Backports into beta (#2512)

* RocksDB version bump

* Preserve cache on reverting the snapshot (#2488)

* Preserve cache on reverting the snapshot

* Renamed merge_with into replace_with

* Renamed and documented snapshotting methods

* Track dirty accounts in the state (#2461)

* State to track dirty accounts

* Removed clone_for_snapshot

* Renaming stuff

* Documentation and other minor fixes

* Replaced MaybeAccount with Option

* Adjustable stack size for EVM (#2483)

* stack size for io workers & evm threshold

* rust way to remember stack size

* right value

* 24kb size

* some stack reduction

* Fixed overflow panic in handshake_panic (#2495)

Cargo.lock

@@ -237,7 +237,7 @@ version = "0.5.4"
 source = "git+https://github.com/ethcore/rust-secp256k1#a9a0b1be1f39560ca86e8fc8e55e205a753ff25c"
 dependencies = [
  "arrayvec 0.3.16 (registry+https://github.com/rust-lang/crates.io-index)",
- "gcc 0.3.28 (registry+https://github.com/rust-lang/crates.io-index)",
+ "gcc 0.3.35 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.12 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.3.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-serialize 0.3.19 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -572,8 +572,11 @@ dependencies = [
 
 [[package]]
 name = "gcc"
-version = "0.3.28"
+version = "0.3.35"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "rayon 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
+]
 
 [[package]]
 name = "glob"
@@ -886,7 +889,7 @@ name = "nanomsg-sys"
 version = "0.5.0"
 source = "git+https://github.com/ethcore/nanomsg.rs.git#c40fe442c9afaea5b38009a3d992ca044dcceb00"
 dependencies = [
- "gcc 0.3.28 (registry+https://github.com/rust-lang/crates.io-index)",
+ "gcc 0.3.35 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.12 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1222,7 +1225,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 [[package]]
 name = "rocksdb"
 version = "0.4.5"
-source = "git+https://github.com/ethcore/rust-rocksdb#485dd747a2c9a9f910fc8ac696fc9edf5fa22aa3"
+source = "git+https://github.com/ethcore/rust-rocksdb#ffc7c82380fe8569f85ae6743f7f620af2d4a679"
 dependencies = [
  "libc 0.2.12 (registry+https://github.com/rust-lang/crates.io-index)",
  "rocksdb-sys 0.3.0 (git+https://github.com/ethcore/rust-rocksdb)",
@@ -1231,9 +1234,9 @@ dependencies = [
 [[package]]
 name = "rocksdb-sys"
 version = "0.3.0"
-source = "git+https://github.com/ethcore/rust-rocksdb#485dd747a2c9a9f910fc8ac696fc9edf5fa22aa3"
+source = "git+https://github.com/ethcore/rust-rocksdb#ffc7c82380fe8569f85ae6743f7f620af2d4a679"
 dependencies = [
- "gcc 0.3.28 (registry+https://github.com/rust-lang/crates.io-index)",
+ "gcc 0.3.35 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.12 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1264,7 +1267,7 @@ name = "rust-crypto"
 version = "0.2.36"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "gcc 0.3.28 (registry+https://github.com/rust-lang/crates.io-index)",
+ "gcc 0.3.35 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.12 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.3.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-serialize 0.3.19 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1332,7 +1335,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 name = "sha3"
 version = "0.1.0"
 dependencies = [
- "gcc 0.3.28 (registry+https://github.com/rust-lang/crates.io-index)",
+ "gcc 0.3.35 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1669,7 +1672,7 @@ dependencies = [
 "checksum elastic-array 0.4.0 (git+https://github.com/ethcore/elastic-array)" = "<none>"
 "checksum env_logger 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)" = "aba65b63ffcc17ffacd6cf5aa843da7c5a25e3bd4bbe0b7def8b214e411250e5"
 "checksum eth-secp256k1 0.5.4 (git+https://github.com/ethcore/rust-secp256k1)" = "<none>"
-"checksum gcc 0.3.28 (registry+https://github.com/rust-lang/crates.io-index)" = "3da3a2cbaeb01363c8e3704fd9fd0eb2ceb17c6f27abd4c1ef040fb57d20dc79"
+"checksum gcc 0.3.35 (registry+https://github.com/rust-lang/crates.io-index)" = "91ecd03771effb0c968fd6950b37e89476a578aaf1c70297d8e92b6516ec3312"
 "checksum glob 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)" = "8be18de09a56b60ed0edf84bc9df007e30040691af7acd1c41874faac5895bfb"
 "checksum hamming 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "65043da274378d68241eb9a8f8f8aa54e349136f7b8e12f63e3ef44043cc30e1"
 "checksum heapsize 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)" = "abb306abb8d398e053cfb1b3e7b72c2f580be048b85745c52652954f8ad1439c"

ethcore/src/account.rs

@@ -16,7 +16,6 @@
 
 //! Single account in the system.
 
