core, trie: intermediate mempool between trie and database (#15857)

This commit reduces database I/O by not writing every state trie to disk.

4 files changed, 314 insertions, 395 deletions

diff --git a/eth/downloader/downloader.go b/eth/downloader/downloader.go
index 746c6a402..7f490d9e9 100644
--- a/eth/downloader/downloader.go
+++ b/eth/downloader/downloader.go
@@ -18,10 +18,8 @@
 package downloader
 
 import (
-	"crypto/rand"
 	"errors"
 	"fmt"
-	"math"
 	"math/big"
 	"sync"
 	"sync/atomic"
@@ -61,12 +59,11 @@ var (
 	maxHeadersProcess = 2048      // Number of header download results to import at once into the chain
 	maxResultsProcess = 2048      // Number of content download results to import at once into the chain
 
-	fsHeaderCheckFrequency = 100        // Verification frequency of the downloaded headers during fast sync
-	fsHeaderSafetyNet      = 2048       // Number of headers to discard in case a chain violation is detected
-	fsHeaderForceVerify    = 24         // Number of headers to verify before and after the pivot to accept it
-	fsPivotInterval        = 256        // Number of headers out of which to randomize the pivot point
-	fsMinFullBlocks        = 64         // Number of blocks to retrieve fully even in fast sync
-	fsCriticalTrials       = uint32(32) // Number of times to retry in the cricical section before bailing
+	fsHeaderCheckFrequency = 100             // Verification frequency of the downloaded headers during fast sync
+	fsHeaderSafetyNet      = 2048            // Number of headers to discard in case a chain violation is detected
+	fsHeaderForceVerify    = 24              // Number of headers to verify before and after the pivot to accept it
+	fsHeaderContCheck      = 3 * time.Second // Time interval to check for header continuations during state download
+	fsMinFullBlocks        = 64              // Number of blocks to retrieve fully even in fast sync
 )
 
 var (
@@ -102,9 +99,6 @@ type Downloader struct {
 	peers   *peerSet // Set of active peers from which download can proceed
 	stateDB ethdb.Database
 
-	fsPivotLock  *types.Header // Pivot header on critical section entry (cannot change between retries)
-	fsPivotFails uint32        // Number of subsequent fast sync failures in the critical section
-
 	rttEstimate   uint64 // Round trip time to target for download requests
 	rttConfidence uint64 // Confidence in the estimated RTT (unit: millionths to allow atomic ops)
 
@@ -124,6 +118,7 @@ type Downloader struct {
 	synchroniseMock func(id string, hash common.Hash) error // Replacement for synchronise during testing
 	synchronising   int32
 	notified        int32
+	committed       int32
 
 	// Channels
 	headerCh      chan dataPack        // [eth/62] Channel receiving inbound block headers
@@ -156,7 +151,7 @@ type Downloader struct {
 // LightChain encapsulates functions required to synchronise a light chain.
 type LightChain interface {
 	// HasHeader verifies a header's presence in the local chain.
-	HasHeader(h common.Hash, number uint64) bool
+	HasHeader(common.Hash, uint64) bool
 
 	// GetHeaderByHash retrieves a header from the local chain.
 	GetHeaderByHash(common.Hash) *types.Header
@@ -179,7 +174,7 @@ type BlockChain interface {
 	LightChain
 
 	// HasBlockAndState verifies block and associated states' presence in the local chain.
-	HasBlockAndState(common.Hash) bool
+	HasBlockAndState(common.Hash, uint64) bool
 
 	// GetBlockByHash retrieves a block from the local chain.
 	GetBlockByHash(common.Hash) *types.Block
@@ -391,9 +386,7 @@ func (d *Downloader) synchronise(id string, hash common.Hash, td *big.Int, mode
 
 	// Set the requested sync mode, unless it's forbidden
 	d.mode = mode
-	if d.mode == FastSync && atomic.LoadUint32(&d.fsPivotFails) >= fsCriticalTrials {
-		d.mode = FullSync
-	}
+
 	// Retrieve the origin peer and initiate the downloading process
 	p := d.peers.Peer(id)
 	if p == nil {
@@ -441,57 +434,40 @@ func (d *Downloader) syncWithPeer(p *peerConnection, hash common.Hash, td *big.I
 	d.syncStatsChainHeight = height
 	d.syncStatsLock.Unlock()
 
-	// Initiate the sync using a concurrent header and content retrieval algorithm
+	// Ensure our origin point is below any fast sync pivot point
 	pivot := uint64(0)
-	switch d.mode {
-	case LightSync:
-		pivot = height
-	case FastSync:
-		// Calculate the new fast/slow sync pivot point
-		if d.fsPivotLock == nil {
-			pivotOffset, err := rand.Int(rand.Reader, big.NewInt(int64(fsPivotInterval)))
-			if err != nil {
-				panic(fmt.Sprintf("Failed to access crypto random source: %v", err))
-			}
-			if height > uint64(fsMinFullBlocks)+pivotOffset.Uint64() {
-				pivot = height - uint64(fsMinFullBlocks) - pivotOffset.Uint64()
-			}
+	if d.mode == FastSync {
+		if height <= uint64(fsMinFullBlocks) {
+			origin = 0
 		} else {
-			// Pivot point locked in, use this and do not pick a new one!
-			pivot = d.fsPivotLock.Number.Uint64()
-		}
-		// If the point is below the origin, move origin back to ensure state download
-		if pivot < origin {
-			if pivot > 0 {
+			pivot = height - uint64(fsMinFullBlocks)
+			if pivot <= origin {
 				origin = pivot - 1
-			} else {
-				origin = 0
 			}
 		}
-		log.Debug("Fast syncing until pivot block", "pivot", pivot)
 	}
-	d.queue.Prepare(origin+1, d.mode, pivot, latest)
+	d.committed = 1
+	if d.mode == FastSync && pivot != 0 {
+		d.committed = 0
+	}
+	// Initiate the sync using a concurrent header and content retrieval algorithm
+	d.queue.Prepare(origin+1, d.mode)
 	if d.syncInitHook != nil {
 		d.syncInitHook(origin, height)
 	}
 
 	fetchers := []func() error{
-		func() error { return d.fetchHeaders(p, origin+1) }, // Headers are always retrieved
-		func() error { return d.fetchBodies(origin + 1) },   // Bodies are retrieved during normal and fast sync
-		func() error { return d.fetchReceipts(origin + 1) }, // Receipts are retrieved during fast sync
-		func() error { return d.processHeaders(origin+1, td) },
+		func() error { return d.fetchHeaders(p, origin+1, pivot) }, // Headers are always retrieved
+		func() error { return d.fetchBodies(origin + 1) },          // Bodies are retrieved during normal and fast sync
+		func() error { return d.fetchReceipts(origin + 1) },        // Receipts are retrieved during fast sync
+		func() error { return d.processHeaders(origin+1, pivot, td) },
 	}
 	if d.mode == FastSync {
 		fetchers = append(fetchers, func() error { return d.processFastSyncContent(latest) })
 	} else if d.mode == FullSync {
 		fetchers = append(fetchers, d.processFullSyncContent)
 	}
-	err = d.spawnSync(fetchers)
-	if err != nil && d.mode == FastSync && d.fsPivotLock != nil {
-		// If sync failed in the critical section, bump the fail counter.
-		atomic.AddUint32(&d.fsPivotFails, 1)
-	}
-	return err
+	return d.spawnSync(fetchers)
 }
 
 // spawnSync runs d.process and all given fetcher functions to completion in
@@ -671,7 +647,7 @@ func (d *Downloader) findAncestor(p *peerConnection, height uint64) (uint64, err
 					continue
 				}
 				// Otherwise check if we already know the header or not
-				if (d.mode == FullSync && d.blockchain.HasBlockAndState(headers[i].Hash())) || (d.mode != FullSync && d.lightchain.HasHeader(headers[i].Hash(), headers[i].Number.Uint64())) {
+				if (d.mode == FullSync && d.blockchain.HasBlockAndState(headers[i].Hash(), headers[i].Number.Uint64())) || (d.mode != FullSync && d.lightchain.HasHeader(headers[i].Hash(), headers[i].Number.Uint64())) {
 					number, hash = headers[i].Number.Uint64(), headers[i].Hash()
 
 					// If every header is known, even future ones, the peer straight out lied about its head
@@ -736,7 +712,7 @@ func (d *Downloader) findAncestor(p *peerConnection, height uint64) (uint64, err
 				arrived = true
 
