[Revive] Add configuration to set Ethereum gas scale (#10393)

This PR is based on
#10166 (i.e., it merges
into the branch `torsten/gas-fixes`).

This PR adds a new configuration parameter (`GasScale`) to pallet-revive
that allows to change the scale of the Ethereum gas and of the Ethereum
gas price.

Before this PR, the Ethereum gas price is simply the next fee multiplier
of pallet-transaction-payment multiplied by `NativeToEthRatio`. Thus, on
Polkadot this is 100_000_000 when the multiplier has its default value
of 1.

The required gas of a transaction is its total cost divided by the gas
price, where the total cost is the sum of the transaction fee and the
storage deposit.

This leads to a situation where the required gas for a transaction on
revive is usually orders of magnitude larger than the required amount of
gas on Ethereum. This can lead to issues with tools or systems that
interact with revive and hard code expected gas amounts or upper limits
of gas amounts.

Setting `GasScale` has two effects:
- revive's Ethereum gas price is scaled up by the factor `GasScale`
- resulting used/estimated gas amounts get scaled down by the factor
`GasScale`.

## Technical Details
Internally, revive uses exactly the same gas price and gas units as
before. Only at the interface these amounts and prices get scaled by
`GasScale`.

**The actual logical changes are almost trivial and I use `GasScale` at
only three places: in `evm_base_fee` to scale the gas price and in the
functions `from_ethereum_gas` and `to_ethereum_gas`.**

## Recommended
This PR sets `GasScale` for the dev-node to 50_000.

This is motivated by the fact that storing a value in a contract storage
slot costs `DepositPerChildTrieItem + DepositPerByte * 32`, which is
`2_000_000_000 + 10_000_000 * 32` (= `2_320_000_000`) plancks. Before
this change the gas price was 1_000_000 wei, so that this
equated to 2_320_000_000 gas units. In EVM this operation requires
22_100 gas only.

Thus, `GasScale` would need to be about 100_000 in order for `SSTORE` to
have similar worst case gas requirements.

## Resolved Issues
- fixes paritytech/contract-issues#221

This PR addresses
paritytech/contract-issues#18 but we also need
to find an appropriate `GasScale` for a mainnet installment of
pallet-revive (see [this
comment](paritytech/contract-issues#18 (comment))).

---------

Co-authored-by: Alexander Theißen <[email protected]>
Co-authored-by: PG Herveou <[email protected]>
Co-authored-by: Omar Abdulla <[email protected]>
Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Author: 5 people

cumulus/parachains/runtimes/assets/asset-hub-westend/src/lib.rs

@@ -1214,6 +1214,7 @@ impl pallet_revive::Config for Runtime {
 	type FeeInfo = pallet_revive::evm::fees::Info<Address, Signature, EthExtraImpl>;
 	type MaxEthExtrinsicWeight = MaxEthExtrinsicWeight;
 	type DebugEnabled = ConstBool<false>;
+	type GasScale = ConstU32<1000>;
 }
 
 parameter_types! {

cumulus/parachains/runtimes/testing/penpal/src/lib.rs

@@ -842,6 +842,7 @@ impl pallet_revive::Config for Runtime {
 	type FeeInfo = pallet_revive::evm::fees::Info<Address, Signature, EthExtraImpl>;
 	type MaxEthExtrinsicWeight = MaxEthExtrinsicWeight;
 	type DebugEnabled = ConstBool<false>;
+	type GasScale = ConstU32<1000>;
 }
 
