WasmExecutor takes a cache directory (#8057)

That is useful for executors like wasmtime which produces compiled code
and can actually benefit from caching under some circumstances

substrate/client/executor/src/integration_tests/mod.rs

@@ -75,6 +75,7 @@ fn call_in_wasm<E: Externalities>(
 		Some(1024),
 		HostFunctions::host_functions(),
 		8,
+		None,
 	);
 	executor.call_in_wasm(
 		&wasm_binary_unwrap()[..],
@@ -536,6 +537,7 @@ fn should_trap_when_heap_exhausted(wasm_method: WasmExecutionMethod) {
 		Some(17),  // `17` is the initial number of pages compiled into the binary.
 		HostFunctions::host_functions(),
 		8,
+		None,
 	);
 
 	let err = executor.call_in_wasm(
@@ -558,6 +560,7 @@ fn returns_mutable_static(wasm_method: WasmExecutionMethod) {
 		&wasm_binary_unwrap()[..],
 		HostFunctions::host_functions(),
 		true,
+		None,
 	).expect("Creates runtime");
 
 	let instance = runtime.new_instance().unwrap();
@@ -591,6 +594,7 @@ fn restoration_of_globals(wasm_method: WasmExecutionMethod) {
 		&wasm_binary_unwrap()[..],
 		HostFunctions::host_functions(),
 		true,
+		None,
 	).expect("Creates runtime");
 	let instance = runtime.new_instance().unwrap();
 
@@ -611,6 +615,7 @@ fn heap_is_reset_between_calls(wasm_method: WasmExecutionMethod) {
 		&wasm_binary_unwrap()[..],
 		HostFunctions::host_functions(),
 		true,
+		None,
 	).expect("Creates runtime");
 	let instance = runtime.new_instance().unwrap();
 
@@ -634,6 +639,7 @@ fn parallel_execution(wasm_method: WasmExecutionMethod) {
 		Some(1024),
 		HostFunctions::host_functions(),
 		8,
+		None,
 	));
 	let code_hash = blake2_256(wasm_binary_unwrap()).to_vec();
 	let threads: Vec<_> = (0..8).map(|_|

substrate/client/executor/src/lib.rs

@@ -80,6 +80,7 @@ mod tests {
 			Some(8),
 			sp_io::SubstrateHostFunctions::host_functions(),
 			8,
+			None,
 		);
 		let res = executor.call_in_wasm(
 			&wasm_binary_unwrap()[..],

substrate/client/executor/src/native_executor.rs

@@ -26,6 +26,7 @@ use std::{
 	panic::{UnwindSafe, AssertUnwindSafe},
 	result,
 	sync::{Arc, atomic::{AtomicU64, Ordering}, mpsc},
+	path::PathBuf,
 };
 
 use sp_version::{NativeVersion, RuntimeVersion};
@@ -102,6 +103,9 @@ pub struct WasmExecutor {
 	cache: Arc<RuntimeCache>,
 	/// The size of the instances cache.
 	max_runtime_instances: usize,
+	/// The path to a directory which the executor can leverage for a file cache, e.g. put there
+	/// compiled artifacts.
+	cache_path: Option<PathBuf>,
 }
 
 impl WasmExecutor {
@@ -112,19 +116,30 @@ impl WasmExecutor {
 	/// `method` - Method used to execute Wasm code.
 	///
 	/// `default_heap_pages` - Number of 64KB pages to allocate for Wasm execution.
-	/// 	Defaults to `DEFAULT_HEAP_PAGES` if `None` is provided.
+	///   Defaults to `DEFAULT_HEAP_PAGES` if `None` is provided.
+	///
+	/// `host_functions` - The set of host functions to be available for import provided by this
+	///   executor.
+	///
+	/// `max_runtime_instances` - The number of runtime instances to keep in memory ready for reuse.
+	///
+	/// `cache_path` - A path to a directory where the executor can place its files for purposes of
+	///   caching. This may be important in cases when there are many different modules with the
+	///   compiled execution method is used.
 	pub fn new(
 		method: WasmExecutionMethod,
 		default_heap_pages: Option<u64>,
 		host_functions: Vec<&'static dyn Function>,
 		max_runtime_instances: usize,
+		cache_path: Option<PathBuf>,
 	) -> Self {
 		WasmExecutor {
 			method,
 			default_heap_pages: default_heap_pages.unwrap_or(DEFAULT_HEAP_PAGES),
 			host_functions: Arc::new(host_functions),
-			cache: Arc::new(RuntimeCache::new(max_runtime_instances)),
+			cache: Arc::new(RuntimeCache::new(max_runtime_instances, cache_path.clone())),
 			max_runtime_instances,
+			cache_path,
 		}
 	}
 
