Improve XCMP weight metering

Author: serban300

cumulus/pallets/xcmp-queue/src/benchmarking.rs

@@ -55,7 +55,7 @@ mod benchmarks {
 		let fp_before = T::XcmpQueue::footprint(0.into());
 		#[block]
 		{
-			Pallet::<T>::enqueue_xcmp_message(0.into(), msg, &mut WeightMeter::new()).unwrap();
+			Pallet::<T>::enqueue_xcmp_message(0.into(), msg).unwrap();
 		}
 		let fp_after = T::XcmpQueue::footprint(0.into());
 		assert_eq!(fp_after.ready_pages, fp_before.ready_pages + 1);
@@ -77,8 +77,8 @@ mod benchmarks {
 		let fp_before = T::XcmpQueue::footprint(0.into());
 		#[block]
 		{
-			Pallet::<T>::enqueue_xcmp_message(0.into(), msg_1, &mut WeightMeter::new()).unwrap();
-			Pallet::<T>::enqueue_xcmp_message(0.into(), msg_2, &mut WeightMeter::new()).unwrap();
+			Pallet::<T>::enqueue_xcmp_message(0.into(), msg_1).unwrap();
+			Pallet::<T>::enqueue_xcmp_message(0.into(), msg_2).unwrap();
 		}
 		let fp_after = T::XcmpQueue::footprint(0.into());
 		assert_eq!(fp_after.ready_pages, fp_before.ready_pages + 1);

cumulus/pallets/xcmp-queue/src/lib.rs

@@ -640,13 +640,7 @@ impl<T: Config> Pallet<T> {
 	fn enqueue_xcmp_message(
 		sender: ParaId,
 		xcm: BoundedVec<u8, MaxXcmpMessageLenOf<T>>,
-		meter: &mut WeightMeter,
 	) -> Result<(), ()> {
-		if meter.try_consume(T::WeightInfo::enqueue_xcmp_message()).is_err() {
-			defensive!("Out of weight: cannot enqueue XCMP messages; dropping msg");
-			return Err(())
-		}
-
 		let QueueConfigData { drop_threshold, .. } = <QueueConfig<T>>::get();
 		let fp = T::XcmpQueue::footprint(sender);
 		// Assume that it will not fit into the current page:
@@ -794,22 +788,41 @@ impl<T: Config> XcmpMessageHandler for Pallet<T> {
 							},
 						}
 					},
-				XcmpMessageFormat::ConcatenatedVersionedXcm =>
+				XcmpMessageFormat::ConcatenatedVersionedXcm => {
+					let mut new_page = true;
 					while !data.is_empty() {
 						let Ok(xcm) = Self::take_first_concatenated_xcm(&mut data, &mut meter)
 						else {
 							defensive!("HRMP inbound decode stream broke; page will be dropped.",);
 							break
 						};
 
-						if let Err(()) = Self::enqueue_xcmp_message(sender, xcm, &mut meter) {
+						// For simplicity, we consider that each new XCMP page results in a new
+						// message queue page. This is not always true, but it's a good enough
+						// estimation.
+						if meter
+							.try_consume(T::WeightInfo::enqueue_xcmp_message(xcm.len(), new_page))
+							.is_err()
+						{
+							defensive!(
+								"Out of weight: cannot enqueue XCMP messages; dropping msg; \
+								Used weight: ",
+								meter.consumed_ratio()
+							);
+							break;
+						}
+
+						if let Err(()) = Self::enqueue_xcmp_message(sender, xcm) {
 							defensive!(
 								"Could not enqueue XCMP messages. Used weight: ",
 								meter.consumed_ratio()
 							);
 							break
 						}
-					},
+
+						new_page = false;
+					}
+				},
 				XcmpMessageFormat::ConcatenatedEncodedBlob => {
 					defensive!("Blob messages are unhandled - dropping");
 					continue

cumulus/pallets/xcmp-queue/src/weights_ext.rs

@@ -18,11 +18,22 @@
 use crate::weights::WeightInfo;
 
 use frame_support::weights::Weight;
+use sp_runtime::SaturatedConversion;
 
 /// Extended weight info.
 pub trait WeightInfoExt: WeightInfo {
-	fn enqueue_xcmp_message() -> Weight {
-		Self::enqueue_n_bytes_xcmp_message(0)
+	fn enqueue_xcmp_message(size_in_bytes: usize, new_page: bool) -> Weight {
+		let size_in_bytes = size_in_bytes.saturated_into();
+		match new_page {
+			true => Self::enqueue_n_bytes_xcmp_message(size_in_bytes),
+			false => {
+				let size_overhead = Self::enqueue_n_bytes_xcmp_message(size_in_bytes) -
+					Self::enqueue_n_bytes_xcmp_message(0);
+				Self::enqueue_2_empty_xcmp_messages()
+					.saturating_sub(Self::enqueue_n_bytes_xcmp_message(0))
+					.saturating_add(size_overhead)
+			},
+		}
 	}
 }