refactor: extract LargeCoinsCacheThreshold from GetCoinsCacheSizeState

Move-only commit, enabled reusing the large cache size calculation logic later. The only difference is the removal of the `static` keyword  (since in a constexpr function it's a C++23 extension)

src/validation.cpp

@@ -2786,15 +2786,10 @@ CoinsCacheSizeState Chainstate::GetCoinsCacheSizeState(
     int64_t nTotalSpace =
         max_coins_cache_size_bytes + std::max<int64_t>(int64_t(max_mempool_size_bytes) - nMempoolUsage, 0);
 
-    //! No need to periodic flush if at least this much space still available.
-    static constexpr int64_t MAX_BLOCK_COINSDB_USAGE_BYTES = 10 * 1024 * 1024;  // 10MB
-    int64_t large_threshold =
-        std::max((9 * nTotalSpace) / 10, nTotalSpace - MAX_BLOCK_COINSDB_USAGE_BYTES);
-
     if (cacheSize > nTotalSpace) {
         LogPrintf("Cache size (%s) exceeds total space (%s)\n", cacheSize, nTotalSpace);
         return CoinsCacheSizeState::CRITICAL;
-    } else if (cacheSize > large_threshold) {
+    } else if (cacheSize > LargeCoinsCacheThreshold(nTotalSpace)) {
         return CoinsCacheSizeState::LARGE;
     }
     return CoinsCacheSizeState::OK;

src/validation.h

@@ -35,6 +35,7 @@
 #include <util/translation.h>
 #include <versionbits.h>
 
+#include <algorithm>
 #include <atomic>
 #include <cstdint>
 #include <map>
@@ -503,6 +504,15 @@ enum class CoinsCacheSizeState
     OK = 0
 };
 
+constexpr int64_t LargeCoinsCacheThreshold(int64_t nTotalSpace) noexcept
+{
+    //! No need to periodic flush if at least this much space still available.
+    constexpr int64_t MAX_BLOCK_COINSDB_USAGE_BYTES = 10 * 1024 * 1024;  // 10MB
+    int64_t large_threshold =
+        std::max((9 * nTotalSpace) / 10, nTotalSpace - MAX_BLOCK_COINSDB_USAGE_BYTES);
+    return large_threshold;
+}
+
 /**
  * Chainstate stores and provides an API to update our local knowledge of the
  * current best chain.