Ring-buffers can be used for two mappings in PreconfTaskManager.sol

[dantaik]

Maybe it's possible to use two ring-buffers for the following two mappings to save 15000 gas per SSTORE.

    // Maps the epoch timestamp to the lookahead poster.
    // If the lookahead poster has been slashed, it maps to the 0-address.
    // Note: This may be optimised to re-use existing slots and reduce gas cost.
    mapping(uint256 epochTimestamp => address poster) internal lookaheadPosters;

    // Maps the block height to the associated proposer
    // This is required since the stored block in Taiko has the address of this contract as the proposer
    mapping(uint256 blockId => address proposer) internal blockIdToProposer;

[dantaik]

As each epoch has 32 slots (384s) and the lookahead is 64 slots. Maybe we can use the following?

struct PosterInfo {
  address poster;
  uint40 timestamp;
}

struct ProposerInfo {
  address proposer;
  uint64 blockId;
} 
// storage reuse for every 128 blocks (1536 second)
mapping(uint256 epochTimestamp_mod_ 1536 => PosterInfo poster) internal lookaheadPosters;
mapping(uint256 blockId_mod_128 => ProposerInfo proposer) internal blockIdToProposer;

When reading data:

ProposerInfo memory pi =  blockIdToProposer[blockId % 128]
if (pi.blockId != blockId) {
   pi = ProposerInfo(address(0), 0);
}

[AnshuJalan]

Implemented in the open PR: NethermindEth/Taiko-Preconf-AVS#171