired by the audio module 190, and measurement values acquired by the various sensors 180 in the SDRAM (first Storage section) 50 in real time.

  Here, the image data acquired by the camera modules 170-1 and 170-2 may be transferred directly to the SDRAM (first storage unit), for example, by the CPU 210, or the CPU 210 instructs the DMAC 220 to transfer the image data to the SDRAM. The structure to do may be sufficient.

  The camera I / Fs 172-1 and 172-2 are connected to the camera modules 170-1 and 170-2 and perform processing for receiving image data of images captured by the camera modules 170-1 and 170-2. The image processing circuits 160-1 and 160-2 perform image processing such as resizing (cutting) and JPEG compression on the image data received from the camera I / Fs 172-1 and 172-2, and image data in a recording format. JPEG encoders 162-1 and 162-1 are included.

  The camera modules 170-1 and 170-2 include a light receiving element that converts incident light into an electrical signal, and an optical system that makes the light incident on the light receiving element (for example, an optical system configured by an optical element such as a lens or a mirror). A processing unit that performs predetermined processing on the electrical signal output from the light receiving element may be used, and may be realized by a CCD camera, for example. The camera modules 170-1 and 170-2 may be mounted on a moving body such as a car and configured to acquire a plurality of image data in time series. For example, the image data may be acquired at a rate of 30 frames per second. Note that three or more camera modules can be connected.

  The audio I / F 194 is connected to the audio module 190 and performs processing for receiving sound data collected by the audio module 90. The sound processing circuit 192 performs sound processing such as compression on the sound data received from the audio I / F 194 to generate sound data in a recording format.

  The audio module 190 may be constituted by a microphone or the like, for example.

  The various sensors 180 are sensors for detecting an accident such as a collision, for example, and can be realized by, for example, an acceleration sensor or a gyro sensor, but can also be realized by another sensor that can detect an impact of an accident. is there.

  The A / D converter (sensor I / F) 182 is connected to various sensors, receives the measurement values of the various sensors 180, and performs analog / digital conversion of the received measurement values.

  A CF (Compact Flash) / SD (Secure Digital) card 169 is a rewritable nonvolatile memory and functions as a storage medium.

  The data recording processing IC 101 of this embodiment encodes the outputs of the camera modules 170-1 and 170-2 into JPEG data at regular intervals and continues to store them in the SDRAM 150. The SDRAM 150 may be used as a ring buffer. When a data storage event is detected based on the measurement values of the various sensors 180, a trigger is generated. When the trigger is generated, data of several tens of seconds before and after is read from the SDRAM 150 and stored in the CF / SD 160. At the same time, audio input, external pulse input, and analog input data may be continuously stored in the SDRAM 150, and when a trigger occurs, data of several tens of seconds before and after may be read from the SDRAM 150 and stored in the CF / SD 160.

  When the data is read from the SDRAM 150 and stored in the CF / SD 160, the cache control described with reference to FIGS. The cache memory 252 according to this embodiment may be provided in a part of the RAM 250 area.

  For example, different data types may be set for data from the two camera modules 170-1 and 170-2, the audio module 190, and various sensors 180. In this case, in this embodiment, since a plurality of data files having different data types are received, the CPU 210 determines the directory of the writing area according to the data type of each data file, and determines the storage medium. It may be made to function as a data recording area control unit for making a write request to the directory. Then, the write order may be determined so that data files of the same data type are continuously written for a plurality of data files to be written, and a write request may be made according to the determined order. In this way, since the frequency of changing the directory to be accessed can be reduced, a high-speed data recording device with a high cache hit rate can be realized.

  The present invention is not limited to the above-described embodiment, and various modifications can be made. The present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same objects and effects). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

  In the above embodiment, the cache system mounted on the data recording apparatus that records data on the storage medium via the file system has been described as an example, but the present invention is not limited to this. For example, in a cache system mounted on a data recording apparatus that records data on a storage medium, when accessing a storage medium and a cache memory including a plurality of entries that hold data in sector units, A cache control unit that performs a cache hit / miss determination on the cache memory and accesses at least one of the cache memory and the storage medium according to a determination result, and the cache memory includes data smaller than a sector size. A cache system that includes a plurality of entries including an area, and wherein the cache control unit performs control to pass through access to a cache memory when the access is not a read access for searching a writable area of the storage medium. Rights of the present invention Is an internal.

The figure for demonstrating the cache system and data recording device of this embodiment. 2 is a diagram illustrating a configuration example of a cache memory according to the present embodiment. FIG. The flowchart figure which shows the flow of a process of the cache control part of this Embodiment. The flowchart figure which shows the flow of a process of the reading control process of this Embodiment. The flowchart which shows the flow of a process of the write-control process of this Embodiment. The hardware block diagram of the drive recorder which is an example of the image data recording system of this Embodiment.

Explanation of symbols

1 image recording device, 20 cache control unit, 30 file system, 40 application, 50 CF / SD driver, 60 CF / SD, 90 cache system

Claims (7)

A cache system mounted on a data recording apparatus that records data on a storage medium via a file system,
A cache memory including a plurality of entries that hold data in units of sectors;
A cache control unit that determines a cache hit / miss for the cache memory based on an access request from a file system and accesses at least one of the cache memory and the storage medium according to a determination result;
The cache control unit
Control that receives an access command related to an access request from the file system, determines whether the data size to be accessed satisfies a predetermined condition based on the access command, and passes through access to the cache memory based on the determination result A cache system characterized by In claim 1,
The cache control unit
As the predetermined condition, a determination is made as to whether or not the data size to be accessed is a single sector size. If the data size is not a single sector size, control is performed to pass through access to the cache memory. . A cache system mounted on a data recording apparatus for recording data on a storage medium,
A cache memory including a plurality of entries that hold data in units of sectors;
A cache controller that performs a cache hit / miss determination on the cache memory when accessing the storage medium, and accesses at least one of the cache memory and the storage medium according to a determination result;
The cache memory is
Including multiple entries containing a data area smaller than the sector size,
The cache control unit
When the access is not a read access for searching a writable area of the storage medium, control is performed to pass through access to the cache memory.   4. A data recording apparatus comprising the cache system according to claim 1 for recording data on a storage medium. In claim 4,
A data recording area control unit that receives a plurality of data files of different data types, determines a directory of a write area according to the data type of each data file, and makes a write request to the determined directory of the storage medium,
The data recording area control unit
A data recording apparatus, wherein a writing order is determined so that data files of the same data type are continuously written for a plurality of data files to be written, and a writing request is made according to the determined order. A program for controlling a cache system mounted on a data recording apparatus that records data on a storage medium via a file system,
A cache memory including a plurality of entries that hold data in units of sectors;
Based on an access request from a file system, a cache hit / miss is determined for the cache memory, and the computer is caused to function as a cache control unit that accesses at least one of the cache memory and the storage medium according to the determination result,
The cache control unit
Control that receives an access command related to an access request from the file system, determines whether the data size to be accessed satisfies a predetermined condition based on the access command, and passes through access to the cache memory based on the determination result The program characterized by performing. A control method for a cache system mounted on a data recording apparatus for recording data on a storage medium via a file system,
Based on an access request from the file system, a cache hit / miss is determined for a cache memory including a plurality of entries that hold data in units of sectors, and at least one of the cache memory and the storage medium is accessed according to the determination result. When doing
Control that receives an access command related to an access request from the file system, determines whether the data size to be accessed satisfies a predetermined condition based on the access command, and passes through access to the cache memory based on the determination result A control method for a cache system.

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