From 143c4341d8a2231deade6d7341c668d609bd3486 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C3=A9ter=20Szil=C3=A1gyi?= <peterke@gmail.com>
Date: Mon, 4 Jun 2018 10:47:43 +0300
Subject: core, eth, trie: streaming GC for the trie cache (#16810)

* core, eth, trie: streaming GC for the trie cache

* trie: track memcache statistics
---
 core/blockchain.go | 42 ++++++++++++++++++++----------------------
 1 file changed, 20 insertions(+), 22 deletions(-)

(limited to 'core/blockchain.go')

diff --git a/core/blockchain.go b/core/blockchain.go
index f74a0f5b2..3eee75df7 100644
--- a/core/blockchain.go
+++ b/core/blockchain.go
@@ -674,7 +674,7 @@ func (bc *BlockChain) Stop() {
 		for !bc.triegc.Empty() {
 			triedb.Dereference(bc.triegc.PopItem().(common.Hash), common.Hash{})
 		}
-		if size := triedb.Size(); size != 0 {
+		if size, _ := triedb.Size(); size != 0 {
 			log.Error("Dangling trie nodes after full cleanup")
 		}
 	}
@@ -916,33 +916,29 @@ func (bc *BlockChain) WriteBlockWithState(block *types.Block, receipts []*types.
 		bc.triegc.Push(root, -float32(block.NumberU64()))
 
 		if current := block.NumberU64(); current > triesInMemory {
+			// If we exceeded our memory allowance, flush matured singleton nodes to disk
+			var (
+				nodes, imgs = triedb.Size()
+				limit       = common.StorageSize(bc.cacheConfig.TrieNodeLimit) * 1024 * 1024
+			)
+			if nodes > limit || imgs > 4*1024*1024 {
+				triedb.Cap(limit - ethdb.IdealBatchSize)
+			}
 			// Find the next state trie we need to commit
 			header := bc.GetHeaderByNumber(current - triesInMemory)
 			chosen := header.Number.Uint64()
 
-			// Only write to disk if we exceeded our memory allowance *and* also have at
-			// least a given number of tries gapped.
-			var (
-				size  = triedb.Size()
-				limit = common.StorageSize(bc.cacheConfig.TrieNodeLimit) * 1024 * 1024
-			)
-			if size > limit || bc.gcproc > bc.cacheConfig.TrieTimeLimit {
+			// If we exceeded out time allowance, flush an entire trie to disk
+			if bc.gcproc > bc.cacheConfig.TrieTimeLimit {
 				// If we're exceeding limits but haven't reached a large enough memory gap,
 				// warn the user that the system is becoming unstable.
-				if chosen < lastWrite+triesInMemory {
-					switch {
-					case size >= 2*limit:
-						log.Warn("State memory usage too high, committing", "size", size, "limit", limit, "optimum", float64(chosen-lastWrite)/triesInMemory)
-					case bc.gcproc >= 2*bc.cacheConfig.TrieTimeLimit:
-						log.Info("State in memory for too long, committing", "time", bc.gcproc, "allowance", bc.cacheConfig.TrieTimeLimit, "optimum", float64(chosen-lastWrite)/triesInMemory)
-					}
-				}
-				// If optimum or critical limits reached, write to disk
-				if chosen >= lastWrite+triesInMemory || size >= 2*limit || bc.gcproc >= 2*bc.cacheConfig.TrieTimeLimit {
-					triedb.Commit(header.Root, true)
-					lastWrite = chosen
-					bc.gcproc = 0
+				if chosen < lastWrite+triesInMemory && bc.gcproc >= 2*bc.cacheConfig.TrieTimeLimit {
+					log.Info("State in memory for too long, committing", "time", bc.gcproc, "allowance", bc.cacheConfig.TrieTimeLimit, "optimum", float64(chosen-lastWrite)/triesInMemory)
 				}
+				// Flush an entire trie and restart the counters
+				triedb.Commit(header.Root, true)
+				lastWrite = chosen
+				bc.gcproc = 0
 			}
 			// Garbage collect anything below our required write retention
 			for !bc.triegc.Empty() {
@@ -1181,7 +1177,9 @@ func (bc *BlockChain) insertChain(chain types.Blocks) (int, []interface{}, []*ty
 		}
 		stats.processed++
 		stats.usedGas += usedGas
-		stats.report(chain, i, bc.stateCache.TrieDB().Size())
+
+		cache, _ := bc.stateCache.TrieDB().Size()
+		stats.report(chain, i, cache)
 	}
 	// Append a single chain head event if we've progressed the chain
 	if lastCanon != nil && bc.CurrentBlock().Hash() == lastCanon.Hash() {
-- 
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