JP2000339214A - Real time memory management system and real time memory managing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent interruption of a processing of a periodic task for which real time property is required by a garbage recovery processing. SOLUTION: A real time system including the periodic task 102 with time restriction is executed as a preprocessing of each period of the periodic task 102 and provided with a garbage collector 109 to perform a recovery processing of garbage on a memory, a relative starting time storage part 110 to hold execution starting time of the garbage collector 109 by relative time on the basis of each starting time of the periodic task 102 and a garbage collector scheduler 112 to schedule execution of the garbage collector 109 by referring to the relative starting time storage part 110. In this case, the garbage collector 109 is executed as the preprocessing of each period of the periodic task 102 by the garbage collector scheduler 112.

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a real-time memory management system, and more particularly, to a real-time memory management system using a garbage collector and a real-time memory management method.

2. Description of the Related Art Conventionally, such a real-time memory management system has been used in a real-time system including a real-time task having a time constraint for the purpose of improving the development efficiency and reliability of an application program. For example, Japanese Patent Application Laid-Open No. 4-281538 describes a technique using both an incremental garbage collector and a mark-and-sweep garbage collector. In a memory management system using a garbage collector, when the memory allocated to a task is no longer needed,
There is no need for an explicit memory release request in the application program, and the operating system or the runtime library automatically detects and releases unnecessary memory (garbage). Therefore, the development efficiency of the application program is improved, and a bug such as a memory depletion caused by forgetting to release an unnecessary memory does not occur, thereby improving reliability. However, in the case of the mark and sweep garbage collector, other tasks cannot be executed until the garbage collector collects all garbage. The execution is postponed until the garbage collection is completed, resulting in a problem that the time constraint of the real-time task cannot be satisfied. On the other hand, in the incremental garbage collector, it is possible to temporarily suspend the garbage collection process and restart the garbage collection process after executing another task. Therefore, when it becomes time to execute a real-time task during execution of the garbage collector, the real-time task can be executed immediately, and the time constraint of the real-time task can be satisfied. Also, Japanese Patent Application Laid-Open No. 6-16 / 1994
No. 8143 defines a maximum memory allocation per cycle for each task included in a real-time system,
A technique is described in which the execution of a task that requests a memory allocation exceeding the maximum memory allocation amount is postponed until the next cycle. In a real-time system, when a real-time task issues a memory allocation request, it is necessary to end the memory allocation process immediately. For that purpose, when a memory allocation request of a real-time task is made, it is necessary to secure a necessary amount of free memory, and if the garbage collector is executed at the time of the memory allocation request, the time constraint of the real-time task cannot be satisfied. The technology that determines the maximum memory allocation is a real-time system that can determine the maximum memory allocation of each task per fixed period.In real-time systems, by limiting the memory allocation to non-real-time tasks, Free memory to be allocated can always be secured.

As described above, the conventional real-time memory management system and conventional real-time memory management method have the following problems. The first problem is that the use of an incremental garbage collector does not meet the time constraints of a real-time task.
The reason is that the incremental garbage collector
This is because when the real-time task issues a memory allocation request, it is not guaranteed that the requested amount of free memory has been secured. If a garbage collection process is performed at the time when the memory allocation is requested, a necessary amount of free memory can be secured, but this cannot satisfy the time constraint of the real-time task. The second problem is that the technology for determining the maximum memory allocation amount per cycle has a low memory utilization rate. The first reason is that the maximum memory allocation amount per cycle of a certain task is larger than the maximum used memory amount per cycle of the task. The in-use memory amount here refers to a memory amount that is not garbage among the memories allocated in the cycle. For example, in a certain cycle, 2 megabytes of memory is first allocated, and after that memory becomes garbage,
When megabytes of memory are allocated, the used memory amount is a maximum of 2 megabytes, while the memory allocation amount is 4 megabytes. The second reason is that when there are a plurality of tasks, the total sum of the maximum memory allocation amount per cycle is larger than the total sum of the maximum used memory amount per cycle. For example, in a certain cycle, 2 megabytes of memory are allocated to a certain task, the memory allocated after the task has been processed in the cycle becomes garbage, and then 2 megabytes of memory are allocated to another task, and the task is also allocated. When the allocated memory becomes garbage after the periodic processing, the used memory amount is a maximum of 2 megabytes, while the memory allocation amount is 4 megabytes.
It will be megabytes. An object of the present invention is to provide a real-time memory management system and a real-time memory management method that satisfy the time constraint of a periodic real-time task. It is another object of the present invention to provide a real-time memory management system and a real-time memory management method with high memory utilization in a real-time system including periodic real-time tasks.

