core/types: reduce allocations in effectiveGasTip

[MariusVanDerWijden]

Reduces unnecessary allocations in (types.Transaction).EffectiveGasTip.
Halves the allocations, increases speed by 47%

ROUTINE ======================== github.com/ethereum/go-ethereum/core/types.(*Transaction).EffectiveGasTip in github.com/ethereum/go-ethereum/core/types/transaction.go
     4.40s    370.90s (flat, cum)  1.61% of Total
     480ms      480ms    357:func (tx *Transaction) EffectiveGasTip(baseFee *big.Int) (*big.Int, error) {
     450ms      450ms    358:	if baseFee == nil {
         .          .    359:		return tx.GasTipCap(), nil
         .          .    360:	}
         .          .    361:	var err error
     350ms    232.73s    362:	gasFeeCap := tx.GasFeeCap()
     430ms      8.51s    363:	if gasFeeCap.Cmp(baseFee) < 0 {
     180ms      180ms    364:		err = ErrGasFeeCapTooLow
         .          .    365:	}
     290ms     26.02s    366:	gasFeeCap = gasFeeCap.Sub(gasFeeCap, baseFee)
         .          .    367:
     200ms     95.63s    368:	gasTipCap := tx.GasTipCap()
     680ms      5.56s    369:	if gasTipCap.Cmp(gasFeeCap) < 0 {
     250ms      250ms    370:		return gasTipCap, err
         .          .    371:	}
     1.09s      1.09s    372:	return gasFeeCap, err
         .          .    373:}

Benchmark:

func BenchmarkEffectiveTip(b *testing.B) {
	to := common.Address{}
	tx := NewTx(&DynamicFeeTx{
		ChainID:   big.NewInt(123),
		Nonce:     1,
		Gas:       1000000,
		To:        &to,
		Value:     big.NewInt(1),
		GasTipCap: big.NewInt(500),
		GasFeeCap: big.NewInt(500),
	})
	basefee := big.NewInt(12)
	for i := 0; i < b.N; i++ {
		tx.EffectiveGasTip(basefee)
	}
}

                │ /tmp/old.txt │            /tmp/new.txt             │
                │    sec/op    │    sec/op     vs base               │
EffectiveTip-14   97.83n ± ∞ ¹   57.26n ± ∞ ¹  -41.47% (p=0.008 n=5)
¹ need >= 6 samples for confidence interval at level 0.95

                │ /tmp/old.txt │            /tmp/new.txt            │
                │     B/op     │    B/op      vs base               │
EffectiveTip-14    80.00 ± ∞ ¹   40.00 ± ∞ ¹  -50.00% (p=0.008 n=5)
¹ need >= 6 samples for confidence interval at level 0.95

                │ /tmp/old.txt │            /tmp/new.txt            │
                │  allocs/op   │  allocs/op   vs base               │
EffectiveTip-14    4.000 ± ∞ ¹   2.000 ± ∞ ¹  -50.00% (p=0.008 n=5)
¹ need >= 6 samples for confidence interval at level 0.95

[MariusVanDerWijden]

NVM I have a better idea...

[MariusVanDerWijden]

                │ /tmp/old.txt │            /tmp/new.txt             │
                │    sec/op    │   sec/op     vs base                │
EffectiveTip-14    211.6n ± 1%   111.8n ± 5%  -47.19% (p=0.000 n=10)

                │ /tmp/old.txt │            /tmp/new.txt            │
                │     B/op     │    B/op     vs base                │
EffectiveTip-14    160.00 ± 0%   80.00 ± 0%  -50.00% (p=0.000 n=10)

                │ /tmp/old.txt │            /tmp/new.txt            │
                │  allocs/op   │ allocs/op   vs base                │
EffectiveTip-14     8.000 ± 0%   4.000 ± 0%  -50.00% (p=0.000 n=10)

[MariusVanDerWijden]

I would love to get rid of this allocation, but I can't

[fjl]

One thing to keep in mind with these optimizations, is that the TxData methods (like gasTipCap) do not always return copies. So the rule is basically that anything returned by them must be copied in the Transaction accessor before returning.

There is also a PR with an alternative approach here: #31598