perf: use tiny cache for best chainlock in CbTx instead running heavy ReadBlockFromDisk

Author: knst

src/evo/cbtx.cpp

@@ -331,13 +331,26 @@ bool CheckCbTxBestChainlock(const CBlock& block, const CBlockIndex* pindex,
         return true;
     }
 
+    static Mutex cached_mutex;
+    static const CBlockIndex* cached_pindex GUARDED_BY(cached_mutex){nullptr};
+    static std::optional<std::pair<CBLSSignature, uint32_t>> cached_chainlock GUARDED_BY(cached_mutex){std::nullopt};
+
     auto best_clsig = chainlock_handler.GetBestChainLock();
     if (best_clsig.getHeight() == pindex->nHeight - 1 && cbTx.bestCLHeightDiff == 0 && cbTx.bestCLSignature == best_clsig.getSig()) {
         // matches our best clsig which still hold values for the previous block
+        LOCK(cached_mutex);
+        cached_chainlock = std::make_pair(cbTx.bestCLSignature, cbTx.bestCLHeightDiff);
+        cached_pindex = pindex;
         return true;
     }
 
-    const auto prevBlockCoinbaseChainlock = GetNonNullCoinbaseChainlock(pindex->pprev);
+    std::optional<std::pair<CBLSSignature, uint32_t>> prevBlockCoinbaseChainlock{std::nullopt};
+    if (LOCK(cached_mutex); cached_pindex == pindex->pprev) {
+        prevBlockCoinbaseChainlock = cached_chainlock;
+    }
+    if (!prevBlockCoinbaseChainlock.has_value()) {
+        prevBlockCoinbaseChainlock = GetNonNullCoinbaseChainlock(pindex->pprev);
+    }
     // If std::optional prevBlockCoinbaseChainlock is empty, then up to the previous block, coinbase Chainlock is null.
     if (prevBlockCoinbaseChainlock.has_value()) {
         // Previous block Coinbase has a non-null Chainlock: current block's Chainlock must be non-null and at least as new as the previous one
@@ -355,12 +368,18 @@ bool CheckCbTxBestChainlock(const CBlock& block, const CBlockIndex* pindex,
         int curBlockCoinbaseCLHeight = pindex->nHeight - static_cast<int>(cbTx.bestCLHeightDiff) - 1;
         if (best_clsig.getHeight() == curBlockCoinbaseCLHeight && best_clsig.getSig() == cbTx.bestCLSignature) {
             // matches our best (but outdated) clsig, no need to verify it again
+            LOCK(cached_mutex);
+            cached_chainlock = std::make_pair(cbTx.bestCLSignature, cbTx.bestCLHeightDiff);
+            cached_pindex = pindex;
             return true;
         }
         uint256 curBlockCoinbaseCLBlockHash = pindex->GetAncestor(curBlockCoinbaseCLHeight)->GetBlockHash();
         if (chainlock_handler.VerifyChainLock(llmq::CChainLockSig(curBlockCoinbaseCLHeight, curBlockCoinbaseCLBlockHash, cbTx.bestCLSignature)) != llmq::VerifyRecSigStatus::Valid) {
             return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS, "bad-cbtx-invalid-clsig");
         }
+        LOCK(cached_mutex);
+        cached_chainlock = std::make_pair(cbTx.bestCLSignature, cbTx.bestCLHeightDiff);
+        cached_pindex = pindex;
     } else if (cbTx.bestCLHeightDiff != 0) {
         // Null bestCLSignature is allowed only with bestCLHeightDiff = 0
         return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS, "bad-cbtx-cldiff");