Shared code cache (#2921)

* add a global code cache

* extract memory-limited lru cache to util

* use memory-limited code cache

* account for code cache size in mem_used

util/Cargo.toml

@@ -36,6 +36,7 @@ ansi_term = "0.7"
 tiny-keccak= "1.0"
 ethcore-bloom-journal = { path = "bloom" }
 regex = "0.1"
+lru-cache = "0.1.0"
 
 [features]
 default = []

util/src/cache.rs

@@ -0,0 +1,79 @@
+// Copyright 2015, 2016 Ethcore (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Lru-cache related utilities as quick-and-dirty wrappers around the lru-cache
+//! crate.
+// TODO: push changes upstream in a clean way.
+
+use heapsize::HeapSizeOf;
+use lru_cache::LruCache;
+
+use std::hash::Hash;
+
+const INITIAL_CAPACITY: usize = 4;
+
+/// An LRU-cache which operates on memory used.
+pub struct MemoryLruCache<K: Eq + Hash, V: HeapSizeOf> {
+	inner: LruCache<K, V>,
+	cur_size: usize,
+	max_size: usize,
+}
+
+impl<K: Eq + Hash, V: HeapSizeOf> MemoryLruCache<K, V> {
+	/// Create a new cache with a maximum size in bytes.
+	pub fn new(max_size: usize) -> Self {
+		MemoryLruCache {
+			inner: LruCache::new(INITIAL_CAPACITY),
+			max_size: max_size,
+			cur_size: 0,
+		}
+	}
+
+	/// Insert an item.
+	pub fn insert(&mut self, key: K, val: V) {
+		let cap = self.inner.capacity();
+
+		// grow the cache as necessary; it operates on amount of items
+		// but we're working based on memory usage.
+		if self.inner.len() == cap && self.cur_size < self.max_size {
+			self.inner.set_capacity(cap * 2);
+		}
+
+		// account for any element displaced from the cache.
+		if let Some(lru) = self.inner.insert(key, val) {
+			self.cur_size -= lru.heap_size_of_children();
+		}
+
+		// remove elements until we are below the memory target.
+		while self.cur_size > self.max_size {
+			match self.inner.remove_lru() {
+				Some((_, v)) => self.cur_size -= v.heap_size_of_children(),
+				_ => break,
+			}
+		}
+	}
+
+	/// Get a reference to an item in the cache. It is a logic error for its
+	/// heap size to be altered while borrowed.
+	pub fn get_mut(&mut self, key: &K) -> Option<&mut V> {
+		self.inner.get_mut(key)
+	}
+
+	/// Currently-used size of values in bytes.
+	pub fn current_size(&self) -> usize {
+		self.cur_size
+	}
+}

util/src/lib.rs

@@ -105,6 +105,7 @@ extern crate ansi_term;
 extern crate tiny_keccak;
 extern crate rlp;
 extern crate regex;
+extern crate lru_cache;
 
 #[macro_use]
 extern crate heapsize;
@@ -143,6 +144,7 @@ pub mod semantic_version;
 pub mod log;
 pub mod path;
 pub mod snappy;
+pub mod cache;
 mod timer;
 
 pub use common::*;