State cache and other performance optimizations (#1345)

* State caching

* Better code caching

* Execution optimizaton

* More optimizations

* Updated wasmi

* Caching test

* Style

* Style

* Reverted some minor changes

* Style and typos

* Style and typos

* Removed panics on missing memory

substrate/core/state-machine/src/lib.rs

@@ -65,9 +65,6 @@ pub use proving_backend::{create_proof_check_backend, create_proof_check_backend
 pub use trie_backend_essence::{TrieBackendStorage, Storage};
 pub use trie_backend::TrieBackend;
 
-/// Default num of pages for the heap
-const DEFAULT_HEAP_PAGES :u64 = 1024;
-
 /// State Machine Error bound.
 ///
 /// This should reflect WASM error type bound for future compatibility.
@@ -98,10 +95,15 @@ impl fmt::Display for ExecutionError {
 
 /// Externalities: pinned to specific active address.
 pub trait Externalities<H: Hasher> {
-	/// Read storage of current contract being called.
+	/// Read runtime storage.
 	fn storage(&self, key: &[u8]) -> Option<Vec<u8>>;
 
-	/// Read child storage of current contract being called.
+	/// Get storage value hash. This may be optimized for large values.
+	fn storage_hash(&self, key: &[u8]) -> Option<H::Out> {
+		self.storage(key).map(|v| H::hash(&v))
+	}
+
+	/// Read child runtime storage.
 	fn child_storage(&self, storage_key: &[u8], key: &[u8]) -> Option<Vec<u8>>;
 
 	/// Set storage entry `key` of current contract being called (effective immediately).
@@ -171,8 +173,6 @@ pub trait CodeExecutor<H: Hasher>: Sized + Send + Sync {
 	fn call<E: Externalities<H>>(
 		&self,
 		ext: &mut E,
-		heap_pages: usize,
-		code: &[u8],
 		method: &str,
 		data: &[u8],
 		use_native: bool
@@ -297,14 +297,6 @@ where
 {
 	let strategy: ExecutionStrategy = (&manager).into();
 
-	// make a copy.
-	let code = try_read_overlay_value(overlay, backend, well_known_keys::CODE)?
-		.ok_or_else(|| Box::new(ExecutionError::CodeEntryDoesNotExist) as Box<Error>)?
-		.to_vec();
-
-	let heap_pages = try_read_overlay_value(overlay, backend, well_known_keys::HEAP_PAGES)?
-		.and_then(|v| u64::decode(&mut &v[..])).unwrap_or(DEFAULT_HEAP_PAGES) as usize;
-
 	// read changes trie configuration. The reason why we're doing it here instead of the
 	// `OverlayedChanges` constructor is that we need proofs for this read as a part of
 	// proof-of-execution on light clients. And the proof is recorded by the backend which
@@ -328,8 +320,6 @@ where
 				let mut externalities = ext::Ext::new(overlay, backend, changes_trie_storage);
 				let retval = exec.call(
 					&mut externalities,
-					heap_pages,
-					&code,
 					method,
 					call_data,
 					// attempt to run native first, if we're not directed to run wasm only
@@ -357,8 +347,6 @@ where
 					let mut externalities = ext::Ext::new(overlay, backend, changes_trie_storage);
 					let retval = exec.call(
 						&mut externalities,
-						heap_pages,
-						&code,
 						method,
 						call_data,
 						false,
@@ -614,8 +602,6 @@ mod tests {
 		fn call<E: Externalities<H>>(
 			&self,
 			ext: &mut E,
-			_heap_pages: usize,
-			_code: &[u8],
 			_method: &str,
 			_data: &[u8],
 			use_native: bool