diff --git a/client/transaction-pool/graph/src/lib.rs b/client/transaction-pool/graph/src/lib.rs
index b4646c6055bf6..bf220ce22973a 100644
--- a/client/transaction-pool/graph/src/lib.rs
+++ b/client/transaction-pool/graph/src/lib.rs
@@ -32,6 +32,7 @@ mod pool;
 mod ready;
 mod rotator;
 mod validated_pool;
+mod tracked_map;
 
 pub mod base_pool;
 pub mod watcher;
diff --git a/client/transaction-pool/graph/src/ready.rs b/client/transaction-pool/graph/src/ready.rs
index b5807ffce4480..47289f26f02a9 100644
--- a/client/transaction-pool/graph/src/ready.rs
+++ b/client/transaction-pool/graph/src/ready.rs
@@ -25,15 +25,17 @@ use std::{
 
 use serde::Serialize;
 use log::trace;
-use parking_lot::RwLock;
 use sp_runtime::traits::Member;
 use sp_runtime::transaction_validity::{
 	TransactionTag as Tag,
 };
 use sp_transaction_pool::error;
 
-use crate::future::WaitingTransaction;
-use crate::base_pool::Transaction;
+use crate::{
+	base_pool::Transaction,
+	future::WaitingTransaction,
+	tracked_map::{self, ReadOnlyTrackedMap, TrackedMap},
+};
 
 /// An in-pool transaction reference.
 ///
@@ -113,11 +115,17 @@ pub struct ReadyTransactions<Hash: hash::Hash + Eq, Ex> {
 	/// tags that are provided by Ready transactions
 	provided_tags: HashMap<Tag, Hash>,
 	/// Transactions that are ready (i.e. don't have any requirements external to the pool)
-	ready: Arc<RwLock<HashMap<Hash, ReadyTx<Hash, Ex>>>>,
+	ready: TrackedMap<Hash, ReadyTx<Hash, Ex>>,
 	/// Best transactions that are ready to be included to the block without any other previous transaction.
 	best: BTreeSet<TransactionRef<Hash, Ex>>,
 }
 
+impl<Hash, Ex> tracked_map::Size for ReadyTx<Hash, Ex> {
+	fn size(&self) -> usize {
+		self.transaction.transaction.bytes
+	}
+}
+
 impl<Hash: hash::Hash + Eq, Ex> Default for ReadyTransactions<Hash, Ex> {
 	fn default() -> Self {
 		ReadyTransactions {
@@ -468,18 +476,18 @@ impl<Hash: hash::Hash + Member + Serialize, Ex> ReadyTransactions<Hash, Ex> {
 
 	/// Returns number of transactions in this queue.
 	pub fn len(&self) -> usize {
-		self.ready.read().len()
+		self.ready.len()
 	}
 
 	/// Returns sum of encoding lengths of all transactions in this queue.
 	pub fn bytes(&self) -> usize {
-		self.ready.read().values().fold(0, |acc, tx| acc + tx.transaction.transaction.bytes)
+		self.ready.bytes()
 	}
 }
 