 impl pallet_sudo::Config for Runtime {

prdoc/pr_10393.prdoc

@@ -0,0 +1,39 @@
+title: Add configuration to set Ethereum gas scale
+doc:
+- audience: Runtime Dev
+  description: |-
+    This PR adds a new configuration parameter (`GasScale`) to pallet-revive that allows to change the scale of the Ethereum gas and of the Ethereum gas price.
+
+    Before this PR, the Ethereum gas price is simply the next fee multiplier of pallet-transaction-payment multiplied by `NativeToEthRatio`. Thus, on Polkadot this is 100_000_000 when the multiplier has its default value of 1.
+
+    The required gas of a transaction is its total cost divided by the gas price, where the total cost is the sum of the transaction fee and the storage deposit.
+
+    This leads to a situation where the required gas for a transaction on revive is usually orders of magnitude larger than the required amount of gas on Ethereum. This can lead to issues with tools or systems that interact with revive and hard code expected gas amounts or upper limits of gas amounts.
+
+    Setting `GasScale` has two effects:
+    - revive's Ethereum gas price is scaled up by the factor `GasScale`
+    - resulting used/estimated gas amounts get scaled down by the factor `GasScale`.
+
+    ## Technical Details
+    Internally, revive uses exactly the same gas price and gas units as before. Only at the interface these amounts and prices get scaled by `GasScale`.
+
+    ## Recommended
+    This PR sets `GasScale` for the dev-node to 50_000.
+
+    This is motivated by the fact that storing a value in a contract storage slot costs `DepositPerChildTrieItem + DepositPerByte * 32`, which is `2_000_000_000 + 10_000_000 * 32` (= `2_320_000_000`) plancks. Before this change the gas price was 1_000_000 wei, so that this
+    equated to 2_320_000_000 gas units. In EVM this operation requires 22_100 gas only.
+
+    Thus, `GasScale` would need to be about 100_000 in order for `SSTORE` to have similar worst case gas requirements.
+
+    ## Resolved Issues
+
+    This PR addresses https://github.com/paritytech/contract-issues/issues/18 but we also need to find an appropriate `GasScale` for a mainnet installment of pallet-revive.
+crates:
+- name: revive-dev-runtime
+  bump: patch
+- name: pallet-revive
+  bump: major
+- name: asset-hub-westend-runtime
+  bump: patch
+- name: penpal-runtime
+  bump: patch

substrate/bin/node/runtime/src/lib.rs

@@ -1539,6 +1539,7 @@ impl pallet_revive::Config for Runtime {
 	type FeeInfo = pallet_revive::evm::fees::Info<Address, Signature, EthExtraImpl>;
 	type MaxEthExtrinsicWeight = MaxEthExtrinsicWeight;
 	type DebugEnabled = ConstBool<false>;
+	type GasScale = ConstU32<1000>;
 }
 
 impl pallet_sudo::Config for Runtime {

substrate/frame/revive/dev-node/runtime/src/lib.rs

@@ -71,7 +71,7 @@ pub mod genesis_config_presets {
 	use alloc::{vec, vec::Vec};
 	use serde_json::Value;
 
-	pub const ENDOWMENT: Balance = 1_000_000_001 * DOLLARS;
+	pub const ENDOWMENT: Balance = 10_000_000_000_001 * DOLLARS;
 
 	fn well_known_accounts() -> Vec<AccountId> {
 		Sr25519Keyring::well_known()
@@ -356,6 +356,7 @@ impl pallet_revive::Config for Runtime {
 	type Time = Timestamp;
 	type FeeInfo = FeeInfo<Address, Signature, EthExtraImpl>;
 	type DebugEnabled = ConstBool<false>;
+	type GasScale = ConstU32<50000>;
 }
 
 pallet_revive::impl_runtime_apis_plus_revive_traits!(

substrate/frame/revive/src/lib.rs

@@ -347,6 +347,27 @@ pub mod pallet {
 		/// Allows debug-mode configuration, such as enabling unlimited contract size.
 		#[pallet::constant]
 		type DebugEnabled: Get<bool>;
+
+		/// This determines the relative scale of our gas price and gas estimates.
+		///
+		/// By default, the gas price (in wei) is `FeeInfo::next_fee_multiplier()` multiplied by
+		/// `NativeToEthRatio`. `GasScale` allows to scale this value: the actual gas price is the
+		/// default gas price multiplied by `GasScale`.
+		///
+		/// As a consequence, gas cost (gas estimates and actual gas usage during transaction) is
+		/// scaled down by the same factor. Thus, the total transaction cost is not affected by
+		/// `GasScale` – apart from rounding differences: the transaction cost is always a multiple
+		/// of the gas price and is derived by rounded up, so that with higher `GasScales` this can
+		/// lead to higher gas cost as the rounding difference would be larger.
+		///
+		/// The main purpose of changing the `GasScale` is to tune the gas cost so that it is closer
+		/// to standard EVM gas cost and contracts will not run out of gas when tools or code
+		/// assume hard coded gas limits.
+		///
+		/// Requirement: `GasScale` must not be 0
+		#[pallet::constant]
+		#[pallet::no_default_bounds]
+		type GasScale: Get<u32>;
 	}
 
