内核中进程内存测量的更新速度/频率有多快？

在回答问题时，在Linux上多长时间更新一次proc文件系统？，乔纳森·本·阿夫拉罕（Jonathan Ben-Avraham）表示，/proc/.../statm一旦您阅读它，它就会立即生效，因为阅读它会直接触发内核回调。

这些内核回调读取的数据如何？这是否总是正确的，还是在malloc /新请求的内存和内核之间提供了可供使用的度量值/proc/.../statm？

我试图找到一种方法来测量通过malloc或分配的对象的当前大小new。

运行一个分配一些数据的小型测试程序，/proc/.../statm调用和调用sbrk()似乎都不会立即与该进程分配的内存量相关。

有没有办法获取准确的信息？

程序分配64KB和128KB块

$ ./a.out
MALLOC TEST. Size = 131072
0 ALLOC: HEAP SIZE: 0   MEMORY USAGE (statm): 1083 201 173 2 0 341 0
1 ALLOC: HEAP SIZE: 135168  MEMORY USAGE (statm): 1083 211 182 2 0 341 0
2 ALLOC: HEAP SIZE: 135168  MEMORY USAGE (statm): 1116 215 185 2 0 374 0
3 ALLOC: HEAP SIZE: 135168  MEMORY USAGE (statm): 1149 216 185 2 0 407 0
4 ALLOC: HEAP SIZE: 135168  MEMORY USAGE (statm): 1182 217 185 2 0 440 0
5 ALLOC: HEAP SIZE: 135168  MEMORY USAGE (statm): 1215 218 185 2 0 473 0
6 ALLOC: HEAP SIZE: 135168  MEMORY USAGE (statm): 1248 219 185 2 0 506 0
7 ALLOC: HEAP SIZE: 135168  MEMORY USAGE (statm): 1281 220 185 2 0 539 0
8 ALLOC: HEAP SIZE: 135168  MEMORY USAGE (statm): 1314 221 185 2 0 572 0
9 ALLOC: HEAP SIZE: 135168  MEMORY USAGE (statm): 1347 222 185 2 0 605 0

$ ./a.out
MALLOC TEST. Size = 65536
0 ALLOC: HEAP SIZE: 0   MEMORY USAGE (statm): 1067 201 174 2 0 325 0
1 ALLOC: HEAP SIZE: 0   MEMORY USAGE (statm): 1067 211 182 2 0 325 0
2 ALLOC: HEAP SIZE: 0   MEMORY USAGE (statm): 1067 215 185 2 0 325 0
3 ALLOC: HEAP SIZE: 196608  MEMORY USAGE (statm): 1115 216 185 2 0 373 0
4 ALLOC: HEAP SIZE: 196608  MEMORY USAGE (statm): 1115 217 185 2 0 373 0
5 ALLOC: HEAP SIZE: 196608  MEMORY USAGE (statm): 1115 218 185 2 0 373 0
6 ALLOC: HEAP SIZE: 393216  MEMORY USAGE (statm): 1163 219 185 2 0 421 0
7 ALLOC: HEAP SIZE: 393216  MEMORY USAGE (statm): 1163 220 185 2 0 421 0
8 ALLOC: HEAP SIZE: 393216  MEMORY USAGE (statm): 1163 221 185 2 0 421 0
9 ALLOC: HEAP SIZE: 589824  MEMORY USAGE (statm): 1211 222 185 2 0 469 0

测试程序

class CfgProfileList
{
public:
    bool obtainSystemProfileList();
    void leakTest();
    void leakObjTest();
    std::set<std::string> mProfileList;
private:
    char dummy[1024 * 1024]; // use up some space
};

class ComUtil
{
public:
    static void printMemoryUsage();

private:
    static unsigned int mHeapOrigin;
};

/* static */
unsigned int ComUtil::mHeapOrigin = 0;

// Print current process memory utilization
/* static */ void
ComUtil::printMemoryUsage()
{
    unsigned int pHeap = (unsigned int)sbrk(0);
    if (mHeapOrigin == 0)
        mHeapOrigin = pHeap;

    printf("HEAP SIZE: %u\t", pHeap - mHeapOrigin);

    char fname[256], line[256];
    sprintf(fname, "/proc/%d/statm", getpid());

    FILE *pFile = fopen(fname, "r");
    if (!pFile)
        return;

    fgets(line, 255, pFile);
    fclose(pFile);
    printf("MEMORY USAGE (statm): %s", line);
}



void
CfgProfileList::leakTest()
{
    char *pointerList[50];
    int  n = 10;
    int  sleep = 1; 
    int  size  = 64 * 1024;

    printf("MALLOC TEST. Size = %d\n", size);

    for (int i = 0; i < n; i++)
    {
        pointerList[i] = (char *)malloc(size);
        printf("%d ALLOC: ", i);
        ComUtil::printMemoryUsage();
        usleep(sleep);
    }
}

int
main(int argc, char **argv)
{
    CfgProfileList pl;
    pl.leakTest();
}