From 9a026ec1cf1e1f6beb44a5226680a3aaf3b5a340 Mon Sep 17 00:00:00 2001
From: DaniPopes <57450786+DaniPopes@users.noreply.github.com>
Date: Wed, 4 Feb 2026 21:09:04 +0100
Subject: [PATCH] perf: use num_threads for prewarm concurrency (#21826)

---
 crates/engine/primitives/src/config.rs | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/crates/engine/primitives/src/config.rs b/crates/engine/primitives/src/config.rs
index 7529e15cda..700b8852d0 100644
--- a/crates/engine/primitives/src/config.rs
+++ b/crates/engine/primitives/src/config.rs
@@ -44,8 +44,17 @@ pub const DEFAULT_MULTIPROOF_TASK_CHUNK_SIZE_V2: usize = DEFAULT_MULTIPROOF_TASK
 /// This will be deducted from the thread count of main reth global threadpool.
 pub const DEFAULT_RESERVED_CPU_CORES: usize = 1;
 
-/// Default maximum concurrency for prewarm task.
-pub const DEFAULT_PREWARM_MAX_CONCURRENCY: usize = 16;
+/// Returns the default maximum concurrency for prewarm task based on available parallelism.
+fn default_prewarm_max_concurrency() -> usize {
+    #[cfg(feature = "std")]
+    {
+        std::thread::available_parallelism().map_or(16, |n| n.get())
+    }
+    #[cfg(not(feature = "std"))]
+    {
+        16
+    }
+}
 
 /// Default depth for sparse trie pruning.
 ///
@@ -192,7 +201,7 @@ impl Default for TreeConfig {
             precompile_cache_disabled: false,
             state_root_fallback: false,
             always_process_payload_attributes_on_canonical_head: false,
-            prewarm_max_concurrency: DEFAULT_PREWARM_MAX_CONCURRENCY,
+            prewarm_max_concurrency: default_prewarm_max_concurrency(),
             allow_unwind_canonical_header: false,
             storage_worker_count: default_storage_worker_count(),
             account_worker_count: default_account_worker_count(),