eth/gasestimator: allow slight estimation error in favor of less iter…

…ations (ethereum#28618)

* eth/gasestimator: early exit for plain transfer and error allowance

* core, eth/gasestimator: hard guess at a possible required gas

* internal/ethapi: update estimation tests with the error ratio

* eth/gasestimator: I hate you linter

* graphql: fix gas estimation test

---------

Co-authored-by: Oren <[email protected]>

core/state_transition.go

@@ -32,9 +32,10 @@ import (
 // ExecutionResult includes all output after executing given evm
 // message no matter the execution itself is successful or not.
 type ExecutionResult struct {
-	UsedGas    uint64 // Total used gas but include the refunded gas
-	Err        error  // Any error encountered during the execution(listed in core/vm/errors.go)
-	ReturnData []byte // Returned data from evm(function result or data supplied with revert opcode)
+	UsedGas     uint64 // Total used gas, not including the refunded gas
+	RefundedGas uint64 // Total gas refunded after execution
+	Err         error  // Any error encountered during the execution(listed in core/vm/errors.go)
+	ReturnData  []byte // Returned data from evm(function result or data supplied with revert opcode)
 }
 
 // Unwrap returns the internal evm error which allows us for further
@@ -419,12 +420,13 @@ func (st *StateTransition) TransitionDb() (*ExecutionResult, error) {
 		ret, st.gasRemaining, vmerr = st.evm.Call(sender, st.to(), msg.Data, st.gasRemaining, msg.Value)
 	}
 
+	var gasRefund uint64
 	if !rules.IsLondon {
 		// Before EIP-3529: refunds were capped to gasUsed / 2
-		st.refundGas(params.RefundQuotient)
+		gasRefund = st.refundGas(params.RefundQuotient)
 	} else {
 		// After EIP-3529: refunds are capped to gasUsed / 5
-		st.refundGas(params.RefundQuotientEIP3529)
+		gasRefund = st.refundGas(params.RefundQuotientEIP3529)
 	}
 	effectiveTip := msg.GasPrice
 	if rules.IsLondon {
@@ -442,13 +444,14 @@ func (st *StateTransition) TransitionDb() (*ExecutionResult, error) {
 	}
 
 	return &ExecutionResult{
-		UsedGas:    st.gasUsed(),
-		Err:        vmerr,
-		ReturnData: ret,
+		UsedGas:     st.gasUsed(),
+		RefundedGas: gasRefund,
+		Err:         vmerr,
+		ReturnData:  ret,
 	}, nil
 }
 
-func (st *StateTransition) refundGas(refundQuotient uint64) {
+func (st *StateTransition) refundGas(refundQuotient uint64) uint64 {
 	// Apply refund counter, capped to a refund quotient
 	refund := st.gasUsed() / refundQuotient
 	if refund > st.state.GetRefund() {
@@ -463,6 +466,8 @@ func (st *StateTransition) refundGas(refundQuotient uint64) {
 	// Also return remaining gas to the block gas counter so it is
 	// available for the next transaction.
 	st.gp.AddGas(st.gasRemaining)
+
+	return refund
 }
 
 // gasUsed returns the amount of gas used up by the state transition.

eth/gasestimator/gasestimator.go

@@ -42,6 +42,8 @@ type Options struct {
 	Chain  core.ChainContext   // Chain context to access past block hashes
 	Header *types.Header       // Header defining the block context to execute in
 	State  *state.StateDB      // Pre-state on top of which to estimate the gas
+
+	ErrorRatio float64 // Allowed overestimation ratio for faster estimation termination
 }
 
