Added a test that shows catastrophic behaviour of mimalloc

dbms/src/Common/tests/CMakeLists.txt

@@ -75,3 +75,6 @@ target_link_libraries (cow_compositions PRIVATE clickhouse_common_io)
 
 add_executable (stopwatch stopwatch.cpp)
 target_link_libraries (stopwatch PRIVATE clickhouse_common_io)
+
+add_executable (mi_malloc_test mi_malloc_test.cpp)
+target_link_libraries (mi_malloc_test PRIVATE clickhouse_common_io)

dbms/src/Common/tests/mi_malloc_test.cpp

@@ -0,0 +1,92 @@
+#include <Common/config.h>
+
+//#undef USE_MIMALLOC
+//#define USE_MIMALLOC 0
+
+#if USE_MIMALLOC
+
+#include <mimalloc.h>
+#define malloc mi_malloc
+#define free mi_free
+
+#else
+
+#include <stdlib.h>
+
+#endif
+
+#include <map>
+#include <vector>
+#include <cstdint>
+#include <random>
+#include <stdexcept>
+#include <iostream>
+
+
+size_t total_size{0};
+
+struct Allocation
+{
+    void * ptr = nullptr;
+    size_t size = 0;
+
+    Allocation() {}
+
+    Allocation(size_t size)
+        : size(size)
+    {
+        ptr = malloc(size);
+        if (!ptr)
+            throw std::runtime_error("Cannot allocate memory");
+        total_size += size;
+    }
+
+    ~Allocation()
+    {
+        if (ptr)
+        {
+            free(ptr);
+            total_size -= size;
+        }
+        ptr = nullptr;
+    }
+
+    Allocation(const Allocation &) = delete;
+
+    Allocation(Allocation && rhs)
+    {
+        ptr = rhs.ptr;
+        size = rhs.size;
+        rhs.ptr = nullptr;
+        rhs.size = 0;
+    }
+};
+
+
+int main(int, char **)
+{
+    std::vector<Allocation> allocations;
+
+    constexpr size_t limit = 100000000;
+    constexpr size_t min_alloc_size = 65536;
+    constexpr size_t max_alloc_size = 10000000;
+
+    std::mt19937 rng;
+    auto distribution = std::uniform_int_distribution(min_alloc_size, max_alloc_size);
+
+    size_t total_allocations = 0;
+
+    while (true)
+    {
+        size_t size = distribution(rng);
+
+        while (total_size + size > limit)
+            allocations.pop_back();
+
+        allocations.emplace_back(size);
+
+        ++total_allocations;
+        if (total_allocations % (1ULL << 20) == 0)
+            std::cerr << "Total allocations: " << total_allocations << "\n";
+    }
+}