Coretime Feature branch (relay chain) (#1694)

Also fixes: https://github.com/paritytech/polkadot-sdk/issues/1417 - [x] CoreIndex -> AssignmentProvider mapping will be able to change any time. - [x] Implement - [x] Provide Migrations - [x] Add and fix tests - [x] Implement bulk assigner logic - [x] bulk assigner tests - [x] Port over current assigner to use bulk designer (+ share on-demand with bulk): top-level assigner has core ranges: legacy, bulk - [x] Adjust migrations to reflect new assigner structure - [x] Move migration code to Assignment code directly and make it recursive (make it possible to skip releases) -> follow up ticket. - [x] Test migrations - [x] Add migration PR to runtimes repo -> follow up ticket. - [x] Wire up with actual UMP messages - [x] Write PR docs --------- Co-authored-by: eskimor <eskimor@no-such-url.com> Co-authored-by: Bradley Olson <34992650+BradleyOlson64@users.noreply.github.com> Co-authored-by: BradleyOlson64 <lotrftw9@gmail.com> Co-authored-by: Anton Vilhelm Ásgeirsson <antonva@users.noreply.github.com> Co-authored-by: antonva <anton.asgeirsson@parity.io> Co-authored-by: Bastian Köcher <git@kchr.de> Co-authored-by: Marcin S. <marcin@realemail.net> Co-authored-by: Bastian Köcher <info@kchr.de> Co-authored-by: command-bot <>
2026-07-18 15:15:42 +00:00 · 2023-12-21 19:06:58 +01:00
parent 18d53dbf91
commit 69434d9a32
71 changed files with 4059 additions and 1213 deletions
@@ -0,0 +1,73 @@
+// Copyright (C) Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Polkadot is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+//! On demand assigner pallet benchmarking.
+
+#![cfg(feature = "runtime-benchmarks")]
+
+use super::*;
+use frame_benchmarking::v2::*;
+use frame_support::traits::OriginTrait;
+use pallet_broker::CoreIndex as BrokerCoreIndex;
+
+#[benchmarks]
+mod benchmarks {
+	use super::*;
+	use assigner_coretime::PartsOf57600;
+
+	#[benchmark]
+	fn request_core_count() {
+		// Setup
+		let root_origin = <T as frame_system::Config>::RuntimeOrigin::root();
+
+		#[extrinsic_call]
+		_(
+			root_origin as <T as frame_system::Config>::RuntimeOrigin,
+			// random core count
+			100,
+		)
+	}
+
+	#[benchmark]
+	fn assign_core(s: Linear<1, 100>) {
+		// Setup
+		let root_origin = <T as frame_system::Config>::RuntimeOrigin::root();
+
+		// Use parameterized assignment count
+		let mut assignments: Vec<(CoreAssignment, PartsOf57600)> = vec![0u16; s as usize - 1]
+			.into_iter()
+			.enumerate()
+			.map(|(index, parts)| {
+				(CoreAssignment::Task(index as u32), PartsOf57600::new_saturating(parts))
+			})
+			.collect();
+		// Parts must add up to exactly 57600. Here we add all the parts in one assignment, as
+		// it won't effect the weight and splitting up the parts into even groupings may not
+		// work for every value `s`.
+		assignments.push((CoreAssignment::Task(s as u32), PartsOf57600::FULL));
+
+		let core_index: BrokerCoreIndex = 0;
+
+		#[extrinsic_call]
+		_(
+			root_origin as <T as frame_system::Config>::RuntimeOrigin,
+			core_index,
+			BlockNumberFor::<T>::from(5u32),
+			assignments,
+			Some(BlockNumberFor::<T>::from(20u32)),
+		)
+	}
+}
@@ -0,0 +1,285 @@
+// Copyright (C) Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Polkadot is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Migrations for the Coretime pallet.
+
+pub use v_coretime::{GetLegacyLease, MigrateToCoretime};
+
+mod v_coretime {
+	#[cfg(feature = "try-runtime")]
+	use crate::scheduler::common::AssignmentProvider;
+	use crate::{
+		assigner_coretime, configuration,
+		coretime::{mk_coretime_call, Config, PartsOf57600, WeightInfo},
+		paras,
+	};
+	#[cfg(feature = "try-runtime")]
+	use frame_support::ensure;
+	use frame_support::{
+		traits::{OnRuntimeUpgrade, PalletInfoAccess, StorageVersion},
+		weights::Weight,
+	};
+	use frame_system::pallet_prelude::BlockNumberFor;
+	use pallet_broker::{CoreAssignment, CoreMask, ScheduleItem};
+	#[cfg(feature = "try-runtime")]
+	use parity_scale_codec::Decode;
+	#[cfg(feature = "try-runtime")]
+	use parity_scale_codec::Encode;
+	use polkadot_parachain_primitives::primitives::IsSystem;
+	use primitives::{CoreIndex, Id as ParaId};
+	use sp_arithmetic::traits::SaturatedConversion;
+	use sp_core::Get;
+	use sp_runtime::BoundedVec;
+	#[cfg(feature = "try-runtime")]
+	use sp_std::vec::Vec;
+	use sp_std::{iter, prelude::*, result};
+	use xcm::v3::{
+		send_xcm, Instruction, Junction, Junctions, MultiLocation, SendError, WeightLimit, Xcm,
+	};
+
+	/// Return information about a legacy lease of a parachain.
+	pub trait GetLegacyLease<N> {
+		/// If parachain is a lease holding parachain, return the block at which the lease expires.
+		fn get_parachain_lease_in_blocks(para: ParaId) -> Option<N>;
+	}
+
+	/// Migrate a chain to use coretime.
+	///
+	/// This assumes that the `Coretime` and the `AssignerCoretime` pallets are added at the same
+	/// time to a runtime.
+	pub struct MigrateToCoretime<T, SendXcm, LegacyLease>(
+		sp_std::marker::PhantomData<(T, SendXcm, LegacyLease)>,
+	);
+
+	impl<T: Config, SendXcm: xcm::v3::SendXcm, LegacyLease: GetLegacyLease<BlockNumberFor<T>>>
+		MigrateToCoretime<T, SendXcm, LegacyLease>
+	{
+		fn already_migrated() -> bool {
+			// We are using the assigner coretime because the coretime pallet doesn't has any
+			// storage data. But both pallets are introduced at the same time, so this is fine.
+			let name_hash = assigner_coretime::Pallet::<T>::name_hash();
+			let mut next_key = name_hash.to_vec();
+			let storage_version_key = StorageVersion::storage_key::<assigner_coretime::Pallet<T>>();
+
+			loop {
+				match sp_io::storage::next_key(&next_key) {
+					// StorageVersion is initialized before, so we need to ingore it.
+					Some(key) if &key == &storage_version_key => {
+						next_key = key;
+					},
+					// If there is any other key with the prefix of the pallet,
+					// we already have executed the migration.
+					Some(key) if key.starts_with(&name_hash) => {
+						log::info!("`MigrateToCoretime` already executed!");
+						return true
+					},
+					// Any other key/no key means that we did not yet have migrated.
+					None | Some(_) => return false,
+				}
+			}
+		}
+	}
+
+	impl<
+			T: Config + crate::dmp::Config,
+			SendXcm: xcm::v3::SendXcm,
+			LegacyLease: GetLegacyLease<BlockNumberFor<T>>,
+		> OnRuntimeUpgrade for MigrateToCoretime<T, SendXcm, LegacyLease>
+	{
+		fn on_runtime_upgrade() -> Weight {
+			if Self::already_migrated() {
+				return Weight::zero()
+			}
+
+			log::info!("Migrating existing parachains to coretime.");
+			migrate_to_coretime::<T, SendXcm, LegacyLease>()
+		}
+
+		#[cfg(feature = "try-runtime")]
+		fn pre_upgrade() -> Result<Vec<u8>, sp_runtime::DispatchError> {
+			if Self::already_migrated() {
+				return Ok(Vec::new())
+			}
+
+			let legacy_paras = paras::Parachains::<T>::get();
+			let config = <configuration::Pallet<T>>::config();
+			let total_core_count = config.coretime_cores + legacy_paras.len() as u32;
+
+			let dmp_queue_size =
+				crate::dmp::Pallet::<T>::dmq_contents(T::BrokerId::get().into()).len() as u32;
+
+			let total_core_count = total_core_count as u32;
+
+			Ok((total_core_count, dmp_queue_size).encode())
+		}
+
+		#[cfg(feature = "try-runtime")]
+		fn post_upgrade(state: Vec<u8>) -> Result<(), sp_runtime::DispatchError> {
+			if state.is_empty() {
+				return Ok(())
+			}
+
+			log::trace!("Running post_upgrade()");
+
+			let (prev_core_count, prev_dmp_queue_size) =
+				<(u32, u32)>::decode(&mut &state[..]).unwrap();
+
+			let dmp_queue_size =
+				crate::dmp::Pallet::<T>::dmq_contents(T::BrokerId::get().into()).len() as u32;
+			let new_core_count = assigner_coretime::Pallet::<T>::session_core_count();
+			ensure!(new_core_count == prev_core_count, "Total number of cores need to not change.");
+			ensure!(
+				dmp_queue_size == prev_dmp_queue_size + 1,
+				"There should have been enqueued one DMP message."
+			);
+
+			Ok(())
+		}
+	}
+
+	// Migrate to Coretime.
+	//
+	// NOTE: Also migrates coretime_cores config value in configuration::ActiveConfig.
+	fn migrate_to_coretime<
+		T: Config,
+		SendXcm: xcm::v3::SendXcm,
+		LegacyLease: GetLegacyLease<BlockNumberFor<T>>,
+	>() -> Weight {
+		let legacy_paras = paras::Pallet::<T>::parachains();
+		let legacy_count = legacy_paras.len() as u32;
+		let now = <frame_system::Pallet<T>>::block_number();
+		for (core, para_id) in legacy_paras.into_iter().enumerate() {
+			let r = assigner_coretime::Pallet::<T>::assign_core(
+				CoreIndex(core as u32),
+				now,
+				vec![(CoreAssignment::Task(para_id.into()), PartsOf57600::FULL)],
+				None,
+			);
+			if let Err(err) = r {
+				log::error!(
+					"Creating assignment for existing para failed: {:?}, error: {:?}",
+					para_id,
+					err
+				);
+			}
+		}
+
+		let config = <configuration::Pallet<T>>::config();
+		// coretime_cores was on_demand_cores until now:
+		for on_demand in 0..config.coretime_cores {
+			let core = CoreIndex(legacy_count.saturating_add(on_demand as _));
+			let r = assigner_coretime::Pallet::<T>::assign_core(
+				core,
+				now,
+				vec![(CoreAssignment::Pool, PartsOf57600::FULL)],
+				None,
+			);
+			if let Err(err) = r {
+				log::error!("Creating assignment for existing on-demand core, failed: {:?}", err);
+			}
+		}
+		let total_cores = config.coretime_cores + legacy_count;
+		configuration::ActiveConfig::<T>::mutate(|c| {
+			c.coretime_cores = total_cores;
+		});
+
+		if let Err(err) = migrate_send_assignments_to_coretime_chain::<T, SendXcm, LegacyLease>() {
+			log::error!("Sending legacy chain data to coretime chain failed: {:?}", err);
+		}
+
+		let single_weight = <T as Config>::WeightInfo::assign_core(1);
+		single_weight
+			.saturating_mul(u64::from(legacy_count.saturating_add(config.coretime_cores)))
+			// Second read from sending assignments to the coretime chain.