In order to achieve the above object, a real-time memory management system according to the present invention is executed as preprocessing of each cycle of a periodic task in a real-time system including a periodic task having a time constraint. Garbage collection means for performing garbage collection processing on the memory; relative start time storage means for holding the execution start time of the garbage collection means as a relative time with respect to each start time of the periodic task; A garbage collector scheduler for scheduling the execution of the garbage collector with reference to the storage means, wherein the garbage collector scheduler executes the garbage collector as a pre-processing of each cycle of the periodic task. According to the present invention, in the garbage collector's relative start time storage unit, a time sufficient for the periodic task garbage collector to secure a memory allocation amount in each cycle of the periodic task is set. The periodic task garbage collector collects garbage and secures a necessary amount of free memory by the cycle start time of the corresponding periodic task. The real-time memory management system according to the second aspect of the present invention comprises:
It includes a plurality of periodic tasks, and the garbage collector scheduling means executes the garbage collection means individually for each periodic task. According to a third aspect of the present invention, there is provided a real-time memory management system, comprising: a memory allocation storage means for storing a memory allocation per cycle of a periodic task; and a free space for reserving a specified amount of free memory in association with the periodic task. The apparatus further comprises a memory reservation unit, and when the garbage collection unit secures an amount of free memory held in the memory allocation amount storage unit, the garbage collection unit notifies the free memory reservation unit of the amount of free space held in the memory allocation amount storage unit. The memory is reserved and the process is terminated. A real-time memory management system according to a fourth aspect of the present invention is characterized in that the real-time memory management system further includes a memory allocation setting unit that sets or changes a value held by the memory allocation storage after the execution of the periodic task is started. The real-time memory management system according to the fifth aspect of the present invention includes a plurality of periodic tasks, wherein the memory allocation storage unit individually stores a memory allocation per cycle of each periodic task, and the free memory reservation unit includes: Free memory is individually reserved for each periodic task, and the garbage collector scheduling means executes the garbage collection means individually for each periodic task. The real-time memory management system according to claim 6 includes a plurality of periodic tasks, wherein the garbage collector scheduling means sets the garbage collection means to have lower priority than the periodic tasks corresponding to the garbage collection means, and It is characterized in that it is executed prior to the garbage collection means corresponding to the periodic task. In the real-time memory management system according to the present invention, the garbage collection means may include:
If a sufficient amount of free memory held by the memory allocation amount storage unit cannot be secured by the cycle start time of the corresponding periodic task, a cycle cancellation unit that cancels the execution of the cycle of the periodic task is provided. 7. The real-time memory management system according to claim 1, wherein:
In the real-time memory management system according to the present invention, when the garbage collection unit cannot secure the amount of free memory held by the memory allocation amount storage unit by the cycle start time of the corresponding periodic task, A periodic task that responds that the required amount of free memory could not be secured,
Alternatively, a free memory shortage notifying means for notifying an arbitrary task is provided. In the real-time memory management system according to the present invention, the free memory shortage means includes a free memory shortage notifying means having a means for notifying the secured periodic memory amount to a corresponding periodic task or an arbitrary task. It is characterized by having. In a real-time memory management method according to the present invention, in a real-time system including a periodic task having a time constraint, a garbage collection process is executed as preprocessing of each period of the periodic task, and each cycle start time of the periodic task is executed. Until then, an empty memory larger than the memory amount allocated in the cycle is secured. The real-time memory management method according to the eleventh aspect of the present invention is characterized in that a plurality of synchronization tasks are included, and the garbage collection process is executed individually for each synchronization task.
According to a twelfth aspect of the present invention, there is provided a real-time memory management method according to the twelfth aspect, wherein the garbage collection process includes a plurality of synchronization tasks, and the garbage collection process has a lower priority than the synchronization task corresponding to the garbage collection process. It is characterized in that it is executed prior to collection processing. 14. The real-time memory management method according to claim 13, wherein a garbage collection process is executed as a pre-process of each cycle of the periodic task, and a free memory equal to or larger than a memory amount allocated in the cycle by each cycle start time of the periodic task. And reserves the reserved free memory in association with the periodic task, and thereafter executes another task until the cycle start time of the periodic task. Claim 14
In the real-time memory management method of the present invention, in the garbage collection process, when it is not possible to secure a free memory equal to or more than the memory amount allocated in the cycle by the cycle start time of the corresponding periodic task, the execution of the cycle is performed. The feature is to cancel. The real-time memory management method according to the present invention, wherein the garbage collection processing is performed when a free memory equal to or more than the memory amount allocated in the cycle cannot be secured by the cycle start time of the corresponding cycle task. Alternatively, another task is notified that a required amount of free memory could not be secured, or the secured free memory amount was notified.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a first embodiment of the present invention.
Will be described in detail with reference to the drawings. Fig. 1
A real-time memory management system according to a first embodiment of the present invention
FIG. 3 is a block diagram showing the configuration of FIG. Referring to FIG.
Real-time memory management system according to a first embodiment of the invention
The system consists of a periodic task 102 with time constraints and multiple
Task group 10 consisting of inter-tasks 103
1 and garbage collector corresponding to non-real-time task 103
For the periodic task corresponding to the data 109 and the periodic task 102
Garbage collector 108 and application tasks
Memory 104 in response to a memory allocation request from
Is assigned to the application task group 101,
Garbage collector 108 and garbage collector
Application for memory release request from 109
Solve the memory 104 allocated to the task group 101
Release memory management unit 107 and garbage core for periodic tasks
Open the start time of the
Garbage collector relative stored relative to start time
Start time storage unit 110 and garbage collector relative start time
Garbage collector for periodic tasks with reference to the time storage unit 110
Garbage collectors to schedule the execution of data 108
A scheduler, and the CPU 106
Is the task scheduler 111 assigned to the disk group 101
It is composed of The periodic task 102 with the time constraint
It is executed prior to the real-time task 103. App