@@ -210,6 +225,7 @@ impl sp_core::traits::CallInWasm for WasmExecutor {
 				&wasm_code,
 				self.host_functions.to_vec(),
 				allow_missing_host_functions,
+				self.cache_path.as_deref(),
 			)
 				.map_err(|e| format!("Failed to create module: {:?}", e))?;
 
@@ -267,6 +283,7 @@ impl<D: NativeExecutionDispatch> NativeExecutor<D> {
 			default_heap_pages,
 			host_functions,
 			max_runtime_instances,
+			None,
 		);
 
 		NativeExecutor {

substrate/client/executor/src/wasm_runtime.rs

@@ -28,6 +28,7 @@ use codec::Decode;
 use sp_core::traits::{Externalities, RuntimeCode, FetchRuntimeCode};
 use sp_version::RuntimeVersion;
 use std::panic::AssertUnwindSafe;
+use std::path::{Path, PathBuf};
 use sc_executor_common::wasm_runtime::{WasmModule, WasmInstance};
 
 use sp_wasm_interface::Function;
@@ -152,14 +153,22 @@ pub struct RuntimeCache {
 	runtimes: Mutex<[Option<Arc<VersionedRuntime>>; MAX_RUNTIMES]>,
 	/// The size of the instances cache for each runtime.
 	max_runtime_instances: usize,
+	cache_path: Option<PathBuf>,
 }
 
 impl RuntimeCache {
 	/// Creates a new instance of a runtimes cache.
-	pub fn new(max_runtime_instances: usize) -> RuntimeCache {
+	///
+	/// `max_runtime_instances` specifies the number of runtime instances preserved in an in-memory
+	/// cache.
+	///
+	/// `cache_path` allows to specify an optional directory where the executor can store files
+	/// for caching.
+	pub fn new(max_runtime_instances: usize, cache_path: Option<PathBuf>) -> RuntimeCache {
 		RuntimeCache {
 			runtimes: Default::default(),
 			max_runtime_instances,
+			cache_path,
 		}
 	}
 
@@ -235,6 +244,7 @@ impl RuntimeCache {
 					host_functions.into(),
 					allow_missing_func_imports,
 					self.max_runtime_instances,
+					self.cache_path.as_deref(),
 				);
 				if let Err(ref err) = result {
 					log::warn!(target: "wasm-runtime", "Cannot create a runtime: {:?}", err);
@@ -271,22 +281,32 @@ pub fn create_wasm_runtime_with_code(
 	code: &[u8],
 	host_functions: Vec<&'static dyn Function>,
 	allow_missing_func_imports: bool,
+	cache_path: Option<&Path>,
 ) -> Result<Arc<dyn WasmModule>, WasmError> {
 	match wasm_method {
-		WasmExecutionMethod::Interpreted =>
+		WasmExecutionMethod::Interpreted => {
+			// Wasmi doesn't have any need in a cache directory.
+			//
+			// We drop the cache_path here to silence warnings that cache_path is not used if compiling
+			// without the `wasmtime` flag.
+			drop(cache_path);
+
 			sc_executor_wasmi::create_runtime(
 				code,
 				heap_pages,
 				host_functions,
-				allow_missing_func_imports
+				allow_missing_func_imports,
-			).map(|runtime| -> Arc<dyn WasmModule> { Arc::new(runtime) }),
+			)
+			.map(|runtime| -> Arc<dyn WasmModule> { Arc::new(runtime) })
+		}
 		#[cfg(feature = "wasmtime")]
 		WasmExecutionMethod::Compiled =>
 			sc_executor_wasmtime::create_runtime(
 				code,
 				heap_pages,
 				host_functions,
-				allow_missing_func_imports
+				allow_missing_func_imports,
+				cache_path,
 			).map(|runtime| -> Arc<dyn WasmModule> { Arc::new(runtime) }),
 	}
 }
@@ -319,6 +339,7 @@ fn create_versioned_wasm_runtime(
 	host_functions: Vec<&'static dyn Function>,
 	allow_missing_func_imports: bool,
 	max_instances: usize,
+	cache_path: Option<&Path>,
 ) -> Result<VersionedRuntime, WasmError> {
 	#[cfg(not(target_os = "unknown"))]
 	let time = std::time::Instant::now();
@@ -328,6 +349,7 @@ fn create_versioned_wasm_runtime(
 		&code,
 		host_functions,
 		allow_missing_func_imports,
+		cache_path,
 	)?;
 
