What are Ethereum performance optimization technologies? Please explain Layer 2 scaling solutions and gas optimization - 面试题

Ethereum performance optimization is a key technology for improving blockchain throughput, reducing latency, and lowering gas fees. Here's a comprehensive analysis of performance optimization:

Basic Concepts of Performance Optimization

Ethereum performance optimization aims to improve network TPS (transactions per second), reduce transaction confirmation time, and decrease gas consumption.

Layer 2 Scaling Solutions

1. Optimistic Rollups

Assume all transactions are valid, ensure security through fraud proofs.

Features:

Low gas fees
Fast confirmation
Fraud proof delay

Representative Projects:

Arbitrum: Optimistic Rollup
Optimism: Optimistic Rollup

Implementation Example:

solidity
contract OptimisticRollup {
    struct Transaction {
        address from;
        address to;
        uint256 value;
        bytes data;
    }
    
    struct Batch {
        Transaction[] transactions;
        bytes32 stateRoot;
        uint256 timestamp;
        bool challenged;
    }
    
    Batch[] public batches;
    uint256 public challengePeriod = 7 days;
    
    event BatchSubmitted(uint256 indexed batchId, bytes32 stateRoot);
    event BatchChallenged(uint256 indexed batchId, address indexed challenger);
    event BatchFinalized(uint256 indexed batchId);
    
    function submitBatch(Transaction[] memory transactions, bytes32 stateRoot) public {
        bytes32 computedStateRoot = computeStateRoot(transactions);
        require(computedStateRoot == stateRoot, "Invalid state root");
        
        batches.push(Batch({
            transactions: transactions,
            stateRoot: stateRoot,
            timestamp: block.timestamp,
            challenged: false
        }));
        
        emit BatchSubmitted(batches.length - 1, stateRoot);
    }
    
    function challengeBatch(uint256 batchId, bytes32 fraudProof) public {
        Batch storage batch = batches[batchId];
        require(!batch.challenged, "Already challenged");
        require(block.timestamp < batch.timestamp + challengePeriod, "Challenge period expired");
        
        // Verify fraud proof
        require(verifyFraudProof(batch.transactions, fraudProof), "Invalid fraud proof");
        
        batch.challenged = true;
        emit BatchChallenged(batchId, msg.sender);
    }
    
    function finalizeBatch(uint256 batchId) public {
        Batch storage batch = batches[batchId];
        require(!batch.challenged, "Batch challenged");
        require(block.timestamp >= batch.timestamp + challengePeriod, "Challenge period not expired");
        
        emit BatchFinalized(batchId);
    }
    
    function computeStateRoot(Transaction[] memory transactions) internal pure returns (bytes32) {
        bytes32 stateRoot = bytes32(0);
        for (uint256 i = 0; i < transactions.length; i++) {
            stateRoot = keccak256(abi.encodePacked(stateRoot, transactions[i]));
        }
        return stateRoot;
    }
    
    function verifyFraudProof(Transaction[] memory transactions, bytes32 fraudProof) internal pure returns (bool) {
        // Verify fraud proof logic
        return true;
    }
}

2. ZK-Rollups

Use zero-knowledge proofs to verify transaction validity.

Features:

Instant confirmation
High security
Computational complexity

Representative Projects:

zkSync: ZK-Rollup
StarkNet: ZK-Rollup

Implementation Example:

solidity
contract ZKRollup {
    struct State {
        mapping(address => uint256) balances;
        uint256 totalBalance;
    }
    
    State public state;
    bytes32 public currentStateRoot;
    uint256 public batchNumber;
    
    event BatchProcessed(uint256 indexed batchNumber, bytes32 stateRoot);
    
    function processBatch(
        bytes calldata proof,
        bytes32 newStateRoot,
        bytes calldata publicInputs
    ) public {
        // Verify zero-knowledge proof
        require(verifyZKProof(proof, publicInputs), "Invalid proof");
        
        // Update state root
        currentStateRoot = newStateRoot;
        batchNumber++;
        
        emit BatchProcessed(batchNumber, newStateRoot);
    }
    
    function verifyZKProof(bytes calldata proof, bytes calldata publicInputs) internal pure returns (bool) {
        // Verify ZK proof logic
        return true;
    }
}

Gas Optimization Techniques

1. Storage Optimization

solidity
contract StorageOptimization {
    // Bad practice: using multiple storage variables
    uint256 public var1;
    uint256 public var2;
    uint256 public var3;
    
    // Good practice: using struct packing
    struct PackedData {
        uint128 var1;
        uint128 var2;
        uint64 var3;
        uint64 var4;
    }
    PackedData public packedData;
    
    // Use mapping instead of array
    mapping(address => uint256) public balances;
    
    // Use events to record data
    event DataStored(uint256 indexed id, bytes32 data);
    
    function storeData(uint256 id, bytes32 data) public {
        emit DataStored(id, data);
    }
}

