# Staking parachain PoV limits
PoV upper bounds and configs:
```rust
pub const MILLISECS_PER_BLOCK: u64 = 12000;
pub const SLOT_DURATION: u64 = MILLISECS_PER_BLOCK;
/// 0.5 of a second of compute with a ~12 second average block time.
const MAXIMUM_BLOCK_WEIGHT: Weight = Weight::from_parts(
WEIGHT_REF_TIME_PER_SECOND.saturating_div(2), // 500_000_000_000
cumulus_primitives_core::relay_chain::MAX_POV_SIZE as u64, // 5_242_880 (5120kb)
);
// async backing disabled:
const UNINCLUDED_SEGMENT_CAPACITY: u32 = 1;
const BLOCK_PROCESSING_VELOCITY: u32 = 1;
// aura.AllowMultipleBlocksPerSlot = ConstBool<false>;
```
To reproduce:
- follow https://github.com/paritytech/polkadot-sdk/tree/staking-parachain-exp/templates/parachain
*Note*: using unsigned submission only, but PoV should map 1-1 with signed phase (1 paged submission per block)
**Notes**
- It seems that the snapshot creation or the export phase are the bottleneck wrt the amount of storage r/w required per block
- Adding too many stakers in genesis may overflow the wasm allocation:
> going to fail due to allocating 41018542 > Error: Service(Other("wasm call error Requested allocation size is too large"))
### Working bounds/configs
```
*genesis*
n_validators: 1_500
n_nominators: 30_000
(8 edges)
// staking
pub const MaxValidatorSet: u32 = 1_500;
staking.ValidatorCount = 1_500;
// EPM
pub Pages: PageIndex = 3;
pub MaxWinnersPerPage: u32 = 1_500;
pub MaxBackersPerWinner: u32 = 5_000;
pub VoterSnapshotPerBlock: VoterIndex = 10_000;
pub TargetSnapshotPerBlock: TargetIndex = 1_500;
```
```
// Targets snapshot
[Parachain] [#22]: 🎯🎯🎯 🗳 created target snapshot with 1500 targets.
[Parachain] PoV size { header: 0.2177734375kb, extrinsics: 3.5830078125kb, storage_proof: 74.2119140625kb }
// Voters snapshot
page 2:
[Parachain] [#23]: 🎯🎯🎯 🗳 created voter snapshot with 2500 voters.
[Parachain] PoV size { header: 0.2177734375kb, extrinsics: 3.5830078125kb, storage_proof: 3319.3525390625kb }
page 1:
[Parachain] [#24]: 🎯🎯🎯 🗳 voter snapshot progressed: page 1 with 2500 voters
[Parachain] PoV size { header: 0.2177734375kb, extrinsics: 3.5830078125kb, storage_proof: 3350.6201171875kb }
page 0:
[Parachain] [#25]: 🎯🎯🎯 🗳 voter snapshot progressed: page 0 with 2500 voters
[Parachain] PoV size { header: 0.2177734375kb, extrinsics: 3.5830078125kb, storage_proof: 3348.458984375kb }
// Unsigned submission + verification
page 2:
[Parachain] [#27]: 🎯🎯🎯 🗳 now 27 - current phase Unsigned(26), next election 30, remaining: 3
[Parachain] [#27]: 🎯🎯🎯 🗳 queued sync solution with score ElectionScore { minimal_stake: 253309505716, sum_stake: 2744596071297945, sum_stake_squared: 5410361055743539901774942387 } (page 2)
[Parachain] PoV size { header: 0.2177734375kb, extrinsics: 83.9814453125kb, storage_proof: 777.2119140625kb }
page 1:
[Parachain] [#28]: 🎯🎯🎯 🗳 now 28 - current phase Unsigned(26), next election 30, remaining: 2
[Parachain] [#28]: 🎯🎯🎯 🗳 queued sync solution with score ElectionScore { minimal_stake: 253309505716, sum_stake: 2744596071297945, sum_stake_squared: 5410361055743539901774942387 } (page 2)
[Parachain] PoV size { header: 0.2177734375kb, extrinsics: 83.9814453125kb, storage_proof: 777.33984375kb }
page 0 (+ full verification)
[Parachain] [#30]: 🎯🎯🎯 🗳 now 30 - current phase Unsigned(26), next election 30, remaining: 0
[Parachain] PoV size { header: 0.2177734375kb, extrinsics: 3.5830078125kb, storage_proof: 5.2998046875kb }
// elect() + store electable stashes
page 2:
[Parachain] [32]: 🎯🎯🎯 💸 elect(): next election in 3 pages, start fetching solution pages.
