From 3ec065295e3c1cdef2e5a9f80e231fdf67cca898 Mon Sep 17 00:00:00 2001
From: Georgios Konstantopoulos <me@gakonst.com>
Date: Fri, 30 Jan 2026 10:34:15 -0800
Subject: [PATCH] refactor(trie): replace SmallVec with Vec in sparse trie
 buffers (#21637)

Co-authored-by: Amp <amp@ampcode.com>
Co-authored-by: DaniPopes <57450786+DaniPopes@users.noreply.github.com>
---
 Cargo.lock                              | 1 -
 crates/trie/sparse-parallel/Cargo.toml  | 2 +-
 crates/trie/sparse-parallel/src/trie.rs | 4 ++--
 crates/trie/sparse/Cargo.toml           | 2 --
 crates/trie/sparse/src/trie.rs          | 9 ++++-----
 5 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 4f4f3d8ad2..cd823c2f3d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -11255,7 +11255,6 @@ dependencies = [
  "reth-trie",
  "reth-trie-common",
  "reth-trie-db",
- "smallvec",
  "tracing",
 ]
 
diff --git a/crates/trie/sparse-parallel/Cargo.toml b/crates/trie/sparse-parallel/Cargo.toml
index 19893831aa..42e889ca0e 100644
--- a/crates/trie/sparse-parallel/Cargo.toml
+++ b/crates/trie/sparse-parallel/Cargo.toml
@@ -28,8 +28,8 @@ reth-metrics = { workspace = true, optional = true }
 metrics = { workspace = true, optional = true }
 
 # misc
-smallvec.workspace = true
 rayon = { workspace = true, optional = true }
+smallvec.workspace = true
 
 [dev-dependencies]
 # reth
diff --git a/crates/trie/sparse-parallel/src/trie.rs b/crates/trie/sparse-parallel/src/trie.rs
index 589cd81b1e..927916b24f 100644
--- a/crates/trie/sparse-parallel/src/trie.rs
+++ b/crates/trie/sparse-parallel/src/trie.rs
@@ -3248,9 +3248,9 @@ pub struct SparseSubtrieBuffers {
     /// Stack of RLP nodes
     rlp_node_stack: Vec<RlpNodeStackItem>,
     /// Reusable branch child path
-    branch_child_buf: SmallVec<[Nibbles; 16]>,
+    branch_child_buf: Vec<Nibbles>,
     /// Reusable branch value stack
-    branch_value_stack_buf: SmallVec<[RlpNode; 16]>,
+    branch_value_stack_buf: Vec<RlpNode>,
     /// Reusable RLP buffer
     rlp_buf: Vec<u8>,
 }
diff --git a/crates/trie/sparse/Cargo.toml b/crates/trie/sparse/Cargo.toml
index b2c7ee0f56..0955f204f9 100644
--- a/crates/trie/sparse/Cargo.toml
+++ b/crates/trie/sparse/Cargo.toml
@@ -26,7 +26,6 @@ alloy-rlp.workspace = true
 # misc
 auto_impl.workspace = true
 rayon = { workspace = true, optional = true }
-smallvec = { workspace = true, features = ["const_new"] }
 
 # metrics
 reth-metrics = { workspace = true, optional = true }
@@ -80,7 +79,6 @@ arbitrary = [
     "alloy-trie/arbitrary",
     "reth-primitives-traits/arbitrary",
     "reth-trie-common/arbitrary",
-    "smallvec/arbitrary",
 ]
 
 [[bench]]
diff --git a/crates/trie/sparse/src/trie.rs b/crates/trie/sparse/src/trie.rs
index 77dd6218bd..c5889a5192 100644
--- a/crates/trie/sparse/src/trie.rs
+++ b/crates/trie/sparse/src/trie.rs
@@ -24,7 +24,6 @@ use reth_trie_common::{
     LeafNodeRef, Nibbles, ProofTrieNode, RlpNode, TrieMask, TrieNode, CHILD_INDEX_RANGE,
     EMPTY_ROOT_HASH,
 };
-use smallvec::SmallVec;
 use tracing::{debug, instrument, trace};
 
 /// The level below which the sparse trie hashes are calculated in
@@ -2003,9 +2002,9 @@ pub struct RlpNodeBuffers {
     /// Stack of RLP nodes
     rlp_node_stack: Vec<RlpNodeStackItem>,
     /// Reusable branch child path
-    branch_child_buf: SmallVec<[Nibbles; 16]>,
+    branch_child_buf: Vec<Nibbles>,
     /// Reusable branch value stack
-    branch_value_stack_buf: SmallVec<[RlpNode; 16]>,
+    branch_value_stack_buf: Vec<RlpNode>,
 }
 
 impl RlpNodeBuffers {
@@ -2018,8 +2017,8 @@ impl RlpNodeBuffers {
                 is_in_prefix_set: None,
             }],
             rlp_node_stack: Vec::new(),
-            branch_child_buf: SmallVec::<[Nibbles; 16]>::new_const(),
-            branch_value_stack_buf: SmallVec::<[RlpNode; 16]>::new_const(),
+            branch_child_buf: Vec::new(),
+            branch_value_stack_buf: Vec::new(),
         }
     }
 }