-use std::collections::hash_map::Entry;
 use util::*;
 use pod_account::*;
 use account_db::*;
@@ -24,9 +23,11 @@ use lru_cache::LruCache;
 
 use std::cell::{RefCell, Cell};
 
-const STORAGE_CACHE_ITEMS: usize = 4096;
+const STORAGE_CACHE_ITEMS: usize = 8192;
 
 /// Single account in the system.
+/// Keeps track of changes to the code and storage.
+/// The changes are applied in `commit_storage` and `commit_code`
 pub struct Account {
 	// Balance of the account.
 	balance: U256,
@@ -46,8 +47,6 @@ pub struct Account {
 	code_size: Option<u64>,
 	// Code cache of the account.
 	code_cache: Arc<Bytes>,
-	// Account is new or has been modified.
-	filth: Filth,
 	// Account code new or has been modified.
 	code_filth: Filth,
 	// Cached address hash.
@@ -67,7 +66,6 @@ impl Account {
 			code_hash: code.sha3(),
 			code_size: Some(code.len() as u64),
 			code_cache: Arc::new(code),
-			filth: Filth::Dirty,
 			code_filth: Filth::Dirty,
 			address_hash: Cell::new(None),
 		}
@@ -89,7 +87,6 @@ impl Account {
 			code_filth: Filth::Dirty,
 			code_size: Some(pod.code.as_ref().map_or(0, |c| c.len() as u64)),
 			code_cache: Arc::new(pod.code.map_or_else(|| { warn!("POD account with unknown code is being created! Assuming no code."); vec![] }, |c| c)),
-			filth: Filth::Dirty,
 			address_hash: Cell::new(None),
 		}
 	}
@@ -105,7 +102,6 @@ impl Account {
 			code_hash: SHA3_EMPTY,
 			code_cache: Arc::new(vec![]),
 			code_size: Some(0),
-			filth: Filth::Dirty,
 			code_filth: Filth::Clean,
 			address_hash: Cell::new(None),
 		}
@@ -123,7 +119,6 @@ impl Account {
 			code_hash: r.val_at(3),
 			code_cache: Arc::new(vec![]),
 			code_size: None,
-			filth: Filth::Clean,
 			code_filth: Filth::Clean,
 			address_hash: Cell::new(None),
 		}
@@ -141,7 +136,6 @@ impl Account {
 			code_hash: SHA3_EMPTY,
 			code_cache: Arc::new(vec![]),
 			code_size: None,
-			filth: Filth::Dirty,
 			code_filth: Filth::Clean,
 			address_hash: Cell::new(None),
 		}
@@ -153,7 +147,6 @@ impl Account {
 		self.code_hash = code.sha3();
 		self.code_cache = Arc::new(code);
 		self.code_size = Some(self.code_cache.len() as u64);
-		self.filth = Filth::Dirty;
 		self.code_filth = Filth::Dirty;
 	}
 
@@ -164,17 +157,7 @@ impl Account {
 
 	/// Set (and cache) the contents of the trie's storage at `key` to `value`.
 	pub fn set_storage(&mut self, key: H256, value: H256) {
-		match self.storage_changes.entry(key) {
+		self.storage_changes.insert(key, value);
-			Entry::Occupied(ref mut entry) if entry.get() != &value => {
-				entry.insert(value);
-				self.filth = Filth::Dirty;
-			},
-			Entry::Vacant(entry) => {
-				entry.insert(value);
-				self.filth = Filth::Dirty;
-			},
-			_ => {},
-		}
 	}
 
 	/// Get (and cache) the contents of the trie's storage at `key`.
@@ -263,17 +246,6 @@ impl Account {
 		!self.code_cache.is_empty() || (self.code_cache.is_empty() && self.code_hash == SHA3_EMPTY)
 	}
 
-	/// Is this a new or modified account?
-	pub fn is_dirty(&self) -> bool {
-		self.filth == Filth::Dirty || self.code_filth == Filth::Dirty || !self.storage_is_clean()
-	}
-
-	/// Mark account as clean.
-	pub fn set_clean(&mut self) {
-		assert!(self.storage_is_clean());
-		self.filth = Filth::Clean
-	}
-
 	/// Provide a database to get `code_hash`. Should not be called if it is a contract without code.
 	pub fn cache_code(&mut self, db: &AccountDB) -> bool {
 		// TODO: fill out self.code_cache;
@@ -326,25 +298,18 @@ impl Account {
 	/// Increment the nonce of the account by one.
 	pub fn inc_nonce(&mut self) {
 		self.nonce = self.nonce + U256::from(1u8);
-		self.filth = Filth::Dirty;
 	}
 
-	/// Increment the nonce of the account by one.
+	/// Increase account balance.
 	pub fn add_balance(&mut self, x: &U256) {
-		if !x.is_zero() {
 		self.balance = self.balance + *x;
-			self.filth = Filth::Dirty;
-		}
 	}
 
-	/// Increment the nonce of the account by one.
+	/// Decrease account balance.
 	/// Panics if balance is less than `x`
 	pub fn sub_balance(&mut self, x: &U256) {
-		if !x.is_zero() {
 		assert!(self.balance >= *x);
 		self.balance = self.balance - *x;
-			self.filth = Filth::Dirty;
-		}
 	}
 
