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.

• The memory waterline indicates the maximum memory used in a memory pool. The waterline value is updated each time the memory is allocated or released. The memory pool size can be optimized based on this value.

• The 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

• You can use LOS_MemInfoGet() to scan the node information in the memory pool and collect the related statistics.

Function Configuration

LOSCFG_MEM_WATERLINE specifies the setting of the memory information statistics function. This function is disabled by default. If you want to obtain the memory waterline, enable it in Debug-> Enable MEM Debug-> Enable memory pool waterline or not.

Development Guidelines

How to Develop

Key structure:

typedef struct {
    UINT32 totalUsedSize;       // Memory usage of the memory pool.
    UINT32 totalFreeSize;       // Remaining size of 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 function is disabled by default and can be enabled using the **menuconfig** tool.
    UINT32 usageWaterLine;      // Waterline of the memory pool.
#endif
} LOS_MEM_POOL_STATUS;

To obtain the memory waterline, call LOS_MemInfoGet(VOID *pool, LOS_MEM_POOL_STATUS *poolStatus). The first parameter specifies the start address of the memory pool, and the second parameter specifies 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

You can compile and verify the sample code in kernel/liteos_a/testsuites/kernel/src/osTest.c. The MemTest() function is called in TestTaskEntry.

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);
    dprintf("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) {
        dprintf("task create failed\n");
        return LOS_NOK;
    }
    return LOS_OK;
}

Verification

The result is as follows:

The data may vary depending on the running environment.

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