2. Memory Optimization

solidity
contract MemoryOptimization {
    function optimizedFunction(uint256[] calldata data) public pure returns (uint256) {
        uint256 sum = 0;
        uint256 length = data.length;
        
        for (uint256 i = 0; i < length; i++) {
            sum += data[i];
        }
        
        return sum;
    }
    
    function unoptimizedFunction(uint256[] memory data) public pure returns (uint256) {
        uint256 sum = 0;
        
        for (uint256 i = 0; i < data.length; i++) {
            sum += data[i];
        }
        
        return sum;
    }
}

3. Loop Optimization

solidity
contract LoopOptimization {
    // Bad practice: storage operations in loop
    function badLoop(address[] memory recipients, uint256 amount) public {
        for (uint256 i = 0; i < recipients.length; i++) {
            balances[recipients[i]] += amount;
        }
    }
    
    // Good practice: batch processing
    function goodLoop(address[] calldata recipients, uint256 amount) public {
        uint256 totalAmount = recipients.length * amount;
        require(balanceOf[msg.sender] >= totalAmount, "Insufficient balance");
        
        balanceOf[msg.sender] -= totalAmount;
        
        for (uint256 i = 0; i < recipients.length; i++) {
            balances[recipients[i]] += amount;
        }
    }
    
    mapping(address => uint256) public balances;
    mapping(address => uint256) public balanceOf;
}

State Channels

1. Payment Channel

solidity
contract PaymentChannel {
    address payable public sender;
    address payable public receiver;
    uint256 public amount;
    uint256 public expiration;
    bytes32 public channelId;
    bool public closed;
    
    mapping(bytes32 => bool) public usedSignatures;
    
    event ChannelOpened(bytes32 indexed channelId, address indexed sender, address indexed receiver, uint256 amount);
    event ChannelClosed(bytes32 indexed channelId, uint256 senderAmount, uint256 receiverAmount);
    
    constructor(address payable _receiver, uint256 _amount, uint256 _duration) payable {
        sender = payable(msg.sender);
        receiver = _receiver;
        amount = _amount;
        expiration = block.timestamp + _duration;
        channelId = keccak256(abi.encodePacked(sender, receiver, amount, expiration));
        
        emit ChannelOpened(channelId, sender, receiver, amount);
    }
    
    function closeChannel(uint256 senderAmount, uint256 receiverAmount, bytes memory signature) public {
        require(!closed, "Channel already closed");
        require(msg.sender == sender || msg.sender == receiver, "Not participant");
        
        bytes32 messageHash = keccak256(abi.encodePacked(channelId, senderAmount, receiverAmount));
        bytes32 ethSignedMessageHash = keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n32", messageHash));
        
        address signer = recoverSigner(ethSignedMessageHash, signature);
        require(signer == sender, "Invalid signature");
        
        require(senderAmount + receiverAmount == amount, "Invalid amounts");
        
        closed = true;
        
        if (senderAmount > 0) {
            sender.transfer(senderAmount);
        }
        if (receiverAmount > 0) {
            receiver.transfer(receiverAmount);
        }
        
        emit ChannelClosed(channelId, senderAmount, receiverAmount);
    }
    
    function timeoutClose() public {
        require(!closed, "Channel already closed");
        require(block.timestamp >= expiration, "Not expired");
        
        closed = true;
        sender.transfer(amount);
        
        emit ChannelClosed(channelId, amount, 0);
    }
    
    function recoverSigner(bytes32 messageHash, bytes memory signature) internal pure returns (address) {
        (bytes32 r, bytes32 s, uint8 v) = splitSignature(signature);
        return ecrecover(messageHash, v, r, s);
    }
    
    function splitSignature(bytes memory sig) internal pure returns (bytes32 r, bytes32 s, uint8 v) {
        require(sig.length == 65, "Invalid signature length");
        assembly {
            r := mload(add(sig, 32))
            s := mload(add(sig, 64))
            v := byte(0, mload(add(sig, 96)))
        }
    }
    
    receive() external payable {}
}

Sharding Technology

1. State Sharding

solidity
contract StateSharding {
    uint256 public shardCount = 64;
    mapping(uint256 => mapping(address => uint256)) public shardBalances;
    
    function getShard(address account) public pure returns (uint256) {
        return uint256(uint160(account)) % 64;
    }
    
    function transfer(address to, uint256 amount) public {
        uint256 fromShard = getShard(msg.sender);
        uint256 toShard = getShard(to);
        
        if (fromShard == toShard) {
            // Same shard transfer
            shardBalances[fromShard][msg.sender] -= amount;
            shardBalances[fromShard][to] += amount;
        } else {
            // Cross-shard transfer
            shardBalances[fromShard][msg.sender] -= amount;
            shardBalances[toShard][to] += amount;
        }
    }
}

Performance Optimization Best Practices

1. Smart Contract Optimization

Reduce storage operations
Use calldata instead of memory
Batch process transactions
Use events to record data

2. Architecture Optimization

Use Layer 2 solutions
Implement state channels
Adopt sidechains
Use sharding technology

3. Development Optimization

Use optimized libraries
Avoid storage operations in loops
Use precompiled contracts
Optimize algorithm complexity

Famous Performance Optimization Projects

Arbitrum: Optimistic Rollup
Optimism: Optimistic Rollup
zkSync: ZK-Rollup
StarkNet: ZK-Rollup
Polygon: Sidechain solution

Ethereum performance optimization is driving mass adoption of blockchain, improving scalability and usability.