 	/// Commit the `storage_changes` to the backing DB and update `storage_root`.
@@ -406,7 +371,6 @@ impl Account {
 			code_hash: self.code_hash.clone(),
 			code_size: self.code_size.clone(),
 			code_cache: self.code_cache.clone(),
-			filth: self.filth,
 			code_filth: self.code_filth,
 			address_hash: self.address_hash.clone(),
 		}
@@ -427,10 +391,10 @@ impl Account {
 		account
 	}
 
-	/// Replace self with the data from other account merging storage cache
+	/// Replace self with the data from other account merging storage cache.
-	pub fn merge_with(&mut self, other: Account) {
+	/// Basic account data and all modifications are overwritten
-		assert!(self.storage_is_clean());
+	/// with new values.
-		assert!(other.storage_is_clean());
+	pub fn overwrite_with(&mut self, other: Account) {
 		self.balance = other.balance;
 		self.nonce = other.nonce;
 		self.storage_root = other.storage_root;
@@ -443,6 +407,7 @@ impl Account {
 		for (k, v) in other.storage_cache.into_inner().into_iter() {
 			cache.insert(k.clone() , v.clone()); //TODO: cloning should not be required here
 		}
+		self.storage_changes = other.storage_changes;
 	}
 }
 

ethcore/src/executive.rs

@@ -26,10 +26,10 @@ use trace::{FlatTrace, Tracer, NoopTracer, ExecutiveTracer, VMTrace, VMTracer, E
 use crossbeam;
 pub use types::executed::{Executed, ExecutionResult};
 
-/// Max depth to avoid stack overflow (when it's reached we start a new thread with VM)
+/// Roughly estimate what stack size each level of evm depth will use
 /// TODO [todr] We probably need some more sophisticated calculations here (limit on my machine 132)
 /// Maybe something like here: `https://github.com/ethereum/libethereum/blob/4db169b8504f2b87f7d5a481819cfb959fc65f6c/libethereum/ExtVM.cpp`
-const MAX_VM_DEPTH_FOR_THREAD: usize = 64;
+const STACK_SIZE_PER_DEPTH: usize = 24*1024;
 
 /// Returns new address created from address and given nonce.
 pub fn contract_address(address: &Address, nonce: &U256) -> Address {
@@ -148,12 +148,13 @@ impl<'a> Executive<'a> {
 
 		// TODO: we might need bigints here, or at least check overflows.
 		let balance = self.state.balance(&sender);
-		let gas_cost = U512::from(t.gas) * U512::from(t.gas_price);
+		let gas_cost = t.gas.full_mul(t.gas_price);
 		let total_cost = U512::from(t.value) + gas_cost;
 
 		// avoid unaffordable transactions
-		if U512::from(balance) < total_cost {
+		let balance512 = U512::from(balance);
-			return Err(From::from(ExecutionError::NotEnoughCash { required: total_cost, got: U512::from(balance) }));
+		if balance512 < total_cost {
+			return Err(From::from(ExecutionError::NotEnoughCash { required: total_cost, got: balance512 }));
 		}
 
 		// NOTE: there can be no invalid transactions from this point.
@@ -212,8 +213,11 @@ impl<'a> Executive<'a> {
 		tracer: &mut T,
 		vm_tracer: &mut V
 	) -> evm::Result<U256> where T: Tracer, V: VMTracer {
+
+		let depth_threshold = ::io::LOCAL_STACK_SIZE.with(|sz| sz.get() / STACK_SIZE_PER_DEPTH);
+
 		// Ordinary execution - keep VM in same thread
-		if (self.depth + 1) % MAX_VM_DEPTH_FOR_THREAD != 0 {
+		if (self.depth + 1) % depth_threshold != 0 {
 			let vm_factory = self.vm_factory;
 			let mut ext = self.as_externalities(OriginInfo::from(&params), unconfirmed_substate, output_policy, tracer, vm_tracer);
 			trace!(target: "executive", "ext.schedule.have_delegate_call: {}", ext.schedule().have_delegate_call);
@@ -265,7 +269,7 @@ impl<'a> Executive<'a> {
 			let cost = self.engine.cost_of_builtin(&params.code_address, data);
 			if cost <= params.gas {
 				self.engine.execute_builtin(&params.code_address, data, &mut output);
-				self.state.clear_snapshot();
+				self.state.discard_snapshot();
 
 				// trace only top level calls to builtins to avoid DDoS attacks
 				if self.depth == 0 {
@@ -285,7 +289,7 @@ impl<'a> Executive<'a> {
 				Ok(params.gas - cost)
 			} else {
 				// just drain the whole gas
-				self.state.revert_snapshot();
+				self.state.revert_to_snapshot();
 
 				tracer.trace_failed_call(trace_info, vec![]);
 
