core/txpool/blobpool: update blobpool eviction policy

Previously, blobpool eviction priority did not differentiate well
transactions that are close to the basefee limit and transactions that
are way under the limit. Here we improve this differentiation, giving
more priority to transactions that are closer to the current base fee
and/or blob fee, thus potentially includable in a shorter time.

Signed-off-by: Csaba Kiraly <csaba.kiraly@gmail.com>

core/txpool/blobpool/blobpool.go

@@ -281,47 +281,48 @@ func newBlobTxMeta(id uint64, size uint64, storageSize uint32, tx *types.Transac
 //     solve after every block.
 //
 //   - The first observation is that comparing 1559 base fees or 4844 blob fees
-//     needs to happen in the context of their dynamism. Since these fees jump
-//     up or down in ~1.125 multipliers (at max) across blocks, comparing fees
-//     in two transactions should be based on log1.125(fee) to eliminate noise.
+//     needs to happen in the context of their dynamism. Since base fees are
+//     adjusted continuously and fluctuate, and we want to optimize for effective
+//     miner fees, it is better to disregard small base fee cap differences.
+//     Instead of considering the exact fee cap values, we should group
+//     transactions into buckets based on fee cap values, allowing us to use
+//     the miner tip meaningfully as a splitter inside a bucket.
 //
-//   - The second observation is that the basefee and blobfee move independently,
-//     so there's no way to split mixed txs on their own (A has higher base fee,
-//     B has higher blob fee). Rather than look at the absolute fees, the useful
-//     metric is the max time it can take to exceed the transaction's fee caps.
+//     To create these buckets, rather than looking at the absolute fee
+//     differences, the useful metric is the max time it can take to exceed the
+//     transaction's fee caps. Base fee changes are multiplicative, so we use a
+//     logarithmic scale. Fees jumps up or down in ~1.125 multipliers at max
+//     across blocks, so we use log1.125(fee) and rounding to eliminate noise.
 //     Specifically, we're interested in the number of jumps needed to go from
 //     the current fee to the transaction's cap:
 //
-//     jumps = log1.125(txfee) - log1.125(basefee)
+//     jumps = floor(log1.125(txfee) - log1.125(basefee))
+
+//   - The second observation is that when ranking executable blob txs, it
+//     does not make sense to grant a later eviction priority to txs with high
+//     fee caps since it could enable pool wars. As such, any positive priority
+//     will be grouped together.
 //
-//   - The third observation is that the base fee tends to hover around rather
-//     than swing wildly. The number of jumps needed from the current fee starts
-//     to get less relevant the higher it is. To remove the noise here too, the
-//     pool will use log(jumps) as the delta for comparing transactions.
+//     priority = min(jumps, 0)
+
+//   - The third observation is that the basefee and blobfee move independently,
+//     so there's no way to split mixed txs on their own (A has higher base fee,
+//     B has higher blob fee).
 //
-//     delta = sign(jumps) * log(abs(jumps))
-//
-//   - To establish a total order, we need to reduce the dimensionality of the
+//     To establish a total order, we need to reduce the dimensionality of the
 //     two base fees (log jumps) to a single value. The interesting aspect from
 //     the pool's perspective is how fast will a tx get executable (fees going
 //     down, crossing the smaller negative jump counter) or non-executable (fees
 //     going up, crossing the smaller positive jump counter). As such, the pool
 //     cares only about the min of the two delta values for eviction priority.
 //
-//     priority = min(deltaBasefee, deltaBlobfee)
+//     priority = min(deltaBasefee, deltaBlobfee, 0)
 //
 //   - The above very aggressive dimensionality and noise reduction should result
 //     in transaction being grouped into a small number of buckets, the further
 //     the fees the larger the buckets. This is good because it allows us to use
 //     the miner tip meaningfully as a splitter.
 //
-//   - For the scenario where the pool does not contain non-executable blob txs
-//     anymore, it does not make sense to grant a later eviction priority to txs
-//     with high fee caps since it could enable pool wars. As such, any positive
-//     priority will be grouped together.
-//
-//     priority = min(deltaBasefee, deltaBlobfee, 0)
-//
 // Optimisation tradeoffs:
 //
 //   - Eviction relies on 3 fee minimums per account (exec tip, exec cap and blob

core/txpool/blobpool/priority.go

@@ -43,11 +43,8 @@ func evictionPriority(basefeeJumps float64, txBasefeeJumps, blobfeeJumps, txBlob
 // described in the BlobPool docs for a single fee component.
 func evictionPriority1D(basefeeJumps float64, txfeeJumps float64) int {
 	jumps := txfeeJumps - basefeeJumps
-	if int(jumps) == 0 {
-		return 0 // can't log2 0
-	}
-	if jumps < 0 {
-		return -intLog2(uint(-math.Floor(jumps)))
+	if jumps <= 0 {
+		return int(math.Floor(jumps))
 	}
 	return intLog2(uint(math.Ceil(jumps)))
 }

core/txpool/blobpool/priority_test.go

@@ -30,12 +30,12 @@ func TestPriorityCalculation(t *testing.T) {
 		txfee   uint64
 		result  int
 	}{
-		{basefee: 7, txfee: 10, result: 2},                          // 3.02 jumps, 4 ceil, 2 log2
-		{basefee: 17_200_000_000, txfee: 17_200_000_000, result: 0}, // 0 jumps, special case 0 log2
-		{basefee: 9_853_941_692, txfee: 11_085_092_510, result: 0},  // 0.99 jumps, 1 ceil, 0 log2
-		{basefee: 11_544_106_391, txfee: 10_356_781_100, result: 0}, // -0.92 jumps, -1 floor, 0 log2
-		{basefee: 17_200_000_000, txfee: 7, result: -7},             // -183.57 jumps, -184 floor, -7 log2
-		{basefee: 7, txfee: 17_200_000_000, result: 7},              // 183.57 jumps, 184 ceil, 7 log2
+		{basefee: 7, txfee: 10, result: 2},                           // 3.02 jumps, 4 ceil, 2 log2
+		{basefee: 17_200_000_000, txfee: 17_200_000_000, result: 0},  // 0 jumps, special case 0 log2
+		{basefee: 9_853_941_692, txfee: 11_085_092_510, result: 0},   // 0.99 jumps, 1 ceil, 0 log2
+		{basefee: 11_544_106_391, txfee: 10_356_781_100, result: -1}, // -0.92 jumps, -1 floor
+		{basefee: 17_200_000_000, txfee: 7, result: -184},            // -183.57 jumps, -184 floor
+		{basefee: 7, txfee: 17_200_000_000, result: 7},               // 183.57 jumps, 184 ceil, 7 log2
 	}
 	for i, tt := range tests {
 		var (