Merge #1510: Merge bitcoin#32530: node: cap -maxmempool and -dbcache for 32 bit systems.

8ea4b7a Merge bitcoin/bitcoin#32530: node: cap `-maxmempool` and `-dbcache` values for 32-bit (merge-script)

Pull request description:

  Backport of bitcoin/bitcoin#32530

ACKs for top commit:
  delta1:
    ACK 8ea4b7a

Tree-SHA512: fc8aea76fd49e05ca2499c40e657451890d84b5424c124b594768821a231138eef64d9b331ccbfa7a2f0e224def45f7f4630a15a7a609d32b68ebfcba76ac64b

Author: delta1

src/init.cpp

@@ -131,6 +131,7 @@ static const bool DEFAULT_REST_ENABLE = false;
 #endif
 
 static const char* DEFAULT_ASMAP_FILENAME="ip_asn.map";
+static constexpr int MAX_32BIT_MEMPOOL_MB{500};
 
 /**
  * The PID file facilities.
@@ -976,6 +977,10 @@ bool AppInitParameterInteraction(const ArgsManager& args)
     int64_t nMempoolSizeMin = args.GetIntArg("-limitdescendantsize", DEFAULT_DESCENDANT_SIZE_LIMIT) * 1000 * 40;
     if (nMempoolSizeMax < 0 || nMempoolSizeMax < nMempoolSizeMin)
         return InitError(strprintf(_("-maxmempool must be at least %d MB"), std::ceil(nMempoolSizeMin / 1000000.0)));
+    constexpr bool is_32bit{sizeof(void*) == 4};
+    if (is_32bit && nMempoolSizeMax > MAX_32BIT_MEMPOOL_MB * 1000000) {
+        return InitError(strprintf(_("-maxmempool is set to %i but can't be over %i MB on 32-bit systems"), std::ceil(nMempoolSizeMax / 1000000.0), MAX_32BIT_MEMPOOL_MB));
+    }
     // incremental relay fee sets the minimum feerate increase necessary for BIP 125 replacement in the mempool
     // and the amount the mempool min fee increases above the feerate of txs evicted due to mempool limiting.
     if (args.IsArgSet("-incrementalrelayfee")) {

src/node/caches.cpp

@@ -8,12 +8,16 @@
 #include <util/system.h>
 #include <validation.h>
 
+//! Maximum dbcache size on 32-bit systems.
+static constexpr int64_t MAX_32BIT_DBCACHE = 1ULL << 30;  // 1 GiB
+
 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
     nTotalCache = std::min(nTotalCache, nMaxDbCache << 20); // total cache cannot be greater than nMaxDbcache
+    if (sizeof(void*) == 4) nTotalCache = std::min(nTotalCache, MAX_32BIT_DBCACHE);
     CacheSizes sizes;
     sizes.block_tree_db = std::min(nTotalCache / 8, nMaxBlockDBCache << 20);
     nTotalCache -= sizes.block_tree_db;