perf: make read origin a small vec

Cargo.toml

@@ -18,6 +18,7 @@ bitvec = "1.0.1"
 dashmap = "6.0.1"
 defer-drop = "1.3.0"
 serde = "1.0.204"
+smallvec = "1.13.2"
 
 # Let's do our best to port needed REVM changes upstream
 revm = { git = "https://github.com/risechain/revm", rev = "7b42abb672deacde9e0538e8e74209e1943dabff", features = [

src/lib.rs

@@ -6,6 +6,7 @@ use std::collections::HashMap;
 use std::hash::{BuildHasherDefault, Hasher};
 
 use alloy_primitives::{Address, B256, U256};
+use smallvec::SmallVec;
 
 // We take the last 8 bytes of an address as its hash. This
 // seems fine as the addresses themselves are hash suffixes,
@@ -151,7 +152,7 @@ enum ReadOrigin {
 
 // For validation: a list of read origins (previous transaction versions)
 // for each read memory location.
-type ReadSet = HashMap<MemoryLocationHash, Vec<ReadOrigin>, BuildIdentityHasher>;
+type ReadSet = HashMap<MemoryLocationHash, SmallVec<[ReadOrigin; 1]>, BuildIdentityHasher>;
 
 // The updates made by this transaction incarnation, which is applied
 // to the multi-version data structure at the end of execution.

src/vm.rs

@@ -9,6 +9,7 @@ use revm::{
     },
     Context, Database, Evm, EvmContext,
 };
+use smallvec::SmallVec;
 use std::collections::HashMap;
 
 use crate::{
@@ -238,7 +239,7 @@ impl<'a, S: Storage, C: PevmChain> Database for VmDb<'a, S, C> {
         // We accumulate new origins to either:
         // - match with the previous origins to check consistency
         // - register origins on the first read
-        let mut new_origins = Vec::new();
+        let mut new_origins = SmallVec::new();
 
         let mut final_account = None;
         let mut balance_addition = U256::ZERO;