Add pool based memory resource & allocator

A memory resource similar to std::pmr::unsynchronized_pool_resource, but
optimized for node-based containers.

Co-Authored-By: Pieter Wuille <[email protected]>

Author: martinus

src/Makefile.am

@@ -261,6 +261,7 @@ BITCOIN_CORE_H = \
   shutdown.h \
   signet.h \
   streams.h \
+  support/allocators/pool.h \
   support/allocators/secure.h \
   support/allocators/zeroafterfree.h \
   support/cleanse.h \

src/Makefile.bench.include

@@ -42,6 +42,7 @@ bench_bench_bitcoin_SOURCES = \
   bench/nanobench.h \
   bench/peer_eviction.cpp \
   bench/poly1305.cpp \
+  bench/pool.cpp \
   bench/prevector.cpp \
   bench/rollingbloom.cpp \
   bench/rpc_blockchain.cpp \

src/Makefile.test.include

@@ -116,6 +116,7 @@ BITCOIN_TESTS =\
   test/pmt_tests.cpp \
   test/policy_fee_tests.cpp \
   test/policyestimator_tests.cpp \
+  test/pool_tests.cpp \
   test/pow_tests.cpp \
   test/prevector_tests.cpp \
   test/raii_event_tests.cpp \

src/Makefile.test_util.include

@@ -15,6 +15,7 @@ TEST_UTIL_H = \
   test/util/logging.h \
   test/util/mining.h \
   test/util/net.h \
+  test/util/poolresourcetester.h \
   test/util/random.h \
   test/util/script.h \
   test/util/setup_common.h \

src/bench/pool.cpp

@@ -0,0 +1,50 @@
+// Copyright (c) 2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <bench/bench.h>
+#include <support/allocators/pool.h>
+
+#include <unordered_map>
+
+template <typename Map>
+void BenchFillClearMap(benchmark::Bench& bench, Map& map)
+{
+    size_t batch_size = 5000;
+
+    // make sure each iteration of the benchmark contains exactly 5000 inserts and one clear.
+    // do this at least 10 times so we get reasonable accurate results
+
+    bench.batch(batch_size).minEpochIterations(10).run([&] {
+        auto rng = ankerl::nanobench::Rng(1234);
+        for (size_t i = 0; i < batch_size; ++i) {
+            map[rng()];
+        }
+        map.clear();
+    });
+}
+
+static void PoolAllocator_StdUnorderedMap(benchmark::Bench& bench)
+{
+    auto map = std::unordered_map<uint64_t, uint64_t>();
+    BenchFillClearMap(bench, map);
+}
+
+static void PoolAllocator_StdUnorderedMapWithPoolResource(benchmark::Bench& bench)
+{
+    using Map = std::unordered_map<uint64_t,
+                                   uint64_t,
+                                   std::hash<uint64_t>,
+                                   std::equal_to<uint64_t>,
+                                   PoolAllocator<std::pair<const uint64_t, uint64_t>,
+                                                 sizeof(std::pair<const uint64_t, uint64_t>) + 4 * sizeof(void*),
+                                                 alignof(void*)>>;
+
+    // make sure the resource supports large enough pools to hold the node. We do this by adding the size of a few pointers to it.
+    auto pool_resource = Map::allocator_type::ResourceType();
+    auto map = Map{0, std::hash<uint64_t>{}, std::equal_to<uint64_t>{}, &pool_resource};
+    BenchFillClearMap(bench, map);
+}
+
+BENCHMARK(PoolAllocator_StdUnorderedMap, benchmark::PriorityLevel::HIGH);
+BENCHMARK(PoolAllocator_StdUnorderedMapWithPoolResource, benchmark::PriorityLevel::HIGH);