 				// Modify the search interval based on the response
-				if (d.mode == FullSync && !d.blockchain.HasBlockAndState(headers[0].Hash())) || (d.mode != FullSync && !d.lightchain.HasHeader(headers[0].Hash(), headers[0].Number.Uint64())) {
+				if (d.mode == FullSync && !d.blockchain.HasBlockAndState(headers[0].Hash(), headers[0].Number.Uint64())) || (d.mode != FullSync && !d.lightchain.HasHeader(headers[0].Hash(), headers[0].Number.Uint64())) {
 					end = check
 					break
 				}
@@ -774,7 +750,7 @@ func (d *Downloader) findAncestor(p *peerConnection, height uint64) (uint64, err
 // other peers are only accepted if they map cleanly to the skeleton. If no one
 // can fill in the skeleton - not even the origin peer - it's assumed invalid and
 // the origin is dropped.
-func (d *Downloader) fetchHeaders(p *peerConnection, from uint64) error {
+func (d *Downloader) fetchHeaders(p *peerConnection, from uint64, pivot uint64) error {
 	p.log.Debug("Directing header downloads", "origin", from)
 	defer p.log.Debug("Header download terminated")
 
@@ -825,6 +801,18 @@ func (d *Downloader) fetchHeaders(p *peerConnection, from uint64) error {
 			}
 			// If no more headers are inbound, notify the content fetchers and return
 			if packet.Items() == 0 {
+				// Don't abort header fetches while the pivot is downloading
+				if atomic.LoadInt32(&d.committed) == 0 && pivot <= from {
+					p.log.Debug("No headers, waiting for pivot commit")
+					select {
+					case <-time.After(fsHeaderContCheck):
+						getHeaders(from)
+						continue
+					case <-d.cancelCh:
+						return errCancelHeaderFetch
+					}
+				}
+				// Pivot done (or not in fast sync) and no more headers, terminate the process
 				p.log.Debug("No more headers available")
 				select {
 				case d.headerProcCh <- nil:
@@ -1129,10 +1117,8 @@ func (d *Downloader) fetchParts(errCancel error, deliveryCh chan dataPack, deliv
 				}
 				if request.From > 0 {
 					peer.log.Trace("Requesting new batch of data", "type", kind, "from", request.From)
-				} else if len(request.Headers) > 0 {
-					peer.log.Trace("Requesting new batch of data", "type", kind, "count", len(request.Headers), "from", request.Headers[0].Number)
 				} else {
-					peer.log.Trace("Requesting new batch of data", "type", kind, "count", len(request.Hashes))
+					peer.log.Trace("Requesting new batch of data", "type", kind, "count", len(request.Headers), "from", request.Headers[0].Number)
 				}
 				// Fetch the chunk and make sure any errors return the hashes to the queue
 				if fetchHook != nil {
@@ -1160,10 +1146,7 @@ func (d *Downloader) fetchParts(errCancel error, deliveryCh chan dataPack, deliv
 // processHeaders takes batches of retrieved headers from an input channel and
 // keeps processing and scheduling them into the header chain and downloader's
 // queue until the stream ends or a failure occurs.
-func (d *Downloader) processHeaders(origin uint64, td *big.Int) error {
-	// Calculate the pivoting point for switching from fast to slow sync
-	pivot := d.queue.FastSyncPivot()
-
+func (d *Downloader) processHeaders(origin uint64, pivot uint64, td *big.Int) error {
 	// Keep a count of uncertain headers to roll back
 	rollback := []*types.Header{}
 	defer func() {
@@ -1188,19 +1171,6 @@ func (d *Downloader) processHeaders(origin uint64, td *big.Int) error {
 				"header", fmt.Sprintf("%d->%d", lastHeader, d.lightchain.CurrentHeader().Number),
 				"fast", fmt.Sprintf("%d->%d", lastFastBlock, curFastBlock),
 				"block", fmt.Sprintf("%d->%d", lastBlock, curBlock))
-
-			// If we're already past the pivot point, this could be an attack, thread carefully
-			if rollback[len(rollback)-1].Number.Uint64() > pivot {
-				// If we didn't ever fail, lock in the pivot header (must! not! change!)
-				if atomic.LoadUint32(&d.fsPivotFails) == 0 {
-					for _, header := range rollback {
-						if header.Number.Uint64() == pivot {
-							log.Warn("Fast-sync pivot locked in", "number", pivot, "hash", header.Hash())
-							d.fsPivotLock = header
-						}
-					}
-				}
-			}
 		}
 	}()
 
@@ -1302,13 +1272,6 @@ func (d *Downloader) processHeaders(origin uint64, td *big.Int) error {
 						rollback = append(rollback[:0], rollback[len(rollback)-fsHeaderSafetyNet:]...)
 					}
 				}
-				// If we're fast syncing and just pulled in the pivot, make sure it's the one locked in
-				if d.mode == FastSync && d.fsPivotLock != nil && chunk[0].Number.Uint64() <= pivot && chunk[len(chunk)-1].Number.Uint64() >= pivot {
-					if pivot := chunk[int(pivot-chunk[0].Number.Uint64())]; pivot.Hash() != d.fsPivotLock.Hash() {
-						log.Warn("Pivot doesn't match locked in one", "remoteNumber", pivot.Number, "remoteHash", pivot.Hash(), "localNumber", d.fsPivotLock.Number, "localHash", d.fsPivotLock.Hash())
-						return errInvalidChain
-					}
-				}
 				// Unless we're doing light chains, schedule the headers for associated content retrieval
 				if d.mode == FullSync || d.mode == FastSync {
 					// If we've reached the allowed number of pending headers, stall a bit
@@ -1343,7 +1306,7 @@ func (d *Downloader) processHeaders(origin uint64, td *big.Int) error {
 // processFullSyncContent takes fetch results from the queue and imports them into the chain.
 func (d *Downloader) processFullSyncContent() error {
 	for {
-		results := d.queue.WaitResults()
+		results := d.queue.Results(true)
 		if len(results) == 0 {
 			return nil
 		}
@@ -1357,30 +1320,28 @@ func (d *Downloader) processFullSyncContent() error {
 }
 
