test relationship between number of storage items and CPU overehead

test_acct_size_cost.rs

#[test]
fn test_timing() {
	use std::time::{Instant, Duration};
	use frame_benchmarking::{account};
	use frame_support::traits::ExistenceRequirement;

	println!("test_timing() .........");

	/// Create a funded user
	fn create_funded_user<T: Config>(
		string: &'static str,
		n: u32,
		amount: BalanceOf<T>
	) -> T::AccountId {
		const SEED: u32 = 0;
		let user = account(string, n, SEED);
		T::Currency::make_free_balance_be(&user, amount);
		T::Currency::issue(amount);

		user
	}

	new_test_ext().execute_with(|| {
		let test_start = Instant::now();

		let mut num_created = 0;

		let first_acct: <mock::Test as frame_system::Config>::AccountId = create_funded_user::<Test>("first", u32::MAX.into(), 1u32.into());

		for n in 2..30 {
			let next_max = 2u32.pow(n);
			let next_start = Instant::now();
			let mut num_created_batch = 0u32;
			let mut last_acct_created: Option<<mock::Test as frame_system::Config>::AccountId> = None;
			for na in num_created..next_max {
				let new_acct: <mock::Test as frame_system::Config>::AccountId = create_funded_user::<Test>("foo", na.into(), 100000000u32.into());
				num_created += 1;
				num_created_batch += 1;
				last_acct_created = Some(new_acct);
			}
			let step_duration = next_start.elapsed();
			let time_per_acct = num_created_batch as f64 / step_duration.as_secs_f64();
			println!("step {} took {} micros ({} each)", n, step_duration.as_micros(), time_per_acct);

			// try sending money to the initial account and time it
			let send_start = Instant::now();
			for i in 1..100000 {
				let result = <mock::Test as Config>::Currency::force_transfer(
					RawOrigin::Root.into(),
					last_acct_created.expect("set above..."),
					first_acct,
					10u32.into());
				if let Err(err) = result {
					panic!("force_transfer failed");
				}
			}
			let elapsed = send_start.elapsed();
			println!("send after step {} took {} micros", n, elapsed.as_micros());
		}

		let test_duration = test_start.elapsed();
	});
}