@@ -331,7 +335,7 @@ impl<'a> Executive<'a> {
 				res
 			} else {
 				// otherwise it's just a basic transaction, only do tracing, if necessary.
-				self.state.clear_snapshot();
+				self.state.discard_snapshot();
 
 				tracer.trace_call(trace_info, U256::zero(), trace_output, vec![]);
 				Ok(params.gas)
@@ -413,7 +417,7 @@ impl<'a> Executive<'a> {
 
 		// real ammount to refund
 		let gas_left_prerefund = match result { Ok(x) => x, _ => 0.into() };
-		let refunded = cmp::min(refunds_bound, (t.gas - gas_left_prerefund) / U256::from(2));
+		let refunded = cmp::min(refunds_bound, (t.gas - gas_left_prerefund) >> 1);
 		let gas_left = gas_left_prerefund + refunded;
 
 		let gas_used = t.gas - gas_left;
@@ -473,10 +477,10 @@ impl<'a> Executive<'a> {
 				| Err(evm::Error::BadInstruction {.. })
 				| Err(evm::Error::StackUnderflow {..})
 				| Err(evm::Error::OutOfStack {..}) => {
-					self.state.revert_snapshot();
+					self.state.revert_to_snapshot();
 			},
 			Ok(_) | Err(evm::Error::Internal) => {
-				self.state.clear_snapshot();
+				self.state.discard_snapshot();
 				substate.accrue(un_substate);
 			}
 		}

ethcore/src/state.rs

@@ -15,7 +15,7 @@
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.
 
 use std::cell::{RefCell, RefMut};
-
+use std::collections::hash_map::Entry;
 use common::*;
 use engines::Engine;
 use executive::{Executive, TransactOptions};
@@ -38,42 +38,83 @@ pub struct ApplyOutcome {
 /// Result type for the execution ("application") of a transaction.
 pub type ApplyResult = Result<ApplyOutcome, Error>;
 
-#[derive(Debug)]
+#[derive(Eq, PartialEq, Clone, Copy, Debug)]
-enum AccountEntry {
+/// Account modification state. Used to check if the account was
-	/// Contains account data.
+/// Modified in between commits and overall.
-	Cached(Account),
+enum AccountState {
-	/// Account has been deleted.
+	/// Account was never modified in this state object.
-	Killed,
+	Clean,
-	/// Account does not exist.
+	/// Account has been modified and is not committed to the trie yet.
-	Missing,
+	/// This is set than any of the account data is changed, including
+	/// storage and code.
+	Dirty,
+	/// Account was modified and committed to the trie.
+	Commited,
 }
 
+#[derive(Debug)]
+/// In-memory copy of the account data. Holds the optional account
+/// and the modification status.
+/// Account entry can contain existing (`Some`) or non-existing
+/// account (`None`)
+struct AccountEntry {
+	account: Option<Account>,
+	state: AccountState,
+}
+
+// Account cache item. Contains account data and
+// modification state
 impl AccountEntry {
 	fn is_dirty(&self) -> bool {
-		match *self {
+		self.state == AccountState::Dirty
-			AccountEntry::Cached(ref a) => a.is_dirty(),
-			AccountEntry::Killed => true,
-			AccountEntry::Missing => false,
-		}
 	}
 
-	/// Clone dirty data into new `AccountEntry`.
+	/// Clone dirty data into new `AccountEntry`. This includes
+	/// basic account data and modified storage keys.
 	/// Returns None if clean.
-	fn clone_dirty(&self) -> Option<AccountEntry> {
+	fn clone_if_dirty(&self) -> Option<AccountEntry> {
-		match *self {
+		match self.is_dirty() {
-			AccountEntry::Cached(ref acc) if acc.is_dirty() => Some(AccountEntry::Cached(acc.clone_dirty())),
+			true => Some(self.clone_dirty()),
-			AccountEntry::Killed => Some(AccountEntry::Killed),
+			false => None,
-			_ => None,
 		}
 	}
 