 	/// Container for different types that implement [`DefaultConfig`]` of this pallet.
@@ -375,6 +396,7 @@ pub mod pallet {
 			pub const DepositPerByte: Balance = deposit(0, 1);
 			pub const CodeHashLockupDepositPercent: Perbill = Perbill::from_percent(0);
 			pub const MaxEthExtrinsicWeight: FixedU128 = FixedU128::from_rational(9, 10);
+			pub const GasScale: u32 = 10u32;
 		}
 
 		/// A type providing default configurations for this pallet in testing environment.
@@ -429,6 +451,7 @@ pub mod pallet {
 			type FeeInfo = ();
 			type MaxEthExtrinsicWeight = MaxEthExtrinsicWeight;
 			type DebugEnabled = ConstBool<false>;
+			type GasScale = GasScale;
 		}
 	}
 
@@ -892,6 +915,8 @@ pub mod pallet {
 		fn integrity_test() {
 			assert!(T::ChainId::get() > 0, "ChainId must be greater than 0");
 
+			assert!(T::GasScale::get() > 0u32.into(), "GasScale must not be 0");
+
 			T::FeeInfo::integrity_test();
 
 			// The memory available in the block building runtime
@@ -2114,8 +2139,12 @@ impl<T: Config> Pallet<T> {
 
 	/// Get the base gas price.
 	pub fn evm_base_fee() -> U256 {
+		let gas_scale = <T as Config>::GasScale::get();
 		let multiplier = T::FeeInfo::next_fee_multiplier();
-		multiplier.saturating_mul_int::<u128>(T::NativeToEthRatio::get().into()).into()
+		multiplier
+			.saturating_mul_int::<u128>(T::NativeToEthRatio::get().into())
+			.saturating_mul(gas_scale.saturated_into())
+			.into()
 	}
 
 	/// Build an EVM tracer from the given tracer type.

substrate/frame/revive/src/metering/gas.rs

@@ -13,10 +13,11 @@
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
-// limitations under the License.
+// limitations under the License
 
 use crate::{evm::fees::InfoT, BalanceOf, Config, StorageDeposit};
 use frame_support::DebugNoBound;
+use sp_core::Get;
 use sp_runtime::{FixedPointNumber, Saturating};
 
 /// The type for negative and positive gas amounts.
@@ -52,7 +53,8 @@ impl<T: Config> SignedGas<T> {
 	/// Transform an Ethereum gas amount coming from outside the metering system and transform into
 	/// the internally used SignedGas.
 	pub fn from_ethereum_gas(gas: BalanceOf<T>) -> Self {
-		Self::Positive(gas)
+		let gas_scale = <T as Config>::GasScale::get();
+		Self::Positive(gas.saturating_mul(gas_scale.into()))
 	}
 
 	/// Transform a storage deposit into a gas value. The value will be adjusted by dividing it
@@ -80,8 +82,11 @@ impl<T: Config> SignedGas<T> {
 	/// Transform the gas amount to an Ethereum gas amount usable for external purposes
 	/// Returns None if the gas amount is negative.
 	pub fn to_ethereum_gas(&self) -> Option<BalanceOf<T>> {
+		let gas_scale: BalanceOf<T> = <T as Config>::GasScale::get().into();
+
 		match self {
-			Positive(amount) => Some(*amount),
+			Positive(amount) =>
+				Some((amount.saturating_add(gas_scale.saturating_sub(1u32.into()))) / gas_scale),
 			Negative(..) => None,
 		}
 	}