linux 에서 프로세스의 RSS 값이 바로 갱신이 안됩니다. 왜 그런가요?

#define CHUNK_SIZE (1024 * 100)
 
 
int g_mem_alloc = 0;
int g_mem_free = 0;
 
void sig_handler(int signum)
{
    if (signum == SIGUSR1)
        g_mem_alloc = 1;
    else if (signum == SIGUSR2)
        g_mem_free = 1;
 
}
 
int main(int ac, char *av[])
{
    int i;
    TAILQ_HEAD(, mem_chunk) mem_chunk_head;
    unsigned char *chunk = NULL;
    struct mem_chunk *entry = NULL;
 
    TAILQ_INIT(&mem_chunk_head);
 
    signal(SIGUSR1, sig_handler);
    signal(SIGUSR2, sig_handler);
 
    while (1)
    {
        if (g_mem_alloc)
        {
            g_mem_alloc = 0;
 
            for (i = 0; i < 100; i++)
            {
                entry = malloc(sizeof(*entry));
                if (entry)
                {
                    chunk = malloc(CHUNK_SIZE);
 
                    if (chunk)
                    {
                        chunk[0] = '\0';
                        chunk[CHUNK_SIZE-1] = '\0';
                        entry->data = chunk;
                        TAILQ_INSERT_TAIL(&mem_chunk_head, entry, l);
                        printf("alloc \n");
                    }
                    else
                        free(entry);
                }
            }
        }
        if (g_mem_free)
        {
            g_mem_free = 0;
 
            while ((entry = TAILQ_FIRST(&mem_chunk_head)))
            {
                TAILQ_REMOVE(&mem_chunk_head, entry, l);
                free(entry->data);
                free(entry);
                printf("free \n");
            }
        }
        usleep(100);
    }
 
    return 0;
}