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78 lines
2.7 KiB
Plaintext
78 lines
2.7 KiB
Plaintext
:source-highlighter: highlight.js
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:highlightjs-languages: rust
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:github-icon: pass:[<svg class="icon"><use href="#github-icon"/></svg>]
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= Weights & Fees
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Weight provides a metric to estimate the time it takes to execute code.
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By assigning a weight to every transaction, Substrate uses this metric to bound the time it takes to execute and verify each batch of transactions organized into a block.
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By converting the transaction's weight to fees, Substrate charges the transaction's caller with fees in proportion to the cost of execution.
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Table of Contents:
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** Limit and bound non-linear complexity
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** Weights should be conservative
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** Underestimating weight exposes DDOS
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** Steps To Generate Runtime-Specific Weights
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** References
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== Limit and bound non-linear complexity
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TODO
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== Weights should be conservative
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To limit the execution time for each block, runtime constraints on Weight implicitly enforce upper bounds on computation and storage changes per block.
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TODO: which runtime constraints and how are they enforced?
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TODO
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== Underestimating weight exposes DDOS
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* Important that benchmarking hardware is not significantly more high performance than the hardware used by nodes participating in network consensus (i.e. validators, collators)
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* Using worse hardware (i.e. developer hardware) does take longer and, therefore, indirectly underestimates weights.
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== Steps to Generate Runtime-Specific Weights
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TODO: why are runtime-specific weights important
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1. Ensure Compilation With Runtime Benchmarks
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2. Generate Weights Using Production Hardware
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3. Write Weights to Runtime
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4. Automate via Bench Bot
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=== Ensure Compilation With Runtime Benchmarks
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* compile `cargo build --features runtime-benchmarks`
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* compile `cargo build --release --features runtime-benchmarks`
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* Enforce with CI
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=== Generate Weights Using Production Hardware
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Technically, *Weight* represents the time it takes to execute code on *production hardware* used by nodes actively participating in the network's consensus.
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```
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1 unit of weight = 1 picosecond of execution time on target reference hardware
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```
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https://wiki.polkadot.network/docs/maintain-guides-how-to-validate-polkadot#:~:text=Reference%20Hardware%E2%80%8B,instance%20on%20GCP%20and%20c6i.[Polkadot Reference Hardware Docs] provides more information on Polkadot validator hardware requirements.
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It is important to ONLY generate weights by running `cargo build --features runtime-benchmarks --release` on *production hardware*.
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=== Write Weights to Runtime.
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TODO: where/why
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=== Automate via Bench Bot
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* examples and references
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== References
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** *https://www.shawntabrizi.com/blog/substrate/substrate-weight-and-fees/[Substrate Weight & Fees] by https://github.com/shawntabrizi/[Shawn Tabrizi]*
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