-	/// Clone account entry data that needs to be saved in the snapshot.
+	/// Clone dirty data into new `AccountEntry`. This includes
-	/// This includes basic account information and all locally cached storage keys
+	/// basic account data and modified storage keys.
-	fn clone_for_snapshot(&self) -> AccountEntry {
+	fn clone_dirty(&self) -> AccountEntry {
-		match *self {
+		AccountEntry {
-			AccountEntry::Cached(ref acc) => AccountEntry::Cached(acc.clone_all()),
+			account: self.account.as_ref().map(Account::clone_dirty),
-			AccountEntry::Killed => AccountEntry::Killed,
+			state: self.state,
-			AccountEntry::Missing => AccountEntry::Missing,
+		}
+	}
+
+	// Create a new account entry and mark it as dirty.
+	fn new_dirty(account: Option<Account>) -> AccountEntry {
+		AccountEntry {
+			account: account,
+			state: AccountState::Dirty,
+		}
+	}
+
+	// Create a new account entry and mark it as clean.
+	fn new_clean(account: Option<Account>) -> AccountEntry {
+		AccountEntry {
+			account: account,
+			state: AccountState::Clean,
+		}
+	}
+
+	// Replace data with another entry but preserve storage cache.
+	fn overwrite_with(&mut self, other: AccountEntry) {
+		self.state = other.state;
+		match other.account {
+			Some(acc) => match self.account {
+				Some(ref mut ours) => {
+					ours.overwrite_with(acc);
+				},
+				None => {},
+			},
+			None => self.account = None,
 		}
 	}
 }
@@ -86,6 +127,9 @@ impl AccountEntry {
 /// locally from previous commits. Global cache reflects the database
 /// state and never contains any changes.
 ///
+/// Cache items contains account data, or the flag that account does not exist
+/// and modification state (see `AccountState`)
+///
 /// Account data can be in the following cache states:
 /// * In global but not local - something that was queried from the database,
 /// but never modified
@@ -99,12 +143,32 @@ impl AccountEntry {
 /// then global state cache. If data is not found in any of the caches
 /// it is loaded from the DB to the local cache.
 ///
+/// **** IMPORTANT *************************************************************
+/// All the modifications to the account data must set the `Dirty` state in the
+/// `AccountEntry`. This is done in `require` and `require_or_from`. So just
+/// use that.
+/// ****************************************************************************
+///
 /// Upon destruction all the local cache data merged into the global cache.
 /// The merge might be rejected if current state is non-canonical.
+///
+/// State snapshotting.
+///
+/// A new snapshot can be created with `snapshot()`. Snapshots can be
+/// created in a hierarchy.
+/// When a snapshot is active all changes are applied directly into
+/// `cache` and the original value is copied into an active snapshot.
+/// Reverting a snapshot with `revert_to_snapshot` involves copying
+/// original values from the latest snapshot back into `cache`. The code
+/// takes care not to overwrite cached storage while doing that.
+/// Snapshot can be discateded with `discard_snapshot`. All of the orignal
+/// backed-up values are moved into a parent snapshot (if any).
+///
 pub struct State {
 	db: StateDB,
 	root: H256,
 	cache: RefCell<HashMap<Address, AccountEntry>>,
+	// The original account is preserved in
 	snapshots: RefCell<Vec<HashMap<Address, Option<AccountEntry>>>>,
 	account_start_nonce: U256,
 	trie_factory: TrieFactory,
@@ -158,35 +222,48 @@ impl State {
 		Ok(state)
 	}
 
-	/// Create a recoverable snaphot of this state
+	/// Create a recoverable snaphot of this state.
 	pub fn snapshot(&mut self) {
 		self.snapshots.borrow_mut().push(HashMap::new());
 	}
 
-	/// Merge last snapshot with previous
+	/// Merge last snapshot with previous.
-	pub fn clear_snapshot(&mut self) {
+	pub fn discard_snapshot(&mut self) {
 		// merge with previous snapshot
 		let last = self.snapshots.borrow_mut().pop();
 		if let Some(mut snapshot) = last {
 			if let Some(ref mut prev) = self.snapshots.borrow_mut().last_mut() {
+				if prev.is_empty() {
+					**prev = snapshot;
+				} else {
 					for (k, v) in snapshot.drain() {
 						prev.entry(k).or_insert(v);
 					}
 				}
 			}
 		}
+	}
 
-	/// Revert to snapshot
+	/// Revert to the last snapshot and discard it.
-	pub fn revert_snapshot(&mut self) {
+	pub fn revert_to_snapshot(&mut self) {
 		if let Some(mut snapshot) = self.snapshots.borrow_mut().pop() {
 			for (k, v) in snapshot.drain() {
 				match v {
 					Some(v) => {
-						self.cache.borrow_mut().insert(k, v);
+						match self.cache.borrow_mut().entry(k) {
+							Entry::Occupied(mut e) => {
+								// Merge snapshotted changes back into the main account
+								// storage preserving the cache.
+								e.get_mut().overwrite_with(v);
+							},
+							Entry::Vacant(e) => {
+								e.insert(v);
+							}
+						}
 					},
 					None => {
 						match self.cache.borrow_mut().entry(k) {
-							::std::collections::hash_map::Entry::Occupied(e) => {
+							Entry::Occupied(e) => {
 								if e.get().is_dirty() {
 									e.remove();
 								}
@@ -200,19 +277,26 @@ impl State {
 	}
 
 	fn insert_cache(&self, address: &Address, account: AccountEntry) {
+		// Dirty account which is not in the cache means this is a new account.
+		// It goes directly into the snapshot as there's nothing to rever to.
+		//
+		// In all other cases account is read as clean first, and after that made
+		// dirty in and added to the snapshot with `note_cache`.
+		if account.is_dirty() {
 			if let Some(ref mut snapshot) = self.snapshots.borrow_mut().last_mut() {
 				if !snapshot.contains_key(address) {
 					snapshot.insert(address.clone(), self.cache.borrow_mut().insert(address.clone(), account));
 					return;
 				}
 			}
+		}
 		self.cache.borrow_mut().insert(address.clone(), account);
 	}
 
