Benchmark Transfer PoV Size with Increasing Numbers of Users

frame/balances/src/benchmarking.rs

@@ -143,6 +143,39 @@ benchmarks_instance_pallet! {
 		assert_eq!(Balances::<T, I>::free_balance(&source), Zero::zero());
 		assert_eq!(Balances::<T, I>::free_balance(&recipient), transfer_amount);
 	}
+
+	// This benchmark performs the same operation as `transfer` in the worst case scenario,
+	// but additionally introduces many new users into the storage, increasing the the merkle
+	// trie and PoV size.
+	#[extra]
+	transfer_increasing_users {
+		// 1_000 is not very much, but this upper bound can be controlled by the CLI.
+		let u in 0 .. 1_000;
+		let existential_deposit = T::ExistentialDeposit::get();
+		let caller = whitelisted_caller();
+
+		// Give some multiple of the existential deposit + creation fee + transfer fee
+		let balance = existential_deposit.saturating_mul(ED_MULTIPLIER.into());
+		let _ = <Balances<T, I> as Currency<_>>::make_free_balance_be(&caller, balance);
+
+		// Transfer `e - 1` existential deposits + 1 unit, which guarantees to create one account,
+		// and reap this user.
+		let recipient: T::AccountId = account("recipient", 0, SEED);
+		let recipient_lookup: <T::Lookup as StaticLookup>::Source = T::Lookup::unlookup(recipient.clone());
+		let transfer_amount = existential_deposit.saturating_mul((ED_MULTIPLIER - 1).into()) + 1u32.into();
+
+		// Create a bunch of users in storage.
+		for i in 0 .. u {
+			// The `account` function uses `blake2_256` to generate unique accounts, so these
+			// should be quite random and evenly distributed in the trie.
+			let new_user: T::AccountId = account("new_user", i, SEED);
+			let _ = <Balances<T, I> as Currency<_>>::make_free_balance_be(&new_user, balance);
+		}
+	}: transfer(RawOrigin::Signed(caller.clone()), recipient_lookup, transfer_amount)
+	verify {
+		assert_eq!(Balances::<T, I>::free_balance(&caller), Zero::zero());
+		assert_eq!(Balances::<T, I>::free_balance(&recipient), transfer_amount);
+	}
 }
 
 impl_benchmark_test_suite!(

frame/balances/src/weights.rs

@@ -17,8 +17,8 @@
 
 //! Autogenerated weights for pallet_balances
 //!
-//! THIS FILE WAS AUTO-GENERATED USING THE SUBSTRATE BENCHMARK CLI VERSION 2.0.0
-//! DATE: 2021-01-06, STEPS: \[50, \], REPEAT: 20, LOW RANGE: [], HIGH RANGE: []
+//! THIS FILE WAS AUTO-GENERATED USING THE SUBSTRATE BENCHMARK CLI VERSION 3.0.0
+//! DATE: 2021-04-08, STEPS: `[50, ]`, REPEAT: 20, LOW RANGE: `[]`, HIGH RANGE: `[]`
 //! EXECUTION: Some(Wasm), WASM-EXECUTION: Compiled, CHAIN: Some("dev"), DB CACHE: 128
 
 // Executed Command:
@@ -55,27 +55,27 @@ pub trait WeightInfo {
 pub struct SubstrateWeight<T>(PhantomData<T>);
 impl<T: frame_system::Config> WeightInfo for SubstrateWeight<T> {
 	fn transfer() -> Weight {
-		(100_698_000 as Weight)
+		(81_909_000 as Weight)
 			.saturating_add(T::DbWeight::get().reads(1 as Weight))
 			.saturating_add(T::DbWeight::get().writes(1 as Weight))
 	}
 	fn transfer_keep_alive() -> Weight {
-		(69_407_000 as Weight)
+		(61_075_000 as Weight)
 			.saturating_add(T::DbWeight::get().reads(1 as Weight))
 			.saturating_add(T::DbWeight::get().writes(1 as Weight))
 	}
 	fn set_balance_creating() -> Weight {
-		(38_489_000 as Weight)
+		(32_255_000 as Weight)
 			.saturating_add(T::DbWeight::get().reads(1 as Weight))
 			.saturating_add(T::DbWeight::get().writes(1 as Weight))
 	}
 	fn set_balance_killing() -> Weight {
-		(48_458_000 as Weight)
+		(38_513_000 as Weight)
 			.saturating_add(T::DbWeight::get().reads(1 as Weight))
 			.saturating_add(T::DbWeight::get().writes(1 as Weight))
 	}
 	fn force_transfer() -> Weight {
-		(99_320_000 as Weight)
+		(80_448_000 as Weight)
 			.saturating_add(T::DbWeight::get().reads(2 as Weight))
 			.saturating_add(T::DbWeight::get().writes(2 as Weight))
 	}
@@ -84,27 +84,27 @@ impl<T: frame_system::Config> WeightInfo for SubstrateWeight<T> {
 // For backwards compatibility and tests
 impl WeightInfo for () {
 	fn transfer() -> Weight {
-		(100_698_000 as Weight)
+		(81_909_000 as Weight)
 			.saturating_add(RocksDbWeight::get().reads(1 as Weight))
 			.saturating_add(RocksDbWeight::get().writes(1 as Weight))
 	}
 	fn transfer_keep_alive() -> Weight {
-		(69_407_000 as Weight)
+		(61_075_000 as Weight)
 			.saturating_add(RocksDbWeight::get().reads(1 as Weight))
 			.saturating_add(RocksDbWeight::get().writes(1 as Weight))
 	}
 	fn set_balance_creating() -> Weight {
-		(38_489_000 as Weight)
+		(32_255_000 as Weight)
 			.saturating_add(RocksDbWeight::get().reads(1 as Weight))
 			.saturating_add(RocksDbWeight::get().writes(1 as Weight))
 	}
 	fn set_balance_killing() -> Weight {
-		(48_458_000 as Weight)
+		(38_513_000 as Weight)
 			.saturating_add(RocksDbWeight::get().reads(1 as Weight))
 			.saturating_add(RocksDbWeight::get().writes(1 as Weight))
 	}
 	fn force_transfer() -> Weight {
-		(99_320_000 as Weight)
+		(80_448_000 as Weight)
 			.saturating_add(RocksDbWeight::get().reads(2 as Weight))
 			.saturating_add(RocksDbWeight::get().writes(2 as Weight))
 	}