cache manager and clearing tracing cache (#1769)

* removed configure_cache method

* generic cache_manager struct

* fixed #1743, tracing caches are cleared

* removed deadlocks in garbage_collect, implemented HeapSizeOf for traces

* trace cache config

* fixed carbage typo

ethcore/src/cache_manager.rs

@@ -0,0 +1,69 @@
+// 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/>.
+
+use std::collections::{VecDeque, HashSet};
+use std::hash::Hash;
+
+const COLLECTION_QUEUE_SIZE: usize = 8;
+
+pub struct CacheManager<T> where T: Eq + Hash {
+	pref_cache_size: usize,
+	max_cache_size: usize,
+	bytes_per_cache_entry: usize,
+	cache_usage: VecDeque<HashSet<T>>
+}
+
+impl<T> CacheManager<T> where T: Eq + Hash {
+	pub fn new(pref_cache_size: usize, max_cache_size: usize, bytes_per_cache_entry: usize) -> Self {
+		CacheManager {
+			pref_cache_size: pref_cache_size,
+			max_cache_size: max_cache_size,
+			bytes_per_cache_entry: bytes_per_cache_entry,
+			cache_usage: (0..COLLECTION_QUEUE_SIZE).into_iter().map(|_| Default::default()).collect(),
+		}
+	}
+
+	pub fn note_used(&mut self, id: T) {
+		if !self.cache_usage[0].contains(&id) {
+			if let Some(c) = self.cache_usage.iter_mut().skip(1).find(|e| e.contains(&id)) {
+				c.remove(&id);
+			}
+			self.cache_usage[0].insert(id);
+		}
+	}
+
+	pub fn collect_garbage<C, F>(&mut self, current_size: C, mut notify_unused: F) where C: Fn() -> usize, F: FnMut(HashSet<T>) {
+		if current_size() < self.pref_cache_size {
+			self.rotate_cache_if_needed();
+			return;
+		}
+
+		for _ in 0..COLLECTION_QUEUE_SIZE {
+			notify_unused(self.cache_usage.pop_back().unwrap());
+			self.cache_usage.push_front(Default::default());
+			if current_size() < self.max_cache_size {
+				break;
+			}
+		}
+	}
+
+	fn rotate_cache_if_needed(&mut self) {
+		if self.cache_usage[0].len() * self.bytes_per_cache_entry > self.pref_cache_size / COLLECTION_QUEUE_SIZE {
+			let cache = self.cache_usage.pop_back().unwrap();
+			self.cache_usage.push_front(cache);
+		}
+	}
+}