Question

我正在尝试研究基于pthread的多线程代码修改对基于64位Centos的Linux系统上的VIRTUAL内存的影响

我附加了一个电子表格，其中观察是在VIRTUAL MEMORY上进行的（使用基于Linux的top命令），增加了线程数，每个线程分配1MB。

我粘贴用于观察的C ++代码（如下）作为参考：

从下表所示的观察结果来看，对于分配1MB数据的单个线程，使用的VIRTUAL内存为89.824MB，对于2个线程，每个VIRTUAL内存分配1MB为165.604MB，对于3个线程，每个VIRTUAL内存分配1MB为235MB然后，每个线程的VIRTUAL内存增加1MB。

Click here to view the table having observations made

总结一下，VIRTUAL内存以89MB开始，加入第二个线程后变为双倍，加入第三个线程后再变为几乎加倍，然后每个线程增加1MB，每个分配1MB的堆。

任何人都可以解释为什么系统会出现这种行为？

如果您需要任何其他详细信息，请发布。期待着帮助。

注意：
代码是用g ++编译的（g ++ -o vma CODE_FILE.cpp -lpthread）
每个线程只分配了1MB的堆，但没有填充生成的二进制大小只有~9KB（使用ls命令获得）

#include <iostream>
#include <pthread.h>

using namespace std;

/*
  NOTE: Make sure you provide NUM_THREADS in the range (1..5)
*/
#define NUM_THREADS 5

struct thread_struct
{
    int id;
    char *msg;
};

void *thrdFunc(void *i)
{
    char *it = (char*)i;
    cout << "\nthis is thread named :"<< it ;

    char *mallocBlk = new char [1000000];
}

int main()
{
    int rc = 0;
    void *status;
    char threadNames[8][8] = { "Thread1" , "Thread2", "Thread3",  "Thread4", "Thread5", "Thread6", "Thread7", "Thread8"};

    pthread_t     threads[NUM_THREADS];
    thread_struct thrStructs[NUM_THREADS];

    cout << "\nIn Main, creating threads!" ;

    /*
       Create threads
    */
    for (int i = 0; i < NUM_THREADS; i++)
    {
        rc = pthread_create(&threads[i], NULL, thrdFunc, &threadNames[i] );

        if (rc)
        {
            cout << "Thrd" << i+1 << " cant be created";
        }
    }

    /*
       Wait till all the threads complete
   */
    for (int i = 0; i < NUM_THREADS; i++)
    {
        pthread_join(threads[i], &status);
    }
    cout << endl;

    cout << "Done! Waiting for your input!";
    cin.get();
    return 0;
}

下面是5个线程的内存映射：

[rebaca @ localhost stackoverflow] $ cat / proc / 31528 / maps 00400000-00401000 r-xp 00000000 fd：02 20451094 / home / rebaca / stackoverflow / vma 00601000-00602000 rw-p 00001000 fd：02 20451094 / home / rebaca / stackoverflow / vma 01784000-017a5000 rw-p 00000000 00:00 0 [堆] 305b400000-305b420000 r-xp 00000000 fd：00 1703944 /lib64/ld-2.12.so 305b61f000-305b620000 r - p 0001f000 fd：00 1703944 /lib64/ld-2.12.so 305b620000-305b621000 rw-p 00020000 fd：00 1703944 /lib64/ld-2.12.so 305b621000-305b622000 rw-p 00000000 00:00 0 305b800000-305b98a000 r-xp 00000000 fd：00 1703966 /lib64/libc-2.12.so 305b98a000-305bb8a000 --- p 0018a000 fd：00 1703966 /lib64/libc-2.12.so 305bb8a000-305bb8e000 r - p 0018a000 fd：00 1703966 /lib64/libc-2.12.so 305bb8e000-305bb90000 rw-p 0018e000 fd：00 1703966 /lib64/libc-2.12.so 305bb90000-305bb94000 rw-p 00000000 00:00 0 305bc00000-305bc17000 r-xp 00000000 fd：00 1703968 /lib64/libpthread-2.12.so 305bc17000-305be17000 --- p 00017000 fd：00 1703968 /lib64/libpthread-2.12.so 305be17000-305be18000 r - p 00017000 fd：00 1703968 /lib64/libpthread-2.12.so 305be18000-305be19000 rw-p 00018000 fd：00 1703968 /lib64/libpthread-2.12.so 305be19000-305be1d000 rw-p 00000000 00:00 0 305c800000-305c883000 r-xp 00000000 fd：00 1704110 /lib64/libm-2.12.so 305c883000-305ca82000 --- p 00083000 fd：00 1704110 /lib64/libm-2.12.so 305ca82000-305ca83000 r - p 00082000 fd：00 1704110 /lib64/libm-2.12.so 305ca83000-305ca84000 rw-p 00083000 fd：00 1704110 /lib64/libm-2.12.so 3066800000-3066816000 r-xp 00000000 fd：00 1704139 /lib64/libgcc_s-4.4.7-20120601.so.1 3066816000-3066a15000 --- p 00016000 fd：00 1704139 /lib64/libgcc_s-4.4.7-20120601.so.1 3066a15000-3066a16000 rw-p 00015000 fd：00 1704139 /lib64/libgcc_s-4.4.7-20120601.so.1 3066c00000-3066ce8000 r-xp 00000000 fd：00 809560 /usr/lib64/libstdc++.so.6.0.13 3066ce8000-3066ee8000 --- p 000e8000 fd：00 809560 /usr/lib64/libstdc++.so.6.0.13 3066ee8000-3066eef000 r - p 000e8000 fd：00 809560 /usr/lib64/libstdc++.so.6.0.13 3066eef000-3066ef1000 rw-p 000ef000 fd：00 809560 /usr/lib64/libstdc++.so.6.0.13 3066ef1000-3066f06000 rw-p 00000000 00:00 0 7fd3ec000000-7fd3ec115000 rw-p 00000000 00:00 0 7fd3ec115000-7fd3f0000000 --- p 00000000 00:00 0 7fd3f0000000-7fd3f0115000 rw-p 00000000 00:00 0 7fd3f0115000-7fd3f4000000 --- p 00000000 00:00 0 7fd3f4000000-7fd3f4115000 rw-p 00000000 00:00 0 7fd3f4115000-7fd3f8000000 --- p 00000000 00:00 0 7fd3f8000000-7fd3f8115000 rw-p 00000000 00:00 0 7fd3f8115000-7fd3fc000000 --- p 00000000 00:00 0 7fd3fc000000-7fd3fc115000 rw-p 00000000 00:00 0 7fd3fc115000-7fd400000000 --- p 00000000 00:00 0 7fd4032b6000-7fd4032b7000 --- p 00000000 00:00 0 7fd4032b7000-7fd403cb7000 rw-p 00000000 00:00 0 7fd403cb7000-7fd403cb8000 --- p 00000000 00:00 0 7fd403cb8000-7fd4046b8000 rw-p 00000000 00:00 0 7fd4046b8000-7fd4046b9000 --- p 00000000 00:00 0 7fd4046b9000-7fd4050b9000 rw-p 00000000 00:00 0 7fd4064bb000-7fd4064c1000 rw-p 00000000 00:00 0 7fd4064db000-7fd4064de000 rw-p 00000000 00:00 0 7ffc72456000-7ffc7246b000 rw-p 00000000 00:00 0 [堆栈] 7ffc72568000-7ffc72569000 r-xp 00000000 00:00 0 [vdso] ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall]

用于多线程代码堆分配的无法解释的VIRTUAL内存行为

0 个答案: