kernel: Move kernel-specific cache size options to kernel

Carrying non-kernel related fields in the cache sizes for the indexes is
confusing for kernel library users. The cache sizes also are set
currently with magic numbers in bitcoin-chainstate. The comments for the
cache size calculations are also not completely clear.

Solve these things by moving the kernel-specific cache size fields to
their own struct.

This slightly changes the way the cache is allocated if the txindex
and/or blockfilterindex is used. Since they are now given precedence
over the block tree db cache, this results in a bit less cache being
allocated to the block tree db, coinsdb and coins caches. The effect is
negligible though, i.e. cache sizes with default dbcache reported
through the logs are:

master:
Cache configuration:
* Using 2.0 MiB for block index database
* Using 56.0 MiB for transaction index database
* Using 49.0 MiB for basic block filter index database
* Using 8.0 MiB for chain state database
* Using 335.0 MiB for in-memory UTXO set (plus up to 286.1 MiB of unused mempool space)

this branch:
Cache configuration:
* Using 2.0 MiB for block index database
* Using 56.2 MiB for transaction index database
* Using 49.2 MiB for basic block filter index database
* Using 8.0 MiB for chain state database
* Using 334.5 MiB for in-memory UTXO set (plus up to 286.1 MiB of unused mempool space)

src/bitcoin-chainstate.cpp

@@ -123,10 +123,7 @@ int main(int argc, char* argv[])
     util::SignalInterrupt interrupt;
     ChainstateManager chainman{interrupt, chainman_opts, blockman_opts};
 
-    node::CacheSizes cache_sizes;
+    kernel::CacheSizes cache_sizes{nDefaultDbCache << 20};
-    cache_sizes.block_tree_db = 2 << 20;
-    cache_sizes.coins_db = 2 << 22;
-    cache_sizes.coins = (450 << 20) - (2 << 20) - (2 << 22);
     node::ChainstateLoadOptions options;
     auto [status, error] = node::LoadChainstate(chainman, cache_sizes, options);
     if (status != node::ChainstateLoadStatus::SUCCESS) {

src/init.cpp

@@ -32,6 +32,7 @@
 #include <interfaces/ipc.h>
 #include <interfaces/mining.h>
 #include <interfaces/node.h>
+#include <kernel/caches.h>
 #include <kernel/context.h>
 #include <key.h>
 #include <logging.h>
@@ -121,7 +122,6 @@ using common::ResolveErrMsg;
 
 using node::ApplyArgsManOptions;
 using node::BlockManager;
-using node::CacheSizes;
 using node::CalculateCacheSizes;
 using node::ChainstateLoadResult;
 using node::ChainstateLoadStatus;
@@ -1177,7 +1177,7 @@ static ChainstateLoadResult InitAndLoadChainstate(
     NodeContext& node,
     bool do_reindex,
     const bool do_reindex_chainstate,
-    CacheSizes& cache_sizes,
+    const kernel::CacheSizes& cache_sizes,
     const ArgsManager& args)
 {
     const CChainParams& chainparams = Params();
@@ -1603,18 +1603,18 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
     ReadNotificationArgs(args, kernel_notifications);
 
     // cache size calculations
-    CacheSizes cache_sizes = CalculateCacheSizes(args, g_enabled_filter_types.size());
+    const auto [index_cache_sizes, kernel_cache_sizes] = CalculateCacheSizes(args, g_enabled_filter_types.size());
 
-    LogPrintf("Cache configuration:\n");
+    LogInfo("Cache configuration:");
-    LogPrintf("* Using %.1f MiB for block index database\n", cache_sizes.block_tree_db * (1.0 / 1024 / 1024));
+    LogInfo("* Using %.1f MiB for block index database", kernel_cache_sizes.block_tree_db * (1.0 / 1024 / 1024));
     if (args.GetBoolArg("-txindex", DEFAULT_TXINDEX)) {
-        LogPrintf("* Using %.1f MiB for transaction index database\n", cache_sizes.tx_index * (1.0 / 1024 / 1024));
+        LogInfo("* Using %.1f MiB for transaction index database", index_cache_sizes.tx_index * (1.0 / 1024 / 1024));
     }
     for (BlockFilterType filter_type : g_enabled_filter_types) {
-        LogPrintf("* Using %.1f MiB for %s block filter index database\n",
+        LogInfo("* Using %.1f MiB for %s block filter index database",
-                  cache_sizes.filter_index * (1.0 / 1024 / 1024), BlockFilterTypeName(filter_type));
+                  index_cache_sizes.filter_index * (1.0 / 1024 / 1024), BlockFilterTypeName(filter_type));
     }
-    LogPrintf("* Using %.1f MiB for chain state database\n", cache_sizes.coins_db * (1.0 / 1024 / 1024));
+    LogInfo("* Using %.1f MiB for chain state database", kernel_cache_sizes.coins_db * (1.0 / 1024 / 1024));
 
     assert(!node.mempool);
     assert(!node.chainman);
@@ -1627,7 +1627,7 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
         node,
         do_reindex,
         do_reindex_chainstate,
-        cache_sizes,
+        kernel_cache_sizes,
         args);
     if (status == ChainstateLoadStatus::FAILURE && !do_reindex && !ShutdownRequested(node)) {
         // suggest a reindex
@@ -1646,7 +1646,7 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
             node,
             do_reindex,
             do_reindex_chainstate,
-            cache_sizes,
+            kernel_cache_sizes,
             args);
     }
     if (status != ChainstateLoadStatus::SUCCESS && status != ChainstateLoadStatus::INTERRUPTED) {
@@ -1672,12 +1672,12 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
     // ********************************************************* Step 8: start indexers
 
     if (args.GetBoolArg("-txindex", DEFAULT_TXINDEX)) {
-        g_txindex = std::make_unique<TxIndex>(interfaces::MakeChain(node), cache_sizes.tx_index, false, do_reindex);
+        g_txindex = std::make_unique<TxIndex>(interfaces::MakeChain(node), index_cache_sizes.tx_index, false, do_reindex);
         node.indexes.emplace_back(g_txindex.get());
     }
 
     for (const auto& filter_type : g_enabled_filter_types) {
-        InitBlockFilterIndex([&]{ return interfaces::MakeChain(node); }, filter_type, cache_sizes.filter_index, false, do_reindex);
+        InitBlockFilterIndex([&]{ return interfaces::MakeChain(node); }, filter_type, index_cache_sizes.filter_index, false, do_reindex);
         node.indexes.emplace_back(GetBlockFilterIndex(filter_type));
     }
 

src/kernel/caches.h

@@ -0,0 +1,34 @@
+// Copyright (c) 2024-present The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_KERNEL_CACHES_H
+#define BITCOIN_KERNEL_CACHES_H
+
+#include <util/byte_units.h>
+
+#include <algorithm>
+
+//! Max memory allocated to block tree DB specific cache (bytes)
+static constexpr size_t MAX_BLOCK_DB_CACHE{2_MiB};
+//! Max memory allocated to coin DB specific cache (bytes)
+static constexpr size_t MAX_COINS_DB_CACHE{8_MiB};
+
+namespace kernel {
+struct CacheSizes {
+    size_t block_tree_db;
+    size_t coins_db;
+    size_t coins;
+
+    CacheSizes(size_t total_cache)
+    {
+        block_tree_db = std::min(total_cache / 8, MAX_BLOCK_DB_CACHE);
+        total_cache -= block_tree_db;
+        coins_db = std::min(total_cache / 2, MAX_COINS_DB_CACHE);
+        total_cache -= coins_db;
+        coins = total_cache; // the rest goes to the coins cache
+    }
+};
+} // namespace kernel
+
+#endif // BITCOIN_KERNEL_CACHES_H

src/node/caches.cpp

@@ -6,27 +6,25 @@
 
 #include <common/args.h>
 #include <index/txindex.h>
+#include <kernel/caches.h>
 #include <txdb.h>
 
+#include <algorithm>
+#include <string>
+
 namespace node {
 CacheSizes CalculateCacheSizes(const ArgsManager& args, size_t n_indexes)
 {
     int64_t nTotalCache = (args.GetIntArg("-dbcache", nDefaultDbCache) << 20);
     nTotalCache = std::max(nTotalCache, nMinDbCache << 20); // total cache cannot be less than nMinDbCache
-    CacheSizes sizes;
+    IndexCacheSizes sizes;
-    sizes.block_tree_db = std::min(nTotalCache / 8, nMaxBlockDBCache << 20);
-    nTotalCache -= sizes.block_tree_db;
     sizes.tx_index = std::min(nTotalCache / 8, args.GetBoolArg("-txindex", DEFAULT_TXINDEX) ? nMaxTxIndexCache << 20 : 0);
     nTotalCache -= sizes.tx_index;
-    sizes.filter_index = 0;
     if (n_indexes > 0) {
         int64_t max_cache = std::min(nTotalCache / 8, max_filter_index_cache << 20);
         sizes.filter_index = max_cache / n_indexes;
         nTotalCache -= sizes.filter_index * n_indexes;
     }
-    sizes.coins_db = std::min(nTotalCache / 2, nMaxCoinsDBCache << 20);
+    return {sizes, kernel::CacheSizes{static_cast<size_t>(nTotalCache)}};
-    nTotalCache -= sizes.coins_db;
-    sizes.coins = nTotalCache; // the rest goes to in-memory cache
-    return sizes;
 }
 } // namespace node

src/node/caches.h

@@ -5,18 +5,21 @@
 #ifndef BITCOIN_NODE_CACHES_H
 #define BITCOIN_NODE_CACHES_H
 
+#include <kernel/caches.h>
+
 #include <cstddef>
 #include <cstdint>
 
 class ArgsManager;
 
 namespace node {
+struct IndexCacheSizes {
+    int64_t tx_index{0};
+    int64_t filter_index{0};
+};
 struct CacheSizes {
-    int64_t block_tree_db;
+    IndexCacheSizes index;
-    int64_t coins_db;
+    kernel::CacheSizes kernel;
-    int64_t coins;
-    int64_t tx_index;
-    int64_t filter_index;
 };
 CacheSizes CalculateCacheSizes(const ArgsManager& args, size_t n_indexes = 0);
 } // namespace node

src/node/chainstate.cpp

@@ -8,9 +8,9 @@
 #include <chain.h>
 #include <coins.h>
 #include <consensus/params.h>
+#include <kernel/caches.h>
 #include <logging.h>
 #include <node/blockstorage.h>
-#include <node/caches.h>
 #include <sync.h>
 #include <threadsafety.h>
 #include <tinyformat.h>
@@ -29,6 +29,8 @@
 #include <memory>
 #include <vector>
 
+using kernel::CacheSizes;
+
 namespace node {
 // Complete initialization of chainstates after the initial call has been made
 // to ChainstateManager::InitializeChainstate().

src/node/chainstate.h

@@ -14,9 +14,11 @@
 
 class CTxMemPool;
 
-namespace node {
+namespace kernel {
-
 struct CacheSizes;
+} // namespace kernel
+
+namespace node {
 
 struct ChainstateLoadOptions {
     CTxMemPool* mempool{nullptr};
@@ -69,7 +71,7 @@ using ChainstateLoadResult = std::tuple<ChainstateLoadStatus, bilingual_str>;
  *
  *  LoadChainstate returns a (status code, error string) tuple.
  */
-ChainstateLoadResult LoadChainstate(ChainstateManager& chainman, const CacheSizes& cache_sizes,
+ChainstateLoadResult LoadChainstate(ChainstateManager& chainman, const kernel::CacheSizes& cache_sizes,
                                     const ChainstateLoadOptions& options);
 ChainstateLoadResult VerifyLoadedChainstate(ChainstateManager& chainman, const ChainstateLoadOptions& options);
 } // namespace node

src/test/util/setup_common.cpp

@@ -66,7 +66,6 @@ using kernel::BlockTreeDB;
 using node::ApplyArgsManOptions;
 using node::BlockAssembler;
 using node::BlockManager;
-using node::CalculateCacheSizes;
 using node::KernelNotifications;
 using node::LoadChainstate;
 using node::RegenerateCommitments;
@@ -228,8 +227,6 @@ ChainTestingSetup::ChainTestingSetup(const ChainType chainType, TestOpts opts)
     Assert(error.empty());
     m_node.warnings = std::make_unique<node::Warnings>();
 
-    m_cache_sizes = CalculateCacheSizes(m_args);
-
     m_node.notifications = std::make_unique<KernelNotifications>(Assert(m_node.shutdown_request), m_node.exit_status, *Assert(m_node.warnings));
 
     m_make_chainman = [this, &chainparams, opts] {
@@ -255,7 +252,7 @@ ChainTestingSetup::ChainTestingSetup(const ChainType chainType, TestOpts opts)
         LOCK(m_node.chainman->GetMutex());
         m_node.chainman->m_blockman.m_block_tree_db = std::make_unique<BlockTreeDB>(DBParams{
             .path = m_args.GetDataDirNet() / "blocks" / "index",
-            .cache_bytes = static_cast<size_t>(m_cache_sizes.block_tree_db),
+            .cache_bytes = static_cast<size_t>(m_kernel_cache_sizes.block_tree_db),
             .memory_only = true,
         });
     };
@@ -291,7 +288,7 @@ void ChainTestingSetup::LoadVerifyActivateChainstate()
     options.check_blocks = m_args.GetIntArg("-checkblocks", DEFAULT_CHECKBLOCKS);
     options.check_level = m_args.GetIntArg("-checklevel", DEFAULT_CHECKLEVEL);
     options.require_full_verification = m_args.IsArgSet("-checkblocks") || m_args.IsArgSet("-checklevel");
-    auto [status, error] = LoadChainstate(chainman, m_cache_sizes, options);
+    auto [status, error] = LoadChainstate(chainman, m_kernel_cache_sizes, options);
     assert(status == node::ChainstateLoadStatus::SUCCESS);
 
     std::tie(status, error) = VerifyLoadedChainstate(chainman, options);

src/test/util/setup_common.h

@@ -6,6 +6,7 @@
 #define BITCOIN_TEST_UTIL_SETUP_COMMON_H
 
 #include <common/args.h> // IWYU pragma: export
+#include <kernel/caches.h>
 #include <kernel/context.h>
 #include <key.h>
 #include <node/caches.h>
@@ -103,7 +104,7 @@ struct BasicTestingSetup {
  * initialization behaviour.
  */
 struct ChainTestingSetup : public BasicTestingSetup {
-    node::CacheSizes m_cache_sizes{};
+    kernel::CacheSizes m_kernel_cache_sizes{node::CalculateCacheSizes(m_args).kernel};
     bool m_coins_db_in_memory{true};
     bool m_block_tree_db_in_memory{true};
     std::function<void()> m_make_chainman{};

src/txdb.h

@@ -27,16 +27,12 @@ static const int64_t nDefaultDbCache = 450;
 static const int64_t nDefaultDbBatchSize = 16 << 20;
 //! min. -dbcache (MiB)
 static const int64_t nMinDbCache = 4;
-//! Max memory allocated to block tree DB specific cache (MiB)
-static const int64_t nMaxBlockDBCache = 2;
 // Unlike for the UTXO database, for the txindex scenario the leveldb cache make
 // a meaningful difference: https://github.com/bitcoin/bitcoin/pull/8273#issuecomment-229601991
 //! Max memory allocated to tx index DB specific cache in MiB.
 static const int64_t nMaxTxIndexCache = 1024;
 //! Max memory allocated to all block filter index caches combined in MiB.
 static const int64_t max_filter_index_cache = 1024;
-//! Max memory allocated to coin DB specific cache (MiB)
-static const int64_t nMaxCoinsDBCache = 8;
 
 //! User-controlled performance and debug options.
 struct CoinsViewOptions {