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90 lines
3.2 KiB
90 lines
3.2 KiB
// Copyright 2023 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package blobpool
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import (
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"math"
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"math/bits"
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"github.com/holiman/uint256"
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)
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// log2_1_125 is used in the eviction priority calculation.
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var log2_1_125 = math.Log2(1.125)
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// evictionPriority calculates the eviction priority based on the algorithm
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// described in the BlobPool docs for both fee components.
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//
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// This method takes about 8ns on a very recent laptop CPU, recalculating about
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// 125 million transaction priority values per second.
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func evictionPriority(basefeeJumps float64, txBasefeeJumps, blobfeeJumps, txBlobfeeJumps float64) int {
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var (
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basefeePriority = evictionPriority1D(basefeeJumps, txBasefeeJumps)
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blobfeePriority = evictionPriority1D(blobfeeJumps, txBlobfeeJumps)
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)
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if basefeePriority < blobfeePriority {
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return basefeePriority
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}
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return blobfeePriority
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}
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// evictionPriority1D calculates the eviction priority based on the algorithm
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// described in the BlobPool docs for a single fee component.
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func evictionPriority1D(basefeeJumps float64, txfeeJumps float64) int {
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jumps := txfeeJumps - basefeeJumps
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if int(jumps) == 0 {
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return 0 // can't log2 0
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}
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if jumps < 0 {
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return -intLog2(uint(-math.Floor(jumps)))
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}
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return intLog2(uint(math.Ceil(jumps)))
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}
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// dynamicFeeJumps calculates the log1.125(fee), namely the number of fee jumps
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// needed to reach the requested one. We only use it when calculating the jumps
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// between 2 fees, so it doesn't matter from what exact number with returns.
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// it returns the result from (0, 1, 1.125).
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//
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// This method is very expensive, taking about 75ns on a very recent laptop CPU,
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// but the result does not change with the lifetime of a transaction, so it can
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// be cached.
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func dynamicFeeJumps(fee *uint256.Int) float64 {
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if fee.IsZero() {
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return 0 // can't log2 zero, should never happen outside tests, but don't choke
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}
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return math.Log2(fee.Float64()) / log2_1_125
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}
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// intLog2 is a helper to calculate the integral part of a log2 of an unsigned
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// integer. It is a very specific calculation that's not particularly useful in
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// general, but it's what we need here (it's fast).
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func intLog2(n uint) int {
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switch {
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case n == 0:
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panic("log2(0) is undefined")
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case n < 2048:
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return bits.UintSize - bits.LeadingZeros(n) - 1
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default:
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// The input is log1.125(uint256) = log2(uint256) / log2(1.125). At the
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// most extreme, log2(uint256) will be a bit below 257, and the constant
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// log2(1.125) ~= 0.17. The larges input thus is ~257 / ~0.17 ~= ~1511.
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panic("dynamic fee jump diffs cannot reach this")
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}
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}
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