+			.saturating_add(T::DbWeight::get().reads_writes(2, 1))
+	}
+
+	fn migrate_send_assignments_to_coretime_chain<
+		T: Config,
+		SendXcm: xcm::v3::SendXcm,
+		LegacyLease: GetLegacyLease<BlockNumberFor<T>>,
+	>() -> result::Result<(), SendError> {
+		let legacy_paras = paras::Pallet::<T>::parachains();
+		let legacy_paras_count = legacy_paras.len();
+		let (system_chains, lease_holding): (Vec<_>, Vec<_>) =
+			legacy_paras.into_iter().partition(IsSystem::is_system);
+
+		let reservations = system_chains.into_iter().map(|p| {
+			let schedule = BoundedVec::truncate_from(vec![ScheduleItem {
+				mask: CoreMask::complete(),
+				assignment: CoreAssignment::Task(p.into()),
+			}]);
+			mk_coretime_call(crate::coretime::CoretimeCalls::Reserve(schedule))
+		});
+
+		let leases = lease_holding.into_iter().filter_map(|p| {
+			log::trace!(target: "coretime-migration", "Preparing sending of lease holding para {:?}", p);
+			let Some(valid_until) = LegacyLease::get_parachain_lease_in_blocks(p) else {
+				log::error!("Lease holding chain with no lease information?!");
+				return None
+			};
+			let valid_until: u32 = match valid_until.try_into() {
+				Ok(val) => val,
+				Err(_) => {
+					log::error!("Converting block number to u32 failed!");
+					return None
+				},
+			};
+			// We assume the coretime chain set this parameter to the recommened value in RFC-1:
+			const TIME_SLICE_PERIOD: u32 = 80;
+			let round_up = if valid_until % TIME_SLICE_PERIOD > 0 { 1 } else { 0 };
+			let time_slice = valid_until / TIME_SLICE_PERIOD + TIME_SLICE_PERIOD * round_up;
+			log::trace!(target: "coretime-migration", "Sending of lease holding para {:?}, valid_until: {:?}, time_slice: {:?}", p, valid_until, time_slice);
+			Some(mk_coretime_call(crate::coretime::CoretimeCalls::SetLease(p.into(), time_slice)))
+		});
+
+		let core_count: u16 = configuration::Pallet::<T>::config().coretime_cores.saturated_into();
+		let set_core_count = iter::once(mk_coretime_call(
+			crate::coretime::CoretimeCalls::NotifyCoreCount(core_count),
+		));
+
+		let pool = (legacy_paras_count..core_count.into()).map(|_| {
+			let schedule = BoundedVec::truncate_from(vec![ScheduleItem {
+				mask: CoreMask::complete(),
+				assignment: CoreAssignment::Pool,
+			}]);
+			// Reserved cores will come before lease cores, so cores will change their assignments
+			// when coretime chain sends us their assign_core calls -> Good test.
+			mk_coretime_call(crate::coretime::CoretimeCalls::Reserve(schedule))
+		});
+
+		let message_content = iter::once(Instruction::UnpaidExecution {
+			weight_limit: WeightLimit::Unlimited,
+			check_origin: None,
+		})
+		.chain(reservations)
+		.chain(pool)
+		.chain(leases)
+		.chain(set_core_count)
+		.collect();
+
+		let message = Xcm(message_content);
+
+		send_xcm::<SendXcm>(
+			MultiLocation {
+				parents: 0,
+				interior: Junctions::X1(Junction::Parachain(T::BrokerId::get())),
+			},
+			message,
+		)?;
+		Ok(())
+	}
+}
@@ -0,0 +1,251 @@
+// Copyright (C) Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Polkadot is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Extrinsics implementing the relay chain side of the Coretime interface.
+//!
+//! <https://github.com/polkadot-fellows/RFCs/blob/main/text/0005-coretime-interface.md>
+
+use sp_std::{prelude::*, result};
+
+use frame_support::{pallet_prelude::*, traits::Currency};
+use frame_system::pallet_prelude::*;
+pub use pallet::*;
+use pallet_broker::{CoreAssignment, CoreIndex as BrokerCoreIndex};
+use primitives::{CoreIndex, Id as ParaId};
+use sp_arithmetic::traits::SaturatedConversion;
+use xcm::v3::{
+	send_xcm, Instruction, Junction, Junctions, MultiLocation, OriginKind, SendXcm, Xcm,
+};
+
+use crate::{
+	assigner_coretime::{self, PartsOf57600},
+	initializer::{OnNewSession, SessionChangeNotification},
+	origin::{ensure_parachain, Origin},
+};
+
+mod benchmarking;
+pub mod migration;
+
+pub trait WeightInfo {
+	fn request_core_count() -> Weight;
+	//fn request_revenue_info_at() -> Weight;
+	//fn credit_account() -> Weight;
+	fn assign_core(s: u32) -> Weight;
+}
+
+/// A weight info that is only suitable for testing.
