Don't use fixed nominator count for report_equivocation weight calculation (#14471)

* babe: fix report_equivocation weight calculation

* grandpa: fix report_equivocation weight calculation

* beefy: fix report_equivocation weight calculation

* runtime: add missing MaxNominators constant

substrate/frame/babe/src/default_weights.rs

@@ -28,15 +28,11 @@ impl crate::WeightInfo for () {
 		DbWeight::get().writes(1)
 	}
 
-	fn report_equivocation(validator_count: u32) -> Weight {
+	fn report_equivocation(validator_count: u32, max_nominators_per_validator: u32) -> Weight {
 		// we take the validator set count from the membership proof to
 		// calculate the weight but we set a floor of 100 validators.
 		let validator_count = validator_count.max(100) as u64;
 
-		// worst case we are considering is that the given offender
-		// is backed by 200 nominators
-		const MAX_NOMINATORS: u64 = 200;
-
 		// checking membership proof
 		Weight::from_parts(35u64 * WEIGHT_REF_TIME_PER_MICROS, 0)
 			.saturating_add(
@@ -49,10 +45,10 @@ impl crate::WeightInfo for () {
 			// report offence
 			.saturating_add(Weight::from_parts(110u64 * WEIGHT_REF_TIME_PER_MICROS, 0))
 			.saturating_add(Weight::from_parts(
-				25u64 * WEIGHT_REF_TIME_PER_MICROS * MAX_NOMINATORS,
+				25u64 * WEIGHT_REF_TIME_PER_MICROS * max_nominators_per_validator as u64,
 				0,
 			))
-			.saturating_add(DbWeight::get().reads(14 + 3 * MAX_NOMINATORS))
-			.saturating_add(DbWeight::get().writes(10 + 3 * MAX_NOMINATORS))
+			.saturating_add(DbWeight::get().reads(14 + 3 * max_nominators_per_validator as u64))
+			.saturating_add(DbWeight::get().writes(10 + 3 * max_nominators_per_validator as u64))
 	}
 }

substrate/frame/babe/src/lib.rs

@@ -72,7 +72,7 @@ pub use pallet::*;
 
 pub trait WeightInfo {
 	fn plan_config_change() -> Weight;
-	fn report_equivocation(validator_count: u32) -> Weight;
+	fn report_equivocation(validator_count: u32, max_nominators_per_validator: u32) -> Weight;
 }
 
 /// Trigger an epoch change, if any should take place.
@@ -153,6 +153,10 @@ pub mod pallet {
 		#[pallet::constant]
 		type MaxAuthorities: Get<u32>;
 
+		/// The maximum number of nominators for each validator.
+		#[pallet::constant]
+		type MaxNominators: Get<u32>;
+
 		/// The proof of key ownership, used for validating equivocation reports.
 		/// The proof must include the session index and validator count of the
 		/// session at which the equivocation occurred.
@@ -407,6 +411,7 @@ pub mod pallet {
 		#[pallet::call_index(0)]
 		#[pallet::weight(<T as Config>::WeightInfo::report_equivocation(
 			key_owner_proof.validator_count(),
+			T::MaxNominators::get(),
 		))]
 		pub fn report_equivocation(
 			origin: OriginFor<T>,
@@ -433,6 +438,7 @@ pub mod pallet {
 		#[pallet::call_index(1)]
 		#[pallet::weight(<T as Config>::WeightInfo::report_equivocation(
 			key_owner_proof.validator_count(),
+			T::MaxNominators::get(),
 		))]
 		pub fn report_equivocation_unsigned(
 			origin: OriginFor<T>,

substrate/frame/babe/src/mock.rs

@@ -223,6 +223,7 @@ impl Config for Test {
 	type DisabledValidators = Session;
 	type WeightInfo = ();
 	type MaxAuthorities = ConstU32<10>;
+	type MaxNominators = ConstU32<100>;
 	type KeyOwnerProof = <Historical as KeyOwnerProofSystem<(KeyTypeId, AuthorityId)>>::Proof;
 	type EquivocationReportSystem =
 		super::EquivocationReportSystem<Self, Offences, Historical, ReportLongevity>;

substrate/frame/babe/src/tests.rs

@@ -815,7 +815,7 @@ fn report_equivocation_has_valid_weight() {
 	// the weight depends on the size of the validator set,
 	// but there's a lower bound of 100 validators.
 	assert!((1..=100)
-		.map(<Test as Config>::WeightInfo::report_equivocation)
+		.map(|validators| <Test as Config>::WeightInfo::report_equivocation(validators, 1000))
 		.collect::<Vec<_>>()
 		.windows(2)
 		.all(|w| w[0] == w[1]));
@@ -823,7 +823,7 @@ fn report_equivocation_has_valid_weight() {
 	// after 100 validators the weight should keep increasing
 	// with every extra validator.
 	assert!((100..=1000)
-		.map(<Test as Config>::WeightInfo::report_equivocation)
+		.map(|validators| <Test as Config>::WeightInfo::report_equivocation(validators, 1000))
 		.collect::<Vec<_>>()
 		.windows(2)
 		.all(|w| w[0].ref_time() < w[1].ref_time()));