Application task group 101 requires memory allocation during execution
Request, and memory that is no longer needed
Veg collector 108 and garbage collector 109
Automatically released. Application task group 1
01 shares the memory space for allocating memory during execution.
Or have independent memory space. Also,
Combinations of these are also conceivable. Application
The disk group 101 uses the application task group 101.
The memory management unit 107 determines that the total
The total memory that can be allocated to the task group 101
It is designed not to rotate. In-use note here
The memory amount is determined by the memory management unit 107 as the application status.
Not garbage in the memory allocated to the cluster 101
It is the amount of memory. Therefore, the application
When the disk group 101 issues a memory allocation request,
Even if the required amount of free memory does not exist,
-Required amount of free memory by performing the veggie collection process
Can be secured. The memory management unit 107 has a normal operation
Provides the same function as the memory management unit of the operating system
And can be realized by various known methods. Gaube
The collector 109 is an incremental counter such as a reference counter.
A mental garbage collector is preferred. The reason is,
Garbage for periodic tasks during processing of garbage collector 109
Short enough if the start time of the
Garbage collector 108 for periodic tasks
Because it can move. Start garbage collector 109
How to start the application periodically, application
When the task group 101 issues a memory allocation request,
The required amount of free memory does not exist, or
Starts when the garbage collector start condition is met
Method, always run at low priority, application
Is activated by an explicit activation request from the task group
Known methods such as methods and methods to combine these methods
Law is applicable. Garbage collector 108 for periodic tasks
Garbage as pre-processing of each cycle of the periodic task 102
It is started by the collector scheduler 112. Soshi
Ends when all garbage has been collected
Or when the cycle start time is reached,
It is terminated by the lector scheduler 112. Week
Garbage collector 108 is a garbage collector.
Incremental garbage collector as well as
Is desirable. The reason is that the periodic task 102 starts the cycle.
Activate periodic task 102 at a sufficiently short delay time
Because you can. Garbage collector 10 for periodic tasks
8 and the garbage collector 109
Memory and non-real-time task 103
Both of the allocated memories are targeted for garbage collection. Was
However, limit each garbage collection target to either
It does not matter. Task scheduler 111
A method for scheduling the task group 101 is known.
Various methods can be applied. For example, fixed priority CPU
A preemptive method or a periodic task with a shorter cycle is better
The above-mentioned rate monotonic method is conceivable. Gar
The veg collector scheduler 112
Of the periodic task 102
From the time, the garbage collector relative start time storage unit 110
The garbage for periodic tasks is added to the time obtained by subtracting the holding time.
Activate the dicollector 108 and periodically open the periodic task 102
At the start time, the periodic task garbage collector 108
If the task is in progress, after terminating it,
Execute The garbage collector scheduler 112
The start time of the garbage collector for periodic tasks 108
Executed by time task 103 or garbage collector 109
In the middle, the garbage collector 108 for periodic tasks is
Run first. Garbage collector relative start time storage
The value of 110 is set before the periodic task 102 starts executing.
Set. For example, set the value at system startup.
I just need. Also, dynamically after the start of the execution of the periodic task 102,
It can be changed. Garbage collector relative start
The value of the time storage unit 110 is the garbage collector for the periodic task.
108, the periodic task 102
Time to collect garbage equivalent to the amount of memory
Set. For example, if the periodic task 102
When allocating 0 megabytes of memory, periodic tasks
Garbage collector 108 for 1 ms in 10 ms
Garbage collection if you have the ability to collect garbage
The value of the relative start time storage unit 110 is set to 100 milliseconds.
It should be fixed. Also, for example, the periodic task 102
Allocating 10 megabytes of memory during the period
Per hour of the garbage collector 108 for periodic tasks
Garbage recovery capacity cannot be estimated, but in 200 milliseconds
If you know you can collect all garbage
For example, the value of the garbage cocreta relative start time storage unit 110 is
What is necessary is just to set to 200 milliseconds. Next, FIG. 1 to FIG.
Reference to a real-time memory management system according to the present embodiment
Will be described in detail. FIG. 2 to FIG.
Gar in a real-time memory management system according to an embodiment
Flow showing operation of veg collector scheduler 112
Fig. 2 shows a garbage collector for periodic tasks.
Operation at the start time of 108, FIG.
The operation at the cycle start time 2 is shown in FIG.
FIG. 5 shows the operation at the end of the second cycle, and FIG.
Shows the work. Note that the task scheduler 111
Scheduled task 102 and non-real-time task 103
Is known and is particularly relevant to the present invention.
The description of the parts that are not performed is omitted. Referring to FIG.
The start time of the periodic task garbage collector 108 has been reached.
Then, the timer is triggered by an interrupt from the timer 105 or the like.
The veg collector scheduler 112 operates and the periodic task
Make the garbage collector 108 executable (step
201), CPU allocation processing is performed. Please refer to FIG.
Then, when the cycle start time of the periodic task 102 is reached,
Garbage collection by interrupt from timer 105, etc.
The scheduler scheduler 112 operates, and the periodic task
-Check if the veg collector 108 is still processing
(Step 202) If processing is being performed, a garbage collector for periodic tasks
The processing of the veg collector 108 is terminated (step 20).
3). Then, make the periodic task 102 executable
(Step 204) CPU allocation processing is performed. FIG.
See garbage collector at the end of the periodic task
The scheduler 112 operates, and the next cycle of the periodic task 102 is executed.
Garbage collector relative start time storage unit 1 from the period start time
Periodic task by subtracting the time that 10 holds
Garbage collector 108 is started (step
205), opening the garbage collector 108 for periodic tasks
The garbage collector scheduler 112 operates at the start time
Is set (step 206) so that C
Perform PU allocation processing. Referring to FIG.
In the assignment process, the periodic task 102 in the executable state
Non-real-time task 103 in executable state,
Task garbage collector 108 or executable
Whether the garbage collector 109 is in a state
(Step 207), and if there is one,
Allocate the CPU 106 to the one with the higher priority (step
208). The priority here is the task schedule
Depending on the scheduling system of the controller 111
And, especially, the priority in the fixed priority method, etc.
Not something. The garbage collector for periodic tasks 1
08 ends processing before the cycle start time of the periodic task 102
Is completed, the time until the cycle start time of the periodic task 102 is reached.
The duration can be other executable tasks or garbage collectors.
CPU 106 is not assigned to the As explained above
In the real-time memory management system according to the present embodiment,
Indicates that the periodic task garbage collector 108
By the start time of each cycle of 102
Free memory until the start of the cycle.
Since the real-time task 103 is not executed, the periodic task 1
02 memory allocation request is processed promptly
The time constraint of the task 102 can be satisfied. Ma
Also, in the real-time memory management system according to the present embodiment,
Sets the periodic task garbage collector 108 to the periodic task
Since it is executed as preprocessing immediately before each cycle of 102,
Preprocessing of the next cycle after each cycle of the period task 102 is completed
Until the periodic task garbage collector 108 starts
