From e8e087fc37b6e5aa78bd15eb32f8fb7dec3bb6d9 Mon Sep 17 00:00:00 2001
From: Wei Tang <accounts@that.world>
Date: Mon, 14 Jan 2019 15:33:10 +0100
Subject: [PATCH] Skip locking in statedb for non-canon blocks (#10141)

---
 ethcore/src/state_db.rs | 37 ++++++++++++++++++-------------------
 1 file changed, 18 insertions(+), 19 deletions(-)

diff --git a/ethcore/src/state_db.rs b/ethcore/src/state_db.rs
index 6b3186452..1ceb8ff0c 100644
--- a/ethcore/src/state_db.rs
+++ b/ethcore/src/state_db.rs
@@ -379,14 +379,7 @@ impl StateDB {
 
 	/// Check if the account can be returned from cache by matching current block parent hash against canonical
 	/// state and filtering out account modified in later blocks.
-	fn is_allowed(addr: &Address, parent_hash: &Option<H256>, modifications: &VecDeque<BlockChanges>) -> bool {
-		let mut parent = match *parent_hash {
-			None => {
-				trace!("Cache lookup skipped for {:?}: no parent hash", addr);
-				return false;
-			}
-			Some(ref parent) => parent,
-		};
+	fn is_allowed(addr: &Address, parent_hash: &H256, modifications: &VecDeque<BlockChanges>) -> bool {
 		if modifications.is_empty() {
 			return true;
 		}
@@ -395,6 +388,7 @@ impl StateDB {
 		// We search for our parent in that list first and then for
 		// all its parent until we hit the canonical block,
 		// checking against all the intermediate modifications.
+		let mut parent = parent_hash;
 		for m in modifications {
 			if &m.hash == parent {
 				if m.is_canon {
@@ -434,20 +428,25 @@ impl state::Backend for StateDB {
 	}
 
 	fn get_cached_account(&self, addr: &Address) -> Option<Option<Account>> {
-		let mut cache = self.account_cache.lock();
-		if !Self::is_allowed(addr, &self.parent_hash, &cache.modifications) {
-			return None;
-		}
-		cache.accounts.get_mut(addr).map(|a| a.as_ref().map(|a| a.clone_basic()))
+		self.parent_hash.as_ref().and_then(|parent_hash| {
+			let mut cache = self.account_cache.lock();
+			if !Self::is_allowed(addr, parent_hash, &cache.modifications) {
+				return None;
+			}
+			cache.accounts.get_mut(addr).map(|a| a.as_ref().map(|a| a.clone_basic()))
+		})
 	}
 
 	fn get_cached<F, U>(&self, a: &Address, f: F) -> Option<U>
-		where F: FnOnce(Option<&mut Account>) -> U {
-		let mut cache = self.account_cache.lock();
-		if !Self::is_allowed(a, &self.parent_hash, &cache.modifications) {
-			return None;
-		}
-		cache.accounts.get_mut(a).map(|c| f(c.as_mut()))
+		where F: FnOnce(Option<&mut Account>) -> U
+	{
+		self.parent_hash.as_ref().and_then(|parent_hash| {
+			let mut cache = self.account_cache.lock();
+			if !Self::is_allowed(a, parent_hash, &cache.modifications) {
+				return None;
+			}
+			cache.accounts.get_mut(a).map(|c| f(c.as_mut()))
+		})
 	}
 
 	fn get_cached_code(&self, hash: &H256) -> Option<Arc<Vec<u8>>> {