# Memory Information Statistics
- [Basic Concepts](#section52691565235)
- [Function Configuration](#section470611682411)
- [Development Guidelines](#section9368374243)
- [How to Develop](#section679912407257)
- [Development Example](#section1025453412611)
- [Sample Code](#section165277971315)
- [Verification](#section3460102414271)
## 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 \(described in [Memory Management](kernel-mini-basic-memory-basic.md)\) 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. Creates a monitoring task to obtain information about the memory pool.
2. Calls **LOS\_MemInfoGet** to obtain the basic information about the memory pool.
3. Calculates the memory usage and fragmentation rate.
### Sample Code
The sample code is as follows:
```
#include
#include
#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
```