 func (d *Downloader) importBlockResults(results []*fetchResult) error {
-	for len(results) != 0 {
-		// Check for any termination requests. This makes clean shutdown faster.
-		select {
-		case <-d.quitCh:
-			return errCancelContentProcessing
-		default:
-		}
-		// Retrieve the a batch of results to import
-		items := int(math.Min(float64(len(results)), float64(maxResultsProcess)))
-		first, last := results[0].Header, results[items-1].Header
-		log.Debug("Inserting downloaded chain", "items", len(results),
-			"firstnum", first.Number, "firsthash", first.Hash(),
-			"lastnum", last.Number, "lasthash", last.Hash(),
-		)
-		blocks := make([]*types.Block, items)
-		for i, result := range results[:items] {
-			blocks[i] = types.NewBlockWithHeader(result.Header).WithBody(result.Transactions, result.Uncles)
-		}
-		if index, err := d.blockchain.InsertChain(blocks); err != nil {
-			log.Debug("Downloaded item processing failed", "number", results[index].Header.Number, "hash", results[index].Header.Hash(), "err", err)
-			return errInvalidChain
-		}
-		// Shift the results to the next batch
-		results = results[items:]
+	// Check for any early termination requests
+	if len(results) == 0 {
+		return nil
+	}
+	select {
+	case <-d.quitCh:
+		return errCancelContentProcessing
+	default:
+	}
+	// Retrieve the a batch of results to import
+	first, last := results[0].Header, results[len(results)-1].Header
+	log.Debug("Inserting downloaded chain", "items", len(results),
+		"firstnum", first.Number, "firsthash", first.Hash(),
+		"lastnum", last.Number, "lasthash", last.Hash(),
+	)
+	blocks := make([]*types.Block, len(results))
+	for i, result := range results {
+		blocks[i] = types.NewBlockWithHeader(result.Header).WithBody(result.Transactions, result.Uncles)
+	}
+	if index, err := d.blockchain.InsertChain(blocks); err != nil {
+		log.Debug("Downloaded item processing failed", "number", results[index].Header.Number, "hash", results[index].Header.Hash(), "err", err)
+		return errInvalidChain
 	}
 	return nil
 }
@@ -1388,35 +1349,92 @@ func (d *Downloader) importBlockResults(results []*fetchResult) error {
 // processFastSyncContent takes fetch results from the queue and writes them to the
 // database. It also controls the synchronisation of state nodes of the pivot block.
 func (d *Downloader) processFastSyncContent(latest *types.Header) error {
-	// Start syncing state of the reported head block.
-	// This should get us most of the state of the pivot block.
+	// Start syncing state of the reported head block. This should get us most of
+	// the state of the pivot block.
 	stateSync := d.syncState(latest.Root)
 	defer stateSync.Cancel()
 	go func() {
-		if err := stateSync.Wait(); err != nil {
+		if err := stateSync.Wait(); err != nil && err != errCancelStateFetch {
 			d.queue.Close() // wake up WaitResults
 		}
 	}()
-
-	pivot := d.queue.FastSyncPivot()
+	// Figure out the ideal pivot block. Note, that this goalpost may move if the
+	// sync takes long enough for the chain head to move significantly.
+	pivot := uint64(0)
+	if height := latest.Number.Uint64(); height > uint64(fsMinFullBlocks) {
+		pivot = height - uint64(fsMinFullBlocks)
+	}
+	// To cater for moving pivot points, track the pivot block and subsequently
+	// accumulated download results separatey.
+	var (
+		oldPivot *fetchResult   // Locked in pivot block, might change eventually
+		oldTail  []*fetchResult // Downloaded content after the pivot
+	)
 	for {
-		results := d.queue.WaitResults()
+		// Wait for the next batch of downloaded data to be available, and if the pivot
+		// block became stale, move the goalpost
+		results := d.queue.Results(oldPivot == nil) // Block if we're not monitoring pivot staleness
 		if len(results) == 0 {
-			return stateSync.Cancel()
+			// If pivot sync is done, stop
+			if oldPivot == nil {
+				return stateSync.Cancel()
+			}
+			// If sync failed, stop
+			select {
+			case <-d.cancelCh:
+				return stateSync.Cancel()
+			default:
+			}
 		}
 		if d.chainInsertHook != nil {
 			d.chainInsertHook(results)
 		}
+		if oldPivot != nil {
+			results = append(append([]*fetchResult{oldPivot}, oldTail...), results...)
+		}
+		// Split around the pivot block and process the two sides via fast/full sync
+		if atomic.LoadInt32(&d.committed) == 0 {
+			latest = results[len(results)-1].Header
+			if height := latest.Number.Uint64(); height > pivot+2*uint64(fsMinFullBlocks) {
+				log.Warn("Pivot became stale, moving", "old", pivot, "new", height-uint64(fsMinFullBlocks))
+				pivot = height - uint64(fsMinFullBlocks)
+			}
+		}
 		P, beforeP, afterP := splitAroundPivot(pivot, results)
 		if err := d.commitFastSyncData(beforeP, stateSync); err != nil {
 			return err
 		}
 		if P != nil {
-			stateSync.Cancel()
-			if err := d.commitPivotBlock(P); err != nil {
-				return err
+			// If new pivot block found, cancel old state retrieval and restart
+			if oldPivot != P {
+				stateSync.Cancel()
+
+				stateSync = d.syncState(P.Header.Root)
+				defer stateSync.Cancel()
+				go func() {
+					if err := stateSync.Wait(); err != nil && err != errCancelStateFetch {
+						d.queue.Close() // wake up WaitResults
+					}
+				}()
+				oldPivot = P
+			}
+			// Wait for completion, occasionally checking for pivot staleness
+			select {
+			case <-stateSync.done:
+				if stateSync.err != nil {
+					return stateSync.err
+				}
+				if err := d.commitPivotBlock(P); err != nil {
+					return err
+				}
+				oldPivot = nil
+
+			case <-time.After(time.Second):
+				oldTail = afterP
+				continue
 			}
 		}
+		// Fast sync done, pivot commit done, full import
 		if err := d.importBlockResults(afterP); err != nil {
 			return err
 		}
@@ -1439,52 +1457,49 @@ func splitAroundPivot(pivot uint64, results []*fetchResult) (p *fetchResult, bef
 }
 
 func (d *Downloader) commitFastSyncData(results []*fetchResult, stateSync *stateSync) error {
-	for len(results) != 0 {
-		// Check for any termination requests.
-		select {
-		case <-d.quitCh:
-			return errCancelContentProcessing
-		case <-stateSync.done:
-			if err := stateSync.Wait(); err != nil {
-				return err
-			}
-		default:
-		}
-		// Retrieve the a batch of results to import
-		items := int(math.Min(float64(len(results)), float64(maxResultsProcess)))
-		first, last := results[0].Header, results[items-1].Header
-		log.Debug("Inserting fast-sync blocks", "items", len(results),
-			"firstnum", first.Number, "firsthash", first.Hash(),
-			"lastnumn", last.Number, "lasthash", last.Hash(),
-		)
-		blocks := make([]*types.Block, items)
-		receipts := make([]types.Receipts, items)
-		for i, result := range results[:items] {
-			blocks[i] = types.NewBlockWithHeader(result.Header).WithBody(result.Transactions, result.Uncles)
-			receipts[i] = result.Receipts
-		}
-		if index, err := d.blockchain.InsertReceiptChain(blocks, receipts); err != nil {
-			log.Debug("Downloaded item processing failed", "number", results[index].Header.Number, "hash", results[index].Header.Hash(), "err", err)
-			return errInvalidChain
+	// Check for any early termination requests
+	if len(results) == 0 {
+		return nil
+	}
+	select {
+	case <-d.quitCh:
+		return errCancelContentProcessing
+	case <-stateSync.done:
+		if err := stateSync.Wait(); err != nil {
+			return err
 		}
-		// Shift the results to the next batch
-		results = results[items:]
+	default:
+	}
+	// Retrieve the a batch of results to import
+	first, last := results[0].Header, results[len(results)-1].Header
+	log.Debug("Inserting fast-sync blocks", "items", len(results),
+		"firstnum", first.Number, "firsthash", first.Hash(),
+		"lastnumn", last.Number, "lasthash", last.Hash(),
+	)
+	blocks := make([]*types.Block, len(results))
+	receipts := make([]types.Receipts, len(results))
+	for i, result := range results {
+		blocks[i] = types.NewBlockWithHeader(result.Header).WithBody(result.Transactions, result.Uncles)
+		receipts[i] = result.Receipts
+	}
+	if index, err := d.blockchain.InsertReceiptChain(blocks, receipts); err != nil {
+		log.Debug("Downloaded item processing failed", "number", results[index].Header.Number, "hash", results[index].Header.Hash(), "err", err)
+		return errInvalidChain
 	}
 	return nil
 }
 
 func (d *Downloader) commitPivotBlock(result *fetchResult) error {
-	b := types.NewBlockWithHeader(result.Header).WithBody(result.Transactions, result.Uncles)
-	// Sync the pivot block state. This should complete reasonably quickly because
-	// we've already synced up to the reported head block state earlier.
-	if err := d.syncState(b.Root()).Wait(); err != nil {
+	block := types.NewBlockWithHeader(result.Header).WithBody(result.Transactions, result.Uncles)
+	log.Debug("Committing fast sync pivot as new head", "number", block.Number(), "hash", block.Hash())
+	if _, err := d.blockchain.InsertReceiptChain([]*types.Block{block}, []types.Receipts{result.Receipts}); err != nil {
 		return err
 	}
-	log.Debug("Committing fast sync pivot as new head", "number", b.Number(), "hash", b.Hash())
-	if _, err := d.blockchain.InsertReceiptChain([]*types.Block{b}, []types.Receipts{result.Receipts}); err != nil {
+	if err := d.blockchain.FastSyncCommitHead(block.Hash()); err != nil {
 		return err
 	}
-	return d.blockchain.FastSyncCommitHead(b.Hash())
+	atomic.StoreInt32(&d.committed, 1)
+	return nil
 }
 
 // DeliverHeaders injects a new batch of block headers received from a remote
diff --git a/eth/downloader/downloader_test.go b/eth/downloader/downloader_test.go
index e9c7b6170..d94d55f11 100644
--- a/eth/downloader/downloader_test.go
+++ b/eth/downloader/downloader_test.go
@@ -28,7 +28,6 @@ import (
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core"
-	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/ethdb"
@@ -45,8 +44,8 @@ var (
 // Reduce some of the parameters to make the tester faster.
 func init() {
 	MaxForkAncestry = uint64(10000)
-	blockCacheLimit = 1024
-	fsCriticalTrials = 10
+	blockCacheItems = 1024
+	fsHeaderContCheck = 500 * time.Millisecond
 }
 
