From aa983b49af8fddc4ef74ac7f9f7bfb78dcd98fc2 Mon Sep 17 00:00:00 2001
From: YK <chiayongkang@hotmail.com>
Date: Wed, 11 Feb 2026 14:48:48 -0500
Subject: [PATCH] perf(engine): add PrewarmMode::Skipped to avoid spawning idle
 workers (#22066)

Co-authored-by: Amp <amp@ampcode.com>
Co-authored-by: Ubuntu <ubuntu@dev-yk.tail388b2e.ts.net>
---
 crates/engine/tree/src/tree/payload_processor/mod.rs | 12 +++++-------
 .../tree/src/tree/payload_processor/prewarm.rs       |  9 ++++++++-
 2 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/crates/engine/tree/src/tree/payload_processor/mod.rs b/crates/engine/tree/src/tree/payload_processor/mod.rs
index 5798e24576..3c7be7b5bd 100644
--- a/crates/engine/tree/src/tree/payload_processor/mod.rs
+++ b/crates/engine/tree/src/tree/payload_processor/mod.rs
@@ -422,7 +422,7 @@ where
     fn spawn_caching_with<P>(
         &self,
         env: ExecutionEnv<Evm>,
-        mut transactions: mpsc::Receiver<impl ExecutableTxFor<Evm> + Clone + Send + 'static>,
+        transactions: mpsc::Receiver<impl ExecutableTxFor<Evm> + Clone + Send + 'static>,
         provider_builder: StateProviderBuilder<N, P>,
         to_multi_proof: Option<CrossbeamSender<MultiProofMessage>>,
         bal: Option<Arc<BlockAccessList>>,
@@ -431,11 +431,7 @@ where
     where
         P: BlockReader + StateProviderFactory + StateReader + Clone + 'static,
     {
-        if self.disable_transaction_prewarming {
-            // if no transactions should be executed we clear them but still spawn the task for
-            // caching updates
-            transactions = mpsc::channel().1;
-        }
+        let skip_prewarm = self.disable_transaction_prewarming;
 
         let saved_cache = self.disable_state_cache.not().then(|| self.cache_for(env.parent_hash));
 
@@ -464,7 +460,9 @@ where
         {
             let to_prewarm_task = to_prewarm_task.clone();
             self.executor.spawn_blocking(move || {
-                let mode = if let Some(bal) = bal {
+                let mode = if skip_prewarm {
+                    PrewarmMode::Skipped
+                } else if let Some(bal) = bal {
                     PrewarmMode::BlockAccessList(bal)
                 } else {
                     PrewarmMode::Transactions(transactions)
diff --git a/crates/engine/tree/src/tree/payload_processor/prewarm.rs b/crates/engine/tree/src/tree/payload_processor/prewarm.rs
index 2ce8d83b3e..c0828d5c7d 100644
--- a/crates/engine/tree/src/tree/payload_processor/prewarm.rs
+++ b/crates/engine/tree/src/tree/payload_processor/prewarm.rs
@@ -49,13 +49,16 @@ use std::{
 };
 use tracing::{debug, debug_span, instrument, trace, warn, Span};
 
-/// Determines the prewarming mode: transaction-based or BAL-based.
+/// Determines the prewarming mode: transaction-based, BAL-based, or skipped.
 #[derive(Debug)]
 pub enum PrewarmMode<Tx> {
     /// Prewarm by executing transactions from a stream.
     Transactions(Receiver<Tx>),
     /// Prewarm by prefetching slots from a Block Access List.
     BlockAccessList(Arc<BlockAccessList>),
+    /// Transaction prewarming is skipped (e.g. small blocks where the overhead exceeds the
+    /// benefit). No workers are spawned.
+    Skipped,
 }
 
 /// A wrapper for transactions that includes their index in the block.
@@ -416,6 +419,10 @@ where
             PrewarmMode::BlockAccessList(bal) => {
                 self.run_bal_prewarm(bal, actions_tx);
             }
+            PrewarmMode::Skipped => {
+                let _ = actions_tx
+                    .send(PrewarmTaskEvent::FinishedTxExecution { executed_transactions: 0 });
+            }
         }
 
         let mut final_execution_outcome = None;