Memory Information Statistics

Basic Concepts

Memory information includes the memory pool size, memory usage, remaining memory size, maximum free memory, memory waterline, number of memory nodes, and fragmentation rate.

• Memory waterline: indicates the maximum memory used in a memory pool. The waterline value is updated upon each memory allocation and release. The memory pool size can be optimized based on this value.

• Fragmentation rate: indicates the fragmentation degree of the memory pool. If the fragmentation rate is high, there are a large number of free memory blocks in the memory pool but each block is small. You can use the following formula to calculate the fragmentation rate:

  Fragmentation rate = 100 – 100 x Maximum free memory block size/Remaining memory size

• Other parameters: You can call APIs (described in Memory Management) to scan node information in the memory pool and collect statistics.

Function Configuration

LOSCFG_MEM_WATERLINE: specifies the setting of the memory information statistics function. This function is enabled by default. To disable the function, set this macro to 0 in target_config.h. If you want to obtain the memory waterline, you must enable this macro.

Development Guidelines

How to Develop

Key structure:

typedef struct {
    UINT32 totalUsedSize; // Memory usage of the memory pool
    UINT32 totalFreeSize; // Remaining memory in the memory pool
    UINT32 maxFreeNodeSize; // Maximum size of the free memory block in the memory pool
    UINT32 usedNodeNum; // Number of non-free memory blocks in the memory pool
    UINT32 freeNodeNum; // Number of free memory blocks in the memory pool
#if (LOSCFG_MEM_WATERLINE == 1) // This macro is enabled by default. To disable it, set it to 0 in target_config.h.
    UINT32 usageWaterLine; // Waterline of the memory pool
#endif
} LOS_MEM_POOL_STATUS;

• To obtain the memory waterline, call LOS_MemInfoGet. The first parameter in the API is the start address of the memory pool, and the second parameter is the handle of the LOS_MEM_POOL_STATUS type. The usageWaterLine field indicates the waterline.

• To calculate the memory fragmentation rate, call LOS_MemInfoGet to obtain the remaining memory size and the maximum free memory block size in the memory pool, and then calculate the fragmentation rate of the dynamic memory pool as follows:

  Fragmentation rate = 100 – 100 x Maximum free memory block size/Remaining memory size

Development Example

This example implements the following:

1. Create a monitoring task to obtain information about the memory pool.

2. Call LOS_MemInfoGet to obtain the basic information about the memory pool.

3. Calculate the memory usage and fragmentation rate.

Sample Code

The sample code is as follows:

#include <stdio.h>
#include <string.h>
#include "los_task.h"
#include "los_memory.h"
#include "los_config.h"


void MemInfoTaskFunc(void)
{
    LOS_MEM_POOL_STATUS poolStatus = {0};

    /* pool is the memory address of the information to be collected. OS_SYS_MEM_ADDR is used as an example.*/
    void *pool = OS_SYS_MEM_ADDR;
    LOS_MemInfoGet(pool, &poolStatus);
    /* Calculate the fragmentation rate of the memory pool. */
    unsigned char fragment = 100 - poolStatus.maxFreeNodeSize * 100 / poolStatus.totalFreeSize;
    /* Calculate the memory usage of the memory pool. */
    unsigned char usage = LOS_MemTotalUsedGet(pool) * 100 / LOS_MemPoolSizeGet(pool);
    printf("usage = %d, fragment = %d, maxFreeSize = %d, totalFreeSize = %d, waterLine = %d\n", usage, fragment, poolStatus.maxFreeNodeSize, 
           poolStatus.totalFreeSize, poolStatus.usageWaterLine);
}

int MemTest(void)
{
    unsigned int ret;
    unsigned int taskID;
    TSK_INIT_PARAM_S taskStatus = {0};
    taskStatus.pfnTaskEntry = (TSK_ENTRY_FUNC)MemInfoTaskFunc;
    taskStatus.uwStackSize  = 0x1000;
    taskStatus.pcName       = "memInfo";
    taskStatus.usTaskPrio   = 10;
    ret = LOS_TaskCreate(&taskID, &taskStatus);
    if (ret != LOS_OK) {
        printf("task create failed\n");
        return -1;
    }
    return 0;
}

Verification

The result is as follows:

usage = 22, fragment = 3, maxFreeSize = 49056, totalFreeSize = 50132, waterLine = 1414

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