lotus/chain/vm/burn.go

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package vm
import (
"github.com/filecoin-project/specs-actors/actors/abi"
"github.com/filecoin-project/specs-actors/actors/abi/big"
)
const (
gasOveruseNum = 11
gasOveruseDenom = 10
)
type GasOutputs struct {
BaseFeeBurn abi.TokenAmount
OverEstimationBurn abi.TokenAmount
MinerPenalty abi.TokenAmount
MinerTip abi.TokenAmount
Refund abi.TokenAmount
GasRefund int64
GasBurned int64
}
// ComputeGasOverestimationBurn computes amount of gas to be refunded and amount of gas to be burned
// Result is (refund, burn)
func ComputeGasOverestimationBurn(gasUsed, gasLimit int64) (int64, int64) {
if gasUsed == 0 {
return 0, gasLimit
}
// over = gasLimit/gasUsed - 1 - 0.3
// over = min(over, 1)
// gasToBurn = (gasLimit - gasUsed) * over
// so to factor out division from `over`
// over*gasUsed = min(gasLimit - (13*gasUsed)/10, gasUsed)
// gasToBurn = ((gasLimit - gasUsed)*over*gasUsed) / gasUsed
over := gasLimit - (gasOveruseNum*gasUsed)/gasOveruseDenom
if over < 0 {
return gasLimit - gasUsed, 0
}
// if we want sharper scaling it goes here:
// over *= 2
if over > gasUsed {
over = gasUsed
}
// needs bigint, as it overflows in pathological case gasLimit > 2^32 gasUsed = gasLimit / 2
gasToBurn := big.NewInt(gasLimit - gasUsed)
gasToBurn = big.Mul(gasToBurn, big.NewInt(over))
gasToBurn = big.Div(gasToBurn, big.NewInt(gasUsed))
return gasLimit - gasUsed - gasToBurn.Int64(), gasToBurn.Int64()
}
func ComputeGasOutputs(gasUsed, gasLimit int64, baseFee, feeCap, gasPremium abi.TokenAmount) GasOutputs {
gasUsedBig := big.NewInt(gasUsed)
out := GasOutputs{
BaseFeeBurn: big.Zero(),
OverEstimationBurn: big.Zero(),
MinerPenalty: big.Zero(),
MinerTip: big.Zero(),
Refund: big.Zero(),
}
baseFeeToPay := baseFee
if baseFee.Cmp(feeCap.Int) > 0 {
baseFeeToPay = feeCap
out.MinerPenalty = big.Mul(big.Sub(baseFee, feeCap), gasUsedBig)
}
out.BaseFeeBurn = big.Mul(baseFeeToPay, big.NewInt(gasUsed))
minerTip := gasPremium
if big.Cmp(big.Add(baseFeeToPay, minerTip), feeCap) > 0 {
minerTip = big.Sub(feeCap, baseFeeToPay)
}
out.MinerTip = big.Mul(minerTip, big.NewInt(gasLimit))
out.GasRefund, out.GasBurned = ComputeGasOverestimationBurn(gasUsed, gasLimit)
if out.GasBurned != 0 {
gasBurnedBig := big.NewInt(out.GasBurned)
out.OverEstimationBurn = big.Mul(baseFeeToPay, gasBurnedBig)
minerPenalty := big.Mul(big.Sub(baseFee, baseFeeToPay), gasBurnedBig)
out.MinerPenalty = big.Add(out.MinerPenalty, minerPenalty)
}
requiredFunds := big.Mul(big.NewInt(gasLimit), feeCap)
refund := big.Sub(requiredFunds, out.BaseFeeBurn)
refund = big.Sub(refund, out.MinerTip)
refund = big.Sub(refund, out.OverEstimationBurn)
out.Refund = refund
return out
}