[Parachain] [32]: 🎯🎯🎯 💸 new validator set of size 1500 has been processed for era 1
[Parachain] PoV size { header: 0.2177734375kb, extrinsics: 3.5830078125kb, storage_proof: 1084.013671875kb }
page 1:
[Parachain] [#32]: 🎯🎯🎯 🗳 now 32 - current phase Export(32), next election 32, remaining: 0
[Parachain] PoV size { header: 0.2177734375kb, extrinsics: 3.5830078125kb, storage_proof: 1084.013671875kb }
❌ [Parachain] panicked at /Users/gpestana/.rustup/toolchains/nightly-aarch64-apple-darwin/lib/rustlib/src/rust/library/alloc/src/vec/mod.rs:2162:13:
`at` split index (is 52) should be <= len (is 14)
2024-05-07 01:50:36.086 ERROR tokio-runtime-worker aura::cumulus: [Parachain] err=Error { inner: Proposing
....
```
---
**Test case 1.** single-page, 10K voters/ snapshot page ❌
bricking the collation by overflowing the storage proof.
- 10K voters per snapshot overflows the storage proof by ~3600kb
```
*genesis*
n_validators: 1_000
n_nominators: 10_000
// staking
pub const MaxValidatorSet: u32 = 1_000;
staking.ValidatorCount = 1_000;
// EPM
pub Pages: PageIndex = 1;
pub MaxWinnersPerPage: u32 = 1_000;
pub MaxBackersPerWinner: u32 = 5_000;
pub VoterSnapshotPerBlock: VoterIndex = 10_000;
pub TargetSnapshotPerBlock: TargetIndex = 1_000;
```
```
// Target snapshot
[Parachain] [#7]: 🎯🎯🎯 🗳 created target snapshot with 1000 targets.
[Parachain] [#7]: 🎯🎯🎯 🗳 target snapshot created with 1000 targets
Parachain] PoV size { header: 0.216796875kb, extrinsics: 3.5810546875kb, storage_proof: 50.9462890625kb }
[Parachain] Compressed PoV size: 47.9091796875kb
// Voter snapshot
[#8]: 🎯🎯🎯 🗳 now 8 - current phase Snapshot(1), next election 10, remaining: 2
Parachain] [8]: 🎯🎯🎯 💸 generated 10000 npos voters, 481 from validators and 9519 nominators
[Parachain] [#8]: 🎯🎯🎯 🗳 created voter snapshot with 10000 voters.
[#8]: 🎯🎯🎯 🗳 voter snapshot progressed: page 0 with 10000 voters
[Parachain] PoV size { header: 0.216796875kb, extrinsics: 3.5810546875kb, storage_proof: 8787.5908203125kb }
[Parachain] Compressed PoV size: 2300.1845703125kb
parachain::collator-protocol: [Relaychain] Collation wasn't advertised to any validator. candidate_hash=0x8ba7a25f4e96b533930373d7fb80797b3dbff3d4049c72535ac516ddc7faf694 pov_hash=0xd74d1799fed57cfa1c6057db5c5fd0a344be46bedc038ce813f9e7b62563b6e5 traceID=185633098290831878312032420129021131131
> bricked, parachain blocks not progressing
```
**Test case 2.** single-page, 5K voters/ snapshot page ✅
- Voter snapshot (5k/page) in the limit of the storage proof size (5115kb vs 5120 kb max)
```rust!
