c++ map中key用非简单数据类型时候性能消耗

typedef pair<long, int> PAIR_X;
map<long, int> mLongInt;
map<PAIR_X, int> mPairx;

#define LOOP_MAX    1000000

int main(void)
{
    time_t tSimpleInsert, tSimpleQuery;
    {
        time_t tBgn = clock();
        for (int i = 0; i < LOOP_MAX; i++)
        {
            mLongInt[i] = i + 100;
        }
        int xCount = 0;
        time_t tInsert = clock();
        tSimpleInsert = tInsert - tBgn;
        for (int i = 0; i < LOOP_MAX; i++)
        {
            auto it = mLongInt.find(i);
            if (it != mLongInt.end())
            {
                xCount++;
            }
        }
        time_t tQuery = clock();
        tSimpleQuery = tQuery - tInsert;
    }
    
    time_t tPairInsert, tPairQuery;
    {
        time_t tBgn = clock();
        for (int i = 0; i < LOOP_MAX; i++)
        {
            PAIR_X px(i, i + 1);
            mPairx[px] = i + 100;
        }
        int xCount = 0;
        time_t tInsert = clock();
        tPairInsert = tInsert - tBgn;
        for (int i = 0; i < LOOP_MAX; i++)
        {
            PAIR_X px(i, i + 1);
            auto it = mPairx.find(px);
            if (it != mPairx.end())
            {
                xCount++;
            }
        }
        time_t tQuery = clock();
        tPairQuery = tQuery - tInsert;
    }



    return 0;
}