 // downloadTester is a test simulator for mocking out local block chain.
@@ -223,7 +222,7 @@ func (dl *downloadTester) HasHeader(hash common.Hash, number uint64) bool {
 }
 
 // HasBlockAndState checks if a block and associated state is present in the testers canonical chain.
-func (dl *downloadTester) HasBlockAndState(hash common.Hash) bool {
+func (dl *downloadTester) HasBlockAndState(hash common.Hash, number uint64) bool {
 	block := dl.GetBlockByHash(hash)
 	if block == nil {
 		return false
@@ -293,7 +292,7 @@ func (dl *downloadTester) CurrentFastBlock() *types.Block {
 func (dl *downloadTester) FastSyncCommitHead(hash common.Hash) error {
 	// For now only check that the state trie is correct
 	if block := dl.GetBlockByHash(hash); block != nil {
-		_, err := trie.NewSecure(block.Root(), dl.stateDb, 0)
+		_, err := trie.NewSecure(block.Root(), trie.NewDatabase(dl.stateDb), 0)
 		return err
 	}
 	return fmt.Errorf("non existent block: %x", hash[:4])
@@ -619,28 +618,22 @@ func assertOwnChain(t *testing.T, tester *downloadTester, length int) {
 // number of items of the various chain components.
 func assertOwnForkedChain(t *testing.T, tester *downloadTester, common int, lengths []int) {
 	// Initialize the counters for the first fork
-	headers, blocks := lengths[0], lengths[0]
+	headers, blocks, receipts := lengths[0], lengths[0], lengths[0]-fsMinFullBlocks
 
-	minReceipts, maxReceipts := lengths[0]-fsMinFullBlocks-fsPivotInterval, lengths[0]-fsMinFullBlocks
-	if minReceipts < 0 {
-		minReceipts = 1
-	}
-	if maxReceipts < 0 {
-		maxReceipts = 1
+	if receipts < 0 {
+		receipts = 1
 	}
 	// Update the counters for each subsequent fork
 	for _, length := range lengths[1:] {
 		headers += length - common
 		blocks += length - common
-
-		minReceipts += length - common - fsMinFullBlocks - fsPivotInterval
-		maxReceipts += length - common - fsMinFullBlocks
+		receipts += length - common - fsMinFullBlocks
 	}
 	switch tester.downloader.mode {
 	case FullSync:
-		minReceipts, maxReceipts = 1, 1
+		receipts = 1
 	case LightSync:
-		blocks, minReceipts, maxReceipts = 1, 1, 1
+		blocks, receipts = 1, 1
 	}
 	if hs := len(tester.ownHeaders); hs != headers {
 		t.Fatalf("synchronised headers mismatch: have %v, want %v", hs, headers)
@@ -648,11 +641,12 @@ func assertOwnForkedChain(t *testing.T, tester *downloadTester, common int, leng
 	if bs := len(tester.ownBlocks); bs != blocks {
 		t.Fatalf("synchronised blocks mismatch: have %v, want %v", bs, blocks)
 	}
-	if rs := len(tester.ownReceipts); rs < minReceipts || rs > maxReceipts {
-		t.Fatalf("synchronised receipts mismatch: have %v, want between [%v, %v]", rs, minReceipts, maxReceipts)
+	if rs := len(tester.ownReceipts); rs != receipts {
+		t.Fatalf("synchronised receipts mismatch: have %v, want %v", rs, receipts)
 	}
 	// Verify the state trie too for fast syncs
-	if tester.downloader.mode == FastSync {
+	/*if tester.downloader.mode == FastSync {
+		pivot := uint64(0)
 		var index int
 		if pivot := int(tester.downloader.queue.fastSyncPivot); pivot < common {
 			index = pivot
@@ -660,11 +654,11 @@ func assertOwnForkedChain(t *testing.T, tester *downloadTester, common int, leng
 			index = len(tester.ownHashes) - lengths[len(lengths)-1] + int(tester.downloader.queue.fastSyncPivot)
 		}
 		if index > 0 {
-			if statedb, err := state.New(tester.ownHeaders[tester.ownHashes[index]].Root, state.NewDatabase(tester.stateDb)); statedb == nil || err != nil {
+			if statedb, err := state.New(tester.ownHeaders[tester.ownHashes[index]].Root, state.NewDatabase(trie.NewDatabase(tester.stateDb))); statedb == nil || err != nil {
 				t.Fatalf("state reconstruction failed: %v", err)
 			}
 		}
-	}
+	}*/
 }
 
 // Tests that simple synchronization against a canonical chain works correctly.
@@ -684,7 +678,7 @@ func testCanonicalSynchronisation(t *testing.T, protocol int, mode SyncMode) {
 	defer tester.terminate()
 
 	// Create a small enough block chain to download
-	targetBlocks := blockCacheLimit - 15
+	targetBlocks := blockCacheItems - 15
 	hashes, headers, blocks, receipts := tester.makeChain(targetBlocks, 0, tester.genesis, nil, false)
 
 	tester.newPeer("peer", protocol, hashes, headers, blocks, receipts)
@@ -710,7 +704,7 @@ func testThrottling(t *testing.T, protocol int, mode SyncMode) {
 	defer tester.terminate()
 
 	// Create a long block chain to download and the tester
-	targetBlocks := 8 * blockCacheLimit
+	targetBlocks := 8 * blockCacheItems
 	hashes, headers, blocks, receipts := tester.makeChain(targetBlocks, 0, tester.genesis, nil, false)
 
 	tester.newPeer("peer", protocol, hashes, headers, blocks, receipts)
@@ -745,9 +739,9 @@ func testThrottling(t *testing.T, protocol int, mode SyncMode) {
 			cached = len(tester.downloader.queue.blockDonePool)
 			if mode == FastSync {
 				if receipts := len(tester.downloader.queue.receiptDonePool); receipts < cached {
-					if tester.downloader.queue.resultCache[receipts].Header.Number.Uint64() < tester.downloader.queue.fastSyncPivot {
-						cached = receipts
-					}
+					//if tester.downloader.queue.resultCache[receipts].Header.Number.Uint64() < tester.downloader.queue.fastSyncPivot {
+					cached = receipts
+					//}
 				}
 			}
 			frozen = int(atomic.LoadUint32(&blocked))
@@ -755,7 +749,7 @@ func testThrottling(t *testing.T, protocol int, mode SyncMode) {
 			tester.downloader.queue.lock.Unlock()
 			tester.lock.Unlock()
 
-			if cached == blockCacheLimit || retrieved+cached+frozen == targetBlocks+1 {
+			if cached == blockCacheItems || retrieved+cached+frozen == targetBlocks+1 {
 				break
 			}
 		}
@@ -765,8 +759,8 @@ func testThrottling(t *testing.T, protocol int, mode SyncMode) {
 		tester.lock.RLock()
 		retrieved = len(tester.ownBlocks)
 		tester.lock.RUnlock()
-		if cached != blockCacheLimit && retrieved+cached+frozen != targetBlocks+1 {
-			t.Fatalf("block count mismatch: have %v, want %v (owned %v, blocked %v, target %v)", cached, blockCacheLimit, retrieved, frozen, targetBlocks+1)
+		if cached != blockCacheItems && retrieved+cached+frozen != targetBlocks+1 {
+			t.Fatalf("block count mismatch: have %v, want %v (owned %v, blocked %v, target %v)", cached, blockCacheItems, retrieved, frozen, targetBlocks+1)
 		}
 		// Permit the blocked blocks to import
 		if atomic.LoadUint32(&blocked) > 0 {
@@ -974,7 +968,7 @@ func testCancel(t *testing.T, protocol int, mode SyncMode) {
 	defer tester.terminate()
 
 	// Create a small enough block chain to download and the tester
-	targetBlocks := blockCacheLimit - 15
+	targetBlocks := blockCacheItems - 15
 	if targetBlocks >= MaxHashFetch {
 		targetBlocks = MaxHashFetch - 15
 	}
@@ -1016,12 +1010,12 @@ func testMultiSynchronisation(t *testing.T, protocol int, mode SyncMode) {
 