// single page election score
ElectionScore {
minimal_stake: 13_042_714_285_497,
sum_stake: 14_261_412_733_134_461,
sum_stake_squared: 203451499923879607620859254597
}
```
```
*genesis*
n_validators: 1_000
n_nominators: 10_000
// staking
pub const MaxValidatorSet: u32 = 1_000;
staking.ValidatorCount = 1_000;
// EPM
pub Pages: PageIndex = 1;
pub MaxWinnersPerPage: u32 = 1_000;
pub MaxBackersPerWinner: u32 = 5_000;
pub VoterSnapshotPerBlock: VoterIndex = 5_000;
pub TargetSnapshotPerBlock: TargetIndex = 1_000;
```
```
// Target snapshot
[Parachain] [#7]: 🎯🎯🎯 🗳 now 7 - current phase Off, next election 10, remaining: 3
[Parachain] [7]: 🎯🎯🎯 💸 generated 1000 npos targets
[Parachain] [#7]: 🎯🎯🎯 🗳 created target snapshot with 1000 targets.
[Parachain] [#7]: 🎯🎯🎯 🗳 target snapshot created with 1000 targets
[Parachain] 🏆 Imported #7 (0x1ebb…493f → 0x77e4…b879)
[Parachain] PoV size { header: 0.216796875kb, extrinsics: 3.5810546875kb, storage_proof: 50.9462890625kb }
[Parachain] Compressed PoV size: 47.9091796875kb
// Voter snapshot
[Parachain] [#8]: 🎯🎯🎯 🗳 now 8 - current phase Snapshot(1), next election 10, remaining: 2
[Parachain] [8]: 🎯🎯🎯 💸 generated 5000 npos voters, 0 from validators and 5000 nominators
[Parachain] [#8]: 🎯🎯🎯 🗳 created voter snapshot with 5000 voters.
[Parachain] [#8]: 🎯🎯🎯 🗳 voter snapshot progressed: page 0 with 5000 voters
[Parachain] PoV size { header: 0.216796875kb, extrinsics: 3.5810546875kb, storage_proof: 5115.0859375kb }
[Parachain] Compressed PoV size: 1705.0869140625kb
// Unsigned submission + verification
[Parachain] [#10]: 🎯🎯🎯 🗳 now 10 - current phase Unsigned(9), next election 10, remaining: 0
[Parachain] [#10]: 🎯🎯🎯 🗳 validate_unsigned OK
[Parachain] [#10]: 🎯🎯🎯 🗳 queued sync solution with score ElectionScore { minimal_stake: 13042714285497, sum_stake: 14261412733134461, sum_stake_squared: 203451499923879607620859254597 } (page 0)
[Parachain] [#10]: 🎯🎯🎯 🗳 finalizing verification of a correct solution, replacing old score None with ElectionScore { minimal_stake: 13042714285497, sum_stake: 14261412733134461, sum_stake_squared: 203451499923879607620859254597 }
[Parachain] [#10]: 🎯🎯🎯 🗳 finalize verification outcome: Ok(())
offchain-worker runtime::multiblock-election: [#10]: 🎯🎯🎯 🗳 offchain miner cache cleared.
[Parachain] PoV size { header: 0.216796875kb, extrinsics: 311.560546875kb, storage_proof: 2736.2041015625kb }
[Parachain] Compressed PoV size: 727.3427734375kb
// elect() + store electable stashes
[Parachain] [14]: 🎯🎯🎯 💸 elect(): next election in 1 pages, start fetching solution pages.
[Parachain] [#14]: 🎯🎯🎯 🗳 elect(): provided the last supports page, rotating round.
[Parachain] [14]: 🎯🎯🎯 💸 new validator set of size 1000 has been processed for era 1
[Parachain] [#14]: 🎯🎯🎯 🗳 now 14 - current phase Off, next election 14, remaining: 0
[Parachain] PoV size { header: 0.216796875kb, extrinsics: 3.5810546875kb, storage_proof: 3850.3623046875kb }
[Parachain] Compressed PoV size: 916.2607421875kb
```
**Test case 4.** single-page, 10k targets and 5K voters/ snapshot page; 10K max backers per winner ❌
bricking the collation by overflowing the storage proof.
