Patent Application
20090083744
This application is based upon and claims the benefit of priority from Japanese patent application No. 2007-250057, filed on Sep. 26, 2007, the disclosure of which is incorporated herein in its entirety by reference.
1. Technical Field
Aspects of the present invention relate to an information recording/reproducing system, an information recording/reproducing method and an information recording/reproducing program, for reading and writing data from and to a recording medium such as a hard disk.
2. Description of the Related Art
An information recording/reproducing system for recording and reproducing information using a hard disk drive or the like involves mechanical actuation in an information reading and writing process. Since the processing speed of a drive system that is responsible for the mechanical actuation is significantly slower than the CPU processing speed of an arithmetic control system that is responsible for the arithmetic, such as command processing, the system response may possibly be unbalanced. For example, the command from the arithmetic control system to the drive system may be stagnated.
Therefore, in a typical information recording/reproducing system, various contrivances are employed to compensate for a difference in the processing speed between the drive system and the arithmetic control system to read or write a large volume of information from or to the hard disk drive or the like. In this connection, an apparatus as disclosed in Japanese Patent Laid-Open No. 2000-181853 (hereinafter “Patent Document 1”) has a means for monitoring the elapsed time for each command after storing a read/write command in the control device, and promptly issuing a command to the disk device, which is not issued to the disk device even after a predetermined time has passed.
However, the apparatus as disclosed in Patent Document 1 only deals with a delay in the command processing after it occurs and there is a risk of overflow of a buffer that temporarily stores write data if the write (writing) command processing is stagnated, which imposes a problem that if a buffer overflow occurs, write data is lost. If the lost data is video data, it is likely that 1 GOP (Group of Picture) of data including this lost data can not be reproduced, which is a significant problem.
An exemplary aspect of the present invention is to solve the above-mentioned problems with the related art, and to provide an information recording/reproducing system for avoiding loss of write data caused by a buffer overflow due to the stagnation of the write command processing. Exemplary embodiments of the present invention also overcome disadvantages not described above and the present invention is not required to overcome the disadvantages described above. Indeed, exemplary embodiments of the present invention may not overcome any of the problems described above.
An exemplary aspect of the invention concerning an information recording/reproducing system includes a thread scheduler unit configured to control a sequence of execution for a plurality of threads, a thread execution unit configured to invoke and execute a write thread or a read thread, a device driver unit configured to issue a write command or a read command corresponding to the thread executed by the thread execution unit, a disk mechanism configured to record and reproduce information in accordance with each command, an end time estimation unit configured to estimate an end time of execution of the issued write command, and a command management unit configured to determine whether or not the estimated end time of execution is greater than an end time designated by command, wherein the thread scheduler unit temporarily suspends execution of at least one read thread of the plurality of threads if it is determined that the estimated end time of execution is greater than the end time designated by command.
Also, an exemplary aspect of the invention concerning an information recording/reproducing method includes a thread scheduling operation of controlling an sequence of execution for a plurality of threads, a thread execution operation of invoking and executing a write thread or read thread, a command issuance operation of issuing a write command or a read command corresponding to the thread executed at the thread execution operation, an information recording/reproducing operation of recording and reproducing information by controlling a disk mechanism in accordance with the issued command, an end time estimation operation of estimating an end time of execution of the issued write command, a determination operation of determining whether or not the end time of execution estimated at the end time estimation operation is greater than an end time designated by command; and a reading limitation operation of temporarily suspending execution of at least one read thread among the plurality of threads if it is determined that the estimated end time of execution is greater than the end time designated by command.
Also, an exemplary aspect of the invention concerning an information recording/reproducing program run on a computer, includes a thread scheduling process to control an sequence of execution for a plurality of threads, a thread execution process to invoke and execute a write thread or read thread in accordance with a sequence, a command issuance process to issue a write command or a read command corresponding to the execution of the thread, an information recording/reproducing process to record and reproduce information by controlling a disk mechanism in accordance with each command, an end time estimation process to calculate the estimated value of the end time of execution of the issued write command, a determination process to determine whether or not the estimated end time of execution calculated at the end time estimation process is greater than the end time designated by command; and a reading limitation process to temporarily suspend execution of at least one read thread among the plurality of threads if it is determined at the determination process that the estimated end time of execution is greater than the end time designated by command.
