KR102380175B1 - A method for deriving an offset of a task for minimizing the load and an apparatus therefor - Google Patents

Abstract

In a method of arranging tasks according to an embodiment of the present invention, the method comprising: sequentially allocating an offset in a unit of load measurement to a task having a period equal to or greater than a reference value among the tasks; allocating the offset sequentially in ascending order from the task having the shortest period to the task having a period less than the reference value among the tasks, the task having the shortest period among the tasks having a period less than the reference value assigning the smallest offset to the first task; and based on a result of comparing the execution time of the first task period and the second task with respect to the second task to be allocated the offset among the remaining tasks except for the first task among the tasks having a period less than the reference value allocating the offset; may include

Description

A method for deriving an offset of a task for minimizing load and an apparatus therefor

The present specification proposes a method and apparatus for arranging tasks in consideration of the cycle of each task in order to minimize preemption between tasks.

Due to the multifunctionality of the current automobile, the number of tasks executed in one ECU (Electronic Control Unit) has increased, and the load applied to the CPU (Central Processing Unit) within the ECU increases as the number of tasks increases. As a result, vehicle developers are actively researching ways to reduce CPU load by efficiently distributing and allocating tasks that have rapidly increased in quantity.

As the number of tasks increases, preemption between tasks according to priority occurs, which causes context switching, which incurs more time overhead than when preemption between tasks does not occur. Therefore, in order to avoid a situation in which these tasks are preempted from each other, a method of arranging them at regular time intervals (Offset) is required.

In order to solve the above problem, the present specification proposes a task offset setting algorithm that minimizes preemption between tasks to reduce the overall CPU load of the ECU and enables efficient use.

In a method of arranging tasks according to an embodiment of the present invention, the method comprising: sequentially allocating an offset in a unit of load measurement to a task having a period equal to or greater than a reference value among the tasks; allocating the offset sequentially in ascending order from the task having the shortest period to the task having a period less than the reference value among the tasks, the task having the shortest period among the tasks having a period less than the reference value assigning the smallest offset to the first task; and based on a result of comparing the execution time of the first task period and the second task with respect to the second task to be allocated the offset among the remaining tasks except for the first task among the tasks having a period less than the reference value allocating the offset; may include

In addition, the allocating the offset based on a result of comparing the execution time of the first task period and the second task may include: when the execution time of the second task is longer than the first task period, the second converting a task to a standby state, and when the execution time of the second task is shorter than the first task period, allocating an offset that minimizes preemption with other tasks to the second task; may include

In addition, the allocating the offset to the second task so that the preemption with the other task is minimized may include a candidate previously assigned to a third task having a shorter period than the second task and having a minimum number of preemptions with the other task. allocating the largest offset among the offsets to the second task; may include

In addition, the third task is a task for which the assignment of the offset has been completed in an order immediately before the second task, and the second task is to be disposed immediately after the third task disposed at the offset assigned to the second task. can

The method of arranging the tasks includes: allocating virtually all offsets to the tasks in the standby state, and allocating offsets having a minimum number of preemptions with other tasks as a result of the virtual assignment; may further include.

In addition, the step of sequentially allocating the offset by the load measurement unit to a task having a period equal to or greater than the reference value among the tasks may include sequentially starting from a task having a shorter period among tasks having a period equal to or greater than the reference value. arranging the tasks so that the offsets are allocated in ascending order, and the allocated offsets are located in the middle of the execution time of the tasks to which the offsets are allocated; may include

Also, the reference value may be determined based on the load measurement unit.

In addition, the reference value and the load measurement unit may be a cycle of a task with the highest load.

In addition, in an ECU (Electronic Control Unit) for arranging tasks according to another embodiment of the present invention, at least one processor; and a memory for storing data; including, wherein the at least one processor sequentially allocates an offset in a load measurement unit to a task having a period equal to or greater than a reference value among the tasks, and assigns an offset to a task having a period less than the reference value among the tasks. In relation to, the offsets are sequentially allocated in ascending order from the task having the shortest period, and the smallest offset is allocated to the first task having the shortest period among tasks having a period less than the reference value, and less than the reference value. The offset may be allocated based on a result of comparing the execution time of the first task period and the second task with respect to the second task to be allocated the offset among the remaining tasks except the first task among the tasks having a period. there is.

