The following code example is taken from the book
C++17 - The Complete Guide by Nicolai M. Josuttis, Leanpub, 2017
The code is licensed under a Creative Commons Attribution 4.0 International License. Creative Commons License

// raw code

#include "tracker.hpp"
#include <iostream>
#include <string>
#include <vector>
#include <memory_resource>

int main()
   // track allocating chunks of memory (starting with 10k) without deallocating:
   Tracker track1{"keeppool:"};
   std::pmr::monotonic_buffer_resource keeppool{10000, &track1};
     Tracker track2{"  syncpool:", &keeppool};
     std::pmr::synchronized_pool_resource pool{&track2};

     for (int j=0; j < 100; ++j) {
        std::pmr::vector<std::pmr::string> coll{&pool};
        for (int i=0; i < 100; ++i) {
           coll.emplace_back("just a non-SSO string");
        if (j==2) std::cout << "--- third iteration done\n";
     } // deallocations are given back to pool, but not deallocated
     // so far nothing was allocated
     std::cout << "--- leave scope of pool\n";
   std::cout << "--- leave scope of keeppool\n";
  } // deallocates all allocated memory