气体计数。燃烧过的煤气和用过的煤气有什么区别？

Question

在交易执行期间，我们正在计算我们“燃烧了多少气体”和“使用了多少气体”。为什么我们必须单独跟踪这些计数器？

Answer 1

在写这个答案时，@MaksymZavershynskyi 也回答了。

他的回答应该被认为是权威的，而我的只是猜测。

看看源代码让我觉得

• gas_used 是生产存储和计算的成本（完成不会失败的工作）
• gas_burnt 是非生产性传输、存储和计算的成本（从 A 点到 B 点获取数据、尝试执行功能但在执行过程中失败或导致错误等）

---

这是一堆给我留下这种印象的源代码链接的sn-ps

来自nearcore/runtime/runtime/src/lib.rs

fn generate_refund_receipts(
    &self,
    receipt: &Receipt,
    action_receipt: &ActionReceipt,
    result: &mut ActionResult,
) -> Result<(), RuntimeError> {
    /// ... snip ...
    let gas_refund = if result.result.is_err() {
        safe_add_gas(prepaid_gas, exec_gas)? - result.gas_burnt
    } else {
        safe_add_gas(prepaid_gas, exec_gas)? - result.gas_used
    };
    /// ... snip ...
}

source

---

来自nearcore/runtime/runtime/src/actions.rs

pub(crate) fn action_function_call(
    state_update: &mut TrieUpdate,
    apply_state: &ApplyState,
    account: &mut Option<Account>,
    receipt: &Receipt,
    action_receipt: &ActionReceipt,
    promise_results: &[PromiseResult],
    result: &mut ActionResult,
    account_id: &AccountId,
    function_call: &FunctionCallAction,
    action_hash: &CryptoHash,
    config: &RuntimeConfig,
    is_last_action: bool,
) -> Result<(), StorageError> {
    /// ... snip ...
    if let Some(outcome) = outcome {
        result.gas_burnt += outcome.burnt_gas;
        result.gas_burnt_for_function_call += outcome.burnt_gas;
        // Runtime in `generate_refund_receipts` takes care of using proper value for refunds.
        // It uses `gas_used` for success and `gas_burnt` for failures. So it's not an issue to
        // return a real `gas_used` instead of the `gas_burnt` into `ActionResult` for
        // `FunctionCall`s.
        result.gas_used += outcome.used_gas;
        result.logs.extend(outcome.logs.into_iter());
    }
    /// ... snip ...
}

source

---

来自nearcore/core/primitives/src/types.rs

pub struct ChunkExtra {
  /// ... snip ...

  /// Actually how much gas were used.
  pub gas_used: Gas

/// ... snip ...
}

source

---

来自nearcore/core/primitives/src/sharding.rs

pub struct ShardChunkHeaderInner {
  /// ... snip ...

  /// Gas used in this chunk.
  pub gas_used: Gas,

  /// ... snip ...
}

source

---

来自nearcore/runtime/runtime/src/config.rs

/// ... snip ...

pub fn tx_cost(
    config: &RuntimeFeesConfig,
    transaction: &Transaction,
    gas_price: Balance,
    sender_is_receiver: bool,
) -> Result<(Gas, Gas, Balance), IntegerOverflowError> {
    let mut gas_burnt: Gas = config.action_receipt_creation_config.send_fee(sender_is_receiver);
    gas_burnt = safe_add_gas(
        gas_burnt,
        total_send_fees(&config, sender_is_receiver, &transaction.actions)?,
    )?;
    let mut gas_used = safe_add_gas(gas_burnt, config.action_receipt_creation_config.exec_fee())?;
    gas_used = safe_add_gas(gas_used, total_exec_fees(&config, &transaction.actions)?)?;
    gas_used = safe_add_gas(gas_used, total_prepaid_gas(&transaction.actions)?)?;
    let mut total_cost = safe_gas_to_balance(gas_price, gas_used)?;
    total_cost = safe_add_balance(total_cost, total_deposit(&transaction.actions)?)?;
    Ok((gas_burnt, gas_used, total_cost))
}
/// ... snip ...


/// Total sum of gas that would need to be burnt before we start executing the given actions.
pub fn total_exec_fees(
    config: &RuntimeFeesConfig,
    actions: &[Action],
) -> Result<Gas, IntegerOverflowError> {
  /// ... snip ...
}

/// Get the total sum of deposits for given actions.
pub fn total_deposit(
    actions: &[Action]
) -> Result<Balance, IntegerOverflowError> {
  /// ... snip ...
}

/// Get the total sum of prepaid gas for given actions.
pub fn total_prepaid_gas(
    actions: &[Action]
) -> Result<Gas, IntegerOverflowError> {
  /// ... snip ...
}

source

Answer 2

• 使用的气体包括燃烧的气体，所以gas_used >= gas_burnt，总是这样；
• 收取任何费用时，均计入gas_burnt 和gas_used；
• 当合约执行跨合约调用并将X 数量的gas 附加到此调用时，X 计入gas_used 但不计入gas_burnt。这是gas_used 和gas_burnt 之间差异的唯一来源。如果智能合约在完成执行之前失败，则不会执行任何跨合约调用（或由合约创建的交易）并退还附加的 gas；
• 根据前面的要点，当合约失败时，gas_used - gas_burnt 将被退还给账户，而gas_burnt 将永远丢失（因为gas_burnt 对应于实际花费验证者一些计算工作的费用)。