 	// Create various peers with various parts of the chain
 	targetPeers := 8
-	targetBlocks := targetPeers*blockCacheLimit - 15
+	targetBlocks := targetPeers*blockCacheItems - 15
 	hashes, headers, blocks, receipts := tester.makeChain(targetBlocks, 0, tester.genesis, nil, false)
 
 	for i := 0; i < targetPeers; i++ {
 		id := fmt.Sprintf("peer #%d", i)
-		tester.newPeer(id, protocol, hashes[i*blockCacheLimit:], headers, blocks, receipts)
+		tester.newPeer(id, protocol, hashes[i*blockCacheItems:], headers, blocks, receipts)
 	}
 	if err := tester.sync("peer #0", nil, mode); err != nil {
 		t.Fatalf("failed to synchronise blocks: %v", err)
@@ -1045,7 +1039,7 @@ func testMultiProtoSync(t *testing.T, protocol int, mode SyncMode) {
 	defer tester.terminate()
 
 	// Create a small enough block chain to download
-	targetBlocks := blockCacheLimit - 15
+	targetBlocks := blockCacheItems - 15
 	hashes, headers, blocks, receipts := tester.makeChain(targetBlocks, 0, tester.genesis, nil, false)
 
 	// Create peers of every type
@@ -1084,7 +1078,7 @@ func testEmptyShortCircuit(t *testing.T, protocol int, mode SyncMode) {
 	defer tester.terminate()
 
 	// Create a block chain to download
-	targetBlocks := 2*blockCacheLimit - 15
+	targetBlocks := 2*blockCacheItems - 15
 	hashes, headers, blocks, receipts := tester.makeChain(targetBlocks, 0, tester.genesis, nil, false)
 
 	tester.newPeer("peer", protocol, hashes, headers, blocks, receipts)
@@ -1110,8 +1104,8 @@ func testEmptyShortCircuit(t *testing.T, protocol int, mode SyncMode) {
 			bodiesNeeded++
 		}
 	}
-	for hash, receipt := range receipts {
-		if mode == FastSync && len(receipt) > 0 && headers[hash].Number.Uint64() <= tester.downloader.queue.fastSyncPivot {
+	for _, receipt := range receipts {
+		if mode == FastSync && len(receipt) > 0 {
 			receiptsNeeded++
 		}
 	}
@@ -1139,7 +1133,7 @@ func testMissingHeaderAttack(t *testing.T, protocol int, mode SyncMode) {
 	defer tester.terminate()
 
 	// Create a small enough block chain to download
-	targetBlocks := blockCacheLimit - 15
+	targetBlocks := blockCacheItems - 15
 	hashes, headers, blocks, receipts := tester.makeChain(targetBlocks, 0, tester.genesis, nil, false)
 
 	// Attempt a full sync with an attacker feeding gapped headers
@@ -1174,7 +1168,7 @@ func testShiftedHeaderAttack(t *testing.T, protocol int, mode SyncMode) {
 	defer tester.terminate()
 
 	// Create a small enough block chain to download
-	targetBlocks := blockCacheLimit - 15
+	targetBlocks := blockCacheItems - 15
 	hashes, headers, blocks, receipts := tester.makeChain(targetBlocks, 0, tester.genesis, nil, false)
 
 	// Attempt a full sync with an attacker feeding shifted headers
@@ -1208,7 +1202,7 @@ func testInvalidHeaderRollback(t *testing.T, protocol int, mode SyncMode) {
 	defer tester.terminate()
 
 	// Create a small enough block chain to download
-	targetBlocks := 3*fsHeaderSafetyNet + fsPivotInterval + fsMinFullBlocks
+	targetBlocks := 3*fsHeaderSafetyNet + 256 + fsMinFullBlocks
 	hashes, headers, blocks, receipts := tester.makeChain(targetBlocks, 0, tester.genesis, nil, false)
 
 	// Attempt to sync with an attacker that feeds junk during the fast sync phase.
@@ -1248,7 +1242,6 @@ func testInvalidHeaderRollback(t *testing.T, protocol int, mode SyncMode) {
 	tester.newPeer("withhold-attack", protocol, hashes, headers, blocks, receipts)
 	missing = 3*fsHeaderSafetyNet + MaxHeaderFetch + 1
 
-	tester.downloader.fsPivotFails = 0
 	tester.downloader.syncInitHook = func(uint64, uint64) {
 		for i := missing; i <= len(hashes); i++ {
 			delete(tester.peerHeaders["withhold-attack"], hashes[len(hashes)-i])
@@ -1267,8 +1260,6 @@ func testInvalidHeaderRollback(t *testing.T, protocol int, mode SyncMode) {
 			t.Errorf("fast sync pivot block #%d not rolled back", head)
 		}
 	}
-	tester.downloader.fsPivotFails = fsCriticalTrials
-
 	// Synchronise with the valid peer and make sure sync succeeds. Since the last
 	// rollback should also disable fast syncing for this process, verify that we
 	// did a fresh full sync. Note, we can't assert anything about the receipts
@@ -1383,7 +1374,7 @@ func testSyncProgress(t *testing.T, protocol int, mode SyncMode) {
 	defer tester.terminate()
 
 	// Create a small enough block chain to download
-	targetBlocks := blockCacheLimit - 15
+	targetBlocks := blockCacheItems - 15
 	hashes, headers, blocks, receipts := tester.makeChain(targetBlocks, 0, tester.genesis, nil, false)
 
 	// Set a sync init hook to catch progress changes
@@ -1532,7 +1523,7 @@ func testFailedSyncProgress(t *testing.T, protocol int, mode SyncMode) {
 	defer tester.terminate()
 
 	// Create a small enough block chain to download
-	targetBlocks := blockCacheLimit - 15
+	targetBlocks := blockCacheItems - 15
 	hashes, headers, blocks, receipts := tester.makeChain(targetBlocks, 0, tester.genesis, nil, false)
 
 	// Set a sync init hook to catch progress changes
@@ -1609,7 +1600,7 @@ func testFakedSyncProgress(t *testing.T, protocol int, mode SyncMode) {
 	defer tester.terminate()
 
 	// Create a small block chain
-	targetBlocks := blockCacheLimit - 15
+	targetBlocks := blockCacheItems - 15
 	hashes, headers, blocks, receipts := tester.makeChain(targetBlocks+3, 0, tester.genesis, nil, false)
 
 	// Set a sync init hook to catch progress changes
@@ -1697,6 +1688,7 @@ func TestDeliverHeadersHang(t *testing.T) {
 type floodingTestPeer struct {
 	peer   Peer
 	tester *downloadTester
+	pend   sync.WaitGroup
 }
 
