kernel: allow setting chainstate `dbcache`

diff --git a/src/kernel/bitcoinkernel.cpp b/src/kernel/bitcoinkernel.cpp
index 52090c44..d27e7e9d 100644
--- a/src/kernel/bitcoinkernel.cpp
+++ b/src/kernel/bitcoinkernel.cpp
@@ -455,6 +455,7 @@ struct ChainstateManagerOptions {
     node::BlockManager::Options m_blockman_options GUARDED_BY(m_mutex);
     std::shared_ptr<const Context> m_context;
     node::ChainstateLoadOptions m_chainstate_load_options GUARDED_BY(m_mutex);
+    uint64_t m_db_cache_bytes GUARDED_BY(m_mutex){DEFAULT_KERNEL_CACHE};
 
     ChainstateManagerOptions(const std::shared_ptr<const Context>& context, const fs::path& data_dir, const fs::path& blocks_dir)
         : m_chainman_options{ChainstateManager::Options{
@@ -1031,6 +1032,20 @@ void btck_chainstate_manager_options_set_worker_threads_num(btck_ChainstateManag
     btck_ChainstateManagerOptions::get(opts).m_chainman_options.worker_threads_num = worker_threads;
 }
 
+int btck_chainstate_manager_options_set_database_cache_bytes(btck_ChainstateManagerOptions* chainman_opts, uint64_t database_cache_bytes)
+{
+    if (database_cache_bytes < MIN_DBCACHE_BYTES || database_cache_bytes > MAX_DBCACHE_BYTES) {
+        LogError("Failed to set database cache: size is outside the supported range.");
+        return -1;
+    }
+
+    auto& opts{btck_ChainstateManagerOptions::get(chainman_opts)};
+    LOCK(opts.m_mutex);
+    opts.m_db_cache_bytes = database_cache_bytes;
+    opts.m_blockman_options.block_tree_db_params.cache_bytes = kernel::CacheSizes{database_cache_bytes}.block_tree_db;
+    return 0;
+}
+
 void btck_chainstate_manager_options_destroy(btck_ChainstateManagerOptions* options)
 {
     delete options;
@@ -1083,7 +1098,7 @@ btck_ChainstateManager* btck_chainstate_manager_create(
     try {
         const auto chainstate_load_opts{WITH_LOCK(opts.m_mutex, return opts.m_chainstate_load_options)};
 
-        kernel::CacheSizes cache_sizes{DEFAULT_KERNEL_CACHE};
+        const kernel::CacheSizes cache_sizes{WITH_LOCK(opts.m_mutex, return opts.m_db_cache_bytes)};
         auto [status, chainstate_err]{node::LoadChainstate(*chainman, cache_sizes, chainstate_load_opts)};
         if (status != node::ChainstateLoadStatus::SUCCESS) {
             LogError("Failed to load chain state from your data directory: %s", chainstate_err.original);
diff --git a/src/kernel/bitcoinkernel.h b/src/kernel/bitcoinkernel.h
index 86ef2e2c..f474a7ca 100644
--- a/src/kernel/bitcoinkernel.h
+++ b/src/kernel/bitcoinkernel.h
@@ -1195,6 +1195,22 @@ BITCOINKERNEL_API void btck_chainstate_manager_options_set_worker_threads_num(
     btck_ChainstateManagerOptions* chainstate_manager_options,
     int worker_threads) BITCOINKERNEL_ARG_NONNULL(1);
 
+/**
+ * @brief Set the total database cache used by the chainstate manager.
+ *
+ * The total cache is split internally between the block tree database,
+ * chainstate database, and in-memory coins cache. If this function is not
+ * called, the total cache defaults to 450 MiB.
+ *
+ * @param[in] chainstate_manager_options Non-null, options to be set.
+ * @param[in] database_cache_bytes       The total database cache size in bytes. Values below 4 MiB are rejected.
+ *                                       On 32-bit systems, values above 1 GiB are also rejected.
+ * @return                               0 if the set was successful, non-zero if the set failed.
+ */
+BITCOINKERNEL_API int BITCOINKERNEL_WARN_UNUSED_RESULT btck_chainstate_manager_options_set_database_cache_bytes(
+    btck_ChainstateManagerOptions* chainstate_manager_options,
+    uint64_t database_cache_bytes) BITCOINKERNEL_ARG_NONNULL(1);
+
 /**
  * @brief Sets wipe db in the options. In combination with calling
  * @ref btck_chainstate_manager_import_blocks this triggers either a full reindex,
diff --git a/src/kernel/bitcoinkernel_wrapper.h b/src/kernel/bitcoinkernel_wrapper.h
index 5f251d30..5dc203b4 100644
--- a/src/kernel/bitcoinkernel_wrapper.h
+++ b/src/kernel/bitcoinkernel_wrapper.h
@@ -1200,6 +1200,11 @@ public:
         btck_chainstate_manager_options_set_worker_threads_num(get(), worker_threads);
     }
 
+    bool SetDatabaseCacheBytes(uint64_t database_cache_bytes)
+    {
+        return btck_chainstate_manager_options_set_database_cache_bytes(get(), database_cache_bytes) == 0;
+    }
+
     bool SetWipeDbs(bool wipe_block_tree, bool wipe_chainstate)
     {
         return btck_chainstate_manager_options_set_wipe_dbs(get(), wipe_block_tree, wipe_chainstate) == 0;
diff --git a/src/test/kernel/test_kernel.cpp b/src/test/kernel/test_kernel.cpp
index 927d2b16..83613dbb 100644
--- a/src/test/kernel/test_kernel.cpp
+++ b/src/test/kernel/test_kernel.cpp
@@ -4,6 +4,7 @@
 
 #include <kernel/bitcoinkernel.h>
 #include <kernel/bitcoinkernel_wrapper.h>
+#include <util/byte_units.h>
 #include <util/fs.h>
 
 #define BOOST_TEST_MODULE Bitcoin Kernel Test Suite
@@ -800,6 +801,9 @@ BOOST_AUTO_TEST_CASE(btck_chainman_tests)
 
     ChainstateManagerOptions chainman_opts{context, PathToString(test_directory.m_directory), PathToString(test_directory.m_directory / "blocks")};
     chainman_opts.SetWorkerThreads(4);
+    BOOST_CHECK(!chainman_opts.SetDatabaseCacheBytes(4_MiB - 1));
+    if constexpr (sizeof(void*) == 4) BOOST_CHECK(!chainman_opts.SetDatabaseCacheBytes(2_GiB));
+    BOOST_CHECK(chainman_opts.SetDatabaseCacheBytes(4_MiB));
     BOOST_CHECK(!chainman_opts.SetWipeDbs(/*wipe_block_tree=*/true, /*wipe_chainstate=*/false));
     BOOST_CHECK(chainman_opts.SetWipeDbs(/*wipe_block_tree=*/true, /*wipe_chainstate=*/true));
     BOOST_CHECK(chainman_opts.SetWipeDbs(/*wipe_block_tree=*/false, /*wipe_chainstate=*/true));