blockchain download and import performance optimizations

alethzero/DownloadView.cpp

@@ -39,13 +39,13 @@ void DownloadView::paintEvent(QPaintEvent*)
 	QPainter p(this);
 
 	p.fillRect(rect(), Qt::white);
-	if (!m_man || m_man->chain().empty() || !m_man->subCount())
+	if (!m_man || m_man->chainEmpty() || !m_man->subCount())
 		return;
 
 	double ratio = (double)rect().width() / rect().height();
 	if (ratio < 1)
 		ratio = 1 / ratio;
-	double n = min(16.0, min(rect().width(), rect().height()) / ceil(sqrt(m_man->chain().size() / ratio)));
+	double n = min(16.0, min(rect().width(), rect().height()) / ceil(sqrt(m_man->chainSize() / ratio)));
 
 //	QSizeF area(rect().width() / floor(rect().width() / n), rect().height() / floor(rect().height() / n));
 	QSizeF area(n, n);

libdevcore/Guards.h

@@ -22,6 +22,7 @@
 #pragma once
 
 #include <mutex>
+#include <atomic>
 #include <boost/thread.hpp>
 
 namespace dev
@@ -61,6 +62,18 @@ struct GenericUnguardSharedBool
 	MutexType& m;
 };
 
+/** @brief Simple lock that waits for release without making context switch */
+class SpinLock
+{
+public:
+	SpinLock() { lck.clear(); }
+	void lock() { while (lck.test_and_set(std::memory_order_acquire)) {} }
+	void unlock() { lck.clear(std::memory_order_release); }
+private:
+	std::atomic_flag lck;
+};
+using SpinGuard = std::lock_guard<SpinLock>;
+
 /** @brief Simple block guard.
  * The expression/block following is guarded though the given mutex.
  * Usage:

libdevcore/Log.cpp

@@ -158,8 +158,8 @@ void dev::setThreadName(string const& _n)
 
 void dev::simpleDebugOut(std::string const& _s, char const*)
 {
-	static Mutex s_lock;
-	Guard l(s_lock);
+	static SpinLock s_lock;
+	SpinGuard l(s_lock);
 
 	cerr << _s << endl << flush;
 

libethcore/EthashAux.cpp

@@ -87,13 +87,10 @@ ethash_params EthashAux::params(h256 const& _seedHash)
 {
 	Guard l(get()->x_epochs);
 	unsigned epoch = 0;
-	try
+	auto epochIter = get()->m_epochs.find(_seedHash);
+	if (epochIter == get()->m_epochs.end())
 	{
-		epoch = get()->m_epochs.at(_seedHash);
-	}
-	catch (...)
-	{
-//		cdebug << "Searching for seedHash " << _seedHash;
+		//		cdebug << "Searching for seedHash " << _seedHash;
 		for (h256 h; h != _seedHash && epoch < 2048; ++epoch, h = sha3(h), get()->m_epochs[h] = epoch) {}
 		if (epoch == 2048)
 		{
@@ -102,6 +99,8 @@ ethash_params EthashAux::params(h256 const& _seedHash)
 			throw std::invalid_argument(error.str());
 		}
 	}
+	else
+		epoch = epochIter->second;
 	return params(epoch * ETHASH_EPOCH_LENGTH);
 }
 

libethereum/BlockChain.cpp

@@ -293,9 +293,14 @@ LastHashes BlockChain::lastHashes(unsigned _n) const
 	Guard l(x_lastLastHashes);
 	if (m_lastLastHashesNumber != _n || m_lastLastHashes.empty())
 	{
-		m_lastLastHashes.resize(256);
+		LastHashes lastHashes(256);
+		//m_lastLastHashes.resize(256);
 		for (unsigned i = 0; i < 256; ++i)
-			m_lastLastHashes[i] = _n >= i ? numberHash(_n - i) : h256();
+		{
+			size_t prevIndex = m_lastLastHashesNumber - _n + i;
+			lastHashes[i] = (prevIndex >= 0 && prevIndex < m_lastLastHashes.size()) ? m_lastLastHashes[prevIndex] : (_n >= i ? numberHash(_n - i) : h256());
+		}
+		m_lastLastHashes = std::move(lastHashes);
 		m_lastLastHashesNumber = _n;
 	}
 	return m_lastLastHashes;
@@ -609,7 +614,6 @@ ImportRoute BlockChain::import(bytes const& _block, OverlayDB const& _db, Import
 		}
 
 		clog(BlockChainNote) << "   Imported and best" << td << " (#" << bi.number << "). Has" << (details(bi.parentHash).children.size() - 1) << "siblings. Route:" << route;
-		noteCanonChanged();
 
 		StructuredLogger::chainNewHead(
 			bi.headerHash(WithoutNonce).abridged(),

libethereum/BlockChain.h

@@ -300,7 +300,6 @@ private:
 	void noteUsed(h256 const& _h, unsigned _extra = (unsigned)-1) const;
 	std::chrono::system_clock::time_point m_lastCollection;
 