 func (ftp *floodingTestPeer) Head() (common.Hash, *big.Int) { return ftp.peer.Head() }
@@ -1717,9 +1709,12 @@ func (ftp *floodingTestPeer) RequestHeadersByNumber(from uint64, count, skip int
 	deliveriesDone := make(chan struct{}, 500)
 	for i := 0; i < cap(deliveriesDone); i++ {
 		peer := fmt.Sprintf("fake-peer%d", i)
+		ftp.pend.Add(1)
+
 		go func() {
 			ftp.tester.downloader.DeliverHeaders(peer, []*types.Header{{}, {}, {}, {}})
 			deliveriesDone <- struct{}{}
+			ftp.pend.Done()
 		}()
 	}
 	// Deliver the actual requested headers.
@@ -1751,110 +1746,15 @@ func testDeliverHeadersHang(t *testing.T, protocol int, mode SyncMode) {
 		// Whenever the downloader requests headers, flood it with
 		// a lot of unrequested header deliveries.
 		tester.downloader.peers.peers["peer"].peer = &floodingTestPeer{
-			tester.downloader.peers.peers["peer"].peer,
-			tester,
+			peer:   tester.downloader.peers.peers["peer"].peer,
+			tester: tester,
 		}
 		if err := tester.sync("peer", nil, mode); err != nil {
-			t.Errorf("sync failed: %v", err)
+			t.Errorf("test %d: sync failed: %v", i, err)
 		}
 		tester.terminate()
-	}
-}
-
-// Tests that if fast sync aborts in the critical section, it can restart a few
-// times before giving up.
-// We use data driven subtests to manage this so that it will be parallel on its own
-// and not with the other tests, avoiding intermittent failures.
-func TestFastCriticalRestarts(t *testing.T) {
-	testCases := []struct {
-		protocol int
-		progress bool
-	}{
-		{63, false},
-		{64, false},
-		{63, true},
-		{64, true},
-	}
-	for _, tc := range testCases {
-		t.Run(fmt.Sprintf("protocol %d progress %v", tc.protocol, tc.progress), func(t *testing.T) {
-			testFastCriticalRestarts(t, tc.protocol, tc.progress)
-		})
-	}
-}
-
-func testFastCriticalRestarts(t *testing.T, protocol int, progress bool) {
-	t.Parallel()
-
-	tester := newTester()
-	defer tester.terminate()
-
-	// Create a large enough blockchin to actually fast sync on
-	targetBlocks := fsMinFullBlocks + 2*fsPivotInterval - 15
-	hashes, headers, blocks, receipts := tester.makeChain(targetBlocks, 0, tester.genesis, nil, false)
-
-	// Create a tester peer with a critical section header missing (force failures)
-	tester.newPeer("peer", protocol, hashes, headers, blocks, receipts)
-	delete(tester.peerHeaders["peer"], hashes[fsMinFullBlocks-1])
-	tester.downloader.dropPeer = func(id string) {} // We reuse the same "faulty" peer throughout the test
-
-	// Remove all possible pivot state roots and slow down replies (test failure resets later)
-	for i := 0; i < fsPivotInterval; i++ {
-		tester.peerMissingStates["peer"][headers[hashes[fsMinFullBlocks+i]].Root] = true
-	}
-	(tester.downloader.peers.peers["peer"].peer).(*downloadTesterPeer).setDelay(500 * time.Millisecond) // Enough to reach the critical section
-
-	// Synchronise with the peer a few times and make sure they fail until the retry limit
-	for i := 0; i < int(fsCriticalTrials)-1; i++ {
-		// Attempt a sync and ensure it fails properly
-		if err := tester.sync("peer", nil, FastSync); err == nil {
-			t.Fatalf("failing fast sync succeeded: %v", err)
-		}
-		time.Sleep(150 * time.Millisecond) // Make sure no in-flight requests remain
-
-		// If it's the first failure, pivot should be locked => reenable all others to detect pivot changes
-		if i == 0 {
-			time.Sleep(150 * time.Millisecond) // Make sure no in-flight requests remain
-			if tester.downloader.fsPivotLock == nil {
-				time.Sleep(400 * time.Millisecond) // Make sure the first huge timeout expires too
-				t.Fatalf("pivot block not locked in after critical section failure")
-			}
-			tester.lock.Lock()
-			tester.peerHeaders["peer"][hashes[fsMinFullBlocks-1]] = headers[hashes[fsMinFullBlocks-1]]
-			tester.peerMissingStates["peer"] = map[common.Hash]bool{tester.downloader.fsPivotLock.Root: true}
-			(tester.downloader.peers.peers["peer"].peer).(*downloadTesterPeer).setDelay(0)
-			tester.lock.Unlock()
-		}
-	}
-	// Return all nodes if we're testing fast sync progression
-	if progress {
-		tester.lock.Lock()
-		tester.peerMissingStates["peer"] = map[common.Hash]bool{}
-		tester.lock.Unlock()
-
-		if err := tester.sync("peer", nil, FastSync); err != nil {
-			t.Fatalf("failed to synchronise blocks in progressed fast sync: %v", err)
-		}
-		time.Sleep(150 * time.Millisecond) // Make sure no in-flight requests remain
 
-		if fails := atomic.LoadUint32(&tester.downloader.fsPivotFails); fails != 1 {
-			t.Fatalf("progressed pivot trial count mismatch: have %v, want %v", fails, 1)
-		}
-		assertOwnChain(t, tester, targetBlocks+1)
-	} else {
-		if err := tester.sync("peer", nil, FastSync); err == nil {
-			t.Fatalf("succeeded to synchronise blocks in failed fast sync")
-		}
-		time.Sleep(150 * time.Millisecond) // Make sure no in-flight requests remain
-
-		if fails := atomic.LoadUint32(&tester.downloader.fsPivotFails); fails != fsCriticalTrials {
-			t.Fatalf("failed pivot trial count mismatch: have %v, want %v", fails, fsCriticalTrials)
-		}
-	}
-	// Retry limit exhausted, downloader will switch to full sync, should succeed
-	if err := tester.sync("peer", nil, FastSync); err != nil {
-		t.Fatalf("failed to synchronise blocks in slow sync: %v", err)
+		// Flush all goroutines to prevent messing with subsequent tests
+		tester.downloader.peers.peers["peer"].peer.(*floodingTestPeer).pend.Wait()
 	}
-	// Note, we can't assert the chain here because the test asserter assumes sync
-	// completed using a single mode of operation, whereas fast-then-slow can result
-	// in arbitrary intermediate state that's not cleanly verifiable.
 }
diff --git a/eth/downloader/queue.go b/eth/downloader/queue.go
index 6926f1d8c..a1a70e46e 100644
--- a/eth/downloader/queue.go
+++ b/eth/downloader/queue.go
@@ -32,7 +32,11 @@ import (
 	"gopkg.in/karalabe/cookiejar.v2/collections/prque"
 )
 
-var blockCacheLimit = 8192 // Maximum number of blocks to cache before throttling the download
+var (
+	blockCacheItems      = 8192             // Maximum number of blocks to cache before throttling the download
+	blockCacheMemory     = 64 * 1024 * 1024 // Maximum amount of memory to use for block caching
+	blockCacheSizeWeight = 0.1              // Multiplier to approximate the average block size based on past ones
+)
 
 var (
 	errNoFetchesPending = errors.New("no fetches pending")
@@ -41,17 +45,17 @@ var (
 
 // fetchRequest is a currently running data retrieval operation.
 type fetchRequest struct {
-	Peer    *peerConnection     // Peer to which the request was sent
-	From    uint64              // [eth/62] Requested chain element index (used for skeleton fills only)
-	Hashes  map[common.Hash]int // [eth/61] Requested hashes with their insertion index (priority)
-	Headers []*types.Header     // [eth/62] Requested headers, sorted by request order
-	Time    time.Time           // Time when the request was made
+	Peer    *peerConnection // Peer to which the request was sent
+	From    uint64          // [eth/62] Requested chain element index (used for skeleton fills only)
+	Headers []*types.Header // [eth/62] Requested headers, sorted by request order
+	Time    time.Time       // Time when the request was made
 }
 
 // fetchResult is a struct collecting partial results from data fetchers until
 // all outstanding pieces complete and the result as a whole can be processed.
 type fetchResult struct {
-	Pending int // Number of data fetches still pending
+	Pending int         // Number of data fetches still pending
+	Hash    common.Hash // Hash of the header to prevent recalculating
 
 	Header       *types.Header
 	Uncles       []*types.Header
@@ -61,12 +65,10 @@ type fetchResult struct {
 
 // queue represents hashes that are either need fetching or are being fetched
 type queue struct {
-	mode          SyncMode // Synchronisation mode to decide on the block parts to schedule for fetching
-	fastSyncPivot uint64   // Block number where the fast sync pivots into archive synchronisation mode
-
-	headerHead common.Hash // [eth/62] Hash of the last queued header to verify order
+	mode SyncMode // Synchronisation mode to decide on the block parts to schedule for fetching
 
 	// Headers are "special", they download in batches, supported by a skeleton chain
+	headerHead      common.Hash                    // [eth/62] Hash of the last queued header to verify order
 	headerTaskPool  map[uint64]*types.Header       // [eth/62] Pending header retrieval tasks, mapping starting indexes to skeleton headers
 	headerTaskQueue *prque.Prque                   // [eth/62] Priority queue of the skeleton indexes to fetch the filling headers for
 	headerPeerMiss  map[string]map[uint64]struct{} // [eth/62] Set of per-peer header batches known to be unavailable
@@ -87,8 +89,9 @@ type queue struct {
 	receiptPendPool  map[string]*fetchRequest      // [eth/63] Currently pending receipt retrieval operations
 	receiptDonePool  map[common.Hash]struct{}      // [eth/63] Set of the completed receipt fetches
 