 	fn note_cache(&self, address: &Address) {
 		if let Some(ref mut snapshot) = self.snapshots.borrow_mut().last_mut() {
 			if !snapshot.contains_key(address) {
-				snapshot.insert(address.clone(), self.cache.borrow().get(address).map(AccountEntry::clone_for_snapshot));
+				snapshot.insert(address.clone(), self.cache.borrow().get(address).map(AccountEntry::clone_dirty));
 			}
 		}
 	}
@@ -231,12 +315,12 @@ impl State {
 	/// Create a new contract at address `contract`. If there is already an account at the address
 	/// it will have its code reset, ready for `init_code()`.
 	pub fn new_contract(&mut self, contract: &Address, balance: U256) {
-		self.insert_cache(contract, AccountEntry::Cached(Account::new_contract(balance, self.account_start_nonce)));
+		self.insert_cache(contract, AccountEntry::new_dirty(Some(Account::new_contract(balance, self.account_start_nonce))));
 	}
 
 	/// Remove an existing account.
 	pub fn kill_account(&mut self, account: &Address) {
-		self.insert_cache(account, AccountEntry::Killed);
+		self.insert_cache(account, AccountEntry::new_dirty(None));
 	}
 
 	/// Determine whether an account exists.
@@ -271,8 +355,8 @@ impl State {
 			let local_cache = self.cache.borrow_mut();
 			let mut local_account = None;
 			if let Some(maybe_acc) = local_cache.get(address) {
-				match *maybe_acc {
+				match maybe_acc.account {
-					AccountEntry::Cached(ref account) => {
+					Some(ref account) => {
 						if let Some(value) = account.cached_storage_at(key) {
 							return value;
 						} else {
@@ -288,7 +372,7 @@ impl State {
 				return result;
 			}
 			if let Some(ref mut acc) = local_account {
-				if let AccountEntry::Cached(ref account) = **acc {
+				if let Some(ref account) = acc.account {
 					return account.storage_at(&AccountDB::from_hash(self.db.as_hashdb(), account.address_hash(address)), key)
 				} else {
 					return H256::new()
@@ -303,10 +387,7 @@ impl State {
 			Err(e) => panic!("Potential DB corruption encountered: {}", e),
 		};
 		let r = maybe_acc.as_ref().map_or(H256::new(), |a| a.storage_at(&AccountDB::from_hash(self.db.as_hashdb(), a.address_hash(address)), key));
-		match maybe_acc {
+		self.insert_cache(address, AccountEntry::new_clean(maybe_acc));
-			Some(account) => self.insert_cache(address, AccountEntry::Cached(account)),
-			None => self.insert_cache(address, AccountEntry::Missing),
-		}
 		r
 	}
 
@@ -330,14 +411,18 @@ impl State {
 	/// Add `incr` to the balance of account `a`.
 	pub fn add_balance(&mut self, a: &Address, incr: &U256) {
 		trace!(target: "state", "add_balance({}, {}): {}", a, incr, self.balance(a));
+		if !incr.is_zero() || !self.exists(a) {
 			self.require(a, false).add_balance(incr);
 		}
+	}
 
 	/// Subtract `decr` from the balance of account `a`.
 	pub fn sub_balance(&mut self, a: &Address, decr: &U256) {
 		trace!(target: "state", "sub_balance({}, {}): {}", a, decr, self.balance(a));
+		if !decr.is_zero() || !self.exists(a) {
 			self.require(a, false).sub_balance(decr);
 		}
+	}
 
 	/// Subtracts `by` from the balance of `from` and adds it to that of `to`.
 	pub fn transfer_balance(&mut self, from: &Address, to: &Address, by: &U256) {
@@ -352,8 +437,10 @@ impl State {
 
 	/// Mutate storage of account `a` so that it is `value` for `key`.
 	pub fn set_storage(&mut self, a: &Address, key: H256, value: H256) {
+		if self.storage_at(a, &key) != value {
 			self.require(a, false).set_storage(key, value)
 		}
+	}
 
 	/// Initialise the code of account `a` so that it is `code`.
 	/// NOTE: Account should have been created with `new_contract`.
@@ -392,10 +479,9 @@ impl State {
 		accounts: &mut HashMap<Address, AccountEntry>
 	) -> Result<(), Error> {
 		// first, commit the sub trees.
-		// TODO: is this necessary or can we dispense with the `ref mut a` for just `a`?
+		for (address, ref mut a) in accounts.iter_mut().filter(|&(_, ref a)| a.is_dirty()) {
-		for (address, ref mut a) in accounts.iter_mut() {
+			match a.account {
-			match a {
+				Some(ref mut account) => {
-				&mut&mut AccountEntry::Cached(ref mut account) if account.is_dirty() => {
 					db.note_account_bloom(&address);
 					let mut account_db = AccountDBMut::from_hash(db.as_hashdb_mut(), account.address_hash(address));
 					account.commit_storage(trie_factory, &mut account_db);
@@ -407,17 +493,15 @@ impl State {
 