 	// Call to determine runtime version.

substrate/client/executor/wasmtime/src/runtime.rs

@@ -25,6 +25,7 @@ use crate::state_holder;
 
 use std::rc::Rc;
 use std::sync::Arc;
+use std::path::Path;
 use sc_executor_common::{
 	error::{Result, WasmError},
 	wasm_runtime::{WasmModule, WasmInstance, InvokeMethod},
@@ -119,20 +120,68 @@ impl WasmInstance for WasmtimeInstance {
 	}
 }
 
+/// Prepare a directory structure and a config file to enable wasmtime caching.
+///
+/// In case of an error the caching will not be enabled.
+fn setup_wasmtime_caching(
+	cache_path: &Path,
+	config: &mut Config,
+) -> std::result::Result<(), String> {
+	use std::fs;
+
+	let wasmtime_cache_root = cache_path.join("wasmtime");
+	fs::create_dir_all(&wasmtime_cache_root)
+		.map_err(|err| format!("cannot create the dirs to cache: {:?}", err))?;
+
+	// Canonicalize the path after creating the directories.
+	let wasmtime_cache_root = wasmtime_cache_root
+		.canonicalize()
+		.map_err(|err| format!("failed to canonicalize the path: {:?}", err))?;
+
+	// Write the cache config file
+	let cache_config_path = wasmtime_cache_root.join("cache-config.toml");
+	let config_content = format!(
+		"\
+[cache]
+enabled = true
+directory = \"{cache_dir}\"
+",
+		cache_dir = wasmtime_cache_root.display()
+	);
+	fs::write(&cache_config_path, config_content)
+		.map_err(|err| format!("cannot write the cache config: {:?}", err))?;
+
+	config
+		.cache_config_load(cache_config_path)
+		.map_err(|err| format!("failed to parse the config: {:?}", err))?;
+
+	Ok(())
+}
+
 /// Create a new `WasmtimeRuntime` given the code. This function performs translation from Wasm to
 /// machine code, which can be computationally heavy.
+///
+/// The `cache_path` designates where this executor implementation can put compiled artifacts.
 pub fn create_runtime(
 	code: &[u8],
 	heap_pages: u64,
 	host_functions: Vec<&'static dyn Function>,
 	allow_missing_func_imports: bool,
+	cache_path: Option<&Path>,
 ) -> std::result::Result<WasmtimeRuntime, WasmError> {
 	// Create the engine, store and finally the module from the given code.
 	let mut config = Config::new();
 	config.cranelift_opt_level(wasmtime::OptLevel::SpeedAndSize);
+	if let Some(cache_path) = cache_path {
+		if let Err(reason) = setup_wasmtime_caching(cache_path, &mut config) {
+			log::warn!(
+				"failed to setup wasmtime cache. Performance may degrade significantly: {}.",
+				reason,
+			);
+		}
+	}
 
 	let engine = Engine::new(&config);
-
 	let module_wrapper = ModuleWrapper::new(&engine, code)
 		.map_err(|e| WasmError::Other(format!("cannot create module: {}", e)))?;
 

substrate/primitives/runtime-interface/test/src/lib.rs

@@ -44,6 +44,7 @@ fn call_wasm_method_with_result<HF: HostFunctionsT>(
 		Some(8),
 		host_functions,
 		8,
+		None,
 	);
 	executor.call_in_wasm(
 		binary,