- 5K (out of 20Ks) voters per snapshot overflows the storage proof by ~1300kb
```
*genesis*
n_validators: 10_000
n_nominators: 20_000
// staking
pub const MaxValidatorSet: u32 = 1_000;
staking.ValidatorCount = 1_000;
// EPM
pub Pages: PageIndex = 1;
pub MaxWinnersPerPage: u32 = 10_000;
pub MaxBackersPerWinner: u32 = 10_000;
pub VoterSnapshotPerBlock: VoterIndex = 5_000;
pub TargetSnapshotPerBlock: TargetIndex = 10_000;
```
```
// Target snapshot
[Parachain] [7]: 🎯🎯🎯 💸 generated 10000 npos targets
[Parachain] [#7]: 🎯🎯🎯 🗳 created target snapshot with 10000 targets.
[Parachain] [#7]: 🎯🎯🎯 🗳 target snapshot created with 10000 targets
[Parachain] PoV size { header: 0.216796875kb, extrinsics: 3.5810546875kb, storage_proof: 463.5048828125kb }
[Parachain] Compressed PoV size: 405.9716796875kb
// Voter snapshot
[Parachain] [8]: 🎯🎯🎯 💸 generated 5000 npos voters, 0 from validators and 5000 nominators
[Parachain] [#8]: 🎯🎯🎯 🗳 created voter snapshot with 5000 voters.
[Parachain] [#8]: 🎯🎯🎯 🗳 voter snapshot progressed: page 0 with 5000 voters
[Parachain] PoV size { header: 0.216796875kb, extrinsics: 3.5810546875kb, storage_proof: 6427.046875kb }
[Parachain] Compressed PoV size: 3703.509765625kb
2024-05-07 00:42:26.074 WARN tokio-runtime-worker parachain::collator-protocol: [Relaychain] Collation wasn't advertised to any validator. candidate_hash=0x21458f63bf60680185843d95f1b9bc8d8a853bc55075c9ca5d722c2b3766a6bf pov_hash=0xa3cc666e0dfe5b18559bdedb385b48db0cc0477c27d7fb6d5c76d20e790a58dc traceID=44225700631530722921976040915954416781
> bricked, parachain blocks not progressing
```
**Test case 5.** multi-page (3), 10k targets and 2.5K voters/ snapshot page; 10K max backers per winner ✅
```
*genesis*
n_validators: 10_000
n_nominators: 20_000
// staking
pub const MaxValidatorSet: u32 = 1_000;
staking.ValidatorCount = 1_000;
// EPM
pub Pages: PageIndex = 3;
pub MaxWinnersPerPage: u32 = 10_000;
pub MaxBackersPerWinner: u32 = 10_000;
pub VoterSnapshotPerBlock: VoterIndex = 2_500;
pub TargetSnapshotPerBlock: TargetIndex = 10_000;
```
---
(*old*)
### Theoretical limits
Dumps from test in
https://github.com/paritytech/polkadot-sdk/blob/gpestana/staking_para_weights/substrate/frame/election-provider-multi-phase/test-staking-e2e/src/lib.rs#L392
Note that we assume only the max `BlockLimit` weight in this exercise, so take it with a pinch of salt.
Given
```rust=
// `MaxActiveValidators` in Polkadot.
let targets = 1_200;
// `MaxElectionVoters` in Polkadot.
let voters = 22_500;
// we assume 1/2 of the voters are active.
let active_voters = 22_500 / 2;
// `MaxWinners` in Polkadot.
let desired_targets = 1_200;
// parachain block limit (using same as AssetHub in Rococo)
let weight_limit = Weight::from_parts(
// ref_time
500_000_000_000,
// proof_size
5_242_880,
);
```
We have:
```
snapshot weight:
Weight { ref_time: 4548650500, proof_size: 0 }.
fits? true.
Max voters: 2830950
submit_unsigned:
Weight { ref_time: 68979654500, proof_size: 12482638 }.
fits? false.
Max voters: 9410
elect weight:
Weight { ref_time: 4447471000, proof_size: 8702723 }.
fits? false
get_npos_voters weight:
Weight { ref_time: 108390856050, proof_size: 44909090 }.
fits? false
get_npos_targets weight:
Weight { ref_time: 5945960664, proof_size: 3027510 }.
fits? true
```
### Practical limits
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