 		{
 			let mut trie = trie_factory.from_existing(db.as_hashdb_mut(), root).unwrap();
-			for (address, ref mut a) in accounts.iter_mut() {
+			for (address, ref mut a) in accounts.iter_mut().filter(|&(_, ref a)| a.is_dirty()) {
-				match **a {
+				a.state = AccountState::Commited;
-					AccountEntry::Cached(ref mut account) if account.is_dirty() => {
+				match a.account {
-						account.set_clean();
+					Some(ref mut account) => {
 						try!(trie.insert(address, &account.rlp()));
 					},
-					AccountEntry::Killed => {
+					None => {
 						try!(trie.remove(address));
-						**a = AccountEntry::Missing;
 					},
-					_ => {},
 				}
 			}
 		}
@@ -427,18 +511,9 @@ impl State {
 
 	fn commit_cache(&mut self) {
 		let mut addresses = self.cache.borrow_mut();
-		for (address, a) in addresses.drain() {
+		trace!("Committing cache {:?} entries", addresses.len());
-			match a {
+		for (address, a) in addresses.drain().filter(|&(_, ref a)| !a.is_dirty()) {
-				AccountEntry::Cached(account) => {
+			self.db.cache_account(address, a.account);
-					if !account.is_dirty() {
-						self.db.cache_account(address, Some(account));
-					}
-				},
-				AccountEntry::Missing => {
-					self.db.cache_account(address, None);
-				},
-				_ => {},
-			}
 		}
 	}
 
@@ -460,7 +535,7 @@ impl State {
 		assert!(self.snapshots.borrow().is_empty());
 		for (add, acc) in accounts.drain().into_iter() {
 			self.db.note_account_bloom(&add);
-			self.cache.borrow_mut().insert(add, AccountEntry::Cached(Account::from_pod(acc)));
+			self.cache.borrow_mut().insert(add, AccountEntry::new_dirty(Some(Account::from_pod(acc))));
 		}
 	}
 
@@ -470,7 +545,7 @@ impl State {
 		// TODO: handle database rather than just the cache.
 		// will need fat db.
 		PodState::from(self.cache.borrow().iter().fold(BTreeMap::new(), |mut m, (add, opt)| {
-			if let AccountEntry::Cached(ref acc) = *opt {
+			if let Some(ref acc) = opt.account {
 				m.insert(add.clone(), PodAccount::from_account(acc));
 			}
 			m
@@ -519,7 +594,7 @@ impl State {
 		where F: Fn(Option<&Account>) -> U {
 		// check local cache first
 		if let Some(ref mut maybe_acc) = self.cache.borrow_mut().get_mut(a) {
-			if let AccountEntry::Cached(ref mut account) = **maybe_acc {
+			if let Some(ref mut account) = maybe_acc.account {
 				Self::update_account_cache(require, account, a, self.db.as_hashdb());
 				return f(Some(account));
 			}
@@ -547,8 +622,8 @@ impl State {
 				}
 				let r = f(maybe_acc.as_ref());
 				match maybe_acc {
-					Some(account) => self.insert_cache(a, AccountEntry::Cached(account)),
+					Some(account) => self.insert_cache(a, AccountEntry::new_clean(Some(account))),
-					None => self.insert_cache(a, AccountEntry::Missing),
+					None => self.insert_cache(a, AccountEntry::new_clean(None)),
 				}
 				r
 			}
@@ -568,36 +643,39 @@ impl State {
 		let contains_key = self.cache.borrow().contains_key(a);
 		if !contains_key {
 			match self.db.get_cached_account(a) {
-				Some(Some(acc)) => self.insert_cache(a, AccountEntry::Cached(acc)),
+				Some(Some(acc)) => self.insert_cache(a, AccountEntry::new_clean(Some(acc))),
-				Some(None) => self.insert_cache(a, AccountEntry::Missing),
+				Some(None) => self.insert_cache(a, AccountEntry::new_clean(None)),
 				None => {
 					let maybe_acc = if self.db.check_account_bloom(a) {
 						let db = self.trie_factory.readonly(self.db.as_hashdb(), &self.root).expect(SEC_TRIE_DB_UNWRAP_STR);
 						let maybe_acc = match db.get(a) {
-							Ok(Some(acc)) => AccountEntry::Cached(Account::from_rlp(acc)),
+							Ok(Some(acc)) => AccountEntry::new_clean(Some(Account::from_rlp(acc))),
-							Ok(None) => AccountEntry::Missing,
+							Ok(None) => AccountEntry::new_clean(None),
 							Err(e) => panic!("Potential DB corruption encountered: {}", e),
 						};
 						maybe_acc
 					}
 					else {
-						AccountEntry::Missing
+						AccountEntry::new_clean(None)
 					};
 					self.insert_cache(a, maybe_acc);
 				}
 			}
-		} else {
+		}
 		self.note_cache(a);
+
+		match &mut self.cache.borrow_mut().get_mut(a).unwrap().account {
+			&mut Some(ref mut acc) => not_default(acc),
+			slot => *slot = Some(default()),
 		}
 
