Merge pull request #2764 from filecoin-project/feat/burn-above-estimate

Burn sclaing amount dependon on how much overestimation there was

chain/validation/applier.go

@@ -2,7 +2,6 @@ package validation
 
 import (
 	"context"
-
 	"golang.org/x/xerrors"
 
 	"github.com/filecoin-project/specs-actors/actors/abi"
@@ -37,6 +36,7 @@ func (a *Applier) ApplyMessage(epoch abi.ChainEpoch, message *vtypes.Message) (v
 	lm := toLotusMsg(message)
 	receipt, penalty, reward, err := a.applyMessage(epoch, lm)
 	return vtypes.ApplyMessageResult{
+		Msg:     *message,
 		Receipt: receipt,
 		Penalty: penalty,
 		Reward:  reward,
@@ -57,6 +57,7 @@ func (a *Applier) ApplySignedMessage(epoch abi.ChainEpoch, msg *vtypes.SignedMes
 	// TODO: Validate the sig first
 	receipt, penalty, reward, err := a.applyMessage(epoch, lm)
 	return vtypes.ApplyMessageResult{
+		Msg:     msg.Message,
 		Receipt: receipt,
 		Penalty: penalty,
 		Reward:  reward,
@@ -176,8 +177,8 @@ func toLotusMsg(msg *vtypes.Message) *types.Message {
 		Nonce:  msg.CallSeqNum,
 		Method: msg.Method,
 
-		Value:    types.BigInt{Int: msg.Value.Int},
+		Value:    msg.Value,
-		GasPrice: types.BigInt{Int: msg.GasPrice.Int},
+		GasPrice: msg.GasPrice,
 		GasLimit: msg.GasLimit,
 
 		Params: msg.Params,

chain/vm/burn.go

@@ -0,0 +1,44 @@
+package vm
+
+import (
+	"math/big"
+)
+
+const (
+	gasOveruseNum   = 11
+	gasOveruseDenom = 10
+)
+
+// ComputeGasOutputs computes amount of gas to be refunded and amount of gas to be burned
+// Result is (refund, burn)
+func ComputeGasOutputs(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 = gasToBurn.Mul(gasToBurn, big.NewInt(over))
+	gasToBurn = gasToBurn.Div(gasToBurn, big.NewInt(gasUsed))
+
+	return gasLimit - gasUsed - gasToBurn.Int64(), gasToBurn.Int64()
+}

chain/vm/burn_test.go

@@ -0,0 +1,39 @@
+package vm
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestGasBurn(t *testing.T) {
+	tests := []struct {
+		used   int64
+		limit  int64
+		refund int64
+		burn   int64
+	}{
+		{100, 200, 10, 90},
+		{100, 150, 30, 20},
+		{1000, 1300, 240, 60},
+		{500, 700, 140, 60},
+		{200, 200, 0, 0},
+		{20000, 21000, 1000, 0},
+		{0, 2000, 0, 2000},
+		{500, 651, 121, 30},
+		{500, 5000, 0, 4500},
+		{7499e6, 7500e6, 1000000, 0},
+		{7500e6 / 2, 7500e6, 375000000, 3375000000},
+		{1, 7500e6, 0, 7499999999},
+	}
+
+	for _, test := range tests {
+		test := test
+		t.Run(fmt.Sprintf("%v", test), func(t *testing.T) {
+			refund, toBurn := ComputeGasOutputs(test.used, test.limit)
+			assert.Equal(t, test.refund, refund, "refund")
+			assert.Equal(t, test.burn, toBurn, "burned")
+		})
+	}
+}

chain/vm/vm.go

@@ -454,12 +454,22 @@ func (vm *VM) ApplyMessage(ctx context.Context, cmsg types.ChainMsg) (*ApplyRet,
 	if gasUsed < 0 {
 		gasUsed = 0
 	}
+	gasRefund, gasToBurn := ComputeGasOutputs(gasUsed, msg.GasLimit)
+
 	// refund unused gas
-	refund := types.BigMul(types.NewInt(uint64(msg.GasLimit-gasUsed)), msg.GasPrice)
+	refund := types.BigMul(types.NewInt(uint64(gasRefund)), msg.GasPrice)
 	if err := vm.transferFromGasHolder(msg.From, gasHolder, refund); err != nil {
 		return nil, xerrors.Errorf("failed to refund gas")
 	}
 