+pub struct TestWeightInfo;
+
+impl WeightInfo for TestWeightInfo {
+	fn request_core_count() -> Weight {
+		Weight::MAX
+	}
+	// TODO: Add real benchmarking functionality for each of these to
+	// benchmarking.rs, then uncomment here and in trait definition.
+	/*fn request_revenue_info_at() -> Weight {
+		Weight::MAX
+	}
+	fn credit_account() -> Weight {
+		Weight::MAX
+	}*/
+	fn assign_core(_s: u32) -> Weight {
+		Weight::MAX
+	}
+}
+
+/// Broker pallet index on the coretime chain. Used to
+///
+/// construct remote calls. The codec index must correspond to the index of `Broker` in the
+/// `construct_runtime` of the coretime chain.
+#[derive(Encode, Decode)]
+enum BrokerRuntimePallets {
+	#[codec(index = 50)]
+	Broker(CoretimeCalls),
+}
+
+/// Call encoding for the calls needed from the Broker pallet.
+#[derive(Encode, Decode)]
+enum CoretimeCalls {
+	#[codec(index = 1)]
+	Reserve(pallet_broker::Schedule),
+	#[codec(index = 3)]
+	SetLease(pallet_broker::TaskId, pallet_broker::Timeslice),
+	#[codec(index = 19)]
+	NotifyCoreCount(u16),
+}
+
+#[frame_support::pallet]
+pub mod pallet {
+	use crate::configuration;
+
+	use super::*;
+
+	#[pallet::pallet]
+	#[pallet::without_storage_info]
+	pub struct Pallet<T>(_);
+
+	#[pallet::config]
+	pub trait Config: frame_system::Config + assigner_coretime::Config {
+		type RuntimeOrigin: From<<Self as frame_system::Config>::RuntimeOrigin>
+			+ Into<result::Result<Origin, <Self as Config>::RuntimeOrigin>>;
+		type RuntimeEvent: From<Event<Self>> + IsType<<Self as frame_system::Config>::RuntimeEvent>;
+		/// The runtime's definition of a Currency.
+		type Currency: Currency<Self::AccountId>;
+		/// The ParaId of the broker system parachain.
+		#[pallet::constant]
+		type BrokerId: Get<u32>;
+		/// Something that provides the weight of this pallet.
+		type WeightInfo: WeightInfo;
+		type SendXcm: SendXcm;
+	}
+
+	#[pallet::event]
+	#[pallet::generate_deposit(pub(super) fn deposit_event)]
+	pub enum Event<T: Config> {
+		/// The broker chain has asked for revenue information for a specific block.
+		RevenueInfoRequested { when: BlockNumberFor<T> },
+		/// A core has received a new assignment from the broker chain.
+		CoreAssigned { core: CoreIndex },
+	}
+
+	#[pallet::error]
+	pub enum Error<T> {
+		/// The paraid making the call is not the coretime brokerage system parachain.
+		NotBroker,
+	}
+
+	#[pallet::hooks]
+	impl<T: Config> Hooks<BlockNumberFor<T>> for Pallet<T> {}
+
+	#[pallet::call]
+	impl<T: Config> Pallet<T> {
+		#[pallet::weight(<T as Config>::WeightInfo::request_core_count())]
+		#[pallet::call_index(1)]
+		pub fn request_core_count(origin: OriginFor<T>, count: u16) -> DispatchResult {
+			// Ignore requests not coming from the broker parachain or root.
+			Self::ensure_root_or_para(origin, <T as Config>::BrokerId::get().into())?;
+
+			configuration::Pallet::<T>::set_coretime_cores_unchecked(u32::from(count))
+		}
+
+		//// TODO Impl me!
+		////#[pallet::weight(<T as Config>::WeightInfo::request_revenue_info_at())]
+		//#[pallet::call_index(2)]
+		//pub fn request_revenue_info_at(
+		//	origin: OriginFor<T>,
+		//	_when: BlockNumberFor<T>,
+		//) -> DispatchResult {
+		//	// Ignore requests not coming from the broker parachain or root.
+		//	Self::ensure_root_or_para(origin, <T as Config>::BrokerId::get().into())?;
+		//	Ok(())
+		//}
+
+		//// TODO Impl me!