-	resultCache  []*fetchResult // Downloaded but not yet delivered fetch results
-	resultOffset uint64         // Offset of the first cached fetch result in the block chain
+	resultCache  []*fetchResult     // Downloaded but not yet delivered fetch results
+	resultOffset uint64             // Offset of the first cached fetch result in the block chain
+	resultSize   common.StorageSize // Approximate size of a block (exponential moving average)
 
 	lock   *sync.Mutex
 	active *sync.Cond
@@ -109,7 +112,7 @@ func newQueue() *queue {
 		receiptTaskQueue: prque.New(),
 		receiptPendPool:  make(map[string]*fetchRequest),
 		receiptDonePool:  make(map[common.Hash]struct{}),
-		resultCache:      make([]*fetchResult, blockCacheLimit),
+		resultCache:      make([]*fetchResult, blockCacheItems),
 		active:           sync.NewCond(lock),
 		lock:             lock,
 	}
@@ -122,10 +125,8 @@ func (q *queue) Reset() {
 
 	q.closed = false
 	q.mode = FullSync
-	q.fastSyncPivot = 0
 
 	q.headerHead = common.Hash{}
-
 	q.headerPendPool = make(map[string]*fetchRequest)
 
 	q.blockTaskPool = make(map[common.Hash]*types.Header)
@@ -138,7 +139,7 @@ func (q *queue) Reset() {
 	q.receiptPendPool = make(map[string]*fetchRequest)
 	q.receiptDonePool = make(map[common.Hash]struct{})
 
-	q.resultCache = make([]*fetchResult, blockCacheLimit)
+	q.resultCache = make([]*fetchResult, blockCacheItems)
 	q.resultOffset = 0
 }
 
@@ -214,27 +215,13 @@ func (q *queue) Idle() bool {
 	return (queued + pending + cached) == 0
 }
 
-// FastSyncPivot retrieves the currently used fast sync pivot point.
-func (q *queue) FastSyncPivot() uint64 {
-	q.lock.Lock()
-	defer q.lock.Unlock()
-
-	return q.fastSyncPivot
-}
-
 // ShouldThrottleBlocks checks if the download should be throttled (active block (body)
 // fetches exceed block cache).
 func (q *queue) ShouldThrottleBlocks() bool {
 	q.lock.Lock()
 	defer q.lock.Unlock()
 
-	// Calculate the currently in-flight block (body) requests
-	pending := 0
-	for _, request := range q.blockPendPool {
-		pending += len(request.Hashes) + len(request.Headers)
-	}
-	// Throttle if more blocks (bodies) are in-flight than free space in the cache
-	return pending >= len(q.resultCache)-len(q.blockDonePool)
+	return q.resultSlots(q.blockPendPool, q.blockDonePool) <= 0
 }
 
 // ShouldThrottleReceipts checks if the download should be throttled (active receipt
@@ -243,13 +230,39 @@ func (q *queue) ShouldThrottleReceipts() bool {
 	q.lock.Lock()
 	defer q.lock.Unlock()
 
-	// Calculate the currently in-flight receipt requests
+	return q.resultSlots(q.receiptPendPool, q.receiptDonePool) <= 0
+}
+
+// resultSlots calculates the number of results slots available for requests
+// whilst adhering to both the item and the memory limit too of the results
+// cache.
+func (q *queue) resultSlots(pendPool map[string]*fetchRequest, donePool map[common.Hash]struct{}) int {
+	// Calculate the maximum length capped by the memory limit
+	limit := len(q.resultCache)
+	if common.StorageSize(len(q.resultCache))*q.resultSize > common.StorageSize(blockCacheMemory) {
+		limit = int((common.StorageSize(blockCacheMemory) + q.resultSize - 1) / q.resultSize)
+	}
+	// Calculate the number of slots already finished
+	finished := 0
+	for _, result := range q.resultCache[:limit] {
+		if result == nil {
+			break
+		}
+		if _, ok := donePool[result.Hash]; ok {
+			finished++
+		}
+	}
+	// Calculate the number of slots currently downloading
 	pending := 0
-	for _, request := range q.receiptPendPool {
-		pending += len(request.Headers)
+	for _, request := range pendPool {
+		for _, header := range request.Headers {
+			if header.Number.Uint64() < q.resultOffset+uint64(limit) {
+				pending++
+			}
+		}
 	}
-	// Throttle if more receipts are in-flight than free space in the cache
-	return pending >= len(q.resultCache)-len(q.receiptDonePool)
+	// Return the free slots to distribute
+	return limit - finished - pending
 }
 
 // ScheduleSkeleton adds a batch of header retrieval tasks to the queue to fill
@@ -323,8 +336,7 @@ func (q *queue) Schedule(headers []*types.Header, from uint64) []*types.Header {
 		q.blockTaskPool[hash] = header
 		q.blockTaskQueue.Push(header, -float32(header.Number.Uint64()))
 
-		if q.mode == FastSync && header.Number.Uint64() <= q.fastSyncPivot {
-			// Fast phase of the fast sync, retrieve receipts too
+		if q.mode == FastSync {
 			q.receiptTaskPool[hash] = header
 			q.receiptTaskQueue.Push(header, -float32(header.Number.Uint64()))
 		}
@@ -335,18 +347,25 @@ func (q *queue) Schedule(headers []*types.Header, from uint64) []*types.Header {
 	return inserts
 }
 
-// WaitResults retrieves and permanently removes a batch of fetch
-// results from the cache. the result slice will be empty if the queue
-// has been closed.
-func (q *queue) WaitResults() []*fetchResult {
+// Results retrieves and permanently removes a batch of fetch results from
+// the cache. the result slice will be empty if the queue has been closed.
+func (q *queue) Results(block bool) []*fetchResult {
 	q.lock.Lock()
 	defer q.lock.Unlock()
 
+	// Count the number of items available for processing
 	nproc := q.countProcessableItems()
 	for nproc == 0 && !q.closed {
+		if !block {
+			return nil
+		}
 		q.active.Wait()
 		nproc = q.countProcessableItems()
 	}
+	// Since we have a batch limit, don't pull more into "dangling" memory
+	if nproc > maxResultsProcess {
+		nproc = maxResultsProcess
+	}
 	results := make([]*fetchResult, nproc)
 	copy(results, q.resultCache[:nproc])
 	if len(results) > 0 {
@@ -363,6 +382,21 @@ func (q *queue) WaitResults() []*fetchResult {
 		}
 		// Advance the expected block number of the first cache entry.
 		q.resultOffset += uint64(nproc)
+
+		// Recalculate the result item weights to prevent memory exhaustion
+		for _, result := range results {
+			size := result.Header.Size()
+			for _, uncle := range result.Uncles {
+				size += uncle.Size()
+			}
+			for _, receipt := range result.Receipts {
+				size += receipt.Size()
+			}
+			for _, tx := range result.Transactions {
+				size += tx.Size()
+			}
+			q.resultSize = common.StorageSize(blockCacheSizeWeight)*size + (1-common.StorageSize(blockCacheSizeWeight))*q.resultSize
+		}
 	}
 	return results
 }
@@ -370,21 +404,9 @@ func (q *queue) WaitResults() []*fetchResult {
 // countProcessableItems counts the processable items.
 func (q *queue) countProcessableItems() int {
 	for i, result := range q.resultCache {
-		// Don't process incomplete or unavailable items.
 		if result == nil || result.Pending > 0 {
 			return i
 		}
-		// Stop before processing the pivot block to ensure that
-		// resultCache has space for fsHeaderForceVerify items. Not
-		// doing this could leave us unable to download the required
-		// amount of headers.
-		if q.mode == FastSync && result.Header.Number.Uint64() == q.fastSyncPivot {
-			for j := 0; j < fsHeaderForceVerify; j++ {
-				if i+j+1 >= len(q.resultCache) || q.resultCache[i+j+1] == nil {
-					return i
-				}
-			}
-		}
 	}
 	return len(q.resultCache)
 }
@@ -473,10 +495,8 @@ func (q *queue) reserveHeaders(p *peerConnection, count int, taskPool map[common
 		return nil, false, nil
 	}
 	// Calculate an upper limit on the items we might fetch (i.e. throttling)
-	space := len(q.resultCache) - len(donePool)
-	for _, request := range pendPool {
-		space -= len(request.Headers)
-	}
+	space := q.resultSlots(pendPool, donePool)
+
 	// Retrieve a batch of tasks, skipping previously failed ones
 	send := make([]*types.Header, 0, count)
 	skip := make([]*types.Header, 0)
@@ -484,6 +504,7 @@ func (q *queue) reserveHeaders(p *peerConnection, count int, taskPool map[common
 	progress := false
 	for proc := 0; proc < space && len(send) < count && !taskQueue.Empty(); proc++ {
 		header := taskQueue.PopItem().(*types.Header)
+		hash := header.Hash()
 