The aspects of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the accompanying drawings, in which:
Hereinafter, exemplary embodiments of the present invention are described with reference to the drawings.
The recording/reproducing control device 100 comprises an OS (Operating System) unit 110 that controls information recording/reproducing process of the recording/reproducing device 200, an AP thread unit 140 as a thread execution unit that retains a plurality of threads generated by execution of an application and executes each of the threads, and a device driver unit 150 that issues a command to the recording/reproducing device 200 in accordance with the thread executed by the AP thread unit 140 and sends or receives the write data and read data corresponding to each command to or from the recording/reproducing device 200. Here, the term “thread” may mean, for example, an execution unit of software, but is not limited to this meaning. In the application software that performs high level processing, a plurality of processes are executed in parallel by running a plurality of threads. Thereby, it is possible to accept data input by an operation of user during arithmetic processing.
The recording/reproducing device 200 comprises a command management unit 210 that receives a write/read command from the recording/reproducing control device 100, an end time estimation unit 220 that estimates an end time of execution of an issued write command, a recording/reproducing device information storage unit 230 that stores information such as specifications of the recording/reproducing device 200, and a disk mechanism 260 that performs reading and writing of information. The disk mechanism 260 comprises a disk 250 that is a storage medium, and a command execution unit 240 that has an arm, head or the like for reading or writing data from or to the disk 250, and controls the driving thereof in accordance with an input command.
The OS unit 110 in the recording/reproducing control device 100 comprises a quantum value holding unit 120 and a thread scheduler unit 130. The quantum value holding unit 120 holds an initial quantum value and a real time quantum value for each thread. The term “quantum value” may mean, for example, a value indicating an executable time of a thread within a scheduling interval time (epoch), but this term is not limited to this definition. The quantum value of a thread being executed is counted down from the initial value at every unit of time, and if the quantum value reaches zero, then the thread is not to be executed within the particular epoch.
The thread scheduler unit 130 instructs the AP thread unit 140 to start/stop the thread based on a priority and a quantum value of the thread, controls a sequence of execution of a plurality of threads, and changes the setting of a quantum value of the quantum value holding unit 120. The thread is associated with a priority, and the thread scheduler unit 130 selects the thread using the associated priority, for example, in descending order of priority, and instructs the execution of the thread. If another thread having a higher priority than a thread being executed becomes on standby during execution of the thread, the other thread having higher priority is executed, even if the quantum value of the thread being executed remains. If such an interruption does not occur, then the thread is continuously executed until the quantum value reaches zero.
The AP thread unit 140 retains a plurality of write threads (writing threads) or read threads (reading threads), invokes and executes threads in accordance with an instruction from the thread scheduler unit 130 and sends a write/read system call to the device driver unit 150.
The device driver unit 150 receives the write/read system call from the AP thread unit 140 and issues a write command or read command based on the received write/read system call. Further, the device driver unit 150 sends write data together with the write command and receives read data corresponding to the read command. Moreover, the device driver unit 150 sends the corresponding thread number to the thread scheduler unit 130 when receiving the read system call.
The command management unit 210 in the recording/reproducing device 200 holds a plurality of write/read commands from the recording/reproducing control device 100 in a state where the write/read commands are sorted according to a sequence of execution. The command management unit 210 sends write data together with the write/read command to the command execution unit 240 and receives read data to transfer the read data to the recording/reproducing control device 100. Further, the command management unit 210 sends the write command also to the end time estimation unit 220, receives the estimated end time of execution of the command, which is calculated by the end time estimation unit 220, and determines whether or not the estimated end time of execution is greater than the end time designated by the write command. If the estimated end time of execution of the command is greater than the end time designated by command, then the command management unit 210 sends a notification of recording crisis to the thread scheduler unit 130.
The end time estimation unit 220 receives the write command from the command management unit 210, acquires information about recording/reproducing device 200 (hereinafter, referenced as “recording/reproducing device information”) from the recording/reproducing device information storage unit 230, and acquires information about a current position of a head (hereinafter, referenced as “head position information”) from the command execution unit 240. And the end time, the estimation unit 220 calculates the estimated value of the end time of execution of the received write command based on the current head position information and the recording/reproducing device information.
The recording/reproducing device information storage unit 230 stores the specifications of the disk mechanism 260 and the current status of the disk mechanism 260 as recording/reproducing device information and sends the recording/reproducing device information upon accepting an instruction from the end time estimation unit 220. The recording/reproducing device information may include, but is not limited to, a track jump speed, a disk rotation speed, a full stroke seek time and a current head position, for example.
The command execution unit 240 receives the write/read command from the command management unit 210, and writes write data to the disk 250, or reads read data from the disk 250 to send the read data to the recording/reproducing control device 100 via the command management unit 210. Further, the command execution unit 240 sends the current head position information to the end time estimation unit 220.
Also, the thread scheduler unit 130 temporarily suspends the execution of all or part of the read threads when receiving the notification of recording crisis from the command management unit 210. Specifically, the thread scheduler unit 130 reduces the quantum value assigned to the read thread at the time of receiving the notification of recording crisis, or lowers the priority of each read thread when receiving the notification of recording crisis. In this way, the write thread can be given priority for being executed, by postponing the sequence of execution of the read thread, and the stagnation of the write command processing can be mitigated.
By way of example, the thread scheduler unit 130, the AP thread unit 140, the device driver unit 150, the command management unit 210, and the end time estimation unit 220 may be realized by a program executed on a computer.
The operation of another exemplary embodiment will be described below. An exemplary method for recording/reproducing information will also be described below by describing each operation of the method.
As shown in
The command management unit 210 determines whether or not the estimated end time of execution, which is calculated by the end time estimation unit 220, is greater than the end time designated by the received write command (
The end time designated by the received write command is held as a designated end time in a command packet. This designated end time is calculated by the AP thread unit 140, and a write command system call including the designated end time is sent to the device driver unit 150. The device driver unit 150 sends this designated end time included in the command packet to the command management unit 210.
The estimated end time of execution and the end time designated by a received write command may indicate the elapsed time from a certain point of time in the past with high accuracy (e.g. to the order of microseconds) with data of enough bits to provide Such accuracy. Further, the, estimated end time of execution and the end time designated by a received write command may increase according to the passage of time.
First of all, the current time is set to F_Time (estimated end time of execution) (
Subsequently, the command held in the command management unit 210 is selected in a scheduled sequence of execution (
Subsequently, it is determined whether or not this Diff.T is greater than the full stroke seek time (
The value of NT is set to the value of CT (
First of all, the device driver unit 150 receives a system call from the AP thread unit 140 (
Thereby, the thread scheduler unit 130 can select the read thread from a plurality of threads held in the AP thread unit 140, based on the thread number notified from the device driver unit 150.
According to the example shown in
First, the thread scheduler unit 130 determines whether or not a specified time has passed since the last notification of recording crisis was received (
For example, the thread scheduler unit 130 sets the initial quantum value to a quantum value indicating the executable time of each thread within the epoch for every scheduling interval time (epoch). The quantum value is decreased while the thread is selected and operating. If the quantum value reaches zero, then the thread is not selected during the same epoch period. In this way, the quantum value indicates the executable time of the thread within an epoch.
On the other hand, the thread scheduler unit 130 selects the thread to be executed in accordance with priority and instructs the execution of the thread. A priority is set for each thread, wherein the thread scheduler unit 130 selects the thread in descending order of priority. If another thread having higher priority than a thread being executed becomes on standby during execution of the thread, then the thread being executed is put on standby, and the other thread having higher priority is executed, even if the quantum value of the thread being executed remains. If such an interruption by a higher priority thread does not occur, then the thread being executed is continuously executed until the quantum value reaches zero.
Hence, according to exemplary information recording/reproducing systems of the present invention, the end time of the write command processing is estimated by the end time estimation unit 220. If the command management unit 210 determines that the estimated end time of execution is beyond the end time designated by the write command, then the thread scheduler unit 130 lowers the priority of the read thread, or reduces the quantum value of the read thread at that time. Therefore, the resource allocation within the system can be concentrated on the write process by temporarily suspending the execution of the read thread, so that the sufficient write speed can be attained. Hence, among other advantages, it is possible to avoid overflow of a buffer for the write data caused by the stagnation of the write command processing and, consequently, avoid loss of write data due to the overflow of buffer.
While exemplary embodiment of the present invention have been described in detail above, it is contemplated that numerous modifications may be made to the above exemplary embodiments without departing from the spirit and scope of the embodiments of the present invention as defined in the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-250057 | Sep 2007 | JP | national |
