benchmarks: add poolmem_fragmentation

This benchmark shows the performance impact when using poolmem. As a
comparison we benchmark against std::string.

core/src/benchmarks/CMakeLists.txt

@@ -59,3 +59,8 @@ bareos_add_benchmark(
   restore_browser_stress_test LINK_LIBRARIES bareos dird_objects bareosfind
   bareoscats bareossql benchmark::benchmark_main
 )
+
+bareos_add_benchmark(
+  poolmem_fragmentation LINK_LIBRARIES bareos benchmark::benchmark_main
+  Threads::Threads
+)

core/src/benchmarks/poolmem_fragmentation.cc

@@ -0,0 +1,100 @@
+/*
+   BAREOS® - Backup Archiving REcovery Open Sourced
+
+   Copyright (C) 2021-2021 Bareos GmbH & Co. KG
+
+   This program is Free Software; you can redistribute it and/or
+   modify it under the terms of version three of the GNU Affero General Public
+   License as published by the Free Software Foundation and included
+   in the file LICENSE.
+
+   This program is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+   Affero General Public License for more details.
+
+   You should have received a copy of the GNU Affero General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+   02110-1301, USA.
+*/
+#include <vector>
+#include <random>
+#include <algorithm>
+
+#include <benchmark/benchmark.h>
+#include <lib/mem_pool.h>
+
+#include <iostream>
+
+namespace bm = benchmark;
+
+double operator"" _percent(unsigned long long int p) { return p / 100.0; }
+
+double operator"" _percent(long double p) { return p / 100.0; }
+
+static void allocate_memory(size_t count, std::vector<POOLMEM*>& handles)
+{
+  for (size_t i{0}; i < count; ++i) {
+    handles.emplace_back(GetPoolMemory(PM_NAME));
+  }
+}
+
+static void fragment_pool_mem(size_t allocations,
+                              double free_percentage,
+                              std::vector<POOLMEM*>& pool_handles)
+{
+  allocate_memory(allocations, pool_handles);
+
+  /*
+   * initialize a mersenne twister RNG with fixed seed, so
+   * we get the same "randomness" everywhere
+   */
+  std::mt19937 stable_rng{1};
+  std::shuffle(pool_handles.begin(), pool_handles.end(), stable_rng);
+
+  const auto free_items{static_cast<size_t>(allocations * free_percentage)};
+  for (size_t i{0}; i < free_items; ++i) {
+    FreePoolMemory(pool_handles.back());
+    pool_handles.pop_back();
+  }
+}
+
+
+class Fragmentator {
+  std::vector<POOLMEM*> pool_handles{};
+
+ public:
+  Fragmentator() { fragment_pool_mem(100'000, 50_percent, pool_handles); }
+
+  ~Fragmentator()
+  {
+    while (pool_handles.size() > 0) {
+      FreePoolMemory(pool_handles.back());
+      pool_handles.pop_back();
+    }
+  }
+};
+
+// constructed before main() is called
+static Fragmentator frag;
+
+static void BM_PoolMem(bm::State& state)
+{
+  for (auto _ : state) {
+    PoolMem string;
+    bm::DoNotOptimize(string);
+  }
+}
+BENCHMARK(BM_PoolMem);
+
+static void BM_stdString(bm::State& state)
+{
+  for (auto _ : state) {
+    std::string string;
+    bm::DoNotOptimize(string);
+  }
+}
+BENCHMARK(BM_stdString);
+
+BENCHMARK_MAIN();

core/src/lib/mem_pool.h

@@ -2,7 +2,7 @@
    BAREOS® - Backup Archiving REcovery Open Sourced
 
    Copyright (C) 2000-2011 Free Software Foundation Europe e.V.
-   Copyright (C) 2016-2019 Bareos GmbH & Co. KG
+   Copyright (C) 2016-2021 Bareos GmbH & Co. KG
 
    This program is Free Software; you can redistribute it and/or
    modify it under the terms of version three of the GNU Affero General Public
@@ -28,6 +28,10 @@
 #ifndef BAREOS_LIB_MEM_POOL_H_
 #define BAREOS_LIB_MEM_POOL_H_
 
+#include <stdarg.h>
+#include <string.h>
+#include <include/bc_types.h>
+
 POOLMEM* GetPoolMemory(int pool);
 POOLMEM* GetMemory(int32_t size);
 int32_t SizeofPoolMemory(POOLMEM* buf);