Introduce exponential length fee for substrate-based fees #1496
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notlesh
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notlesh
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May 12, 2022
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| // left: cost of length fee, right: size in bytes | ||
| // /------------- proportional component: O(N * 1B) | ||
| // | /- exponential component: O(N ** 3) | ||
| // | | | ||
| assert_eq!( 1_000_000_001, calc_fee(1)); | ||
| assert_eq!( 10_000_001_000, calc_fee(10)); | ||
| assert_eq!( 100_001_000_000, calc_fee(100)); | ||
| assert_eq!( 1_001_000_000_000, calc_fee(1_000)); | ||
| assert_eq!( 11_000_000_000_000, calc_fee(10_000)); // inflection point | ||
| assert_eq!( 1_100_000_000_000_000, calc_fee(100_000)); | ||
| assert_eq!( 1_001_000_000_000_000_000, calc_fee(1_000_000)); // one UNIT, ~ 1MB | ||
| assert_eq!( 1_000_010_000_000_000_000_000, calc_fee(10_000_000)); | ||
| assert_eq!(1_000_000_100_000_000_000_000_000, calc_fee(100_000_000)); |
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These are the initial results
girazoki
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May 23, 2022
tests/tests/test-author-mapping.ts
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| expect( | ||
| ((await context.polkadotApi.query.system.account(BALTATHAR)) as any).data.free.toBigInt() | ||
| ).to.eq(1208925818354628766561176n); | ||
| ).to.eq(1208925819614502764560800n); |
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These should have dissapeared if you bring master
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I dont fully understand the concern with runtime upgrades. By looking at https://github.com/paritytech/cumulus/blob/f9bc77c3c801973b4b6943cb6f236fb3934eb993/pallets/parachain-system/src/lib.rs#L406 it seems to me as if this extrinsic does not lead to fee payment. Therefore the LengthToFee implementation should not affect, am I right? |
girazoki
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May 23, 2022
crystalin
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May 23, 2022
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notlesh
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What does it do?
Introduces a non-linear
LengthToFeetransaction length fee (only for Substrate-based transactions -- does not impact Ethereum-based ones). This replaces #1353, and like it will need to be reconciled with #1218.This currently has two components to the length fee:
1byte = 1X)1byte = 1X**3)The result is that the proportional fee dominates from [1byte .. 1000bytes] after which the cubic portion grows very rapidly. The goal is to cause fees to become untenable quickly into the 1MB+ range.
See the rust test assertions for a table-ish of results.
I haven't done much research into what range of txn sizes we typically see in the real world. Ideally, these would be nearly unaffected by the exponential byte fee portion. Furthermore, we need to make some assumptions about runtime upgrades, as these are the only (?) legitimate large transactions. It is acceptable that these be expensive, but (1) they can't be "too" expensive and (2) their exception should not prevent a serious determent to much larger txns.
Another note: Ethereum transactions have a maximum size (implied from the max block size divided by their own per-byte fee). The Ethereum per-byte fee is adjusted by gas price while the
LengthToFeefrompallet-transaction-paymentis unadjusted.Related: paritytech/substrate#10785