+		////#[pallet::weight(<T as Config>::WeightInfo::credit_account())]
+		//#[pallet::call_index(3)]
+		//pub fn credit_account(
+		//	origin: OriginFor<T>,
+		//	_who: T::AccountId,
+		//	_amount: BalanceOf<T>,
+		//) -> DispatchResult {
+		//	// Ignore requests not coming from the broker parachain or root.
+		//	Self::ensure_root_or_para(origin, <T as Config>::BrokerId::get().into())?;
+		//	Ok(())
+		//}
+
+		/// Receive instructions from the `ExternalBrokerOrigin`, detailing how a specific core is
+		/// to be used.
+		///
+		/// Parameters:
+		/// -`origin`: The `ExternalBrokerOrigin`, assumed to be the Broker system parachain.
+		/// -`core`: The core that should be scheduled.
+		/// -`begin`: The starting blockheight of the instruction.
+		/// -`assignment`: How the blockspace should be utilised.
+		/// -`end_hint`: An optional hint as to when this particular set of instructions will end.
+		// The broker pallet's `CoreIndex` definition is `u16` but on the relay chain it's `struct
+		// CoreIndex(u32)`
+		#[pallet::call_index(4)]
+		#[pallet::weight(<T as Config>::WeightInfo::assign_core(assignment.len() as u32))]
+		pub fn assign_core(
+			origin: OriginFor<T>,
+			core: BrokerCoreIndex,
+			begin: BlockNumberFor<T>,
+			assignment: Vec<(CoreAssignment, PartsOf57600)>,
+			end_hint: Option<BlockNumberFor<T>>,
+		) -> DispatchResult {
+			// Ignore requests not coming from the broker parachain or root.
+			Self::ensure_root_or_para(origin, T::BrokerId::get().into())?;
+
+			let core = u32::from(core).into();
+
+			<assigner_coretime::Pallet<T>>::assign_core(core, begin, assignment, end_hint)?;
+			Self::deposit_event(Event::<T>::CoreAssigned { core });
+			Ok(())
+		}
+	}
+}
+
+impl<T: Config> Pallet<T> {
+	/// Ensure the origin is one of Root or the `para` itself.
+	fn ensure_root_or_para(
+		origin: <T as frame_system::Config>::RuntimeOrigin,
+		id: ParaId,
+	) -> DispatchResult {
+		if let Ok(caller_id) = ensure_parachain(<T as Config>::RuntimeOrigin::from(origin.clone()))
+		{
+			// Check if matching para id...
+			ensure!(caller_id == id, Error::<T>::NotBroker);
+		} else {
+			// Check if root...
+			ensure_root(origin.clone())?;
+		}
+		Ok(())
+	}
+
+	pub fn initializer_on_new_session(notification: &SessionChangeNotification<BlockNumberFor<T>>) {
+		let old_core_count = notification.prev_config.coretime_cores;
+		let new_core_count = notification.new_config.coretime_cores;
+		if new_core_count != old_core_count {
+			let core_count: u16 = new_core_count.saturated_into();
+			let message = Xcm(vec![mk_coretime_call(
+				crate::coretime::CoretimeCalls::NotifyCoreCount(core_count),
+			)]);
+			if let Err(err) = send_xcm::<T::SendXcm>(
+				MultiLocation {
+					parents: 0,
+					interior: Junctions::X1(Junction::Parachain(T::BrokerId::get())),
+				},
+				message,
+			) {
+				log::error!("Sending `NotifyCoreCount` to coretime chain failed: {:?}", err);
+			}
+		}
+	}
+}
+
+impl<T: Config> OnNewSession<BlockNumberFor<T>> for Pallet<T> {
+	fn on_new_session(notification: &SessionChangeNotification<BlockNumberFor<T>>) {
+		Self::initializer_on_new_session(notification);
+	}
+}
+
+fn mk_coretime_call(call: crate::coretime::CoretimeCalls) -> Instruction<()> {
+	Instruction::Transact {
+		origin_kind: OriginKind::Native,
+		require_weight_at_most: Weight::from_parts(1000000000, 200000),
+		call: BrokerRuntimePallets::Broker(call).encode().into(),
+	}
+}