In addition, when the at least one processor allocates the offset based on a result of comparing the first task period and the execution time of the second task, the execution time of the second task is longer than the first task period If it is long, the second task may be switched to a standby state, and if the execution time of the second task is shorter than the first task period, an offset that minimizes preemption with other tasks may be assigned to the second task .

In addition, when allocating the offset to the second task so that preemption with the other task is minimized, the at least one processor is pre-allocated to a third task having a shorter period than that of the second task and is associated with the other task. Among the candidate offsets having the minimum number of preemptions, the largest offset may be allocated to the second task.

In addition, the third task is a task for which the assignment of the offset has been completed in an order immediately before the second task, and the second task is to be disposed immediately after the third task disposed at the offset assigned to the second task. can

Also, the at least one processor may virtually allocate all offsets to the task in the standby state, and allocate an offset having a minimum number of preemptions with other tasks as a result of the virtual allocation.

In addition, the at least one processor is configured to select a shorter period among tasks having a period equal to or greater than the reference value when sequentially allocating the offset in the load measurement unit to a task having a period equal to or greater than the reference value among the tasks. The offsets may be sequentially allocated in ascending order from the task having the offset, and the tasks may be arranged such that the allocated offset is located in the middle of the execution time of the task to which the offset is allocated.

Also, the reference value may be determined based on the load measurement unit.

In addition, the reference value and the load measurement unit may be a period of a task having the highest load among tasks.

According to an embodiment of the present invention, when the CPU load is measured at the interval of the cycle of the task with the highest load, the number of preemption of all tasks is reduced. It has the effect that time can be reduced.

In addition, according to an embodiment of the present invention, since optimal offsets for tasks having different periods, execution times, and priorities are derived, there is an effect that the number of preemptions between tasks can be minimized.

In addition, according to an embodiment of the present invention, by reducing the context switching overhead and the load factor of each CPU core, the limited ECU resources are efficiently used, thereby efficiently distributing and allocating tasks to save ECU resources. there is.

1 is a flowchart illustrating a task arrangement method of an ECU according to an embodiment of the present invention.
2 and 3 are diagrams illustrating a task arrangement embodiment according to the task arrangement method of FIG. 1 .

The technology to be described below can apply various changes and can have various embodiments, and specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the technology described below to specific embodiments, and it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the technology described below.

Terms such as first, second, A, and B may be used to describe various components, but the components are not limited by the above terms, and only for the purpose of distinguishing one component from other components. is used only as For example, a first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component without departing from the scope of the present invention. and/or includes a combination of a plurality of related listed items or any of a plurality of related listed items.

In terms of terms used herein, the singular expression should be understood to include the plural expression unless the context clearly dictates otherwise, and terms such as "comprises" refer to the described feature, number step, operation, component, It is to be understood that the presence of parts or combinations thereof does not exclude the possibility of the presence or addition of one or more other features or numbers, step operation components, parts or combinations thereof.

Prior to a detailed description of the drawings, it is intended to clarify that the classification of the constituent parts in the present specification is merely a division according to the main function each constituent unit is responsible for. That is, two or more components to be described below may be combined into one component, or one component may be divided into two or more for each more subdivided function. In addition, each of the constituent units to be described below may additionally perform some or all of the functions of other constituent units in addition to the main function it is responsible for. Of course, it may be carried out by being dedicated to it.

In addition, in performing the method or method of operation, each process constituting the method may occur differently from the specified order unless a specific order is clearly described in context. That is, each process may occur in the same order as specified, may be performed substantially simultaneously, or may be performed in the reverse order.

This specification describes an ECU that performs an efficient task arrangement method that minimizes preemption. The ECU may include at least one hardware component (eg, a processor and/or memory) to perform the task arrangement method described in this specification, and various embodiments may be performed using each component. can Accordingly, various operations/steps described with reference to the ECU in this specification may be understood to be performed using the at least one component without overlapping descriptions.

In addition, the OEM (Original Equipment Manufacturer) measures the load in the cycle/unit of the task with the highest load among the tasks, and determines the peak load value per cycle of the task with the highest load among each task, so it is the most Load The result value of the load measured in the period/unit of the high task has a very important meaning. Therefore, in order to lower the load rate per cycle of the task with the highest load among the tasks, the offset must be adjusted so that the task with the highest load among the tasks operates at a fixed position, and the other tasks are set at the offset that minimizes the number of preemptions. should be placed Hereinafter, a more efficient task arrangement method is proposed in consideration of the offset setting criteria.

1 is a flowchart illustrating a task arrangement method of an ECU according to an embodiment of the present invention, and FIGS. 2 and 3 are diagrams illustrating a task arrangement embodiment according to the task arrangement method of FIG. 1 .

At least one step in the flowchart of FIG. 1 may be deleted or a new step may be added, and the order between steps may be changed. Hereinafter, a task arrangement algorithm will be described in detail with reference to FIGS. 2 and 3 with a focus on FIG. 1 .

First, the ECU may equally arrange the task with the highest load among the tasks so that the load is similarly measured in the cycle/unit of the task with the highest load among the tasks ( S101 ). That is, in the task with the highest load among the tasks, the offset may be set so that the load value is equally measured in a cycle of "Tmax".

For example, the offset value is set so that the offset in “Tmax” is placed at the center of the task with the “Tmax” cycle (or at the center of the task execution time) so that the load is evenly measured in units/cycle of “Tmax”. can be set. That is, an offset of "Tmax" unit is set/arranged at the center of the task, and through this, the effect of equally dividing the task (more precisely, the execution time of the task) in half based on the offset may occur. Referring to FIG. 2 , when a Tmax offset is assigned to a task of a “2×Tmax” period, the 2×Tmax periodic task may be arranged such that the Tmax offset is positioned at the center.

In this case, while avoiding preemption with other tasks, offsets may be sequentially allocated from a task having a small period, and allocated in an ascending order from a small offset. For example, when arranging a task with a period of 2 × Tmax / 4 × Tmax / 10 × Tmax as shown in Fig. 2, offsets are allocated to tasks in ascending order in the order of 2 × Tmax -> 4 × Tmax -> 10 × Tmax. can Accordingly, a Tmax offset may be allocated to a 2×Tmax periodic task and a Tmax offset may be allocated to a 4×Tmax periodic task. In the case of a 10xTmax periodic task, if a 3xTmax offset is allocated, a preemption problem with a 2xTmax periodic task occurs. Therefore, a 4xTmax offset, which is the minimum offset value among the offsets in which the preemption problem does not occur, may be allocated.

Next, the ECU may arrange the tasks having a period equal to or less than Tmax in ascending order, and sequentially designate the offset from the task having a shorter period ( S102 ). In this case, the ECU may adjust the offset of the task having the shortest cycle to 0 (S103).

Next, the ECU may start to adjust the offset value in an ascending order from a task having a low cycle ( S104 ), and the offset value adjustment method may proceed as follows:

First, the ECU may determine whether the execution time of the task to be assigned an offset is longer than the cycle of the task having the shortest cycle (ie, the offset is designated as 0 in step S103) (S105).

If it is determined that the execution time of the target task is longer than the cycle of the shortest task, the ECU may switch the target task to a standby state (S108).

Conversely, if it is determined that the execution time of the target task is shorter than the cycle of the task with the shortest cycle, the ECU sets the target task to the previous task with a shorter cycle than the target task (for example, the task with an offset specified in the previous sequence of the target task). As it is executed later, it is possible to detect/search for an offset in which preemption does not occur (S106). Next, the ECU may adopt the highest offset among the detected/discovered values (S107).

Steps S102 to S108 will be described with reference to the example of FIG. 3 as follows.

Referring to FIG. 3 , since the task having the shortest period Tmin is the task having the highest priority in the arrangement, the offset 0 may be allocated and arranged. Next, the 2×Tmin periodic task with the shorter period may be arranged with an offset specified/adjusted so that it can be executed immediately after the Tmin task is executed. At this time, in order to reduce the number of preemptions for tasks having a period equal to or greater than Tmax, the highest offset (Tmin) among the candidate offsets (0ms, ×Tmin) in which the Tmin periodic task is located is allocated to the 2 × Tmin periodic task. can In this case, the 2×Tmin periodic task may be arranged to be executed immediately after the ×Tmin periodic task placed at the assigned offset “Tmin”. Similarly for the 5×Tmin periodic task, in consideration of the number of preemptions for the periodic task greater than or equal to Tmax, candidate offsets (Tmin, Tmin, 3xTmin), the highest offset (3xTmin) may be allocated. Because the task execution time is long (especially, the execution time is longer than the cycle of the Tmin periodic task, which is the shortest periodic task), the cycle in which the preemption occurs inevitably occurs when the Tmax task is switched to the standby state, and the preemption occurs the fewest times. It may be placed at an offset. This will be described later below.