-	void noteCanonChanged() const { Guard l(x_lastLastHashes); m_lastLastHashes.clear(); }
 	mutable Mutex x_lastLastHashes;
 	mutable LastHashes m_lastLastHashes;
 	mutable unsigned m_lastLastHashesNumber = (unsigned)-1;

libethereum/DownloadMan.cpp

@@ -50,7 +50,7 @@ h256Set DownloadSub::nextFetch(unsigned _n)
 	m_indices.clear();
 	m_remaining.clear();
 
-	if (!m_man || m_man->chain().empty())
+	if (!m_man || m_man->chainEmpty())
 		return h256Set();
 
 	m_asked = (~(m_man->taken() + m_attempted)).lowest(_n);

libethereum/DownloadMan.h

@@ -143,7 +143,8 @@ public:
 		return ret;
 	}
 
-	h256s chain() const { ReadGuard l(m_lock); return m_chain; }
+	size_t chainSize() const { ReadGuard l(m_lock); return m_chain.size(); }
+	size_t chainEmpty() const { ReadGuard l(m_lock); return m_chain.empty(); }
 	void foreachSub(std::function<void(DownloadSub const&)> const& _f) const { ReadGuard l(x_subs); for(auto i: m_subs) _f(*i); }
 	unsigned subCount() const { ReadGuard l(x_subs); return m_subs.size(); }
 	RangeMask<unsigned> blocksGot() const { ReadGuard l(m_lock); return m_blocksGot; }

libethereum/EthereumHost.cpp

@@ -122,7 +122,7 @@ void EthereumHost::noteDoneBlocks(EthereumPeer* _who, bool _clemency)
 		// Done our chain-get.
 		clog(NetNote) << "Chain download complete.";
 		// 1/100th for each useful block hash.
-		_who->addRating(m_man.chain().size() / 100);
+		_who->addRating(m_man.chainSize() / 100);
 		m_man.reset();
 	}
 	else if (_who->isSyncing())

libethereum/EthereumPeer.cpp

@@ -329,9 +329,10 @@ bool EthereumPeer::interpret(unsigned _id, RLP const& _r)
 	case GetTransactionsPacket: break;	// DEPRECATED.
 	case TransactionsPacket:
 	{
-		clog(NetAllDetail) << "Transactions (" << dec << _r.itemCount() << "entries)";
+		unsigned itemCount = _r.itemCount();
+		clog(NetAllDetail) << "Transactions (" << dec << itemCount << "entries)";
 		Guard l(x_knownTransactions);
-		for (unsigned i = 0; i < _r.itemCount(); ++i)
+		for (unsigned i = 0; i < itemCount; ++i)
 		{
 			auto h = sha3(_r[i].data());
 			m_knownTransactions.insert(h);
@@ -373,21 +374,22 @@ bool EthereumPeer::interpret(unsigned _id, RLP const& _r)
 	}
 	case BlockHashesPacket:
 	{
-		clog(NetMessageSummary) << "BlockHashes (" << dec << _r.itemCount() << "entries)" << (_r.itemCount() ? "" : ": NoMoreHashes");
+		unsigned itemCount = _r.itemCount();
+		clog(NetMessageSummary) << "BlockHashes (" << dec << itemCount << "entries)" << (itemCount ? "" : ": NoMoreHashes");
 
 		if (m_asking != Asking::Hashes)
 		{
 			cwarn << "Peer giving us hashes when we didn't ask for them.";
 			break;
 		}
-		if (_r.itemCount() == 0)
+		if (itemCount == 0)
 		{
 			transition(Asking::Blocks);
 			return true;
 		}
 		unsigned knowns = 0;
 		unsigned unknowns = 0;
-		for (unsigned i = 0; i < _r.itemCount(); ++i)
+		for (unsigned i = 0; i < itemCount; ++i)
 		{
 			addRating(1);
 			auto h = _r[i].toHash<h256>();
@@ -454,12 +456,13 @@ bool EthereumPeer::interpret(unsigned _id, RLP const& _r)
 	}
 	case BlocksPacket:
 	{
-		clog(NetMessageSummary) << "Blocks (" << dec << _r.itemCount() << "entries)" << (_r.itemCount() ? "" : ": NoMoreBlocks");
+		unsigned itemCount = _r.itemCount();
+		clog(NetMessageSummary) << "Blocks (" << dec << itemCount << "entries)" << (itemCount ? "" : ": NoMoreBlocks");
 
 		if (m_asking != Asking::Blocks)
 			clog(NetWarn) << "Unexpected Blocks received!";
 
-		if (_r.itemCount() == 0)
+		if (itemCount == 0)
 		{
 			// Got to this peer's latest block - just give up.
 			transition(Asking::Nothing);
@@ -472,7 +475,7 @@ bool EthereumPeer::interpret(unsigned _id, RLP const& _r)
 		unsigned got = 0;
 		unsigned repeated = 0;
 
-		for (unsigned i = 0; i < _r.itemCount(); ++i)
+		for (unsigned i = 0; i < itemCount; ++i)
 		{
 			auto h = BlockInfo::headerHash(_r[i].data());
 			if (m_sub.noteBlock(h))