During the period, all free memory is allocated to other non-real-time tasks 10.
3 can be assigned to improve memory utilization
I do. Next, a preferred implementation to which the first embodiment is applied
An example will be described. FIG. 6 is a block diagram showing the configuration of this embodiment.
It is a lock figure. As shown in FIG.
Reads the document data from the hard disk
A document print task 301 to be output to the printer 311;
Reads moving image data from hard disk 312
A periodic moving image display task displayed on the display 313
Task 302, a document print task 301, and a moving image display task.
In response to a memory allocation request from the
Memory management unit 30 that allocates memory 305 to the task
6 and the required amount of free memory
If the reference is not called from the memory management unit 306,
Illumination counter type garbage collector 304 and one
This is implemented as a task,
Garbage for reference task-based periodic tasks
Collector 303 and garbage collector 30 for periodic tasks
3 corresponds to the start time of each cycle of the moving image display task.
Relative start time storage unit 309 to hold as a relative value
And time information is acquired using the timer 307, and
Fixed priority CPU preemption that allocates CPU 308
It comprises a task scheduler 310 of a possible system.
Target of dynamic memory allocation by the memory management unit 306
There are 10 megabytes of memory. Document print task
301 has no particular time constraint but is fast
Ending printout is a preferred non-real-time task.
The document print task 301 stores a document temporarily.
As a file, a 2-megabyte memo depending on the size of the document
Request reassignment several times. However, if you use
Mori is at most 2 megabytes. Video display task
302 is a liquid crystal display with 10 frames per second
313. The moving image display task 302 has one cycle
Is implemented as a periodic task that displays one frame.
The cycle is 100 milliseconds, and the processing time for each cycle is 30 milliseconds.
Seconds. Also, the moving image display task 302 has a smooth
Since it is necessary to realize moving image display,
-Cannot perform veggie collection. Video display task
Queue 302 serves as a buffer for temporarily storing an image,
At the beginning of the period, an 8 megabyte memory allocation request is made.
However, this memory is not used after the end of the cycle. Video
The image display task 302 includes a document print task 301.
Garbage for periodic tasks.
The same collector as the moving image display task 302
A degree has been given. CPU 308 executes each task
Timer 307 has enough processing power to
Have sufficient granularity and precision to perform each task
You. The garbage collector for periodic tasks 303
All memory in 10 MB of memory to be reallocated
Has the ability to collect all garbage in 20 milliseconds.
You. The value of the relative start time storage unit 309 is
-The veg collector 303 and the moving image display task 302
8 megabytes of memory allocated in the cycle
What is necessary is just to set the time which can collect garbage. This embodiment
In this example, 20 milliseconds at which all garbage can be collected is set. Figure
FIG. 7A shows the activation timing of each task in this embodiment.
FIG. 7B is a timing chart showing the timing chart.
7 is a graph showing the total memory allocation amount at each time.
You. In FIG. 7A, a document print task 301
Execution is indicated by the bar 403 and the document print task
The required amount of free memory is
The garbage collector 304 called when it doesn't exist
Execution is indicated by the bar 404 and the video display task 30
The execution of 2 is indicated by a bar 401, and the moving image display task
For periodic tasks executed as pre-processing of each cycle of 302
The execution of the garbage collector 303 is indicated by a bar 402.
You. Referring to FIG. 7A, document print task 3
01 is activated at time 70 milliseconds and time 240 milliseconds
The process has been completed. Each round of the moving image display task 302
The period starts at 100 ms and 200 ms.
End at 130 ms and 230 ms respectively.
Have completed. The periodic task garbage collector 303
It starts at time 80 ms and time 180 ms.
Time 100 ms and time 200 ms
You. The document print task 301 has a time of 70 milliseconds,
At the time of 140 milliseconds and the time of 160 milliseconds,
Make a request to allocate megabytes of memory. Moving image display
The screen has a cycle start time of 100 milliseconds and an hour.
8 megabytes of memory for each 200 milliseconds
Make a request. Referring to FIG. 7B, first, at time 7
In 0 ms, the document print task 301
Memory is allocated. Periodic task at time 80 milliseconds
Garbage collector 303 is activated, but the garbage
Since it does not exist, the total memory allocation does not change. Next
At time 100 milliseconds, 8
Gigabytes of memory are allocated. At that point,
Memory allocation is 10 megabytes and all memory is
It has been assigned. Next, at the time 140 milliseconds,
Print task 301 allocates 2 MB of memory
Request, but all memory has already been allocated.
Garbage collector 304 is called to collect garbage
I do. At time 145 milliseconds, the required 2 megabytes of space
Processing of the garbage collector 304 that has secured memory
Completed, and a 2-megabyte memo was added to the document print task 301.
Is assigned. Time 160 ms
Time 165 millimeters after the veg collector 304 is called
2 MB of memory for document print task 301 per second
Is assigned. Next, at 180 ms, the periodic task
Garbage collector 303 is activated and the garbage
Make a profit. The actual memory used at this point is
Allocated to document print task 301 at time 165 ms
Only 2 megabytes of memory, time 200
Collect 8 megabytes of garbage by the millisecond. Next
At the time of 200 milliseconds, the video display task
Memory is allocated. In this way, moving image display
The time of 100 ms, which is the activation time of the task 302, and
At time 200 milliseconds, the cycle
Garbage collector 303 for the basket finishes collecting all garbage
Completed, 8 MB free memo allocated in each cycle
Memo of the moving image display task 302
It can be seen that the reallocation request is processed promptly.
Also, when it is the cycle end time of the moving image display task 302
Garbage collector 30 for periodic tasks from 130 milliseconds
The period up to 180 milliseconds, which is the start time of
All available memory is allocated to the document print task 301
In this embodiment, 4 megabytes can be allocated.
Has been applied. Limit maximum quota in each cycle
In the method, 8 MB is added to the moving image display task 302.
In order to guarantee the memory allocation of
The maximum allocated amount of each cycle of the
Document print task 301
Of the period from time 165 ms to time 180 ms
Processing will be postponed after 240 milliseconds.
That is, according to the present invention, the processing of the document print task 301 is performed.
Can end earlier. Also use memory
The rate is also improving. Next, in the second embodiment of the present invention,
This will be described in detail with reference to the drawings. FIG. 8 shows the present invention.
Of the real-time memory management system according to the second embodiment of the present invention.
FIG. 3 is a block diagram illustrating a configuration. Referring to FIG.
A real-time memory management system according to a second embodiment of the present invention
Is a real-time memo according to the first embodiment shown in FIG.
Free memory in the memory management unit 107 as compared with the memory management system.
The addition of the memory reservation means 501, the periodic task 102
Allocation that holds the amount of memory allocated per cycle
Assigned amount storage unit 503 and memory allocation amount storage unit 503
To set and change the value of
The addition of the step 502 indicates that the task scheduler 111
Cancel execution of a specific cycle of the periodic task 102
The difference is that the period canceling means 504 has been added. Figure
9 is a memory management unit 1 including a free memory reservation unit 501.
It is a block diagram which shows the structure of 07. Memory management unit 10
7 adopts a method of managing the memory 104 in page units.
The required amount of memory in the application task
