chore(l2): implement rkyv traits for Node, serialize them directly into the prover guest program instead of its RLP encoding
#5224
+1,062
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Pull Request Overview
This PR refactors the execution witness mechanism to serialize trie Node structures directly using rkyv instead of their RLP-encoded representations. The key changes include implementing rkyv serialization traits for all trie node types, replacing the nodes_hashed field with embedded state_trie and storage_trie_roots, and updating the witness generation and consumption logic throughout the codebase.
Key Changes
- Implemented rkyv serialization traits for
Node,NodeRef,NodeHash,BranchNode,ExtensionNode,LeafNode, andNibbles - Replaced RLP-encoded node storage with direct
Nodeserialization inExecutionWitnessandGuestProgramState - Refactored execution witness generation to build embedded trie structures and removed the need for trie rebuilding logic
Reviewed Changes
Copilot reviewed 18 out of 21 changed files in this pull request and generated 8 comments.
Show a summary per file
| File | Description |
|---|---|
| crates/vm/witness_db.rs | Improved error messages to include actual error details instead of generic messages |
| crates/networking/rpc/debug/execution_witness.rs | Changed From to TryFrom for witness conversion and added trie embedding logic |
| crates/l2/networking/rpc/l2/execution_witness.rs | Updated to use TryFrom with proper error handling |
| crates/common/types/block_execution_witness.rs | Replaced nodes_hashed with state_trie and storage_trie_roots, removed trie rebuild logic |
| crates/l2/prover/src/guest_program/src/execution.rs | Updated to use embedded state trie directly |
| crates/common/trie/*.rs | Added rkyv trait implementations and utility methods for embedded tries |
| crates/blockchain/blockchain.rs | Updated witness generation to create embedded trie structures |
| Cargo.lock files | Added rkyv dependency |
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Motivation
Directly deserializing the
Nodestruct in the prover's guest program allows skipping RLP decoding and resolving the subtries (this is, converting the list of nodes into the tree structure). Though this comes at a cost:memcpyfor unsized types (like vectors of structs, in this caseVec<Node>).Even considering these, the net change is negative: 697k cycles -> 533k cycles, 24% reduction.
This PR also removes the double hashing of nodes (previously we were hashing once at the start and then hashing again to populate the hash cache of each node)
Description
rkyvtraits forNodeand other relevant typesNodeinstead of encoded nodes.Flamegraphs
before:
after: