CPUP

Basic Concepts

The central processing unit percent (CPUP) includes the system CPUP and task CPUP.

The system CPUP is the CPU usage of the system within a period of time. It reflects the CPU load and the system running status (idle or busy) in the given period of time. The valid range of the system CPUP is 0 to 100 in percentage. The precision can be adjusted through configuration. The value 100 indicates that the system runs with full load.

Task CPUP refers to the CPU usage of a single task. It reflects the task status, busy or idle, in a period of time. The valid range of task CPUP is 0 to 100 in percentage. The precision can be adjusted through configuration. The value 100 indicates that the task is being executed for the given period of time.

With the system CPUP, you can determine whether the current system load exceeds the designed specifications.

With the CPUP of each task, you can determine whether the CPU usage of each task meets expectations of the design.

Working Principles

The OpenHarmony LiteOS-M CPUP records the system CPU usage on a task basis. When task switching occurs, the task start time and task switch-out or exit time are recorded. Each time when a task exits, the system accumulates the CPU time used by the task.

You can configure this function in target_config.h.

The OpenHarmony LiteOS-M provides the following types of CPUP information:

• System CPUP
• Task CPUP

The CPUP is calculated as follows:

System CPUP = Total running time of all tasks except idle tasks/Total running time of the system

Task CPUP = Total running time of the task/Total running time of the system

Available APIs

Table 1 Functions

How to Develop

The typical CPUP development process is as follows:

1. Call LOS_SysCpuUsage to obtain the system CPUP.

2. Call LOS_HistorySysCpuUsage to obtain the historical CPUP of the system.

3. Call LOS_TaskCpuUsage to obtain the CPUP of a specified task.

   • If the task has been created, disable interrupt, obtain the CPUP, and then enable interrupt.
   • If the task is not created, return an error code.

4. Call LOS_HistoryTaskCpuUsage to obtain the historical CPUP of a specified task.

   • If the task has been created, disable interrupt, obtain the CPUP in different modes, and then enable interrupt.
   • If the task is not created, return an error code.

5. Call LOS_AllCpuUsage to obtain the CPUP of all tasks.

   • If the CPUP is initialized, disable interrupt, obtain the CPUP in different modes, and then enable interrupt.
   • If CPUP is not initialized or has invalid input parameters, return an error code.

Development Example

Example Description

This example implements the following:

1. Create a task for the CPUP test.
2. Obtain the CPUP of the current system.
3. Obtain the historical system CPUP in different modes.
4. Obtain the CPUP of the created test task.
5. Obtain the CPUP of the created test task in different modes.

Sample Code

Prerequisites

In target_config.h, the LOSCFG_BASE_CORE_CPUP parameter is enabled.

The sample code is as follows:

#include "los_task.h"
#include "los_cpup.h" 
#define  MODE  4
UINT32 g_cpuTestTaskID;  
VOID ExampleCpup(VOID) 
{      
    printf("entry cpup test example\n");
    while(1) {
        usleep(100);
    }
}
UINT32 ItCpupTest(VOID) 
{     
    UINT32 ret;
    UINT32 cpupUse;
    TSK_INIT_PARAM_S cpupTestTask = { 0 };
    memset(&cpupTestTask, 0, sizeof(TSK_INIT_PARAM_S));
    cpupTestTask.pfnTaskEntry = (TSK_ENTRY_FUNC)ExampleCpup;
    cpupTestTask.pcName       = "TestCpupTsk"; 
    cpupTestTask.uwStackSize  = 0x800;
    cpupTestTask.usTaskPrio   = 5;
    ret = LOS_TaskCreate(&g_cpuTestTaskID, &cpupTestTask);
    if(ret != LOS_OK) {
        printf("cpupTestTask create failed .\n");
        return LOS_NOK;
    }

    usleep(100);

 /* Obtain the current CPUP of the system. */
    cpupUse = LOS_SysCpuUsage();
    printf("the current system cpu usage is: %u.%u\n",
            cpupUse / LOS_CPUP_PRECISION_MULT, cpupUse % LOS_CPUP_PRECISION_MULT); 

    cpupUse = LOS_HistorySysCpuUsage(CPU_LESS_THAN_1S);
 /* Obtain the CPUP of the specified task (cpupTestTask in this example).*/
    printf("the history system CPUP in all time: %u.%u\n",
           cpupUse / LOS_CPUP_PRECISION_MULT, cpupUse % LOS_CPUP_PRECISION_MULT);
    cpupUse = LOS_TaskCpuUsage(g_cpuTestTaskID);    
 /* Obtain the CPUP of the specified historical task (cpupTestTask in this example) since the system startup. */
    printf("cpu usage of the cpupTestTask:\n TaskID: %d\n usage: %u.%u\n",
           g_cpuTestTaskID, cpupUse / LOS_CPUP_PRECISION_MULT, cpupUse % LOS_CPUP_PRECISION_MULT); 
    cpupUse = LOS_HistoryTaskCpuUsage(g_cpuTestTaskID, CPU_LESS_THAN_1S);   
    printf("cpu usage of the cpupTestTask in all time:\n TaskID: %d\n usage: %u.%u\n",
           g_cpuTestTaskID, cpupUse / LOS_CPUP_PRECISION_MULT, cpupUse % LOS_CPUP_PRECISION_MULT);   
    return LOS_OK; 
}

Verification

The development is successful if the return result is as follows:

entry cpup test example 
the current system cpu usage is : 1.5
 the history system cpu usage in all time: 3.0
 cpu usage of the cpupTestTask: TaskID:10 usage: 0.0
 cpu usage of the cpupTestTask in all time: TaskID:10 usage: 0.0