Calldata Cost Reduction Checklist

[tynes]

There have been some recent proposals to reduce the gas cost of calldata which would allow for rollups to be cheaper. The L1 portion of the fee (used to cover batch submission) is charged along with the L2 portion of the fee (used to cover L2 execution).

• Transaction calldata gas cost reduction with total calldata limit ethereum/EIPs#4488
• EIP-4490, reducing gas cost prior to the Merge ethereum/EIPs#4490

These changes would cause the GasPriceOracle predeploy to overcharge for the L1 gas price, since the calldata costs are hardcoded in the contract. This means that we need to upgrade the GasPriceOracle contract once this change goes into place. Currently, there is no proxy in front of the GasPriceOracle - perhaps the GasPriceOracleV2 should be deployed behind a proxy so that it is upgradable. See here for the implementation of how the L1 portion of the fee is currently computed.

In the meantime, the price discrepancy can be handled by setting the scalar or overhead values lower.

• optimism/packages/contracts/contracts/L2/predeploys/OVM_GasPriceOracle.sol

  Line 28 in 639e5b1

  uint256 public overhead;

• optimism/packages/contracts/contracts/L2/predeploys/OVM_GasPriceOracle.sol

  Line 30 in 639e5b1

  uint256 public scalar;

TODOs:

• Determine if using a proxy is the correct approach in the future
• Write the GasPriceOracleV2 contract, which should be similar in functionality
• Hardfork/squash fork logic will be required to switch to the new GasPriceOracleV2
• Determine the correct values for the scalar and overhead to compensate for the cheaper calldata costs