+	if gasToBurn > 0 {
+		// burn overallocated gas
+		burn := types.BigMul(types.NewInt(uint64(gasToBurn)), msg.GasPrice)
+		if err := vm.transferFromGasHolder(builtin.BurntFundsActorAddr, gasHolder, burn); err != nil {
+			return nil, xerrors.Errorf("failed to burn over estimated gas")
+		}
+	}
+
 	gasReward := types.BigMul(msg.GasPrice, types.NewInt(uint64(gasUsed)))
 	if err := vm.transferFromGasHolder(builtin.RewardActorAddr, gasHolder, gasReward); err != nil {
 		return nil, xerrors.Errorf("failed to give miner gas reward: %w", err)

go.mod

@@ -18,7 +18,7 @@ require (
 	github.com/drand/drand v1.0.3-0.20200714175734-29705eaf09d4
 	github.com/drand/kyber v1.1.1
 	github.com/fatih/color v1.8.0
-	github.com/filecoin-project/chain-validation v0.0.6-0.20200731192946-f90377ebe789
+	github.com/filecoin-project/chain-validation v0.0.6-0.20200805210314-9844c5869f53
 	github.com/filecoin-project/filecoin-ffi v0.30.4-0.20200716204036-cddc56607e1d
 	github.com/filecoin-project/go-address v0.0.2-0.20200504173055-8b6f2fb2b3ef
 	github.com/filecoin-project/go-amt-ipld/v2 v2.1.1-0.20200731171407-e559a0579161 // indirect

go.sum

@@ -215,8 +215,8 @@ github.com/fatih/color v1.7.0/go.mod h1:Zm6kSWBoL9eyXnKyktHP6abPY2pDugNf5Kwzbycv
 github.com/fatih/color v1.8.0 h1:5bzFgL+oy7JITMTxUPJ00n7VxmYd/PdMp5mHFX40/RY=
 github.com/fatih/color v1.8.0/go.mod h1:3l45GVGkyrnYNl9HoIjnp2NnNWvh6hLAqD8yTfGjnw8=
 github.com/fd/go-nat v1.0.0/go.mod h1:BTBu/CKvMmOMUPkKVef1pngt2WFH/lg7E6yQnulfp6E=
-github.com/filecoin-project/chain-validation v0.0.6-0.20200731192946-f90377ebe789 h1:/q6q6xNQWymV7qVXF2k5poF0QaWdJAqU00LacgANCuM=
+github.com/filecoin-project/chain-validation v0.0.6-0.20200805210314-9844c5869f53 h1:XRrMct6lOMjVe11dOnurq6vsLayQQyotFJi0YW4Wp8E=
-github.com/filecoin-project/chain-validation v0.0.6-0.20200731192946-f90377ebe789/go.mod h1:JICNIbIEZ+qNJ/PQlHxjei6SaeBbW+yV2r4BcShsXfI=
+github.com/filecoin-project/chain-validation v0.0.6-0.20200805210314-9844c5869f53/go.mod h1:JICNIbIEZ+qNJ/PQlHxjei6SaeBbW+yV2r4BcShsXfI=
 github.com/filecoin-project/go-address v0.0.0-20200107215422-da8eea2842b5/go.mod h1:SAOwJoakQ8EPjwNIsiakIQKsoKdkcbx8U3IapgCg9R0=
 github.com/filecoin-project/go-address v0.0.2-0.20200218010043-eb9bb40ed5be/go.mod h1:SAOwJoakQ8EPjwNIsiakIQKsoKdkcbx8U3IapgCg9R0=
 github.com/filecoin-project/go-address v0.0.2-0.20200504173055-8b6f2fb2b3ef h1:Wi5E+P1QfHP8IF27eUiTx5vYfqQZwfPxzq3oFEq8w8U=