I have a question related to memory in C++ on Linux platform.
Here is my source code:

#include <deque>
#include <iostream>
#include <vector>
#include <unistd.h>               // for linux
#include <fstream>

using namespace std;

class dog
{
public:
    dog(size_t size): _size(size),
        _values_1_f(size),
        _values_2_f(size),
        _values_1_uc(_size),
        _values_2_uc(_size)
    {
    }

    virtual ~dog();

    std::vector<unsigned char> values_1_f() const;

private:

    const size_t _size;
    std::vector<unsigned char>                  _values_1_f;
    std::vector<char>                           _values_2_f;

    std::vector<unsigned char>                  _values_1_uc;
    std::vector<unsigned char>                  _values_2_uc;
};


int32_t printMem()
{
    // Open the /proc/self/statm file
    std::ifstream statm_file("/proc/self/statm");

    if (!statm_file) {
        std::cerr << "Error opening /proc/self/statm" << std::endl;
        return 1;
    }

    // Read the contents of the file
    long pages, resident, shared, text, lib, data, dt;
    statm_file >> pages >> resident >> shared >> text >> lib >> data >> dt;

    statm_file.close();

    // Get the page size
    long page_size_kb = sysconf(_SC_PAGESIZE) / 1024;

    // Calculate memory usage in KB
    long total_memory = pages * page_size_kb;
    long resident_memory = resident * page_size_kb;
    long shared_memory = shared * page_size_kb;
    long text_memory = text * page_size_kb;
    long data_memory = data * page_size_kb;

    // Print the memory usage
    std::cout << "Total memory: " << total_memory << " KB" << std::endl;
    std::cout << "Resident memory: " << resident_memory << " KB" << std::endl;
    std::cout << "Shared memory: " << shared_memory << " KB" << std::endl;
    std::cout << "Text memory: " << text_memory << " KB" << std::endl;
    std::cout << "Data memory: " << data_memory << " KB" << std::endl;
}

int main()
{
    std::deque<dog *> _dogs;

    while(1)
    {
        for(int i = 0; i < 800000; i++)
        {
            _dogs.push_back(new dog(800));
        }

        std::cout << "After memory allocation"<< std::endl<< std::endl;;

        printMem();
        std::cout << std::endl<< std::endl;;


        for (auto i = _dogs.begin(); i != _dogs.end() ; ) {
            delete *i;
            i = _dogs.erase(i); // erase returns the next iterator
        }

        _dogs.clear();

        sleep(10);
        std::cout << "After memory clean"<< std::endl;
        printMem();

        std::cout << std::endl<< std::endl;;
    }

    return 0;
}

dog::~dog()
{

}

std::vector<unsigned char> dog::values_1_f() const
{
    return _values_1_f;
}

I try to allocate, in the while loop, a set of dog and push them in the _dogs dequeue.
After allocation I try to deallocate the previously allocated memory.
Here is my problem.
Both the call to printMem print the same message (so it seems no memory has been cleaned, even having a look at htop), but multiple iterations of the while loop do not make the memory grow up.

So my question is: do you have any idea why this happens? If the delete fails, the memory should grow up while performing iterations. If the delete succeds, the memory after the delete should be much lower that after the new operation.
Any hint will be appreciated.
If you have some link explaining my error, please share them, I’m quite lost in programming….