Memory allocation means 601 for allocating to the
Garbage collector 108 for periodic tasks and garbage collector
Application 109
To release the memory allocated to the task group 101
Re-release means 602 and garbage collector 1 for periodic tasks
08 to specify the required amount of free memory.
Free memory to reserve in relation to the specified periodic task
Assignable to approximation means 603 and non-real-time task 103
Free page amount storage unit 604 holding a large free page amount
And the page 60 that can be assigned to the non-real time task 103
6, an empty page list 605 holding the list 6 in a list format;
Reserve the amount of pages reserved for each periodic task 102.
Reserved page amount storage 607 to be held and each periodic task 1
02 reserved pages 609 that are reserved every 02
Reserved pages to be kept in list format for each task 102
And a list 608. FIG. 9 shows an empty memo
5 shows an example of a method of realizing the re-reservation means 501.
Therefore, the present invention is not limited to this realization method.
The method of implementing memory management depends on the target hardware and
Probably depending on the operating system
Free memory reservation means 501 is suitable for the system environment.
It is feasible in a way. Periodic task in this embodiment
Garbage collector 108 before the periodic task 102
The garbage collector scheduler 112
And is terminated at the cycle start time of the periodic task 102.
This is the same as in the first embodiment, except that some
As a result of collecting the pages, the memory allocation amount storage unit 503
If the amount of free memory that can be held in
The processing is terminated at the point of
The amount of free memory held in the free memory reservation means 50
1 to the corresponding periodic task 102
Make a reservation in association with it. Garbage collection for periodic tasks
Is lower in priority than the corresponding periodic task
Tasks that take priority over periodic tasks
Corresponds to periodic tasks with lower priority than periodic tasks
The garbage collector 108 for periodic tasks
Is performed. Stored in the memory allocation storage unit 503
Before starting execution of the periodic task 102, the value
Is set by the amount setting means 502. Also, the periodic task
After the execution of the task 102 has started, the
For example, when the memory allocation per cycle changes due to
Is changed by the memory allocation setting means 502.
It is possible to change it. Task scheduler 111
Is the cycle that the periodic task garbage collector 108 corresponds to.
Completed before the cycle start time of the scheduled task 102
The period up to the cycle start time of the corresponding periodic task 102
In between, the other application task group 101,
Is the CPU 1 for the garbage collector 108 for other periodic tasks.
06 is assigned. Also, the task scheduler 111
Is the cycle corresponding to the cycle start time of the cycle task 102.
Processing of the garbage collector 108 for final tasks does not end
In this case, the period is
Cancel. Next, referring to the drawings,
The operation will be described in detail. FIG. 10 to FIG.
The operation of the task scheduler 111 in the form was shown.
It is a flowchart. Figure 10 shows garbage for periodic tasks
Operation at the start time of the collector 108, FIG.
FIG. 12 shows the operation of the task 102 at the cycle start time.
FIG. 13 shows the operation at the end of the cycle of the
Periodic task 10 corresponding to the garbage collector 108
Operation when processing is completed before cycle start time 2 in FIG.
4 shows the operation of the CPU assignment process. FIG.
The operation of the present embodiment shown in FIG. 12 and FIG.
The operation of the first embodiment shown in FIG. 2, FIG. 4 and FIG.
Since it is the same as the work, it will not be described here. Referring to FIG.
Then, the task scheduler 111 in the present embodiment
The operation of the periodic task 102 at the cycle start time is shown in FIG.
3 is different from the operation of the first embodiment shown in FIG.
If the garbage collector 108 is still in process,
After terminating the garbage collector for periodic tasks (step
203), using the period canceling means 504,
Canceling the corresponding cycle (Step 701)
different. With reference to FIG.
The scheduler 111 is a garbage collector for periodic tasks.
Start time of the periodic task 102 corresponding to the
If you have previously reserved the required amount of free memory and exited,
Other applications that can be executed until the start time
Task group 101, garbage collector 109, or
CPU 106 to the garbage collector 108
Guess. FIG. 15 shows a periodic task according to the present embodiment.
Showing the operation of the garbage collector 108
It is. Referring to FIG. 15, in the present embodiment,
The garbage collector for periodic tasks 108
Garbage when the cycle start time of task 102 comes
Terminated by collector scheduler 112
(Step 801). Period of the corresponding periodic task 102
If not, start some garbage
Is detected (step 802), and the memo of the memory management unit 107 is
Re-release means 602 to call the garbage
From the task group 101 (step 80)
3). Next, the data is stored in the memory quota storage unit 503.
Check whether enough free memory has been secured (step
804) If the memory is secured, the memory management unit 107 becomes empty.
Call up the memory reservation means 501 and
Reservation in association with the corresponding periodic task 102
(Step 805). In step 804,
If free memory is not secured, go back to the beginning
Continue collecting garbage. FIG. 16 to FIG.
A flowchart showing the operation of the memory management unit 107 according to the embodiment.
It is a low chart. FIG. 16 shows that the memory management unit 107 has
The operation of the memory allocating means 601 is shown in FIG.
17 is a memory release unit 60 of the memory management unit 107
FIG. 18 shows the operation of the memory management unit 107.
The operation of the free memory reservation means 603 is shown.
Referring to FIG. 16, the memory allocating means 601 is
Was the periodic task 102 that issued the memory allocation request
It is checked whether the task 103 is the non-real time task 103 (step 901).
When the non-real-time task 103 issues a memory allocation request
In this case, first, the requested
To see if there is a free amount of free pages (step
902), if not, the garbage collector 109
Is called and garbage is collected, and then step 902 is executed.
Is repeated. Requested in step 902
If there is an empty page with the
Allocate a free page 606 held by the
Is assigned to the non-real-time task 103 that requested (step
904), the value of the free page amount storage unit 604 is assigned
Reduce the amount of memory (step 905) and end the process
I do. Periodic task 102 made a memory allocation request
If so, the periodic task 1 in the reserved page list 608
Reserved page 609 held by the entry corresponding to 02
Is assigned to the periodic task 102 that has requested (step 90
6), corresponding entry in the reserved page amount storage unit 107
Is reduced by the allocated memory amount (step 90).
7), the process ends. Referring to FIG. 17, the memory solution
The release unit 602 stores the specified memory in the application
Release from task group 101 (step 908) and release
Inserted into the free page list 605 (step
909), when the value in the free page amount storage unit 604 is released.
The amount is increased by the amount of memory (step 910), and the processing is terminated.
You. Referring to FIG. 18, free memory reservation means 603
Lists the specified amount of free pages 606
605 from the reserved page list 608
Move to the entry corresponding to task 102 (step
911), the value of the free page amount storage unit 604 is moved.
Reduced by the amount of memory (step 912), reserved page amount
Corresponds to the specified periodic task 102 in the storage unit 607
Increase the value of the entry by the amount of reserved memory (step
913), and the process ends. FIG. 16 to FIG.
An example of the operation of the memory management unit 107 according to the embodiment will be described.
Shown, the invention is not limited to this operation
is not. Memory management method depends on the target hardware
And operating system dependencies,
The memory management unit 107 can perform operations suitable for the system environment.
