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 <pieter@wuille.net>

src/test/pool_tests.cpp

@@ -0,0 +1,156 @@
+// 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 <support/allocators/pool.h>
+#include <test/util/poolresourcetester.h>
+#include <test/util/random.h>
+#include <test/util/setup_common.h>
+
+#include <boost/test/unit_test.hpp>
+
+#include <cstddef>
+#include <cstdint>
+#include <unordered_map>
+#include <vector>
+
+BOOST_FIXTURE_TEST_SUITE(pool_tests, BasicTestingSetup)
+
+BOOST_AUTO_TEST_CASE(basic_allocating)
+{
+    auto resource = PoolResource<8, 8>();
+    PoolResourceTester::CheckAllDataAccountedFor(resource);
+
+    // first chunk is already allocated
+    size_t expected_bytes_available = resource.ChunkSizeBytes();
+    BOOST_TEST(expected_bytes_available == PoolResourceTester::AvailableMemoryFromChunk(resource));
+
+    // chunk is used, no more allocation
+    void* block = resource.Allocate(8, 8);
+    expected_bytes_available -= 8;
+    BOOST_TEST(expected_bytes_available == PoolResourceTester::AvailableMemoryFromChunk(resource));
+
+    BOOST_TEST(0 == PoolResourceTester::FreeListSizes(resource)[1]);
+    resource.Deallocate(block, 8, 8);
+    PoolResourceTester::CheckAllDataAccountedFor(resource);
+    BOOST_TEST(1 == PoolResourceTester::FreeListSizes(resource)[1]);
+
+    // alignment is too small, but the best fitting freelist is used. Nothing is allocated.
+    void* b = resource.Allocate(8, 1);
+    BOOST_TEST(b == block); // we got the same block of memory as before
+    BOOST_TEST(0 == PoolResourceTester::FreeListSizes(resource)[1]);
+    BOOST_TEST(expected_bytes_available == PoolResourceTester::AvailableMemoryFromChunk(resource));
+
+    resource.Deallocate(block, 8, 1);
+    PoolResourceTester::CheckAllDataAccountedFor(resource);
+    BOOST_TEST(1 == PoolResourceTester::FreeListSizes(resource)[1]);
+    BOOST_TEST(expected_bytes_available == PoolResourceTester::AvailableMemoryFromChunk(resource));
+
+    // can't use resource because alignment is too big, allocate system memory
+    b = resource.Allocate(8, 16);
+    BOOST_TEST(b != block);
+    block = b;
+    PoolResourceTester::CheckAllDataAccountedFor(resource);
+    BOOST_TEST(1 == PoolResourceTester::FreeListSizes(resource)[1]);
+    BOOST_TEST(expected_bytes_available == PoolResourceTester::AvailableMemoryFromChunk(resource));
+
+    resource.Deallocate(block, 8, 16);
+    PoolResourceTester::CheckAllDataAccountedFor(resource);
+    BOOST_TEST(1 == PoolResourceTester::FreeListSizes(resource)[1]);
+    BOOST_TEST(expected_bytes_available == PoolResourceTester::AvailableMemoryFromChunk(resource));
+
+    // can't use chunk because size is too big
+    block = resource.Allocate(16, 8);
+    PoolResourceTester::CheckAllDataAccountedFor(resource);
+    BOOST_TEST(1 == PoolResourceTester::FreeListSizes(resource)[1]);
+    BOOST_TEST(expected_bytes_available == PoolResourceTester::AvailableMemoryFromChunk(resource));
+
+    resource.Deallocate(block, 16, 8);
+    PoolResourceTester::CheckAllDataAccountedFor(resource);
+    BOOST_TEST(1 == PoolResourceTester::FreeListSizes(resource)[1]);
+    BOOST_TEST(expected_bytes_available == PoolResourceTester::AvailableMemoryFromChunk(resource));
+
+    // it's possible that 0 bytes are allocated, make sure this works. In that case the call is forwarded to operator new
+    // 0 bytes takes one entry from the first freelist
+    void* p = resource.Allocate(0, 1);
+    BOOST_TEST(0 == PoolResourceTester::FreeListSizes(resource)[1]);
+    BOOST_TEST(expected_bytes_available == PoolResourceTester::AvailableMemoryFromChunk(resource));
+
+    resource.Deallocate(p, 0, 1);
+    PoolResourceTester::CheckAllDataAccountedFor(resource);
+    BOOST_TEST(1 == PoolResourceTester::FreeListSizes(resource)[1]);
+    BOOST_TEST(expected_bytes_available == PoolResourceTester::AvailableMemoryFromChunk(resource));
+}
+
+// Allocates from 0 to n bytes were n > the PoolResource's data, and each should work
+BOOST_AUTO_TEST_CASE(allocate_any_byte)
+{
+    auto resource = PoolResource<128, 8>(1024);
+
+    uint8_t num_allocs = 200;
+
+    auto data = std::vector<Span<uint8_t>>();
+
+    // allocate an increasing number of bytes
+    for (uint8_t num_bytes = 0; num_bytes < num_allocs; ++num_bytes) {
+        uint8_t* bytes = new (resource.Allocate(num_bytes, 1)) uint8_t[num_bytes];
+        BOOST_TEST(bytes != nullptr);
+        data.emplace_back(bytes, num_bytes);
+
+        // set each byte to num_bytes
+        std::fill(bytes, bytes + num_bytes, num_bytes);
+    }
+
+    // now that we got all allocated, test if all still have the correct values, and give everything back to the allocator
+    uint8_t val = 0;
+    for (auto const& span : data) {
+        for (auto x : span) {
+            BOOST_TEST(val == x);
+        }
+        std::destroy(span.data(), span.data() + span.size());
+        resource.Deallocate(span.data(), span.size(), 1);
+        ++val;
+    }
+
+    PoolResourceTester::CheckAllDataAccountedFor(resource);
+}
+
+BOOST_AUTO_TEST_CASE(random_allocations)
+{
+    struct PtrSizeAlignment {
+        void* ptr;
+        size_t bytes;
+        size_t alignment;
+    };
+
+    // makes a bunch of random allocations and gives all of them back in random order.
+    auto resource = PoolResource<128, 8>(65536);
+    std::vector<PtrSizeAlignment> ptr_size_alignment{};
+    for (size_t i = 0; i < 1000; ++i) {
+        // make it a bit more likely to allocate than deallocate
+        if (ptr_size_alignment.empty() || 0 != InsecureRandRange(4)) {
+            // allocate a random item
+            std::size_t alignment = std::size_t{1} << InsecureRandRange(8);          // 1, 2, ..., 128
+            std::size_t size = (InsecureRandRange(200) / alignment + 1) * alignment; // multiple of alignment
+            void* ptr = resource.Allocate(size, alignment);
+            BOOST_TEST(ptr != nullptr);
+            BOOST_TEST((reinterpret_cast<uintptr_t>(ptr) & (alignment - 1)) == 0);
+            ptr_size_alignment.push_back({ptr, size, alignment});
+        } else {
+            // deallocate a random item
+            auto& x = ptr_size_alignment[InsecureRandRange(ptr_size_alignment.size())];
+            resource.Deallocate(x.ptr, x.bytes, x.alignment);
+            x = ptr_size_alignment.back();
+            ptr_size_alignment.pop_back();
+        }
+    }
+
+    // deallocate all the rest
+    for (auto const& x : ptr_size_alignment) {
+        resource.Deallocate(x.ptr, x.bytes, x.alignment);
+    }
+
+    PoolResourceTester::CheckAllDataAccountedFor(resource);
+}
+
+BOOST_AUTO_TEST_SUITE_END()