Referring back to FIG. 1 , next, the ECU may determine whether arrangement (ie, offset designation/assignment/adjustment) for all tasks other than the task switched to the standby state is completed ( S109 ). If the arrangement is not completed, the ECU may return to step S104 again, and may continue to perform the arrangement for the remaining tasks. If the arrangement is completed, the ECU may place/assign all the offsets for each of the standby state tasks to check the number of preemptions for each placed/assigned offset (that is, search for an offset having the minimum number of preemptions) (S110).

Finally, according to the search result, by selecting/assigning an offset with the smallest number of preemptions for each standby task, scheduling of all standby tasks can be completed.

Referring to the present invention described above, the conventional invention derives the offset from the result with the lowest load among the results obtained by imagining all the offsets for each task. There is a problem that time and overhead are large. In contrast, in the present invention, since the offset of a specific task is fixed to a specific offset in advance, and offset derivation simulation is performed only for the remaining tasks, the simulation time and overhead are minimized.

Embodiments according to the present invention may be implemented by various means, for example, hardware, firmware, software, or a combination thereof. In the case of implementation by hardware, an embodiment of the present invention provides one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), FPGAs ( field programmable gate arrays), a processor, a controller, a microcontroller, a microprocessor, and the like.

In addition, in the case of implementation by firmware or software, an embodiment of the present invention is implemented in the form of a module, procedure, function, etc. that performs the functions or operations described above, and is stored in a recording medium readable through various computer means. can be recorded. Here, the recording medium may include a program command, a data file, a data structure, etc. alone or in combination. The program instructions recorded on the recording medium may be specially designed and configured for the present invention, or may be known and available to those skilled in the art of computer software. For example, the recording medium includes a magnetic medium such as a hard disk, a floppy disk, and a magnetic tape, an optical recording medium such as a compact disk read only memory (CD-ROM), a digital video disk (DVD), and a floppy disk. Magneto-Optical Media, such as a disk, and hardware devices specially configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions may include high-level language codes that can be executed by a computer using an interpreter or the like as well as machine language codes such as those generated by a compiler. Such hardware devices may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

In addition, the device or terminal according to the present invention may be driven by a command to cause one or more processors to perform the functions and processes described above. For example, such instructions may include interpreted instructions, such as script instructions, such as JavaScript or ECMAScript instructions, or executable code or other instructions stored on a computer-readable medium. Furthermore, the device according to the present invention may be implemented in a distributed manner across a network, such as a server farm, or may be implemented in a single computer device.

Further, a computer program (also known as a program, software, software application, script or code) mounted on the device according to the invention and executing the method according to the invention includes compiled or interpreted language or a priori or procedural language. It can be written in any form of programming language, and can be deployed in any form, including stand-alone programs, modules, components, subroutines, or other units suitable for use in a computer environment. A computer program does not necessarily correspond to a file in a file system. A program may be in a single file provided to the requested program, or in multiple interacting files (eg, files that store one or more modules, subprograms, or portions of code), or portions of files that hold other programs or data. (eg, one or more scripts stored within a markup language document). The computer program may be deployed to be executed on a single computer or multiple computers located at one site or distributed over a plurality of sites and interconnected by a communication network.

Although each drawing is described separately for convenience of description, it is also possible to design to implement a new embodiment by merging the embodiments described in each drawing. In addition, the present invention is not limited to the configuration and method of the described embodiments as described above, but the above-described embodiments are configured by selectively combining all or part of each embodiment so that various modifications can be made. it might be

In addition, although preferred embodiments have been illustrated and described above, the present specification is not limited to the specific embodiments described above, and those of ordinary skill in the art to which the specification belongs without departing from the gist of the claims Various modifications are possible by a person, of course, and these modifications should not be individually understood from the technical spirit or perspective of the present specification.