I just need. As described above, in the second embodiment, the
Periodic task that the garbage collector 108 for
Before the start time of each cycle of
To secure and reserve a free memory,
02 memory allocation request can be processed promptly
The time constraint of the task 102 can be satisfied. Ma
In this embodiment, the garbage collector for periodic tasks
108 completes the processing, and
Until the period start time, the other executable periodic tasks 1
02, executable non-real-time task 103, executable cycle
Garbage collector 108
The use efficiency of the CPU is improved by executing the
I do. In this embodiment, the garbage for periodic tasks
Each period opening of the periodic task 102 corresponding to the collector 108
If the required amount of free memory could not be secured by the start time
Meet the time constraint to cancel the cycle.
Solve problems caused by executing cycles that cannot be performed
Can be turned off. For example, multiple actions by multiple periodic tasks
In the method of displaying images, it is in charge of displaying one moving image
If a periodic task cannot meet the time constraint,
Influences the task and eventually all video display is distorted
May be In such a case, you can not meet the time constraint
Other periodic tasks by canceling the new cycle
Time constraints, and those periodic tasks
The effect that the moving image display in charge is performed smoothly
Can be expected. Next, a specific example to which the second embodiment is applied.
Examples will be described. FIG. 19 shows the configuration of this embodiment.
It is a block diagram showing composition. First implementation shown in FIG.
The difference from the embodiment of the embodiment is that the free memory reservation unit 110
1 and a memory allocation storage unit 1102
It is. The value of the memory allocation storage unit 1102 is
The memory allocation amount per cycle of the image display task 302
Set to 8 megabytes. Memory allocation storage
The value of 1102 is set before the system is started. FIG.
0 (A) is the activation timing of each task in this embodiment.
FIG. 21 is a timing chart showing the timing chart of FIG.
Is a graph showing the total memory allocation at each time.
You. In FIG. 20A, the document print task 30
1 is indicated by the bar 403 and the document print task
Required free memory at the time of memory allocation request
Garbage collector 304 called when there is no
Is indicated by a bar 404, and the moving image display task 3
02 is indicated by a bar 401, and the moving image display task
Garbage collector for periodic tasks executed as pre-processing for each cycle
Execution of the veg collector 303 is indicated by the bar 402.
Referring to FIG. 20A, the document print task 30
1 is activated at time 70 ms and at time 170 ms
Finished. Each cycle of the moving image display task 302
It starts at 100 milliseconds and 200 milliseconds,
End at 130 ms and 230 ms
You. The document print task 301 has a time of 70 milliseconds,
2 megs at 90 ms and 140 ms
Make a byte memory allocation request. Video display task
302 is a cycle start time of 100 milliseconds and
8 MB memory allocation for 200 ms each
Make a guess request. Garbage collector for periodic tasks 303
Starts at 80 ms and 180 ms
8 memories stored in the memory allocation storage 1102.
When gigabytes of free memory is secured,
8 MB free memory by calling about means 1101
Is associated with the moving image display task 302 to make a reservation.
finish. Referring to FIG. 20B, first, at time 70
A 2 megabyte message is sent to the document print task 301 in milliseconds.
Mori is assigned. For a periodic task with a time of 80 milliseconds
The garbage collector 303 starts executing, but has already
Garbage times because gigabytes of free memory is secured
8 MB free memory is reserved,
The process ends immediately. Therefore, document print task 3
01 resumes, 2 MB at 90 ms
Request for memory allocation. Assign to each task at that time
The total memory allocated is 2 megabytes, but 8
The gigabyte is reserved for the moving image display task 302,
Since there is no free memory, the garbage collector 304
Is called to collect garbage. Time to 95 milliseconds
Garbage collector 304 spins 2 MB of garbage
After collecting, 2MB of secured free memory is documented
Assigned to print task 301. Next, at time 100
The moving image display task 302 takes 8 megabytes of memos in milliseconds.
Request a re-allocation and reserve 8 Mbytes
Allocate default memory. From the time 130 milliseconds
Execution of the lint task 301 is resumed, and the time is 140 millimeters.
Makes a request to allocate 2 megabytes of memory per second. At this time
In terms of point, all memory is allocated to each task
Activate the garbage collector 304 and collect garbage
2 MB at 145 ms.
Assign it to the lint task 301. Next time 180 mm
The garbage collector 303 for the periodic task is activated every second,
Collect 8MB of garbage by 195ms
And displays the secured 8 MB free memory as a moving image
A reservation is made in association with the task 302. And time 20
8 megabytes of memory reserved for 0 milliseconds
Assigned task 302. Thus, the moving image
The memory allocation request of the display task 302 is promptly processed.
What is implemented is the implementation of the first embodiment shown in FIG.
Similar to the example, but in this embodiment, the garbage
Is stored in the memory allocation storage unit 1102
When the amount of available memory is reserved and reserved,
CPU usage efficiency to execute print task 301
And the document print task 301 ends as a result.
The time is getting earlier. Next, a third embodiment of the present invention
The state will be described with reference to the drawings. FIG. 21 shows the present invention.
Of the real-time memory management system according to the third embodiment
FIG. 3 is a block diagram illustrating a configuration. Referring to FIG.
Real-time memory management system according to a third embodiment of the invention
The configuration of the system is the same as that of the second embodiment shown in FIG.
In comparison, an empty memo is used instead of the period canceling means 504.
The difference is that a shortage notification unit 1201 is provided. Free note
The re-insufficient notification means 1201 is provided for each cycle of the periodic task 102.
Garbage collector 108 for periodic tasks by the start time
Is the free memory of the amount held by the memory allocation amount storage unit 503.
If memory cannot be secured, the corresponding periodic task 102 or
Or other tasks included in the application task group 101.
That there is not enough free memory on the disk
This is a function to notify the available memory amount. Insufficient free memory
The notification means 1201 opens each cycle of the periodic task 102.
Memory shortage flag was secured as an argument of the function to start
How to pass the amount of memory, notify using global variables
It can be realized by a known technique such as I explained above
As described above, in the third embodiment, each cycle of the periodic task 102
If the required amount of free memory is not available at the start time
In this case, the periodic task is
Can know in advance that the free memory is insufficient.
The amount of memory required to allocate
Reduce and continue processing or cancel the cycle by yourself
Measures can be taken. More preferred
The present invention has been described with reference to the embodiment and the examples.
The invention is not necessarily limited to the above embodiments and examples
Not within the scope of the technical idea.
Modifications can be made. Second embodiment of the present invention
The period canceling means 504 in the form includes a periodic task
The memory allocation amount storage unit 50 at each cycle start time of 102
When there is not enough free memory reserved in 3
Cancels the execution of the cycle,
Whether to cancel the cycle every 02 or continue processing
It is also conceivable to have a form that has a period
It is. Also required at each cycle start time of periodic task 102
If the amount of free memory is not secured,
102, cancel the cycle, or
Notifies the lack of memory or garbage collector for periodic tasks
Continue the processing of 108 or execute other processing.
Can be specified for each periodic task 102
Conceivable.

