Постоянно снижающаяся производительность выделения памяти. Пример кода

Не могли бы вы помочь выяснить, в чем причина постоянного снижения производительности кода ниже. Если вы запустите код, вы увидите, что он печатает количество итераций в секунду. Через 10-15 секунд количество итераций в секунду в 2 раза меньше, чем в начале. Сначала проблема возникла в QT, но я переделал код, чтобы проверить его с помощью std, и проблема воспроизводится.

#include <iostream>
#include <vector>
#include <memory>
#include <string>

#include <chrono>


using namespace std;

int64_t GetUsecTime()
{
    return std::chrono::time_point_cast<std::chrono::microseconds>(std::chrono::high_resolution_clock::now()).time_since_epoch().count();
}

namespace IType {
    enum T {
        oI = 0,
        oI_2 = 1,
    };
}

class BaseClass
{
public:
    BaseClass(IType::T t)
        : m_type(t)
    {}

    virtual ~BaseClass() {}

    IType::T type()
    {
        return m_type;
    }

private:
    IType::T m_type;
};

class InheritedClass : public BaseClass
{
public:
    static shared_ptr<InheritedClass> CreateShared(const string& some)
    {
        //return shared_ptr<InheritedClass>(new InheritedClass(some));
        return make_shared<InheritedClass>(some);
    }

    static shared_ptr<InheritedClass> CreateShared()
    {
        //return shared_ptr<InheritedClass>(new InheritedClass(some));
        return make_shared<InheritedClass>();
    }

    InheritedClass(const string& some)
        : BaseClass(IType::oI)
        , someFiled(some)
    {}

    InheritedClass()
        : BaseClass(IType::oI)
        , someFiled("")
    {}

    void setField(const string& value)
    {
        someFiled = value;
    }
private:
    string someFiled;
};


class InheritedClass_2 : public BaseClass
{
public:
    static shared_ptr<InheritedClass_2> CreateShared()
    {
        //return shared_ptr<InheritedClass_2>(new InheritedClass_2());
        return make_shared<InheritedClass_2>();
    }

    InheritedClass_2()
        : BaseClass(IType::oI_2)
    {}

    void setField(int value)
    {
        someFiled = value;
    }
private:
    int someFiled;
};

class someclass
{
public:
    someclass()
    {
        int64_t dataSize(0);
        int64_t oldDataSize(0);
        int64_t time0(GetUsecTime());
        int64_t time(time0);

        for (int i = 0; i<8000000; i++)
        {
            // TEST CONSTRUCTORS
            //auto instance=InheritedClass::CreateShared(); // No Problem...
            auto instance = InheritedClass::CreateShared(""); // PROBLEM!! With this line, speed is constantly decreasing

                                                              //TEST CODE:
                                                              //instance->setField("just something"); // PROBLEM!! With this line, speed is constantly decreasing

            V.push_back(instance);

            auto instance_2 = InheritedClass_2::CreateShared();
            instance_2->setField(i);
            V.push_back(instance_2);

            dataSize = i;

            if (GetUsecTime() - time > 1000000)
            {
                time = GetUsecTime();

                cout << "Processed: " << dataSize - oldDataSize << endl;

                oldDataSize = dataSize;
            }
        }

        cout << V.size() << " in " << (GetUsecTime() - time0) / 1000.0 << " ms" << endl;
    }
private:
    vector<shared_ptr<BaseClass> > V;
};

int main(int argc, char *argv[])
{
    someclass s;

    return 0;
}

код работал в QT и Visual Studio. Распечатка из программы QT ниже (уменьшение с 220000 до 67000):

Processed: 31681
Processed: 196038
Processed: 234112
Processed: 229468
Processed: 216378
Processed: 227070
Processed: 198330
Processed: 211321
Processed: 197137
Processed: 151333
Processed: 167995
Processed: 168307
Processed: 163719
Processed: 153696
Processed: 110894
Processed: 143917
Processed: 137006
Processed: 129974
Processed: 127678
Processed: 124093
Processed: 124029
Processed: 123018
Processed: 118595
Processed: 116676
Processed: 115023
Processed: 73030
Processed: 111768
Processed: 110222
Processed: 103588
Processed: 106266
Processed: 105271
Processed: 105031
Processed: 102042
Processed: 100258
Processed: 99404
Processed: 98955
Processed: 97007
Processed: 95901
Processed: 93696
Processed: 91405
Processed: 91061
Processed: 90175
Processed: 87727
Processed: 87448
Processed: 85510
Processed: 84238
Processed: 41837
Processed: 76040
Processed: 75694
Processed: 82918
Processed: 81515
Processed: 80957
Processed: 79657
Processed: 80840
Processed: 79110
Processed: 78720
Processed: 76078
Processed: 76067
Processed: 75412
Processed: 75546
Processed: 74052
Processed: 73386
Processed: 69608
Processed: 66880
Processed: 68731
Processed: 70560
Processed: 68979
Processed: 69985
Processed: 70516
Processed: 68464
Processed: 67379
Processed: 67980
Processed: 67746
Processed: 67332
16000000 in 74537 ms

Распечатка из программы VisualSutio ниже (начальные значения меньше, менее стабильны, но не уменьшаются):

Processed: 81138
Processed: 78107
Processed: 81158
Processed: 101733
Processed: 69418
Processed: 99900
Processed: 54649
Processed: 94161
Processed: 95660
Processed: 31477
Processed: 97066
Processed: 97588
Processed: 99001
Processed: 99554
Processed: 492
Processed: 99197
Processed: 100049
Processed: 99765
Processed: 100066
Processed: 97667
Processed: 93807
Processed: 100146
Processed: 99378
Processed: 99824
Processed: 98228
Processed: 97943
Processed: 99552
Processed: 100299
Processed: 99753
Processed: 90703
Processed: 98276
Processed: 99480
Processed: 99569
Processed: 99528
Processed: 99058
Processed: 98939
Processed: 97637
Processed: 99334
Processed: 99713
Processed: 99540
Processed: 99212
Processed: 99339
Processed: 98781
Processed: 40334
Processed: 98810
Processed: 99134
Processed: 99953
Processed: 99884
Processed: 99891
Processed: 100036
Processed: 100037
Processed: 98182
Processed: 98393
Processed: 99091
Processed: 98359
Processed: 99515
Processed: 100710
Processed: 99065
Processed: 100507
Processed: 99915
Processed: 96591
Processed: 97256
Processed: 100400
Processed: 99551
Processed: 7829
Processed: 100520
Processed: 99480
Processed: 100201
Processed: 99145
Processed: 100898
Processed: 100403
Processed: 99873
Processed: 99761
Processed: 99590
Processed: 99795
Processed: 100142
Processed: 99396
Processed: 99607
Processed: 98091
Processed: 97379
Processed: 98045
Processed: 98448
Processed: 97853
Processed: 98633
Processed: 96140
16000000 in 96518.3 ms