S101~S111: Task offset assignment method

Claims (16)

A method of arranging tasks performed by an Electronic Control Unit (ECU), the method comprising:
sequentially allocating, by the ECU, an offset to a task having a period exceeding a reference value, among the tasks, such that loads are evenly distributed in a load measurement unit;
sequentially allocating, by the ECU, the offset to a task having a period less than or equal to the reference value among the tasks in ascending order from a task having the shortest period;
allocating, by the ECU, a smallest offset to a first task having a shortest period among tasks having a period equal to or less than the reference value; and
The ECU compares the first task period and the execution time of the second task with respect to the second task to be the offset assignment among the remaining tasks except for the first task among the tasks having a period less than or equal to the reference value. allocating the offset based on; including,
The reference value and the load measurement unit are a period of a task with the highest load that is a target of load measurement by an original equipment manufacturer (OEM) among tasks. The method of claim 1,
Allocating the offset based on a result of comparing the first task period and the execution time of the second task comprises:
When the execution time of the second task is longer than the first task period, the second task is switched to a standby state,
allocating an offset that minimizes preemption with other tasks to the second task when the execution time of the second task is shorter than the first task period; Including, task placement method. 3. The method of claim 2,
Allocating the offset to the second task so that preemption with the other task is minimized comprises:
allocating a largest offset to the second task among candidate offsets previously assigned to a third task having a shorter period than the second task and having a minimum number of preemptions with the other tasks; Including, task placement method. 4. The method of claim 3,
The third task is a task in which the allocation of the offset is completed in an order immediately preceding the second task,
and the second task is disposed immediately after the third task disposed at an offset assigned to the second task. 3. The method of claim 2,
virtually allocating all offsets to the tasks in the standby state, and allocating offsets having a minimum number of preemptions with other tasks as a result of the virtual assignment; Further comprising, task placement method. 3. The method of claim 2,
The step of sequentially allocating the offset so that the load is evenly distributed in the load measurement unit with respect to the task having a period exceeding the reference value among the tasks,
arranging the task so that the offset is sequentially allocated in ascending order from among the tasks having a period exceeding the reference value, from a task having a shorter period, and the allocated offset is located in the middle of the execution time of the task to which the offset is allocated ; Including, task placement method. delete delete In an ECU (Electronic Control Unit) for arranging a task,
at least one processor; and
memory for storing data; including,
The at least one processor,
Among the tasks, offsets are sequentially allocated so that loads are evenly distributed in a unit of load measurement with respect to a task having a period exceeding the reference value,
Among the tasks, the offset is sequentially allocated in ascending order from the task having the shortest period to a task having a period less than or equal to the reference value,
Allocating the smallest offset to the first task having the shortest period among the tasks having a period less than or equal to the reference value,
Based on a result of comparing the first task period and the execution time of the second task with respect to the second task to be the offset allocation among the remaining tasks except for the first task among the tasks having a period equal to or less than the reference value, the first task period and the execution time of the second task Allocate an offset,
The reference value and the load measurement unit are a cycle of a task with the highest load that is a target of load measurement by an original equipment manufacturer (OEM) among tasks. 10. The method of claim 9,
The at least one processor,
When allocating the offset based on a result of comparing the first task period and the execution time of the second task,
When the execution time of the second task is longer than the first task period, the second task is switched to a standby state,
and when the execution time of the second task is shorter than the first task period, an offset at which preemption with other tasks is minimized is allocated to the second task. 11. The method of claim 10,
The at least one processor,
When allocating the offset to the second task so that preemption with the other task is minimized,
and assigning a largest offset to the second task among candidate offsets previously assigned to a third task having a shorter period than the second task and having a minimum number of preemptions with the other tasks. 12. The method of claim 11,
The third task is a task in which the allocation of the offset is completed in an order immediately preceding the second task,
and the second task is disposed immediately after the third task disposed at an offset assigned to the second task. 11. The method of claim 10,
The at least one processor,
Virtually allocating all offsets to the task in the standby state, and assigning an offset having a minimum number of preemptions with other tasks as a result of the virtual assignment. 11. The method of claim 10,
The at least one processor,
Among the tasks, when the offset is sequentially allocated to a task having a period exceeding the reference value, so that the load is evenly distributed in the load measurement unit,
Disposing the task so that the offset is sequentially allocated in ascending order, starting with a task having a shorter period among tasks having a period exceeding the reference value, and the allocated offset is located in the middle of the execution time of the task to which the offset is allocated, ECU. delete delete

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