-		match self.cache.borrow_mut().get_mut(a).unwrap() {
+		// at this point the account is guaranteed to be in the cache.
-			&mut AccountEntry::Cached(ref mut acc) => not_default(acc),
-			slot => *slot = AccountEntry::Cached(default()),
-		}
-
 		RefMut::map(self.cache.borrow_mut(), |c| {
-			match c.get_mut(a).unwrap() {
+			let mut entry = c.get_mut(a).unwrap();
-				&mut AccountEntry::Cached(ref mut account) => {
+			// set the dirty flag after changing account data.
+			entry.state = AccountState::Dirty;
+			match entry.account {
+				Some(ref mut account) => {
 					if require_code {
 						let addr_hash = account.address_hash(a);
 						account.cache_code(&AccountDB::from_hash(self.db.as_hashdb(), addr_hash));
@@ -621,7 +699,7 @@ impl Clone for State {
 		let cache = {
 			let mut cache: HashMap<Address, AccountEntry> = HashMap::new();
 			for (key, val) in self.cache.borrow().iter() {
-				if let Some(entry) = val.clone_dirty() {
+				if let Some(entry) = val.clone_if_dirty() {
 					cache.insert(key.clone(), entry);
 				}
 			}
@@ -1677,12 +1755,12 @@ fn snapshot_basic() {
 	state.snapshot();
 	state.add_balance(&a, &U256::from(69u64));
 	assert_eq!(state.balance(&a), U256::from(69u64));
-	state.clear_snapshot();
+	state.discard_snapshot();
 	assert_eq!(state.balance(&a), U256::from(69u64));
 	state.snapshot();
 	state.add_balance(&a, &U256::from(1u64));
 	assert_eq!(state.balance(&a), U256::from(70u64));
-	state.revert_snapshot();
+	state.revert_to_snapshot();
 	assert_eq!(state.balance(&a), U256::from(69u64));
 }
 
@@ -1695,9 +1773,9 @@ fn snapshot_nested() {
 	state.snapshot();
 	state.add_balance(&a, &U256::from(69u64));
 	assert_eq!(state.balance(&a), U256::from(69u64));
-	state.clear_snapshot();
+	state.discard_snapshot();
 	assert_eq!(state.balance(&a), U256::from(69u64));
-	state.revert_snapshot();
+	state.revert_to_snapshot();
 	assert_eq!(state.balance(&a), U256::from(0));
 }
 

ethcore/src/state_db.rs

@@ -190,7 +190,7 @@ impl StateDB {
 		for (address, account) in self.cache_overlay.drain(..) {
 			if let Some(&mut Some(ref mut existing)) = cache.accounts.get_mut(&address) {
 				if let Some(new) = account {
-					existing.merge_with(new);
+					existing.overwrite_with(new);
 					continue;
 				}
 			}

util/io/src/lib.rs

@@ -68,6 +68,8 @@ mod panics;
 use mio::{EventLoop, Token};
 use std::fmt;
 
+pub use worker::LOCAL_STACK_SIZE;
+
 #[derive(Debug)]
 /// IO Error
 pub enum IoError {

util/io/src/worker.rs

@@ -22,9 +22,19 @@ use crossbeam::sync::chase_lev;
 use service::{HandlerId, IoChannel, IoContext};
 use IoHandler;
 use panics::*;
+use std::cell::Cell;
 
 use std::sync::{Condvar as SCondvar, Mutex as SMutex};
 
+const STACK_SIZE: usize = 16*1024*1024;
+
+thread_local! {
+	/// Stack size
+	/// Should be modified if it is changed in Rust since it is no way
+	/// to know or get it
+	pub static LOCAL_STACK_SIZE: Cell<usize> = Cell::new(::std::env::var("RUST_MIN_STACK").ok().and_then(|s| s.parse().ok()).unwrap_or(2 * 1024 * 1024));
+}
+
 pub enum WorkType<Message> {
 	Readable,
 	Writable,
@@ -66,8 +76,9 @@ impl Worker {
 			deleting: deleting.clone(),
 			wait_mutex: wait_mutex.clone(),
 		};
-		worker.thread = Some(thread::Builder::new().name(format!("IO Worker #{}", index)).spawn(
+		worker.thread = Some(thread::Builder::new().stack_size(STACK_SIZE).name(format!("IO Worker #{}", index)).spawn(
 			move || {
+				LOCAL_STACK_SIZE.with(|val| val.set(STACK_SIZE));
 				panic_handler.catch_panic(move || {
 					Worker::work_loop(stealer, channel.clone(), wait, wait_mutex.clone(), deleting)
 				}).unwrap()

util/network/src/host.rs

@@ -580,7 +580,8 @@ impl Host {
 	}
 
 	fn handshake_count(&self) -> usize {
-		self.sessions.read().count() - self.session_count()
+		// session_count < total_count is possible because of the data race.
+		self.sessions.read().count().saturating_sub(self.session_count())
 	}
 
 	fn keep_alive(&self, io: &IoContext<NetworkIoMessage>) {