 /// Iterator of ready transactions ordered by priority.
 pub struct BestIterator<Hash, Ex> {
-	all: Arc<RwLock<HashMap<Hash, ReadyTx<Hash, Ex>>>>,
+	all: ReadOnlyTrackedMap<Hash, ReadyTx<Hash, Ex>>,
 	awaiting: HashMap<Hash, (usize, TransactionRef<Hash, Ex>)>,
 	best: BTreeSet<TransactionRef<Hash, Ex>>,
 }
diff --git a/client/transaction-pool/graph/src/tracked_map.rs b/client/transaction-pool/graph/src/tracked_map.rs
new file mode 100644
index 0000000000000..c799eb0b96ea1
--- /dev/null
+++ b/client/transaction-pool/graph/src/tracked_map.rs
@@ -0,0 +1,189 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2018-2020 Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0
+
+// This program 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.
+
+// This program 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 this program. If not, see <https://www.gnu.org/licenses/>.
+
+use std::{
+	collections::HashMap,
+	sync::{Arc, atomic::{AtomicIsize, Ordering as AtomicOrdering}},
+};
+use parking_lot::{RwLock, RwLockWriteGuard, RwLockReadGuard};
+
+/// Something that can report it's size.
+pub trait Size {
+	fn size(&self) -> usize;
+}
+
+/// Map with size tracking.
+///
+/// Size reported might be slightly off and only approximately true.
+#[derive(Debug, parity_util_mem::MallocSizeOf)]
+pub struct TrackedMap<K, V> {
+	index: Arc<RwLock<HashMap<K, V>>>,
+	bytes: AtomicIsize,
+	length: AtomicIsize,
+}
+
+impl<K, V> Default for TrackedMap<K, V> {
+	fn default() -> Self {
+		Self {
+			index: Arc::new(HashMap::default().into()),
+			bytes: 0.into(),
+			length: 0.into(),
+		}
+	}
+}
+
+impl<K, V> TrackedMap<K, V> {
+	/// Current tracked length of the content.
+	pub fn len(&self) -> usize {
+		std::cmp::max(self.length.load(AtomicOrdering::Relaxed), 0) as usize
+	}
+
+	/// Current sum of content length.
+	pub fn bytes(&self) -> usize {
+		std::cmp::max(self.bytes.load(AtomicOrdering::Relaxed), 0) as usize
+	}
+
+	/// Read-only clone of the interior.
+	pub fn clone(&self) -> ReadOnlyTrackedMap<K, V> {
+		ReadOnlyTrackedMap(self.index.clone())
+	}
+
+	/// Lock map for read.
+	pub fn read<'a>(&'a self) -> TrackedMapReadAccess<'a, K, V> {
+		TrackedMapReadAccess {
+			inner_guard: self.index.read(),
+		}
+	}
+
+	/// Lock map for write.
+	pub fn write<'a>(&'a self) -> TrackedMapWriteAccess<'a, K, V> {
+		TrackedMapWriteAccess {
+			inner_guard: self.index.write(),
+			bytes: &self.bytes,
+			length: &self.length,
+		}
+	}
+}
+
+/// Read-only access to map.
+///
+/// The only thing can be done is .read().
+pub struct ReadOnlyTrackedMap<K, V>(Arc<RwLock<HashMap<K, V>>>);
+
+impl<K, V> ReadOnlyTrackedMap<K, V>
+where
+	K: Eq + std::hash::Hash
+{
+	/// Lock map for read.
+	pub fn read<'a>(&'a self) -> TrackedMapReadAccess<'a, K, V> {
+		TrackedMapReadAccess {
+			inner_guard: self.0.read(),
+		}
+	}
+}
+
+pub struct TrackedMapReadAccess<'a, K, V> {
+	inner_guard: RwLockReadGuard<'a, HashMap<K, V>>,
+}
+
+impl<'a, K, V> TrackedMapReadAccess<'a, K, V>
+where
+	K: Eq + std::hash::Hash
+{
+	/// Returns true if map contains key.
+	pub fn contains_key(&self, key: &K) -> bool {
+		self.inner_guard.contains_key(key)
+	}
+
+	/// Returns reference to the contained value by key, if exists.
+	pub fn get(&self, key: &K) -> Option<&V> {
+		self.inner_guard.get(key)
+	}
+
+	/// Returns iterator over all values.
+	pub fn values(&self) -> std::collections::hash_map::Values<K, V> {
+		self.inner_guard.values()
+	}
+}
+
+pub struct TrackedMapWriteAccess<'a, K, V> {
+	bytes: &'a AtomicIsize,
+	length: &'a AtomicIsize,
+	inner_guard: RwLockWriteGuard<'a, HashMap<K, V>>,
+}
+
+impl<'a, K, V> TrackedMapWriteAccess<'a, K, V>
+where
+	K: Eq + std::hash::Hash, V: Size
+{
+	/// Insert value and return previous (if any).
+	pub fn insert(&mut self, key: K, val: V) -> Option<V> {
+		let new_bytes = val.size();
+		self.bytes.fetch_add(new_bytes as isize, AtomicOrdering::Relaxed);
+		self.length.fetch_add(1, AtomicOrdering::Relaxed);
+		self.inner_guard.insert(key, val).and_then(|old_val| {
+			self.bytes.fetch_sub(old_val.size() as isize, AtomicOrdering::Relaxed);
+			self.length.fetch_sub(1, AtomicOrdering::Relaxed);
+			Some(old_val)
+		})
+	}
+
+	/// Remove value by key.
+	pub fn remove(&mut self, key: &K) -> Option<V> {
+		let val = self.inner_guard.remove(key);
+		if let Some(size) = val.as_ref().map(Size::size) {
+			self.bytes.fetch_sub(size as isize, AtomicOrdering::Relaxed);
+			self.length.fetch_sub(1, AtomicOrdering::Relaxed);
+		}
+		val
+	}
+
+	/// Returns mutable reference to the contained value by key, if exists.
+	pub fn get_mut(&mut self, key: &K) -> Option<&mut V> {
+		self.inner_guard.get_mut(key)
+	}
+}
+
+#[cfg(test)]
+mod tests {
+
+	use super::*;
+
+	impl Size for i32 {
+		fn size(&self) -> usize { *self as usize / 10 }
+	}
+
+	#[test]
+	fn basic() {
+		let map = TrackedMap::default();
+		map.write().insert(5, 10);
+		map.write().insert(6, 20);
+
+		assert_eq!(map.bytes(), 3);
+		assert_eq!(map.len(), 2);
+
+		map.write().insert(6, 30);
+
+		assert_eq!(map.bytes(), 4);
+		assert_eq!(map.len(), 2);
+
+		map.write().remove(&6);
+		assert_eq!(map.bytes(), 1);
+		assert_eq!(map.len(), 1);
+	}
+}
\ No newline at end of file