perf: allocate signer vec exact size (#20638)

crates/engine/tree/src/tree/metrics.rs

@@ -64,6 +64,7 @@ impl EngineApiMetrics {
         &self,
         executor: E,
         mut transactions: impl Iterator<Item = Result<impl ExecutableTx<E>, BlockExecutionError>>,
+        transaction_count: usize,
         state_hook: Box<dyn OnStateHook>,
     ) -> Result<(BlockExecutionOutput<E::Receipt>, Vec<Address>), BlockExecutionError>
     where
@@ -75,7 +76,7 @@ impl EngineApiMetrics {
         // be accessible.
         let wrapper = MeteredStateHook { metrics: self.executor.clone(), inner_hook: state_hook };
 
-        let mut senders = Vec::new();
+        let mut senders = Vec::with_capacity(transaction_count);
         let mut executor = executor.with_state_hook(Some(Box::new(wrapper)));
 
         let f = || {
@@ -529,6 +530,7 @@ mod tests {
         let _result = metrics.execute_metered::<_, EmptyDB>(
             executor,
             input.clone_transactions_recovered().map(Ok::<_, BlockExecutionError>),
+            input.transaction_count(),
             state_hook,
         );
 
@@ -585,6 +587,7 @@ mod tests {
         let _result = metrics.execute_metered::<_, EmptyDB>(
             executor,
             input.clone_transactions_recovered().map(Ok::<_, BlockExecutionError>),
+            input.transaction_count(),
             state_hook,
         );
 

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

@@ -643,6 +643,7 @@ where
         let (output, senders) = self.metrics.execute_metered(
             executor,
             handle.iter_transactions().map(|res| res.map_err(BlockExecutionError::other)),
+            input.transaction_count(),
             state_hook,
         )?;
         let execution_finish = Instant::now();
@@ -1291,4 +1292,15 @@ impl<T: PayloadTypes> BlockOrPayload<T> {
         // TODO decode and return `BlockAccessList`
         None
     }
+
+    /// Returns the number of transactions in the payload or block.
+    pub fn transaction_count(&self) -> usize
+    where
+        T::ExecutionData: ExecutionPayload,
+    {
+        match self {
+            Self::Payload(payload) => payload.transaction_count(),
+            Self::Block(block) => block.transaction_count(),
+        }
+    }
 }