As described above, according to the real-time memory management system and the real-time memory management method of the present invention,
The following effects can be obtained. A first effect of the present invention is that a real-time system using a garbage collector can satisfy the time constraint of a real-time periodic task. The reason is that the periodic task garbage collector, which is executed as a pre-process of each cycle of the periodic task, secures the free memory of the memory allocation amount of the cycle by the cycle start time, so that the memory can be promptly allocated at the time of the memory allocation request. Because it can be assigned. A second effect of the present invention is that the memory utilization is high. The reason is that the garbage collector for the periodic task, which executes the pre-processing of the cycle, secures the free memory required for each cycle of the periodic task, so before the time when the garbage collector for the periodic task starts to execute, This is because all free memory can be assigned to the task.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a real-time memory management system according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing an operation of the periodic task garbage collector according to the first embodiment of the present invention at a cycle start time.

FIG. 3 is a flowchart illustrating an operation at a cycle start time of a periodic task according to the first embodiment of this invention.

FIG. 4 is a periodic task 10 according to the first embodiment of this invention.
9 is a flowchart showing an operation at the end of a second cycle.

FIG. 5 is a flowchart illustrating an operation of a CPU assignment process according to the first embodiment of this invention.

FIG. 6 is a block diagram showing a configuration of an example to which the first embodiment of the present invention is applied.

FIG. 7 is a timing chart showing an operation of the example of the first exemplary embodiment of the present invention.

FIG. 8 is a block diagram showing a configuration of a real-time memory management system according to a second embodiment of the present invention.

FIG. 9 is a block diagram illustrating a configuration of a memory management unit according to a second embodiment of this invention.

FIG. 10 is a flowchart illustrating an operation of the periodic task garbage collector according to the second embodiment of the present invention at a start time.

FIG. 11 is a flowchart illustrating an operation at a cycle start time of a periodic task according to the second embodiment of this invention.

FIG. 12 is a flowchart illustrating an operation at the end of a cycle of a periodic task according to the second embodiment of this invention.

FIG. 13 is a flowchart illustrating an operation of the periodic task garbage collector according to the second embodiment of the present invention when the garbage collector finishes processing before the cycle start time of the corresponding periodic task.

FIG. 14 is a flowchart illustrating an operation of a CPU assignment process according to the second embodiment of this invention.

FIG. 15 is a flowchart illustrating an operation of a periodic task garbage collector according to the second embodiment of this invention.

FIG. 16 is a flowchart illustrating an operation of a memory allocating unit included in a memory management unit according to the second embodiment of this invention.

FIG. 17 is a flowchart illustrating an operation of a memory release unit included in the memory management unit according to the second embodiment of this invention.

FIG. 18 is a flowchart illustrating an operation of a free memory reservation unit included in the memory management unit according to the second embodiment of this invention.

FIG. 19 is a block diagram illustrating a configuration of an example to which the second embodiment of the present invention is applied.

FIG. 20 is a timing chart showing the operation of the example of the second exemplary embodiment of the present invention.

FIG. 21 is a block diagram showing a configuration of a real-time memory management system according to a third embodiment of the present invention.

[Explanation of symbols]

 101 Application Task Group 102 Periodic Task 103 Non-Real Time Task 104 Memory 105 Timer 106 CPU 107 Memory Management Unit 108 Garbage Collector for Periodic Task 109 Garbage Collector 110 Garbage Collector Relative Start Time Storage Unit 111 Task Scheduler 112 Garbage Collector Scheduler 301 Document Print Task 302 Moving image display task 303 Garbage collector for periodic task 304 Garbage collector 305 Memory 306 Memory management unit 307 Timer 308 CPU 309 Relative start time storage unit 310 Task scheduler 401 Period for executing periodic task 402 Period for executing garbage collector for periodic task 403 Non Real-time task execution period 404 Garbage collector execution period 501 Free memory reservation Stage 502 Memory allocation setting means 503 Memory allocation storage 504 Period canceling means 601 Memory allocation means 602 Memory release means 603 Free memory reservation means 604 Free page storage 605 Free page list 606 Free pages 607 Reserved page storage 608 Reserved page list 609 Reserved page 1101 Free memory reservation means 1102 Memory allocation amount storage unit 1201 Free memory shortage notification means

Claims (15)

[Claims] 1. A real-time system including a periodic task having a time constraint, comprising: a garbage collection unit that is executed as a pre-process of each period of the periodic task and performs a garbage collection process on a memory; A relative start time storage unit that holds an execution start time as a relative time based on each start time of the periodic task, and schedules execution of the garbage collection unit with reference to the relative start time storage unit. A real-time memory management system comprising garbage collector scheduling means, wherein the garbage collector scheduling means executes the garbage collection means as preprocessing of each cycle of the periodic task. 2. The real-time memory management system according to claim 1, comprising a plurality of said periodic tasks, wherein said garbage collector schedule means executes said garbage collection means individually for each said periodic task. 3. The system further comprises: a memory allocation amount storage unit that stores a memory allocation amount per one cycle of the periodic task; and a free memory reservation unit that reserves a specified amount of free memory in association with the periodic task. The garbage collection unit reserves the free memory of the amount held in the memory allocation amount storage unit by the free memory reservation unit when the amount of free memory held in the memory allocation amount storage unit is secured. 2. The real-time memory management system according to claim 1, wherein the processing is terminated. 4. The real-time memory according to claim 3, further comprising a memory allocation setting unit configured to set or change a value held by the memory allocation storage after the execution of the periodic task is started. Management system. 5. The periodic task includes a plurality of periodic tasks, wherein the memory allocation amount storage unit individually stores the memory allocation amount per one cycle of each periodic task, and the free memory reservation unit stores the memory allocation amount for each of the periodic tasks. 5. The real-time memory management system according to claim 3, wherein the free memory is individually reserved, and the garbage collector schedule means executes the garbage collection means individually for each of the periodic tasks. 6. The garbage collector scheduling means including a plurality of the periodic tasks, wherein the garbage collector scheduling means assigns the garbage collection means to a periodic task having a lower priority than the periodic task corresponding to the garbage collection means, and 6. The real-time memory management system according to claim 2, wherein execution is performed prior to said garbage collection means. 7. If the garbage collection unit cannot secure the amount of free memory held by the memory allocation amount storage unit by the cycle start time of the corresponding periodic task, 7. The real-time memory management system according to claim 1, further comprising a period canceling unit for canceling execution of a period. 8. The garbage collection unit, if the garbage collection unit cannot secure the amount of free memory held by the memory allocation amount storage unit by the cycle start time of the corresponding periodic task, 7. The real-time memory management system according to claim 1, further comprising a free memory shortage notifying unit for notifying the periodic task or any task corresponding to the failure to secure a memory. 9. The free memory shortage means further comprising a free memory shortage notifying means having means for notifying the periodic task or an arbitrary task of the reserved free memory amount to the corresponding periodic task or an arbitrary task. 7. The real-time memory management system according to claim 1. 10. A real-time system including a periodic task having a time constraint, wherein a garbage collection process is executed as a pre-process of each cycle of the periodic task, and the garbage collection process is allocated in the cycle by each cycle start time of the periodic task. A real-time memory management method characterized by securing free memory equal to or larger than a memory amount. 11. The real-time memory management method according to claim 10, wherein a plurality of said synchronization tasks are included, and said garbage collection process is executed individually for each of said synchronization tasks. 12. The garbage collection process including a plurality of the synchronization tasks, wherein the garbage collection process has a lower priority than the synchronization task corresponding to the garbage collection process, and a garbage collection process corresponding to the synchronization task. 12. The real-time memory management method according to claim 10, wherein the method is executed with priority. 13. A garbage collection process is executed as a pre-process of each cycle of the periodic task, and a vacant memory equal to or larger than a memory amount allocated in the cycle is secured by the start time of each cycle of the periodic task. 13. The real-time memory management method according to claim 10, wherein a free memory is reserved in association with the periodic task, and thereafter, another task is executed until a cycle start time of the periodic task. 14. When the garbage collection process fails to secure a free memory equal to or more than the memory amount allocated in the cycle by the cycle start time of the corresponding cycle task, cancels execution of the cycle. 14. The real-time memory management method according to claim 10, wherein: 15. When the garbage collection process fails to secure the free memory equal to or more than the amount of memory allocated in the cycle by the cycle start time of the corresponding periodic task, 14. The real-time memory management method according to claim 10, further comprising notifying that a required amount of said free memory could not be secured, or notifying of the secured free memory amount.