 // Estimate returns the lowest possible gas limit that allows the transaction to
@@ -86,16 +88,28 @@ func Estimate(ctx context.Context, call *core.Message, opts *Options, gasCap uin
 			if transfer == nil {
 				transfer = new(big.Int)
 			}
-			log.Warn("Gas estimation capped by limited funds", "original", hi, "balance", balance,
+			log.Debug("Gas estimation capped by limited funds", "original", hi, "balance", balance,
 				"sent", transfer, "maxFeePerGas", feeCap, "fundable", allowance)
 			hi = allowance.Uint64()
 		}
 	}
 	// Recap the highest gas allowance with specified gascap.
 	if gasCap != 0 && hi > gasCap {
-		log.Warn("Caller gas above allowance, capping", "requested", hi, "cap", gasCap)
+		log.Debug("Caller gas above allowance, capping", "requested", hi, "cap", gasCap)
 		hi = gasCap
 	}
+	// If the transaction is a plain value transfer, short circuit estimation and
+	// directly try 21000. Returning 21000 without any execution is dangerous as
+	// some tx field combos might bump the price up even for plain transfers (e.g.
+	// unused access list items). Ever so slightly wasteful, but safer overall.
+	if len(call.Data) == 0 {
+		if call.To != nil && opts.State.GetCodeSize(*call.To) == 0 {
+			failed, _, err := execute(ctx, call, opts, params.TxGas)
+			if !failed && err == nil {
+				return params.TxGas, nil, nil
+			}
+		}
+	}
 	// We first execute the transaction at the highest allowable gas limit, since if this fails we
 	// can return error immediately.
 	failed, result, err := execute(ctx, call, opts, hi)
@@ -115,8 +129,35 @@ func Estimate(ctx context.Context, call *core.Message, opts *Options, gasCap uin
 	// limit for these cases anyway.
 	lo = result.UsedGas - 1
 
+	// There's a fairly high chance for the transaction to execute successfully
+	// with gasLimit set to the first execution's usedGas + gasRefund. Explicitly
+	// check that gas amount and use as a limit for the binary search.
+	optimisticGasLimit := (result.UsedGas + result.RefundedGas + params.CallStipend) * 64 / 63
+	if optimisticGasLimit < hi {
+		failed, _, err = execute(ctx, call, opts, optimisticGasLimit)
+		if err != nil {
+			// This should not happen under normal conditions since if we make it this far the
+			// transaction had run without error at least once before.
+			log.Error("Execution error in estimate gas", "err", err)
+			return 0, nil, err
+		}
+		if failed {
+			lo = optimisticGasLimit
+		} else {
+			hi = optimisticGasLimit
+		}
+	}
 	// Binary search for the smallest gas limit that allows the tx to execute successfully.
 	for lo+1 < hi {
+		if opts.ErrorRatio > 0 {
+			// It is a bit pointless to return a perfect estimation, as changing
+			// network conditions require the caller to bump it up anyway. Since
+			// wallets tend to use 20-25% bump, allowing a small approximation
+			// error is fine (as long as it's upwards).
+			if float64(hi-lo)/float64(hi) < opts.ErrorRatio {
+				break
+			}
+		}
 		mid := (hi + lo) / 2
 		if mid > lo*2 {
 			// Most txs don't need much higher gas limit than their gas used, and most txs don't

graphql/graphql_test.go

@@ -139,7 +139,7 @@ func TestGraphQLBlockSerialization(t *testing.T) {
 		// should return `estimateGas` as decimal
 		{
 			body: `{"query": "{block{ estimateGas(data:{}) }}"}`,
-			want: `{"data":{"block":{"estimateGas":"0xcf08"}}}`,
+			want: `{"data":{"block":{"estimateGas":"0xd221"}}}`,
 			code: 200,
 		},
 		// should return `status` as decimal

internal/ethapi/api.go

@@ -51,6 +51,10 @@ import (
 	"github.com/tyler-smith/go-bip39"
 )
 
+// estimateGasErrorRatio is the amount of overestimation eth_estimateGas is
+// allowed to produce in order to speed up calculations.
+const estimateGasErrorRatio = 0.015
+
 // EthereumAPI provides an API to access Ethereum related information.
 type EthereumAPI struct {
 	b Backend
@@ -1189,10 +1193,11 @@ func DoEstimateGas(ctx context.Context, b Backend, args TransactionArgs, blockNr
 	}
 	// Construct the gas estimator option from the user input
 	opts := &gasestimator.Options{
-		Config: b.ChainConfig(),
-		Chain:  NewChainContext(ctx, b),
-		Header: header,
-		State:  state,
+		Config:     b.ChainConfig(),
+		Chain:      NewChainContext(ctx, b),
+		Header:     header,
+		State:      state,
+		ErrorRatio: estimateGasErrorRatio,
 	}
 	// Run the gas estimation andwrap any revertals into a custom return
 	call, err := args.ToMessage(gasCap, header.BaseFee)

internal/ethapi/api_test.go

@@ -735,7 +735,7 @@ func TestEstimateGas(t *testing.T) {
 			t.Errorf("test %d: want no error, have %v", i, err)
 			continue
 		}
-		if uint64(result) != tc.want {
+		if float64(result) > float64(tc.want)*(1+estimateGasErrorRatio) {
 			t.Errorf("test %d, result mismatch, have\n%v\n, want\n%v\n", i, uint64(result), tc.want)
 		}
 	}