perf(engine): skip transaction prewarming for small blocks (#22059)

Co-authored-by: yk <yongkang@tempo.xyz>
Co-authored-by: Amp <amp@ampcode.com>

crates/engine/tree/src/tree/payload_processor/mod.rs

@@ -94,6 +94,17 @@ pub const SPARSE_TRIE_MAX_NODES_SHRINK_CAPACITY: usize = 1_000_000;
 /// 144MB.
 pub const SPARSE_TRIE_MAX_VALUES_SHRINK_CAPACITY: usize = 1_000_000;
 
+/// Gas used threshold below which prewarming is skipped for small blocks.
+///
+/// Based on analysis of 100 mainnet blocks (starting at block 24,425,210), reth's `new_payload`
+/// winrate drops from 88% on 40-50M gas blocks to 49% on 0-10M gas blocks. The root cause is the
+/// fixed overhead of spawning prewarm workers (building state providers, creating EVM instances,
+/// wrapping precompiles) which exceeds execution time on small blocks.
+///
+/// 20M gas is used as the threshold because ~23% of recent mainnet blocks fall under this level
+/// where prewarming overhead dominates.
+pub const SMALL_BLOCK_GAS_THRESHOLD: u64 = 20_000_000;
+
 /// Type alias for [`PayloadHandle`] returned by payload processor spawn methods.
 type IteratorPayloadHandle<Evm, I, N> = PayloadHandle<
     WithTxEnv<TxEnvFor<Evm>, <I as ExecutableTxIterator<Evm>>::Recovered>,
@@ -431,7 +442,8 @@ where
     where
         P: BlockReader + StateProviderFactory + StateReader + Clone + 'static,
     {
-        let skip_prewarm = self.disable_transaction_prewarming;
+        let skip_prewarm = self.disable_transaction_prewarming ||
+            (env.gas_used > 0 && env.gas_used < SMALL_BLOCK_GAS_THRESHOLD);
 
         let saved_cache = self.disable_state_cache.not().then(|| self.cache_for(env.parent_hash));
 
@@ -972,6 +984,10 @@ pub struct ExecutionEnv<Evm: ConfigureEvm> {
     /// Used to determine parallel worker count for prewarming.
     /// A value of 0 indicates the count is unknown.
     pub transaction_count: usize,
+    /// Total gas used in the block.
+    /// Used to skip prewarming for small blocks (see [`SMALL_BLOCK_GAS_THRESHOLD`]).
+    /// A value of 0 indicates the gas used is unknown.
+    pub gas_used: u64,
     /// Withdrawals included in the block.
     /// Used to generate prefetch targets for withdrawal addresses.
     pub withdrawals: Option<Vec<Withdrawal>>,
@@ -988,6 +1004,7 @@ where
             parent_hash: Default::default(),
             parent_state_root: Default::default(),
             transaction_count: 0,
+            gas_used: 0,
             withdrawals: None,
         }
     }

crates/engine/tree/src/tree/payload_validator.rs

@@ -412,6 +412,7 @@ where
             parent_hash: input.parent_hash(),
             parent_state_root: parent_block.state_root(),
             transaction_count: input.transaction_count(),
+            gas_used: input.gas_used(),
             withdrawals: input.withdrawals().map(|w| w.to_vec()),
         };
 
@@ -1563,6 +1564,17 @@ impl<T: PayloadTypes> BlockOrPayload<T> {
         }
     }
 
+    /// Returns the total gas used by all transactions in the payload or block.
+    pub fn gas_used(&self) -> u64
+    where
+        T::ExecutionData: ExecutionPayload,
+    {
+        match self {
+            Self::Payload(payload) => payload.gas_used(),
+            Self::Block(block) => block.header().gas_used(),
+        }
+    }
+
     /// Returns the withdrawals from the payload or block.
     pub fn withdrawals(&self) -> Option<&[Withdrawal]>
     where