Enable 6 second block times for people chain (#308)

This is an excerpt from #266. It aims to enable 6-second block times for
`people` parachain only.

If I'm not missing anything, the `people` parachain is the only
parachain not affected by paritytech/polkadot-sdk#3268, and thus,
6-second block times may be enabled without breaking something.

This PR was tested locally using the `kusama-local` relay chain. The
time of the session within which the runtime upgrade was enacted
expectedly deviated, but other than that, no problems were observed.

---------

Co-authored-by: joe petrowski <25483142+joepetrowski@users.noreply.github.com>

CHANGELOG.md

@@ -38,6 +38,10 @@ Note: This release only affects the following runtimes and is not a full system
 
 - Kusama People: clear requested judgements that do not have corresponding deposits reserved ([polkadot-fellows/runtimes#339](https://github.com/polkadot-fellows/runtimes/pull/339))
 
+### Changed
+
+- People chain now uses 6-second block times ([polkadot-fellows/runtimes#308](https://github.com/polkadot-fellows/runtimes/pull/308))
+
 ### Removed
 
 - Removed Identity-related code from Kusama Relay Chain ([polkadot-fellows/runtimes#315](https://github.com/polkadot-fellows/runtimes/pull/315))

system-parachains/people/people-kusama/Cargo.toml

@@ -37,6 +37,7 @@ pallet-timestamp = { workspace = true }
 pallet-transaction-payment = { workspace = true }
 pallet-transaction-payment-rpc-runtime-api = { workspace = true }
 pallet-utility = { workspace = true }
+polkadot-primitives = { workspace = true }
 sp-api = { workspace = true }
 sp-block-builder = { workspace = true }
 sp-consensus-aura = { workspace = true }
@@ -142,6 +143,7 @@ std = [
 	"xcm-builder/std",
 	"xcm-executor/std",
 	"xcm/std",
+	"polkadot-primitives/std"
 ]
 
 runtime-benchmarks = [
@@ -170,6 +172,7 @@ runtime-benchmarks = [
 	"sp-runtime/runtime-benchmarks",
 	"xcm-builder/runtime-benchmarks",
 	"xcm-executor/runtime-benchmarks",
+	"polkadot-primitives/runtime-benchmarks"
 ]
 
 try-runtime = [

system-parachains/people/people-kusama/src/lib.rs

@@ -35,7 +35,7 @@ use frame_support::{
 		tokens::imbalance::ResolveTo, ConstBool, ConstU32, ConstU64, ConstU8, EitherOfDiverse,
 		Everything, InstanceFilter, TransformOrigin,
 	},
-	weights::{ConstantMultiplier, Weight},
+	weights::{constants::WEIGHT_REF_TIME_PER_SECOND, ConstantMultiplier, Weight},
 	PalletId,
 };
 use frame_system::{
@@ -46,8 +46,7 @@ use identity_ops::pallet_identity_ops;
 use pallet_xcm::{EnsureXcm, IsVoiceOfBody};
 use parachains_common::{
 	message_queue::{NarrowOriginToSibling, ParaIdToSibling},
-	AccountId, Balance, BlockNumber, Hash, Header, Nonce, Signature, AVERAGE_ON_INITIALIZE_RATIO,
-	HOURS, MAXIMUM_BLOCK_WEIGHT, NORMAL_DISPATCH_RATIO, SLOT_DURATION,
+	AccountId, Balance, BlockNumber, Hash, Header, Nonce, Signature,
 };
 use polkadot_runtime_common::{BlockHashCount, SlowAdjustingFeeUpdate};
 use sp_api::impl_runtime_apis;
@@ -66,14 +65,51 @@ use sp_std::prelude::*;
 #[cfg(feature = "std")]
 use sp_version::NativeVersion;
 use sp_version::RuntimeVersion;
-use system_parachains_constants::kusama::{consensus::*, currency::*, fee::WeightToFee};
+use system_parachains_constants::kusama::{
+	consensus::RELAY_CHAIN_SLOT_DURATION_MILLIS, currency::*, fee::WeightToFee,
+};
 use weights::{BlockExecutionWeight, ExtrinsicBaseWeight, RocksDbWeight};
 use xcm::latest::prelude::BodyId;
 use xcm_config::{
 	FellowshipLocation, GovernanceLocation, PriceForSiblingParachainDelivery, StakingPot,
 	XcmConfig, XcmOriginToTransactDispatchOrigin,
 };
 
+/// This determines the average expected block time that we are targeting. Blocks will be
+/// produced at a minimum duration defined by `SLOT_DURATION`. `SLOT_DURATION` is picked up by
+/// `pallet_timestamp`, which is in turn picked up by `pallet_aura` to implement `fn
+/// slot_duration()`.
+///
+/// Change this to adjust the block time.
+pub const MILLISECS_PER_BLOCK: u64 = 6_000;
+pub const SLOT_DURATION: u64 = MILLISECS_PER_BLOCK;
+
+// Time is measured by number of blocks.
+pub const MINUTES: BlockNumber = 60_000 / (MILLISECS_PER_BLOCK as BlockNumber);
+pub const HOURS: BlockNumber = MINUTES * 60;
+pub const DAYS: BlockNumber = HOURS * 24;
+
+/// We assume that ~5% of the block weight is consumed by `on_initialize` handlers. This is
+/// used to limit the maximal weight of a single extrinsic.
+pub const AVERAGE_ON_INITIALIZE_RATIO: Perbill = Perbill::from_percent(5);
+/// We allow `Normal` extrinsics to fill up the block up to 75%, the rest can be used by
+/// `Operational` extrinsics.
+pub const NORMAL_DISPATCH_RATIO: Perbill = Perbill::from_percent(75);
+
+/// We allow for 2 seconds of compute with a 6 second average block time.
+pub const MAXIMUM_BLOCK_WEIGHT: Weight = Weight::from_parts(
+	WEIGHT_REF_TIME_PER_SECOND.saturating_mul(2),
+	polkadot_primitives::MAX_POV_SIZE as u64,
+);
+
+/// Maximum number of blocks simultaneously accepted by the Runtime, not yet included
+/// into the relay chain.
+pub const UNINCLUDED_SEGMENT_CAPACITY: u32 = 2;
+
+/// How many parachain blocks are processed by the relay chain per parent. Limits the
+/// number of blocks authored per slot.
+pub const BLOCK_PROCESSING_VELOCITY: u32 = 1;
+
 /// The address format for describing accounts.
 pub type Address = MultiAddress<AccountId, ()>;
 
@@ -198,7 +234,7 @@ impl pallet_timestamp::Config for Runtime {
 	/// A timestamp: milliseconds since the unix epoch.
 	type Moment = u64;
 	type OnTimestampSet = Aura;
-	type MinimumPeriod = ConstU64<{ SLOT_DURATION / 2 }>;
+	type MinimumPeriod = ConstU64<0>;
 	type WeightInfo = weights::pallet_timestamp::WeightInfo<Runtime>;
 }
 
@@ -344,7 +380,7 @@ impl pallet_aura::Config for Runtime {
 	type AuthorityId = AuraId;
 	type DisabledValidators = ();
 	type MaxAuthorities = ConstU32<100_000>;
-	type AllowMultipleBlocksPerSlot = ConstBool<false>;
+	type AllowMultipleBlocksPerSlot = ConstBool<true>;
 	type SlotDuration = ConstU64<SLOT_DURATION>;
 }