70 lines
2.2 KiB
Markdown
70 lines
2.2 KiB
Markdown
---
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title: "GasOptimization"
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type: concept
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tags: []
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last_updated: 2026-05-01
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---
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## Definition
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Gas Optimization 是指在 EVM 智能合约开发中，通过技术手段降低合约执行和部署的 Gas 消耗，直接减少用户费用和以太坊网络的负担。由于每个区块的 Gas 上限固定，优化 Gas 消耗也是提高协议吞吐量的关键。
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## Core Gas Costs (EVM)
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| 操作 | Cold Access | Warm Access |
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|------|-------------|-------------|
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| SLOAD（读取存储） | 2100 gas | 100 gas |
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| SSTORE new（写入新槽） | 20000 gas | - |
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| SSTORE update（更新槽） | 5000 gas | 2900 gas |
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| CALL（外部调用） | 2600 gas + 被调函数 gas | 100 gas |
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| CREATE（创建合约） | 32000 gas | - |
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## Key Patterns
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### 1. Storage Packing（存储打包）
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将多个小类型打包进同一 32 字节槽，节省 SSTORE 次数：
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```solidity
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// ✅ Good: 2 个变量共享一个槽
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struct PackedData {
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uint128 amount; // 16 bytes
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uint128 id; // 16 bytes → 同槽
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}
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```
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### 2. Calldata over Memory
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```solidity
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// ✅ Good: calldata 只读，节省拷贝
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function processIds(uint256[] calldata ids) external pure {}
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// ❌ Bad: memory 需要拷贝到内存
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function processIds(uint256[] memory ids) external pure {}
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```
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### 3. Custom Errors over Require Strings
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```solidity
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// ✅ Good: 节省 ~50 gas/revert
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error InsufficientBalance(uint256 requested, uint256 available);
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require(balance >= amount, "Insufficient balance");
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// ❌ Bad: 错误信息存储在字节码中
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require(balance >= amount, "Insufficient balance for this operation");
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```
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### 4. Immutable over Constant（运行时）
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```solidity
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uint256 public constant MAX_SUPPLY = 1_000_000; // 编译时常量
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address public immutable owner; // 运行时只设置一次
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```
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### 5. External over Public
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- External 函数：调用时参数通过 calldata 传递
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- Public 函数：需要检查是否内部调用，参数通过 memory 传递
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- 仅被内部调用 → public；仅被外部调用 → external
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### 6. Unchecked Math（Safe Math）
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```solidity
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unchecked { counter++; } // 已知 counter 不会溢出
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```
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## Sources
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- [[engineering-solidity-smart-contract-engineer]]
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