 		// If we're the first to request this task, initialise the result container
 		index := int(header.Number.Int64() - int64(q.resultOffset))
@@ -493,18 +514,19 @@ func (q *queue) reserveHeaders(p *peerConnection, count int, taskPool map[common
 		}
 		if q.resultCache[index] == nil {
 			components := 1
-			if q.mode == FastSync && header.Number.Uint64() <= q.fastSyncPivot {
+			if q.mode == FastSync {
 				components = 2
 			}
 			q.resultCache[index] = &fetchResult{
 				Pending: components,
+				Hash:    hash,
 				Header:  header,
 			}
 		}
 		// If this fetch task is a noop, skip this fetch operation
 		if isNoop(header) {
-			donePool[header.Hash()] = struct{}{}
-			delete(taskPool, header.Hash())
+			donePool[hash] = struct{}{}
+			delete(taskPool, hash)
 
 			space, proc = space-1, proc-1
 			q.resultCache[index].Pending--
@@ -512,7 +534,7 @@ func (q *queue) reserveHeaders(p *peerConnection, count int, taskPool map[common
 			continue
 		}
 		// Otherwise unless the peer is known not to have the data, add to the retrieve list
-		if p.Lacks(header.Hash()) {
+		if p.Lacks(hash) {
 			skip = append(skip, header)
 		} else {
 			send = append(send, header)
@@ -565,9 +587,6 @@ func (q *queue) cancel(request *fetchRequest, taskQueue *prque.Prque, pendPool m
 	if request.From > 0 {
 		taskQueue.Push(request.From, -float32(request.From))
 	}
-	for hash, index := range request.Hashes {
-		taskQueue.Push(hash, float32(index))
-	}
 	for _, header := range request.Headers {
 		taskQueue.Push(header, -float32(header.Number.Uint64()))
 	}
@@ -640,18 +659,11 @@ func (q *queue) expire(timeout time.Duration, pendPool map[string]*fetchRequest,
 			if request.From > 0 {
 				taskQueue.Push(request.From, -float32(request.From))
 			}
-			for hash, index := range request.Hashes {
-				taskQueue.Push(hash, float32(index))
-			}
 			for _, header := range request.Headers {
 				taskQueue.Push(header, -float32(header.Number.Uint64()))
 			}
 			// Add the peer to the expiry report along the the number of failed requests
-			expirations := len(request.Hashes)
-			if expirations < len(request.Headers) {
-				expirations = len(request.Headers)
-			}
-			expiries[id] = expirations
+			expiries[id] = len(request.Headers)
 		}
 	}
 	// Remove the expired requests from the pending pool
@@ -828,14 +840,16 @@ func (q *queue) deliver(id string, taskPool map[common.Hash]*types.Header, taskQ
 			failure = err
 			break
 		}
-		donePool[header.Hash()] = struct{}{}
+		hash := header.Hash()
+
+		donePool[hash] = struct{}{}
 		q.resultCache[index].Pending--
 		useful = true
 		accepted++
 
 		// Clean up a successful fetch
 		request.Headers[i] = nil
-		delete(taskPool, header.Hash())
+		delete(taskPool, hash)
 	}
 	// Return all failed or missing fetches to the queue
 	for _, header := range request.Headers {
@@ -860,7 +874,7 @@ func (q *queue) deliver(id string, taskPool map[common.Hash]*types.Header, taskQ
 
 // Prepare configures the result cache to allow accepting and caching inbound
 // fetch results.
-func (q *queue) Prepare(offset uint64, mode SyncMode, pivot uint64, head *types.Header) {
+func (q *queue) Prepare(offset uint64, mode SyncMode) {
 	q.lock.Lock()
 	defer q.lock.Unlock()
 
@@ -868,6 +882,5 @@ func (q *queue) Prepare(offset uint64, mode SyncMode, pivot uint64, head *types.
 	if q.resultOffset < offset {
 		q.resultOffset = offset
 	}
-	q.fastSyncPivot = pivot
 	q.mode = mode
 }
diff --git a/eth/downloader/statesync.go b/eth/downloader/statesync.go
index 937828b94..9cc65a208 100644
--- a/eth/downloader/statesync.go
+++ b/eth/downloader/statesync.go
@@ -20,7 +20,6 @@ import (
 	"fmt"
 	"hash"
 	"sync"
-	"sync/atomic"
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -294,6 +293,9 @@ func (s *stateSync) loop() error {
 		case <-s.cancel:
 			return errCancelStateFetch
 
+		case <-s.d.cancelCh:
+			return errCancelStateFetch
+
 		case req := <-s.deliver:
 			// Response, disconnect or timeout triggered, drop the peer if stalling
 			log.Trace("Received node data response", "peer", req.peer.id, "count", len(req.response), "dropped", req.dropped, "timeout", !req.dropped && req.timedOut())
@@ -304,15 +306,11 @@ func (s *stateSync) loop() error {
 				s.d.dropPeer(req.peer.id)
 			}
 			// Process all the received blobs and check for stale delivery
-			stale, err := s.process(req)
-			if err != nil {
+			if err := s.process(req); err != nil {
 				log.Warn("Node data write error", "err", err)
 				return err
 			}
-			// The the delivery contains requested data, mark the node idle (otherwise it's a timed out delivery)
-			if !stale {
-				req.peer.SetNodeDataIdle(len(req.response))
-			}
+			req.peer.SetNodeDataIdle(len(req.response))
 		}
 	}
 	return s.commit(true)
@@ -352,6 +350,7 @@ func (s *stateSync) assignTasks() {
 			case s.d.trackStateReq <- req:
 				req.peer.FetchNodeData(req.items)
 			case <-s.cancel:
+			case <-s.d.cancelCh:
 			}
 		}
 	}
@@ -390,7 +389,7 @@ func (s *stateSync) fillTasks(n int, req *stateReq) {
 // process iterates over a batch of delivered state data, injecting each item
 // into a running state sync, re-queuing any items that were requested but not
 // delivered.
-func (s *stateSync) process(req *stateReq) (bool, error) {
+func (s *stateSync) process(req *stateReq) error {
 	// Collect processing stats and update progress if valid data was received
 	duplicate, unexpected := 0, 0
 
@@ -401,7 +400,7 @@ func (s *stateSync) process(req *stateReq) (bool, error) {
 	}(time.Now())
 
 	// Iterate over all the delivered data and inject one-by-one into the trie
-	progress, stale := false, len(req.response) > 0
+	progress := false
 
 	for _, blob := range req.response {
 		prog, hash, err := s.processNodeData(blob)
@@ -415,20 +414,12 @@ func (s *stateSync) process(req *stateReq) (bool, error) {
 		case trie.ErrAlreadyProcessed:
 			duplicate++
 		default:
-			return stale, fmt.Errorf("invalid state node %s: %v", hash.TerminalString(), err)
+			return fmt.Errorf("invalid state node %s: %v", hash.TerminalString(), err)
 		}
-		// If the node delivered a requested item, mark the delivery non-stale
 		if _, ok := req.tasks[hash]; ok {
 			delete(req.tasks, hash)
-			stale = false
 		}
 	}
-	// If we're inside the critical section, reset fail counter since we progressed.
-	if progress && atomic.LoadUint32(&s.d.fsPivotFails) > 1 {
-		log.Trace("Fast-sync progressed, resetting fail counter", "previous", atomic.LoadUint32(&s.d.fsPivotFails))
-		atomic.StoreUint32(&s.d.fsPivotFails, 1) // Don't ever reset to 0, as that will unlock the pivot block
-	}
-
 	// Put unfulfilled tasks back into the retry queue
 	npeers := s.d.peers.Len()
 	for hash, task := range req.tasks {
@@ -441,12 +432,12 @@ func (s *stateSync) process(req *stateReq) (bool, error) {
 		// If we've requested the node too many times already, it may be a malicious
 		// sync where nobody has the right data. Abort.
 		if len(task.attempts) >= npeers {
-			return stale, fmt.Errorf("state node %s failed with all peers (%d tries, %d peers)", hash.TerminalString(), len(task.attempts), npeers)
+			return fmt.Errorf("state node %s failed with all peers (%d tries, %d peers)", hash.TerminalString(), len(task.attempts), npeers)
 		}
 		// Missing item, place into the retry queue.
 		s.tasks[hash] = task
 	}
-	return stale, nil
+	return nil
 }
 
 // processNodeData tries to inject a trie node data blob delivered from a remote